----------------------------------------------------------------------
-- AniPhallow - Animation Frame Selector for Aseprite
--
-- Select tiles from a spritesheet to build directional walk animations
-- (Up, Down, Left, Right). Click tiles on the source view to assign
-- them to the currently selected direction.
--
-- Left-click: add tile to current direction
-- Right-click drag: scroll source view
----------------------------------------------------------------------

----------------------------------------------------------------------
-- Configuration
----------------------------------------------------------------------
local DEFAULT_TILE_W       = 16
local DEFAULT_TILE_H       = 24
local DEFAULT_ANIM_SPEED   = 200
local DEFAULT_PREVIEW_ZOOM = 4
local DEFAULT_SOURCE_ZOOM  = 2
local MAX_PREVIEW_ZOOM     = 10
local THUMB_SIZE           = 24
local SOURCE_VIEWPORT_W    = 300
local SOURCE_VIEWPORT_H    = 400

local MAX_ANIMS = 20  -- max number of dynamic animations
local TABS       = { "Animations", "Optimize" }
local DEFAULT_GB_TILE_W = 8   -- Default Game Boy tile width
local DEFAULT_GB_TILE_H = 8   -- Default Game Boy tile height
local GB_COLS    = 16  -- tiles per row in optimized image (128px = GB standard)

----------------------------------------------------------------------
-- Presets paths
----------------------------------------------------------------------
local PRESETS_DIR = app.fs.joinPath(app.fs.userConfigPath, "aniphallow_presets")
local MASTER_FILE = app.fs.joinPath(app.fs.userConfigPath, "aniphallow_master.ini")
local OLD_PREFS_FILE = app.fs.joinPath(app.fs.userConfigPath, "aniphallow_prefs.ini")
local LOCK_FILE = app.fs.joinPath(app.fs.userConfigPath, "aniphallow.lock")

----------------------------------------------------------------------
-- State
----------------------------------------------------------------------
local pc = app.pixelColor

local S = {
    tileW        = DEFAULT_TILE_W,
    tileH        = DEFAULT_TILE_H,
    animSpeed    = DEFAULT_ANIM_SPEED,
    previewZoomAll = DEFAULT_PREVIEW_ZOOM,
    previewZoomOne = DEFAULT_PREVIEW_ZOOM,
    sourceZoom   = DEFAULT_SOURCE_ZOOM,
    animFrame    = 0,
    currentAnim  = 1,       -- index into animNames
    currentTab   = "Animations",
    sourceImage  = nil,
    scrollX      = 0,
    scrollY      = 0,
    dragging     = false,
    dragLastX    = 0,
    dragLastY    = 0,
    useBgColor   = false,
    bgColor      = Color(0, 0, 0),
    -- GB tab state
    gbFlipOpt      = false,
    gbTiles        = {},      -- list of unique tiles: {hash, positions={{x,y,flip},...}}
    gbOptImage     = nil,     -- generated optimized tileset Image
    gbSelectedTile = 0,       -- 1-based index of selected tile in optimized set
    gbScrollX      = 0,
    gbScrollY      = 0,
    gbDragging     = false,
    gbDragLastX    = 0,
    gbDragLastY    = 0,
    gbSrcScrollX   = 0,
    gbSrcScrollY   = 0,
    gbSrcDragging  = false,
    gbSrcDragLastX = 0,
    gbSrcDragLastY = 0,
    gbTotalTiles   = 0,
    gbCols         = GB_COLS,  -- columns in optimized image (matches source width)
    gbSimilarThreshold = 80,   -- percentage of painted pixels that must match (1-100)
    gbOffsetOpt    = false,    -- also check offset combinations when finding similar
    gbCompress     = true,     -- compress: pack unique tiles left-to-right; false: keep layout, blank dupes
    gbSimilarPairs = {},       -- list of {i, j, flip, ox, oy, match} pairs of similar tile indices
    gbZoomOpt      = 3,        -- independent zoom for optimized tileset canvas
    gbZoomSrc      = 2,        -- independent zoom for source occurrences canvas
    gbSilhouette   = false,    -- checkbox state
    gbSilhouetteColor = Color(0, 0, 0), -- silhouette color
    gbSilhouetteColorSet = false, -- tracks if ever set by user
    gbAnalyzeMode  = "pixel",  -- "pixel" or "tile"
    gbLastSavePath = "",       -- remembers last PNG export path
    gbLayerName    = "auto-optimized-tiles", -- default layer name
    gbAlwaysOverwrite = false, -- overwrite layer checkbox
    gbTileW        = DEFAULT_GB_TILE_W,  -- configurable tile width for GB analysis
    gbTileH        = DEFAULT_GB_TILE_H,  -- configurable tile height for GB analysis
    -- Remember if separate preview window was open
    previewWindowOpen = false,
    -- Click vs drag for GB canvases
    gbOptClickX    = 0,
    gbOptClickY    = 0,
    gbOptIsDrag    = false,
    gbSrcClickX    = 0,
    gbSrcClickY    = 0,
    gbSrcIsDrag    = false,
    -- Dynamic animations: each frame is {x, y, flipped, flippedV, offX, offY}
    animNames = {},  -- ordered list of animation names (sorted alphabetically)
    anims = {},      -- name -> list of {x, y, flipped, flippedV, offX, offY}
    -- Frame selection & drag
    selectedFrame  = 0,
    frameDragging  = false,
    frameDragFrom  = 0,
    frameDragTo    = 0,
    -- Source canvas click vs drag
    srcClickX      = 0,
    srcClickY      = 0,
    srcIsDrag      = false,
    -- Preview layout configuration
    previewLayout      = "auto",      -- "auto", "fixedCols", "fixedRows"
    previewLayoutValue = 2,           -- number for fixed cols/rows
    previewMode        = "all",       -- "all" or "single"
    previewSingleIdx   = 1,           -- which animation to show in single mode
    -- Current preset
    currentPreset      = "Default",
}

----------------------------------------------------------------------
-- File-to-preset association map
----------------------------------------------------------------------
local filePresetMap = {}  -- filepath -> presetName
local knownPresetNames = { "Default" }  -- list of all known preset names
local lastSpriteFilename = ""  -- for auto-detect file change

----------------------------------------------------------------------
-- Tab widget IDs (for show/hide)
----------------------------------------------------------------------
-- Setup tab elements (btnConfig removed so it stays visible on all tabs)
local SETUP_IDS = {
    "sepAnims", "cmbAnimList", "btnNewAnim", "btnDelAnim", "btnRenameAnim", "btnCloneAnim",
    "sepSource", "canvasSource",
    "canvasStrips",
    "btnFlipX", "btnFlipY", "btnMoveLeft", "btnMoveRight", "btnRemoveFrame",
    "btnFrameUp", "btnFrameDown", "btnFrameLeft", "btnFrameRight", "btnFrameReset",
}

-- GB tab elements (reordered: Flip, Offset, Silhouette, Compress)
local GB_IDS = {
    "sepGb", "btnAnalyze", "gbFlipOpt", "gbOffsetOpt", "gbSilhouette", "gbCompress",
    "gbAnalyzeMode",
    "gbSimilarThreshold", "btnFindSimilar",
    "sepGbSource", "canvasGbSource",
    "canvasGbOpt",
    "btnGbSaveLayer", "btnGbCopyClipboard", "btnGbSave",
}

-- GB canvas heights (taller to match Animations tab and prevent resize on tab switch)
local GB_SRC_H = 240
local GB_OPT_H = 240

----------------------------------------------------------------------
-- Module-level window/timer variables
----------------------------------------------------------------------
local previewDlg = nil
local previewTimer = nil
local pvRefreshTimer = nil
local mainDlg = nil
local mainAnimTimer = nil
local mainRefreshTimer = nil

-- Forward declarations
local openPreviewWindow
local openMainDialog

----------------------------------------------------------------------
-- Serialize / Deserialize frames
----------------------------------------------------------------------
-- Serialize frames list: "x1,y1,f,fv,ox,oy;x2,y2,f,fv,ox,oy;..."
local function serializeFrames(frames)
    local parts = {}
    for _, f in ipairs(frames) do
        table.insert(parts, f.x .. "," .. f.y .. "," .. (f.flipped and "1" or "0") .. "," .. (f.flippedV and "1" or "0") .. "," .. (f.offX or 0) .. "," .. (f.offY or 0))
    end
    return table.concat(parts, ";")
end

-- Deserialize frames string back to list
local function deserializeFrames(str)
    local frames = {}
    if not str or str == "" then return frames end
    for part in string.gmatch(str, "([^;]+)") do
        local x, y, fh, fv, ox, oy = string.match(part, "([%d-]+),([%d-]+),?(%d?),?(%d?),?([%d-]*),?([%d-]*)")
        if x and y then
            table.insert(frames, {
                x = tonumber(x), y = tonumber(y),
                flipped = (fh == "1"),
                flippedV = (fv == "1"),
                offX = tonumber(ox) or 0,
                offY = tonumber(oy) or 0
            })
        end
    end
    return frames
end

----------------------------------------------------------------------
-- Reset to defaults
----------------------------------------------------------------------
local function resetToDefaults()
    S.tileW = DEFAULT_TILE_W
    S.tileH = DEFAULT_TILE_H
    S.animSpeed = DEFAULT_ANIM_SPEED
    S.sourceZoom = DEFAULT_SOURCE_ZOOM
    S.useBgColor = false
    S.bgColor = Color(0, 0, 0)
    S.gbFlipOpt = false
    S.gbOffsetOpt = false
    S.gbCompress = true
    S.gbSilhouette = false
    S.gbSilhouetteColor = Color(0, 0, 0)
    S.gbSilhouetteColorSet = false
    S.gbAnalyzeMode = "pixel"
    S.gbLayerName = "auto-optimized-tiles"
    S.gbAlwaysOverwrite = false
    S.gbTileW = DEFAULT_GB_TILE_W
    S.gbTileH = DEFAULT_GB_TILE_H
    S.gbSimilarThreshold = 80
    S.animNames = {}
    S.anims = {}
    S.currentAnim = 1
    S.selectedFrame = 0
end

----------------------------------------------------------------------
-- Preset name helpers
----------------------------------------------------------------------
local function addPresetName(name)
    for _, n in ipairs(knownPresetNames) do
        if n == name then return end
    end
    table.insert(knownPresetNames, name)
    table.sort(knownPresetNames, function(a, b) return a:lower() < b:lower() end)
end

local function removePresetName(name)
    for i, n in ipairs(knownPresetNames) do
        if n == name then table.remove(knownPresetNames, i); return end
    end
end

----------------------------------------------------------------------
-- Preset system: save/load preset files and master file
----------------------------------------------------------------------

-- Get list of all known preset names
local function getAllPresetNames()
    -- Ensure "Default" is always first
    local seen = {}
    local result = { "Default" }
    seen["Default"] = true
    for _, name in ipairs(knownPresetNames) do
        if not seen[name] then
            table.insert(result, name)
            seen[name] = true
        end
    end
    return result
end

-- Save current state to a preset file
local function savePreset(presetName)
    -- Create presets dir if needed
    app.fs.makeDirectory(PRESETS_DIR)
    local path = app.fs.joinPath(PRESETS_DIR, presetName .. ".ini")
    local f = io.open(path, "w")
    if not f then return end
    f:write("tileW=" .. S.tileW .. "\n")
    f:write("tileH=" .. S.tileH .. "\n")
    f:write("animSpeed=" .. S.animSpeed .. "\n")
    f:write("sourceZoom=" .. S.sourceZoom .. "\n")
    -- Save current animation name for robust resolution after sort
    local curName = ""
    if S.currentAnim >= 1 and S.currentAnim <= #S.animNames then
        curName = S.animNames[S.currentAnim]
    end
    f:write("currentAnimName=" .. curName .. "\n")
    f:write("currentTab=" .. S.currentTab .. "\n")
    f:write("animNames=" .. table.concat(S.animNames, "|") .. "\n")
    f:write("useBgColor=" .. tostring(S.useBgColor) .. "\n")
    f:write("bgColorR=" .. S.bgColor.red .. "\n")
    f:write("bgColorG=" .. S.bgColor.green .. "\n")
    f:write("bgColorB=" .. S.bgColor.blue .. "\n")
    f:write("gbFlipOpt=" .. tostring(S.gbFlipOpt) .. "\n")
    f:write("gbOffsetOpt=" .. tostring(S.gbOffsetOpt) .. "\n")
    f:write("gbCompress=" .. tostring(S.gbCompress) .. "\n")
    f:write("gbSimilarThreshold=" .. S.gbSimilarThreshold .. "\n")
    f:write("gbZoomOpt=" .. S.gbZoomOpt .. "\n")
    f:write("gbZoomSrc=" .. S.gbZoomSrc .. "\n")
    f:write("gbSilhouette=" .. tostring(S.gbSilhouette) .. "\n")
    f:write("gbSilhouetteColorR=" .. S.gbSilhouetteColor.red .. "\n")
    f:write("gbSilhouetteColorG=" .. S.gbSilhouetteColor.green .. "\n")
    f:write("gbSilhouetteColorB=" .. S.gbSilhouetteColor.blue .. "\n")
    f:write("gbSilhouetteColorSet=" .. tostring(S.gbSilhouetteColorSet) .. "\n")
    f:write("gbAnalyzeMode=" .. S.gbAnalyzeMode .. "\n")
    f:write("gbLastSavePath=" .. S.gbLastSavePath .. "\n")
    f:write("gbLayerName=" .. S.gbLayerName .. "\n")
    f:write("gbAlwaysOverwrite=" .. tostring(S.gbAlwaysOverwrite) .. "\n")
    f:write("gbTileW=" .. S.gbTileW .. "\n")
    f:write("gbTileH=" .. S.gbTileH .. "\n")
    for i, name in ipairs(S.animNames) do
        f:write("anim_" .. (i - 1) .. "=" .. serializeFrames(S.anims[name] or {}) .. "\n")
    end
    f:close()
end

-- Load a preset file into S
local function loadPreset(presetName)
    local path = app.fs.joinPath(PRESETS_DIR, presetName .. ".ini")
    local f = io.open(path, "r")
    if not f then
        -- If preset doesn't exist, reset to defaults
        resetToDefaults()
        S.currentPreset = presetName
        return
    end
    -- Reset animation data before loading
    S.animNames = {}
    S.anims = {}
    local savedAnimName = nil
    for line in f:lines() do
        local k, v = string.match(line, "^([%w_]+)=(.+)$")
        if k == "tileW" then S.tileW = tonumber(v) or DEFAULT_TILE_W end
        if k == "tileH" then S.tileH = tonumber(v) or DEFAULT_TILE_H end
        if k == "animSpeed" then S.animSpeed = tonumber(v) or DEFAULT_ANIM_SPEED end
        if k == "sourceZoom" then S.sourceZoom = tonumber(v) or DEFAULT_SOURCE_ZOOM end
        if k == "currentAnim" then S.currentAnim = tonumber(v) or 1 end
        if k == "currentAnimName" then savedAnimName = v end
        if k == "currentTab" and v ~= "" then
            if v == "Setup" then v = "Animations"
            elseif v == "Render" then v = "Animations"
            elseif v == "Preview" then v = "Animations"
            elseif v == "GB" then v = "Optimize"
            end
            S.currentTab = v
        end
        if k == "animNames" and v ~= "" then
            S.animNames = {}
            for name in string.gmatch(v, "([^|]+)") do
                table.insert(S.animNames, name)
            end
        end
        if k == "useBgColor" then S.useBgColor = (v == "true") end
        if k == "bgColorR" then S.bgColor = Color(tonumber(v) or 0, S.bgColor.green, S.bgColor.blue) end
        if k == "bgColorG" then S.bgColor = Color(S.bgColor.red, tonumber(v) or 0, S.bgColor.blue) end
        if k == "bgColorB" then S.bgColor = Color(S.bgColor.red, S.bgColor.green, tonumber(v) or 0) end
        if k == "gbFlipOpt" then S.gbFlipOpt = (v == "true") end
        if k == "gbOffsetOpt" then S.gbOffsetOpt = (v == "true") end
        if k == "gbCompress" then S.gbCompress = (v == "true") end
        if k == "gbSimilarThreshold" then S.gbSimilarThreshold = tonumber(v) or 80 end
        if k == "gbZoomOpt" then S.gbZoomOpt = tonumber(v) or 3 end
        if k == "gbZoomSrc" then S.gbZoomSrc = tonumber(v) or 2 end
        if k == "gbSilhouette" then S.gbSilhouette = (v == "true") end
        if k == "gbSilhouetteColorR" then S.gbSilhouetteColor = Color(tonumber(v) or 0, S.gbSilhouetteColor.green, S.gbSilhouetteColor.blue) end
        if k == "gbSilhouetteColorG" then S.gbSilhouetteColor = Color(S.gbSilhouetteColor.red, tonumber(v) or 0, S.gbSilhouetteColor.blue) end
        if k == "gbSilhouetteColorB" then S.gbSilhouetteColor = Color(S.gbSilhouetteColor.red, S.gbSilhouetteColor.green, tonumber(v) or 0) end
        if k == "gbSilhouetteColorSet" then S.gbSilhouetteColorSet = (v == "true") end
        if k == "gbAnalyzeMode" then S.gbAnalyzeMode = v end
        if k == "gbLastSavePath" then S.gbLastSavePath = v end
        if k == "gbLayerName" then S.gbLayerName = v end
        if k == "gbAlwaysOverwrite" then S.gbAlwaysOverwrite = (v == "true") end
        if k == "gbTileW" then S.gbTileW = tonumber(v) or DEFAULT_GB_TILE_W end
        if k == "gbTileH" then S.gbTileH = tonumber(v) or DEFAULT_GB_TILE_H end
        if k == "gbTileSize" then
            local ts = tonumber(v) or DEFAULT_GB_TILE_W
            S.gbTileW = ts
            S.gbTileH = ts
        end
        -- Dynamic anim frames: anim_0, anim_1, ...
        local animIdx = k and string.match(k, "^anim_(%d+)$")
        if animIdx then
            local idx = tonumber(animIdx) + 1
            if S.animNames[idx] then
                S.anims[S.animNames[idx]] = deserializeFrames(v)
            end
        end
    end
    f:close()

    -- Sort animation names alphabetically
    table.sort(S.animNames, function(a, b) return a:lower() < b:lower() end)

    -- Resolve current animation by name
    if savedAnimName and savedAnimName ~= "" then
        for i, name in ipairs(S.animNames) do
            if name == savedAnimName then
                S.currentAnim = i
                break
            end
        end
    end
    -- Clamp currentAnim to valid range
    if S.currentAnim < 1 then S.currentAnim = 1 end
    if S.currentAnim > #S.animNames then S.currentAnim = math.max(1, #S.animNames) end

    S.currentPreset = presetName
end

-- Save master file (global prefs + file associations)
local function saveMaster()
    local f = io.open(MASTER_FILE, "w")
    if not f then return end
    f:write("currentPreset=" .. S.currentPreset .. "\n")
    f:write("previewWindowOpen=" .. tostring(S.previewWindowOpen) .. "\n")
    f:write("previewLayout=" .. S.previewLayout .. "\n")
    f:write("previewLayoutValue=" .. S.previewLayoutValue .. "\n")
    f:write("previewMode=" .. S.previewMode .. "\n")
    f:write("previewZoomAll=" .. S.previewZoomAll .. "\n")
    f:write("previewZoomOne=" .. S.previewZoomOne .. "\n")
    f:write("previewSingleIdx=" .. S.previewSingleIdx .. "\n")
    -- File associations
    for filepath, preset in pairs(filePresetMap) do
        if preset ~= "Default" then
            f:write("file_" .. filepath .. "=" .. preset .. "\n")
        end
    end
    -- Preset names list (for discovery since we can't list dir)
    f:write("presetNames=" .. table.concat(getAllPresetNames(), "|") .. "\n")
    f:close()
end

-- Load master file
local function loadMaster()
    local f = io.open(MASTER_FILE, "r")
    if not f then return end
    filePresetMap = {}
    for line in f:lines() do
        local k, v = string.match(line, "^(.-)=(.+)$")
        if k and v then
            if k == "currentPreset" then S.currentPreset = v end
            if k == "previewWindowOpen" then S.previewWindowOpen = (v == "true") end
            if k == "previewLayout" then S.previewLayout = v end
            if k == "previewLayoutValue" then S.previewLayoutValue = tonumber(v) or 2 end
            if k == "previewMode" then S.previewMode = v end
            if k == "previewZoomAll" then S.previewZoomAll = tonumber(v) or DEFAULT_PREVIEW_ZOOM end
            if k == "previewZoomOne" then S.previewZoomOne = tonumber(v) or DEFAULT_PREVIEW_ZOOM end
            if k == "previewSingleIdx" then S.previewSingleIdx = tonumber(v) or 1 end
            if k == "presetNames" and v ~= "" then
                knownPresetNames = {}
                for name in string.gmatch(v, "([^|]+)") do
                    table.insert(knownPresetNames, name)
                end
            end
            -- File associations: keys starting with "file_"
            local filePath = string.match(k, "^file_(.+)$")
            if filePath then
                filePresetMap[filePath] = v
            end
        end
    end
    f:close()
    -- Clamp previewSingleIdx
    if S.previewSingleIdx < 1 then S.previewSingleIdx = 1 end
end

-- Convenience: save both preset and master
local function saveAll()
    savePreset(S.currentPreset)
    saveMaster()
end

----------------------------------------------------------------------
-- Migration from old prefs file
----------------------------------------------------------------------
local function migrateOldPrefs()
    -- Check if old prefs file exists and no presets exist yet
    local oldF = io.open(OLD_PREFS_FILE, "r")
    if not oldF then return false end
    -- Check if Default preset already exists
    local defaultPath = app.fs.joinPath(PRESETS_DIR, "Default.ini")
    local defF = io.open(defaultPath, "r")
    if defF then
        defF:close()
        oldF:close()
        return false  -- Already migrated
    end
    oldF:close()

    -- Load the old prefs into S using the same parsing logic
    local f = io.open(OLD_PREFS_FILE, "r")
    if not f then return false end
    local savedAnimName = nil
    for line in f:lines() do
        local k, v = string.match(line, "^([%w_]+)=(.+)$")
        if k == "tileW" then S.tileW = tonumber(v) or DEFAULT_TILE_W end
        if k == "tileH" then S.tileH = tonumber(v) or DEFAULT_TILE_H end
        if k == "animSpeed" then S.animSpeed = tonumber(v) or DEFAULT_ANIM_SPEED end
        if k == "previewZoom" then
            local pz = tonumber(v) or DEFAULT_PREVIEW_ZOOM
            S.previewZoomAll = pz
            S.previewZoomOne = pz
        end
        if k == "previewZoomAll" then S.previewZoomAll = tonumber(v) or DEFAULT_PREVIEW_ZOOM end
        if k == "previewZoomOne" then S.previewZoomOne = tonumber(v) or DEFAULT_PREVIEW_ZOOM end
        if k == "sourceZoom" then S.sourceZoom = tonumber(v) or DEFAULT_SOURCE_ZOOM end
        if k == "currentAnim" then S.currentAnim = tonumber(v) or 1 end
        if k == "currentAnimName" then savedAnimName = v end
        if k == "currentTab" and v ~= "" then
            if v == "Setup" then v = "Animations"
            elseif v == "Render" then v = "Animations"
            elseif v == "Preview" then v = "Animations"
            elseif v == "GB" then v = "Optimize"
            end
            S.currentTab = v
        end
        if k == "animNames" and v ~= "" then
            S.animNames = {}
            for name in string.gmatch(v, "([^|]+)") do
                table.insert(S.animNames, name)
            end
        end
        if k == "useBgColor" then S.useBgColor = (v == "true") end
        if k == "bgColorR" then S.bgColor = Color(tonumber(v) or 0, S.bgColor.green, S.bgColor.blue) end
        if k == "bgColorG" then S.bgColor = Color(S.bgColor.red, tonumber(v) or 0, S.bgColor.blue) end
        if k == "bgColorB" then S.bgColor = Color(S.bgColor.red, S.bgColor.green, tonumber(v) or 0) end
        if k == "gbFlipOpt" then S.gbFlipOpt = (v == "true") end
        if k == "gbOffsetOpt" then S.gbOffsetOpt = (v == "true") end
        if k == "gbCompress" then S.gbCompress = (v == "true") end
        if k == "gbSimilarThreshold" then S.gbSimilarThreshold = tonumber(v) or 80 end
        if k == "gbZoomOpt" then S.gbZoomOpt = tonumber(v) or 3 end
        if k == "gbZoomSrc" then S.gbZoomSrc = tonumber(v) or 2 end
        if k == "gbSilhouette" then S.gbSilhouette = (v == "true") end
        if k == "gbSilhouetteColorR" then S.gbSilhouetteColor = Color(tonumber(v) or 0, S.gbSilhouetteColor.green, S.gbSilhouetteColor.blue) end
        if k == "gbSilhouetteColorG" then S.gbSilhouetteColor = Color(S.gbSilhouetteColor.red, tonumber(v) or 0, S.gbSilhouetteColor.blue) end
        if k == "gbSilhouetteColorB" then S.gbSilhouetteColor = Color(S.gbSilhouetteColor.red, S.gbSilhouetteColor.green, tonumber(v) or 0) end
        if k == "gbSilhouetteColorSet" then S.gbSilhouetteColorSet = (v == "true") end
        if k == "gbAnalyzeMode" then S.gbAnalyzeMode = v end
        if k == "gbLastSavePath" then S.gbLastSavePath = v end
        if k == "gbLayerName" then S.gbLayerName = v end
        if k == "gbAlwaysOverwrite" then S.gbAlwaysOverwrite = (v == "true") end
        if k == "gbTileW" then S.gbTileW = tonumber(v) or DEFAULT_GB_TILE_W end
        if k == "gbTileH" then S.gbTileH = tonumber(v) or DEFAULT_GB_TILE_H end
        if k == "gbTileSize" then
            local ts = tonumber(v) or DEFAULT_GB_TILE_W
            S.gbTileW = ts
            S.gbTileH = ts
        end
        if k == "previewWindowOpen" then S.previewWindowOpen = (v == "true") end
        if k == "previewLayout" then S.previewLayout = v end
        if k == "previewLayoutValue" then S.previewLayoutValue = tonumber(v) or 2 end
        if k == "previewMode" then S.previewMode = v end
        if k == "previewSingleIdx" then S.previewSingleIdx = tonumber(v) or 1 end
        local animIdx = k and string.match(k, "^anim_(%d+)$")
        if animIdx then
            local idx = tonumber(animIdx) + 1
            if S.animNames[idx] then
                S.anims[S.animNames[idx]] = deserializeFrames(v)
            end
        end
    end
    f:close()

    -- Sort animation names alphabetically
    table.sort(S.animNames, function(a, b) return a:lower() < b:lower() end)

    -- Resolve current animation by name
    if savedAnimName and savedAnimName ~= "" then
        for i, name in ipairs(S.animNames) do
            if name == savedAnimName then
                S.currentAnim = i
                break
            end
        end
    end
    if S.currentAnim < 1 then S.currentAnim = 1 end
    if S.currentAnim > #S.animNames then S.currentAnim = math.max(1, #S.animNames) end
    if S.previewSingleIdx < 1 then S.previewSingleIdx = 1 end
    if #S.animNames > 0 and S.previewSingleIdx > #S.animNames then
        S.previewSingleIdx = #S.animNames
    end

    -- Save as Default preset
    S.currentPreset = "Default"
    savePreset("Default")
    saveMaster()
    return true
end

----------------------------------------------------------------------
-- Initialize: load master, then load appropriate preset
----------------------------------------------------------------------
local function initPresets()
    -- Try migration first
    local migrated = migrateOldPrefs()
    if migrated then return end

    -- Load master file
    loadMaster()

    -- Determine which preset to load
    local presetToLoad = S.currentPreset or "Default"

    -- Check if current sprite has an associated preset
    if app.sprite and app.sprite.filename and app.sprite.filename ~= "" then
        local assoc = filePresetMap[app.sprite.filename]
        if assoc then
            presetToLoad = assoc
        end
    end

    -- Load the preset
    loadPreset(presetToLoad)

    -- Clamp previewSingleIdx
    if S.previewSingleIdx < 1 then S.previewSingleIdx = 1 end
    if #S.animNames > 0 and S.previewSingleIdx > #S.animNames then
        S.previewSingleIdx = #S.animNames
    end
end

initPresets()

----------------------------------------------------------------------
-- Helpers
----------------------------------------------------------------------
local function clamp(v, lo, hi)
    return math.max(lo, math.min(hi, v))
end

local function extractCell(src, sx, sy, tw, th)
    local cell = Image(tw, th, ColorMode.RGB)
    cell:clear(pc.rgba(0, 0, 0, 0))
    for y = 0, th - 1 do
        for x = 0, tw - 1 do
            local rx, ry = sx + x, sy + y
            if rx >= 0 and rx < src.width and ry >= 0 and ry < src.height then
                cell:putPixel(x, y, src:getPixel(rx, ry))
            end
        end
    end
    return cell
end

local function flipImageH(src)
    local flipped = Image(src.width, src.height, ColorMode.RGB)
    flipped:clear(pc.rgba(0, 0, 0, 0))
    for y = 0, src.height - 1 do
        for x = 0, src.width - 1 do
            flipped:putPixel(src.width - 1 - x, y, src:getPixel(x, y))
        end
    end
    return flipped
end

local function flipImageV(src)
    local flipped = Image(src.width, src.height, ColorMode.RGB)
    flipped:clear(pc.rgba(0, 0, 0, 0))
    for y = 0, src.height - 1 do
        for x = 0, src.width - 1 do
            flipped:putPixel(x, src.height - 1 - y, src:getPixel(x, y))
        end
    end
    return flipped
end

local function drawCheckerboard(gc, w, h, zoom, offsetX, offsetY)
    local ox = offsetX or 0
    local oy = offsetY or 0
    local cs = math.max(2, math.floor(zoom / 2))
    for cy = 0, h - 1, cs do
        for cx = 0, w - 1, cs do
            local parity = (math.floor(cx / cs) + math.floor(cy / cs)) % 2
            gc.color = (parity == 0) and Color(50, 50, 50) or Color(70, 70, 70)
            gc:fillRect(Rectangle(ox + cx, oy + cy, cs, cs))
        end
    end
end

local function getSourceContentSize()
    local imgW = S.sourceImage and S.sourceImage.width or 0
    local imgH = S.sourceImage and S.sourceImage.height or 0
    return imgW * S.sourceZoom, imgH * S.sourceZoom
end

local function clampScroll()
    local contentW, contentH = getSourceContentSize()
    local maxScrollX = math.max(0, contentW - SOURCE_VIEWPORT_W)
    local maxScrollY = math.max(0, contentH - SOURCE_VIEWPORT_H)
    S.scrollX = clamp(S.scrollX, 0, maxScrollX)
    S.scrollY = clamp(S.scrollY, 0, maxScrollY)
end

-- Get the darkest color in the current palette (lowest luminance)
local function getDarkestPaletteColor()
    local ok, result = pcall(function()
        local sp = app.sprite
        if not sp then return Color(0, 0, 0) end
        local pal = sp.palettes[1]
        if not pal or #pal == 0 then return Color(0, 0, 0) end
        local darkest = nil
        local darkestLum = math.huge
        for i = 0, #pal - 1 do
            local c = pal:getColor(i)
            if c.alpha > 0 then
                local lum = 0.299 * c.red + 0.587 * c.green + 0.114 * c.blue
                if lum < darkestLum then
                    darkestLum = lum
                    darkest = Color(c.red, c.green, c.blue)
                end
            end
        end
        return darkest or Color(0, 0, 0)
    end)
    if ok then return result end
    return Color(0, 0, 0)
end

----------------------------------------------------------------------
-- Preview grid helper (module-level)
----------------------------------------------------------------------
local function getPreviewGrid(numAnims)
    if numAnims <= 0 then return 1, 1 end
    if S.previewLayout == "fixedCols" then
        local cols = math.max(1, S.previewLayoutValue)
        local rows = math.max(1, math.ceil(numAnims / cols))
        return cols, rows
    elseif S.previewLayout == "fixedRows" then
        local rows = math.max(1, S.previewLayoutValue)
        local cols = math.max(1, math.ceil(numAnims / rows))
        return cols, rows
    else -- auto: tend to square
        local cols = math.max(1, math.ceil(math.sqrt(numAnims)))
        local rows = math.max(1, math.ceil(numAnims / cols))
        return cols, rows
    end
end

-- Get current preview zoom based on mode
local function pvZoom()
    if S.previewMode == "single" then return S.previewZoomOne end
    return S.previewZoomAll
end

----------------------------------------------------------------------
-- Module-level refreshSource
----------------------------------------------------------------------
local function refreshSource()
    if not app.sprite then return end
    local sp = app.sprite
    local rgbSpec = ImageSpec{
        width = sp.width, height = sp.height,
        colorMode = ColorMode.RGB, transparentColor = 0
    }
    local img = Image(rgbSpec)
    img:clear()
    img:drawSprite(sp, app.frame)
    S.sourceImage = img
end

----------------------------------------------------------------------
-- Module-level getFrameImage
----------------------------------------------------------------------
local function getFrameImageGlobal(animName, idx)
    local frames = S.anims[animName]
    if not frames then return nil end
    local f = frames[idx]
    if not f or not S.sourceImage then return nil end
    local img = extractCell(S.sourceImage, f.x, f.y, S.tileW, S.tileH)
    if f.flipped then img = flipImageH(img) end
    if f.flippedV then img = flipImageV(img) end
    return img
end

----------------------------------------------------------------------
-- GB Tile Hashing & Deduplication (parameterized by tw, th)
----------------------------------------------------------------------

-- Hash a tile at position (sx,sy) in source image
local function tileHash(img, sx, sy, tw, th)
    local parts = {}
    for y = 0, th - 1 do
        for x = 0, tw - 1 do
            local rx, ry = sx + x, sy + y
            if rx < img.width and ry < img.height then
                parts[#parts + 1] = tostring(img:getPixel(rx, ry))
            else
                parts[#parts + 1] = "0"
            end
        end
    end
    return table.concat(parts, ",")
end

-- Hash with horizontal flip
local function tileHashFlipH(img, sx, sy, tw, th)
    local parts = {}
    for y = 0, th - 1 do
        for x = tw - 1, 0, -1 do
            local rx, ry = sx + x, sy + y
            if rx < img.width and ry < img.height then
                parts[#parts + 1] = tostring(img:getPixel(rx, ry))
            else
                parts[#parts + 1] = "0"
            end
        end
    end
    return table.concat(parts, ",")
end

-- Hash with vertical flip
local function tileHashFlipV(img, sx, sy, tw, th)
    local parts = {}
    for y = th - 1, 0, -1 do
        for x = 0, tw - 1 do
            local rx, ry = sx + x, sy + y
            if rx < img.width and ry < img.height then
                parts[#parts + 1] = tostring(img:getPixel(rx, ry))
            else
                parts[#parts + 1] = "0"
            end
        end
    end
    return table.concat(parts, ",")
end

-- Hash with both flips
local function tileHashFlipHV(img, sx, sy, tw, th)
    local parts = {}
    for y = th - 1, 0, -1 do
        for x = tw - 1, 0, -1 do
            local rx, ry = sx + x, sy + y
            if rx < img.width and ry < img.height then
                parts[#parts + 1] = tostring(img:getPixel(rx, ry))
            else
                parts[#parts + 1] = "0"
            end
        end
    end
    return table.concat(parts, ",")
end

-- Check if a tile is fully transparent
local function isTileEmpty(img, sx, sy, tw, th)
    for y = 0, th - 1 do
        for x = 0, tw - 1 do
            if pc.rgbaA(img:getPixel(sx + x, sy + y)) > 0 then
                return false
            end
        end
    end
    return true
end

-- Check if tile B (at bx,by) is tile A (at ax,ay) placed with offset+flip
local function tilesMatchOffset(img, ax, ay, bx, by, ox, oy, flipH, flipV, tw, th)
    local txMax = tw - 1
    local tyMax = th - 1
    for y = 0, tyMax do
        for x = 0, txMax do
            local pb = img:getPixel(bx + x, by + y)
            local bPainted = pc.rgbaA(pb) > 0

            local axp = x - ox
            local ayp = y - oy
            if axp >= 0 and axp <= txMax and ayp >= 0 and ayp <= tyMax then
                local srcAx = flipH and (txMax - axp) or axp
                local srcAy = flipV and (tyMax - ayp) or ayp
                local pa = img:getPixel(ax + srcAx, ay + srcAy)
                local aPainted = pc.rgbaA(pa) > 0
                if bPainted ~= aPainted then return false end
                if bPainted and pa ~= pb then return false end
            else
                if bPainted then return false end
            end
        end
    end
    return true
end

-- Analyze source image and build deduplicated tile list
local function analyzeTiles(img, flipOpt, offsetOpt, tw, th)
    local tiles = {}
    local hashIndex = {}
    local totalCount = 0

    local cols = math.floor(img.width / tw)
    local rows = math.floor(img.height / th)

    local flipModes = { {false, false, "none"} }
    if flipOpt then
        flipModes[2] = {true, false, "h"}
        flipModes[3] = {false, true, "v"}
        flipModes[4] = {true, true, "hv"}
    end

    for row = 0, rows - 1 do
        for col = 0, cols - 1 do
            local sx = col * tw
            local sy = row * th

            if isTileEmpty(img, sx, sy, tw, th) then goto continueAnalyze end

            local hash = tileHash(img, sx, sy, tw, th)
            totalCount = totalCount + 1

            if hashIndex[hash] then
                table.insert(tiles[hashIndex[hash]].positions,
                    {x = sx, y = sy, flip = "none", ox = 0, oy = 0})
                goto continueAnalyze
            end

            if flipOpt then
                local hashH  = tileHashFlipH(img, sx, sy, tw, th)
                local hashV  = tileHashFlipV(img, sx, sy, tw, th)
                local hashHV = tileHashFlipHV(img, sx, sy, tw, th)
                if hashIndex[hashH] then
                    table.insert(tiles[hashIndex[hashH]].positions,
                        {x = sx, y = sy, flip = "h", ox = 0, oy = 0})
                    goto continueAnalyze
                elseif hashIndex[hashV] then
                    table.insert(tiles[hashIndex[hashV]].positions,
                        {x = sx, y = sy, flip = "v", ox = 0, oy = 0})
                    goto continueAnalyze
                elseif hashIndex[hashHV] then
                    table.insert(tiles[hashIndex[hashHV]].positions,
                        {x = sx, y = sy, flip = "hv", ox = 0, oy = 0})
                    goto continueAnalyze
                end
            end

            if offsetOpt then
                local found = false
                for ti = 1, #tiles do
                    local posA = tiles[ti].positions[1]
                    for _, fm in ipairs(flipModes) do
                        for ofy = -(th - 1), th - 1 do
                            for ofx = -(tw - 1), tw - 1 do
                                if ofx == 0 and ofy == 0 then goto continueOff end
                                if tilesMatchOffset(img, posA.x, posA.y,
                                        sx, sy, ofx, ofy, fm[1], fm[2], tw, th) then
                                    table.insert(tiles[ti].positions,
                                        {x = sx, y = sy, flip = fm[3], ox = ofx, oy = ofy})
                                    found = true
                                end
                                if found then break end
                                ::continueOff::
                            end
                            if found then break end
                        end
                        if found then break end
                    end
                    if found then break end
                end
                if found then goto continueAnalyze end
            end

            local idx = #tiles + 1
            tiles[idx] = { hash = hash, positions = {{x = sx, y = sy, flip = "none", ox = 0, oy = 0}} }
            hashIndex[hash] = idx

            ::continueAnalyze::
        end
    end

    return tiles, totalCount
end

-- Analyze tiles using tilemap layers (tile mode)
local function analyzeTilesTileMode(sprite, frameNum)
    local tiles = {}
    local hashIndex = {}
    local totalCount = 0
    local tileW = S.gbTileW
    local tileH = S.gbTileH

    local ok, err = pcall(function()
        for _, layer in ipairs(sprite.layers) do
            if not layer.isTilemap then goto continueLayer end

            local cel = layer:cel(frameNum)
            if not cel then goto continueLayer end

            local tileset = layer.tileset
            if not tileset then goto continueLayer end

            local ts = tileset.grid.tileSize
            tileW = ts.width
            tileH = ts.height

            local celImg = cel.image
            local celPos = cel.position
            local imgW = celImg.width
            local imgH = celImg.height

            local placements = {}
            for row = 0, imgH - 1 do
                for col = 0, imgW - 1 do
                    local value = celImg:getPixel(col, row)
                    local tileIdx = 0
                    local pOk, _ = pcall(function()
                        tileIdx = app.pixelColor.tileI(value)
                    end)
                    if not pOk or tileIdx == 0 then goto continueTile end

                    local canvasX = celPos.x + col * ts.width
                    local canvasY = celPos.y + row * ts.height

                    local tsId = layer.name or "ts"
                    local hash = tsId .. ":" .. tileIdx

                    table.insert(placements, {
                        hash = hash,
                        canvasX = canvasX,
                        canvasY = canvasY,
                        tileIdx = tileIdx,
                    })

                    ::continueTile::
                end
            end

            table.sort(placements, function(a, b)
                if a.canvasY ~= b.canvasY then return a.canvasY < b.canvasY end
                return a.canvasX < b.canvasX
            end)

            for _, p in ipairs(placements) do
                totalCount = totalCount + 1
                if hashIndex[p.hash] then
                    table.insert(tiles[hashIndex[p.hash]].positions,
                        {x = p.canvasX, y = p.canvasY, flip = "none", ox = 0, oy = 0})
                else
                    local idx = #tiles + 1
                    tiles[idx] = {
                        hash = p.hash,
                        positions = {{x = p.canvasX, y = p.canvasY, flip = "none", ox = 0, oy = 0}}
                    }
                    hashIndex[p.hash] = idx
                end
            end

            ::continueLayer::
        end
    end)

    if not ok then
        app.alert("Tile mode error: " .. tostring(err))
    end

    return tiles, totalCount, tileW, tileH
end

-- Compare two tile regions with offset and optional flip
local function tileSimilarityEx(img, ax, ay, bx, by, ox, oy, flipH, flipV, tw, th)
    local matches = 0
    local paintedA = 0
    local txMax = tw - 1
    local tyMax = th - 1
    for y = 0, tyMax do
        for x = 0, txMax do
            local pa = img:getPixel(ax + x, ay + y)
            if pc.rgbaA(pa) > 0 then
                paintedA = paintedA + 1
                local bxp = x - ox
                local byp = y - oy
                if bxp >= 0 and bxp <= txMax and byp >= 0 and byp <= tyMax then
                    local srcBx = flipH and (txMax - bxp) or bxp
                    local srcBy = flipV and (tyMax - byp) or byp
                    local pb = img:getPixel(bx + srcBx, by + srcBy)
                    if pa == pb then
                        matches = matches + 1
                    end
                end
            end
        end
    end
    return matches, paintedA
end

-- Count non-transparent pixels in a tile
local function countPaintedPixels(img, sx, sy, tw, th)
    local count = 0
    for y = 0, th - 1 do
        for x = 0, tw - 1 do
            if pc.rgbaA(img:getPixel(sx + x, sy + y)) > 0 then
                count = count + 1
            end
        end
    end
    return count
end

-- Find pairs of unique tiles that are similar (above threshold percentage)
local function findSimilarTiles(img, tiles, thresholdPct, flipOpt, offsetOpt, tw, th)
    local results = {}
    local flipModes = { {false, false, "none"} }
    if flipOpt then
        flipModes[2] = {true, false, "h"}
        flipModes[3] = {false, true, "v"}
        flipModes[4] = {true, true, "hv"}
    end

    local offsets = { {0, 0} }
    if offsetOpt then
        offsets = {}
        for ofy = -(th - 1), th - 1 do
            for ofx = -(tw - 1), tw - 1 do
                table.insert(offsets, {ofx, ofy})
            end
        end
    end

    local paintedCount = {}
    for i = 1, #tiles do
        local p = tiles[i].positions[1]
        paintedCount[i] = countPaintedPixels(img, p.x, p.y, tw, th)
    end

    for i = 1, #tiles do
        local posA = tiles[i].positions[1]
        local paintedA = paintedCount[i]
        if paintedA == 0 then goto continueSI end

        for j = i + 1, #tiles do
            local posB = tiles[j].positions[1]
            local paintedB = paintedCount[j]
            if paintedB == 0 then goto continueSJ end

            local minPainted = math.min(paintedA, paintedB)
            local needed = math.ceil(minPainted * thresholdPct / 100)

            local bestMatch = 0
            local bestFlip = "none"
            local bestOx, bestOy = 0, 0

            for _, fm in ipairs(flipModes) do
                for _, off in ipairs(offsets) do
                    local m = tileSimilarityEx(
                        img, posA.x, posA.y, posB.x, posB.y,
                        off[1], off[2], fm[1], fm[2], tw, th)
                    if m > bestMatch then
                        bestMatch = m
                        bestFlip = fm[3]
                        bestOx = off[1]
                        bestOy = off[2]
                    end
                    if bestMatch >= minPainted then break end
                end
                if bestMatch >= minPainted then break end
            end

            if bestMatch >= needed then
                local pct = minPainted > 0 and math.floor(bestMatch / minPainted * 100) or 0
                table.insert(results, {
                    i = i, j = j,
                    flip = bestFlip,
                    ox = bestOx, oy = bestOy,
                    match = bestMatch,
                    pct = pct
                })
            end
            ::continueSJ::
        end
        ::continueSI::
    end
    return results
end

-- Build optimized tileset image
local function buildOptimizedImage(img, tiles, compress, silhouette, silhouetteColor, tw, th)
    local srcCols = math.floor(img.width / tw)
    if srcCols < 1 then srcCols = 1 end
    local numTiles = #tiles
    if numTiles == 0 then return nil, srcCols end

    if compress then
        local imgRows = math.ceil(numTiles / srcCols)
        local optW = srcCols * tw
        local optH = imgRows * th

        local optImg = Image(optW, optH, ColorMode.RGB)
        optImg:clear(pc.rgba(0, 0, 0, 0))

        for i, tile in ipairs(tiles) do
            local pos = tile.positions[1]
            local destCol = (i - 1) % srcCols
            local destRow = math.floor((i - 1) / srcCols)
            local dx = destCol * tw
            local dy = destRow * th

            for y = 0, th - 1 do
                for x = 0, tw - 1 do
                    local rx, ry = pos.x + x, pos.y + y
                    if rx < img.width and ry < img.height then
                        optImg:putPixel(dx + x, dy + y, img:getPixel(rx, ry))
                    end
                end
            end
        end

        return optImg, srcCols
    else
        local optImg = Image(img.width, img.height, ColorMode.RGB)
        optImg:clear(pc.rgba(0, 0, 0, 0))

        local firstPositions = {}
        for _, tile in ipairs(tiles) do
            local pos = tile.positions[1]
            firstPositions[pos.x .. "," .. pos.y] = true
        end

        for _, tile in ipairs(tiles) do
            local pos = tile.positions[1]
            for y = 0, th - 1 do
                for x = 0, tw - 1 do
                    local rx, ry = pos.x + x, pos.y + y
                    if rx < img.width and ry < img.height then
                        optImg:putPixel(rx, ry, img:getPixel(rx, ry))
                    end
                end
            end
        end

        if silhouette and silhouetteColor then
            local silR = silhouetteColor.red
            local silG = silhouetteColor.green
            local silB = silhouetteColor.blue
            local silPixel = pc.rgba(silR, silG, silB, 255)
            for _, tile in ipairs(tiles) do
                for pi = 2, #tile.positions do
                    local pos = tile.positions[pi]
                    for y = 0, th - 1 do
                        for x = 0, tw - 1 do
                            local rx, ry = pos.x + x, pos.y + y
                            if rx >= 0 and rx < img.width and ry >= 0 and ry < img.height then
                                local srcPx = img:getPixel(rx, ry)
                                if pc.rgbaA(srcPx) > 0 then
                                    optImg:putPixel(rx, ry, silPixel)
                                end
                            end
                        end
                    end
                end
            end
        end

        return optImg, srcCols
    end
end

----------------------------------------------------------------------
-- Lock file helpers
----------------------------------------------------------------------
local function removeLockFile()
    os.remove(LOCK_FILE)
end

----------------------------------------------------------------------
-- Preview Window (primary window)
----------------------------------------------------------------------
openPreviewWindow = function()
    -- Close existing preview window if open
    if previewDlg then
        pcall(function() previewDlg:close() end)
    end
    if previewTimer then
        pcall(function() previewTimer:stop() end)
        previewTimer = nil
    end
    if pvRefreshTimer then
        pcall(function() pvRefreshTimer:stop() end)
        pvRefreshTimer = nil
    end

    local pvAnimFrame = { value = 0 }
    local PV_MARGIN = 2

    -- Clamp previewSingleIdx
    if #S.animNames > 0 then
        if S.previewSingleIdx < 1 then S.previewSingleIdx = 1 end
        if S.previewSingleIdx > #S.animNames then S.previewSingleIdx = #S.animNames end
    else
        S.previewSingleIdx = 1
    end

    -- calcPreviewSize helper
    local function calcPreviewSize()
        local z = pvZoom()
        local ptw = S.tileW * z
        local pth = S.tileH * z
        local cellW = ptw + PV_MARGIN * 2
        local cellH = pth + PV_MARGIN * 2
        if S.previewMode == "single" then
            return cellW, cellH + 14  -- extra space for name label
        else
            local numAnims = #S.animNames
            local cols, rows = getPreviewGrid(numAnims)
            return cols * cellW, rows * cellH
        end
    end

    -- Calculate initial size
    local pvWidth, pvHeight = calcPreviewSize()
    pvWidth = math.max(pvWidth, 120)
    pvHeight = math.max(pvHeight, 40)

    previewDlg = Dialog{
        title = "AniPhallow (" .. S.currentPreset .. ")",
        onclose = function()
            if previewTimer then pcall(function() previewTimer:stop() end) end
            if pvRefreshTimer then pcall(function() pvRefreshTimer:stop() end) end
            previewTimer = nil
            pvRefreshTimer = nil
            previewDlg = nil
            S.previewWindowOpen = false
            saveAll()
            -- If main dialog is also closed, remove lock
            if not mainDlg then removeLockFile() end
        end
    }

    -- All buttons on the same row: Setup, toggle mode, Fit
    previewDlg:button{
        id = "pvSetup",
        text = "Setup",
        onclick = function()
            openMainDialog()
        end
    }

    previewDlg:button{
        id = "pvToggleMode",
        text = S.previewMode == "all" and "All" or "One",
        onclick = function()
            if S.previewMode == "all" then
                S.previewMode = "single"
                if #S.animNames > 0 then
                    if S.previewSingleIdx < 1 then S.previewSingleIdx = 1 end
                    if S.previewSingleIdx > #S.animNames then S.previewSingleIdx = #S.animNames end
                end
            else
                S.previewMode = "all"
            end
            -- Close and reopen to resize canvas
            pcall(function() previewDlg:close() end)
            openPreviewWindow()
        end
    }

    previewDlg:button{
        id = "pvFit",
        text = "Fit",
        onclick = function()
            -- Close and reopen to refit
            pcall(function() previewDlg:close() end)
            openPreviewWindow()
        end
    }

    previewDlg:canvas{
        id = "pvCanvas",
        width = pvWidth,
        height = pvHeight,
        autoscaling = false,
        onpaint = function(ev)
            local gc = ev.context
            local na = #S.animNames
            if na == 0 then return end

            local z = pvZoom()
            local pw = S.tileW * z
            local ph = S.tileH * z
            local cW = pw + PV_MARGIN * 2
            local cH = ph + PV_MARGIN * 2
            local af = pvAnimFrame.value

            if S.previewMode == "single" and S.previewSingleIdx >= 1 and S.previewSingleIdx <= na then
                local name = S.animNames[S.previewSingleIdx]
                local frames = S.anims[name] or {}
                if S.useBgColor then
                    gc.color = S.bgColor
                    gc:fillRect(Rectangle(PV_MARGIN, PV_MARGIN, pw, ph))
                else
                    drawCheckerboard(gc, pw, ph, z, PV_MARGIN, PV_MARGIN)
                end
                local totalFrames = #frames
                if totalFrames > 0 then
                    local idx = (af % totalFrames) + 1
                    local fimg = getFrameImageGlobal(name, idx)
                    local f = frames[idx]
                    local offX = (f.offX or 0) * z
                    local offY = (f.offY or 0) * z
                    if fimg then
                        gc:drawImage(fimg,
                            Rectangle(0, 0, S.tileW, S.tileH),
                            Rectangle(PV_MARGIN + offX, PV_MARGIN + offY, pw, ph))
                    end
                end
            else
                local cols, rows = getPreviewGrid(na)
                for i, name in ipairs(S.animNames) do
                    local col = (i - 1) % cols
                    local row = math.floor((i - 1) / cols)
                    local ox = col * cW
                    local oy = row * cH

                    if S.useBgColor then
                        gc.color = S.bgColor
                        gc:fillRect(Rectangle(ox + PV_MARGIN, oy + PV_MARGIN, pw, ph))
                    else
                        drawCheckerboard(gc, pw, ph, z,
                            ox + PV_MARGIN, oy + PV_MARGIN)
                    end

                    local frames = S.anims[name] or {}
                    local totalFrames = #frames
                    if totalFrames > 0 then
                        local idx = (af % totalFrames) + 1
                        local fimg = getFrameImageGlobal(name, idx)
                        if fimg then
                            local f = frames[idx]
                            local fOffX = (f.offX or 0) * z
                            local fOffY = (f.offY or 0) * z
                            gc:drawImage(fimg,
                                Rectangle(0, 0, S.tileW, S.tileH),
                                Rectangle(ox + PV_MARGIN + fOffX, oy + PV_MARGIN + fOffY, pw, ph))
                        end
                    end
                end
            end
        end,
        onmousedown = function(ev)
            -- In single mode: L-click=prev anim, R-click=next anim
            if S.previewMode == "single" then
                if ev.button == MouseButton.LEFT then
                    if #S.animNames > 0 then
                        S.previewSingleIdx = S.previewSingleIdx - 1
                        if S.previewSingleIdx < 1 then S.previewSingleIdx = #S.animNames end
                        -- Update label text and repaint without closing/reopening
                        pcall(function()
                            previewDlg:modify{ id = "pvAnimName", text = S.animNames[S.previewSingleIdx] or "" }
                        end)
                        previewDlg:repaint()
                    end
                elseif ev.button == MouseButton.RIGHT then
                    if #S.animNames > 0 then
                        S.previewSingleIdx = S.previewSingleIdx + 1
                        if S.previewSingleIdx > #S.animNames then S.previewSingleIdx = 1 end
                        -- Update label text and repaint without closing/reopening
                        pcall(function()
                            previewDlg:modify{ id = "pvAnimName", text = S.animNames[S.previewSingleIdx] or "" }
                        end)
                        previewDlg:repaint()
                    end
                end
            end
        end,
        onwheel = function(ev)
            local dz = ev.deltaY < 0 and 1 or -1
            if S.previewMode == "single" then
                S.previewZoomOne = math.max(1, math.min(MAX_PREVIEW_ZOOM, S.previewZoomOne + dz))
            else
                S.previewZoomAll = math.max(1, math.min(MAX_PREVIEW_ZOOM, S.previewZoomAll + dz))
            end
            previewDlg:repaint()
        end
    }

    -- Animation name label for single mode
    local singleName = ""
    if S.previewSingleIdx >= 1 and S.previewSingleIdx <= #S.animNames then
        singleName = S.animNames[S.previewSingleIdx]
    end
    previewDlg:label{
        id = "pvAnimName",
        text = singleName,
        visible = (S.previewMode == "single")
    }

    previewTimer = Timer{
        interval = S.animSpeed / 1000.0,
        ontick = function()
            pvAnimFrame.value = pvAnimFrame.value + 1
            pcall(function() previewDlg:repaint() end)
        end
    }
    previewTimer:start()

    pvRefreshTimer = Timer{
        interval = 0.5,
        ontick = function()
            refreshSource()
            pcall(function() previewDlg:repaint() end)

            -- Auto-detect file change
            local currentFile = app.sprite and app.sprite.filename or ""
            if currentFile ~= lastSpriteFilename then
                lastSpriteFilename = currentFile
                -- Look up preset for this file
                local presetForFile = filePresetMap[currentFile] or "Default"
                if presetForFile ~= S.currentPreset then
                    loadPreset(presetForFile)
                    S.currentPreset = presetForFile
                    -- Refresh UI if main dialog is open (don't touch preview - avoids repositioning)
                    if mainDlg then
                        pcall(function() mainDlg:close() end)
                        openMainDialog()
                    end
                end
            end
        end
    }
    pvRefreshTimer:start()

    S.previewWindowOpen = true
    saveAll()

    previewDlg:show{ wait = false }
end

----------------------------------------------------------------------
-- Main Dialog (secondary window - setup)
----------------------------------------------------------------------
openMainDialog = function()
    -- If main dialog already open, just bring focus (close and reopen)
    if mainDlg then
        pcall(function() mainDlg:close() end)
    end

    local dlg

    local function currentAnimName()
        if S.currentAnim >= 1 and S.currentAnim <= #S.animNames then
            return S.animNames[S.currentAnim]
        end
        return nil
    end

    local function getFrameImage(animName, idx)
        return getFrameImageGlobal(animName, idx)
    end

    local function captureCell(pixelX, pixelY, flipped)
        if not S.sourceImage then return end
        local name = currentAnimName()
        if not name then
            app.alert("Create an animation first.")
            return
        end
        local gridX = math.floor(pixelX / S.tileW) * S.tileW
        local gridY = math.floor(pixelY / S.tileH) * S.tileH
        if gridX < 0 or gridX + S.tileW > S.sourceImage.width then return end
        if gridY < 0 or gridY + S.tileH > S.sourceImage.height then return end
        if not S.anims[name] then S.anims[name] = {} end
        table.insert(S.anims[name], { x = gridX, y = gridY, flipped = flipped, offX = 0, offY = 0 })
        saveAll()
        dlg:repaint()
    end

    -- Switch visible tab (only Animations and Optimize)
    local function switchTab(tab)
        S.currentTab = tab
        local isSetup  = (tab == "Animations")
        local isOpt    = (tab == "Optimize")
        for _, id in ipairs(SETUP_IDS) do
            pcall(function() dlg:modify{ id = id, visible = isSetup } end)
        end
        for _, id in ipairs(GB_IDS) do
            pcall(function() dlg:modify{ id = id, visible = isOpt } end)
        end
        -- Update tab button labels
        for _, t in ipairs(TABS) do
            local label = (t == tab) and ("[" .. t .. "]") or (" " .. t .. " ")
            pcall(function() dlg:modify{ id = "tab" .. t, text = label } end)
        end
        dlg:repaint()
    end

    local function startAnimTimer()
        if mainAnimTimer then mainAnimTimer:stop() end
        mainAnimTimer = Timer{
            interval = S.animSpeed / 1000.0,
            ontick = function()
                S.animFrame = S.animFrame + 1
                pcall(function() dlg:repaint() end)
            end
        }
        mainAnimTimer:start()
    end

    local contentW, contentH = getSourceContentSize()
    local viewW = math.min(contentW, SOURCE_VIEWPORT_W)
    local viewH = math.min(contentH, SOURCE_VIEWPORT_H)

    dlg = Dialog{
        title = "AniPhallow (" .. S.currentPreset .. ")",
        onclose = function()
            if mainAnimTimer then pcall(function() mainAnimTimer:stop() end) end
            if mainRefreshTimer then pcall(function() mainRefreshTimer:stop() end) end
            mainAnimTimer = nil
            mainRefreshTimer = nil
            mainDlg = nil
            saveAll()
            -- If preview is also closed, remove lock
            if not previewDlg then removeLockFile() end
        end
    }
    mainDlg = dlg

    ----------------------------------------------------------------
    -- TAB BUTTONS (Animations, Optimize)
    ----------------------------------------------------------------
    for _, tab in ipairs(TABS) do
        local label = (tab == S.currentTab) and ("[" .. tab .. "]") or (" " .. tab .. " ")
        dlg:button{
            id = "tab" .. tab,
            text = label,
            onclick = function()
                switchTab(tab)
            end
        }
    end

    ----------------------------------------------------------------
    -- Config button (opens sub-dialog) - visible on ALL tabs
    ----------------------------------------------------------------
    dlg:button{
        id = "btnConfig",
        text = "Config",
        onclick = function()
            local d = Dialog{ title = "Config" }

            --------------------------------------------------------
            -- Presets section
            --------------------------------------------------------
            d:separator{ text = "Presets" }
            d:combobox{ id = "presetSelect", option = S.currentPreset, options = getAllPresetNames() }
            d:button{ id = "presetNew", text = "New", onclick = function()
                local nd = Dialog{ title = "New Preset" }
                nd:entry{ id = "name", label = "Name:", text = "" }
                nd:button{ id = "ok", text = "OK" }
                nd:button{ text = "Cancel" }
                nd:show()
                if nd.data.ok and nd.data.name and nd.data.name ~= "" then
                    local newName = nd.data.name
                    -- Check if exists
                    local exists = false
                    for _, n in ipairs(getAllPresetNames()) do
                        if n == newName then exists = true; break end
                    end
                    if exists then
                        local r = app.alert{ title = "Overwrite?", text = "Preset '" .. newName .. "' already exists. Overwrite?", buttons = {"Overwrite", "Cancel"} }
                        if r ~= 1 then return end
                    end
                    -- Save current preset first
                    savePreset(S.currentPreset)
                    -- Reset to defaults and save as new preset
                    resetToDefaults()
                    S.currentPreset = newName
                    addPresetName(newName)
                    savePreset(newName)
                    local currentFile = app.sprite and app.sprite.filename or ""
                    if currentFile ~= "" then filePresetMap[currentFile] = newName end
                    saveMaster()
                    -- Close config and reopen main
                    d:close()
                    if mainDlg then pcall(function() mainDlg:close() end) end
                    openMainDialog()
                    -- Preview title will be stale but avoids repositioning window
                end
            end }
            d:button{ id = "presetClone", text = "Clone", onclick = function()
                local cd = Dialog{ title = "Clone Preset" }
                cd:entry{ id = "name", label = "New name:", text = S.currentPreset .. "_copy" }
                cd:button{ id = "ok", text = "Clone" }
                cd:button{ text = "Cancel" }
                cd:show()
                if cd.data.ok and cd.data.name and cd.data.name ~= "" then
                    local newName = cd.data.name
                    -- Check if name already exists
                    local exists = false
                    for _, n in ipairs(getAllPresetNames()) do
                        if n == newName then exists = true; break end
                    end
                    if exists then
                        app.alert("Preset '" .. newName .. "' already exists.")
                        return
                    end
                    -- Save current state as the new preset (clone)
                    savePreset(newName)
                    addPresetName(newName)
                    S.currentPreset = newName
                    local currentFile = app.sprite and app.sprite.filename or ""
                    if currentFile ~= "" then filePresetMap[currentFile] = newName end
                    saveMaster()
                    -- Close config and reopen main
                    d:close()
                    if mainDlg then pcall(function() mainDlg:close() end) end
                    openMainDialog()
                    -- Preview title will be stale but avoids repositioning window
                end
            end }
            d:button{ id = "presetRename", text = "Rename", onclick = function()
                if S.currentPreset == "Default" then
                    app.alert("Cannot rename the Default preset.")
                    return
                end
                local rd = Dialog{ title = "Rename Preset" }
                rd:entry{ id = "name", label = "New name:", text = S.currentPreset }
                rd:button{ id = "ok", text = "OK" }
                rd:button{ text = "Cancel" }
                rd:show()
                if rd.data.ok and rd.data.name and rd.data.name ~= "" then
                    local newName = rd.data.name
                    if newName == S.currentPreset then return end
                    -- Check if name already exists
                    local exists = false
                    for _, n in ipairs(getAllPresetNames()) do
                        if n == newName then exists = true; break end
                    end
                    if exists then
                        app.alert("Preset '" .. newName .. "' already exists.")
                        return
                    end
                    local oldName = S.currentPreset
                    -- Rename the preset file
                    local oldPath = app.fs.joinPath(PRESETS_DIR, oldName .. ".ini")
                    local newPath = app.fs.joinPath(PRESETS_DIR, newName .. ".ini")
                    os.rename(oldPath, newPath)
                    -- Update known names
                    removePresetName(oldName)
                    addPresetName(newName)
                    -- Update file associations
                    for filepath, preset in pairs(filePresetMap) do
                        if preset == oldName then
                            filePresetMap[filepath] = newName
                        end
                    end
                    S.currentPreset = newName
                    saveMaster()
                    -- Close config and reopen main
                    d:close()
                    if mainDlg then pcall(function() mainDlg:close() end) end
                    openMainDialog()
                    -- Preview title will be stale but avoids repositioning window
                end
            end }
            d:button{ id = "presetDelete", text = "Delete", onclick = function()
                if S.currentPreset == "Default" then
                    app.alert("Cannot delete the Default preset.")
                    return
                end
                local confirm = app.alert{
                    title = "Delete Preset",
                    text = "Delete preset '" .. S.currentPreset .. "'?",
                    buttons = { "Delete", "Cancel" }
                }
                if confirm ~= 1 then return end
                local deleteName = S.currentPreset
                -- Delete the preset file
                local path = app.fs.joinPath(PRESETS_DIR, deleteName .. ".ini")
                os.remove(path)
                -- Remove from known names
                removePresetName(deleteName)
                -- Remove file associations pointing to this preset
                for filepath, preset in pairs(filePresetMap) do
                    if preset == deleteName then
                        filePresetMap[filepath] = nil
                    end
                end
                -- Switch to Default
                loadPreset("Default")
                S.currentPreset = "Default"
                if app.sprite and app.sprite.filename and app.sprite.filename ~= "" then
                    filePresetMap[app.sprite.filename] = nil
                end
                saveMaster()
                -- Close config and reopen main
                d:close()
                if mainDlg then pcall(function() mainDlg:close() end) end
                openMainDialog()
                -- Reopen preview to update title
                if previewDlg then
                    pcall(function() previewDlg:close() end)
                    openPreviewWindow()
                end
            end }

            --------------------------------------------------------
            -- Animations section
            --------------------------------------------------------
            d:separator{ text = "Animations" }
            d:number{ id = "tileW", label = "Sprite W:", text = tostring(S.tileW), decimals = 0 }
            d:number{ id = "tileH", label = "Sprite H:", text = tostring(S.tileH), decimals = 0 }
            d:slider{ id = "animSpeed", label = "Speed (ms):", min = 50, max = 1000, value = S.animSpeed }
            d:check{ id = "useBgColor", text = "Solid background", selected = S.useBgColor }
            d:color{ id = "bgColor", label = "Bg Color:", color = S.bgColor }

            --------------------------------------------------------
            -- Optimization section
            --------------------------------------------------------
            d:separator{ text = "Optimization" }
            d:number{ id = "gbTileW", label = "Tile W:", text = tostring(S.gbTileW), decimals = 0 }
            d:number{ id = "gbTileH", label = "Tile H:", text = tostring(S.gbTileH), decimals = 0 }
            local silColor = S.gbSilhouetteColor
            if not S.gbSilhouetteColorSet then
                silColor = getDarkestPaletteColor()
            end
            d:color{ id = "silhouetteColor", label = "Silhouette:", color = silColor }
            d:entry{ id = "layerName", label = "Layer name:", text = S.gbLayerName }
            d:check{ id = "alwaysOverwrite", text = "Always overwrite layer", selected = S.gbAlwaysOverwrite }

            --------------------------------------------------------
            -- Preview section
            --------------------------------------------------------
            d:separator{ text = "Preview" }
            d:combobox{ id = "previewLayout", label = "Layout:", option = S.previewLayout, options = {"auto", "fixedCols", "fixedRows"} }
            d:number{ id = "previewLayoutValue", label = "Value:", text = tostring(S.previewLayoutValue), decimals = 0 }
            d:button{ id = "ok", text = "OK" }
            d:button{ text = "Cancel" }
            d:show()
            if d.data.ok then
                local tw = d.data.tileW
                if tw < 4 then tw = 4 elseif tw > 128 then tw = 128 end
                S.tileW = tw
                local th = d.data.tileH
                if th < 4 then th = 4 elseif th > 128 then th = 128 end
                S.tileH = th
                S.animSpeed = d.data.animSpeed
                if mainAnimTimer then mainAnimTimer.interval = S.animSpeed / 1000.0 end
                if previewTimer then previewTimer.interval = S.animSpeed / 1000.0 end
                S.useBgColor = d.data.useBgColor
                S.bgColor = d.data.bgColor
                local gtw = d.data.gbTileW
                if gtw < 1 then gtw = 1 elseif gtw > 128 then gtw = 128 end
                S.gbTileW = gtw
                local gth = d.data.gbTileH
                if gth < 1 then gth = 1 elseif gth > 128 then gth = 128 end
                S.gbTileH = gth
                S.gbSilhouetteColor = d.data.silhouetteColor
                S.gbSilhouetteColorSet = true
                S.gbLayerName = d.data.layerName
                S.gbAlwaysOverwrite = d.data.alwaysOverwrite
                -- Preview layout settings
                S.previewLayout = d.data.previewLayout
                local plv = d.data.previewLayoutValue
                if plv < 1 then plv = 1 elseif plv > 20 then plv = 20 end
                S.previewLayoutValue = plv
                -- Check if preset changed via combobox
                local selectedPreset = d.data.presetSelect
                local presetChanged = false
                if selectedPreset and selectedPreset ~= S.currentPreset then
                    savePreset(S.currentPreset)  -- Save current first
                    loadPreset(selectedPreset)    -- Load new
                    S.currentPreset = selectedPreset
                    local currentFile = app.sprite and app.sprite.filename or ""
                    if currentFile ~= "" then filePresetMap[currentFile] = selectedPreset end
                    presetChanged = true
                end
                saveAll()
                if presetChanged then
                    dlg:close()
                    openMainDialog()
                    -- Preview title will be stale but avoids repositioning window
                    return
                end
                dlg:repaint()
            end
        end
    }

    ----------------------------------------------------------------
    -- Animation selector (combobox, sorted alphabetically)
    ----------------------------------------------------------------
    dlg:separator{ id = "sepAnims", text = "Animations" }

    dlg:combobox{
        id = "cmbAnimList",
        option = currentAnimName() or "",
        options = S.animNames,
        onchange = function()
            local selected = dlg.data.cmbAnimList
            for i, name in ipairs(S.animNames) do
                if name == selected then
                    S.currentAnim = i
                    S.selectedFrame = 0
                    dlg:repaint()
                    break
                end
            end
        end
    }

    dlg:button{
        id = "btnNewAnim",
        text = "+",
        onclick = function()
            local d = Dialog{ title = "New Animation" }
            d:entry{ id = "name", label = "Name:", text = "" }
            d:button{ id = "ok", text = "OK" }
            d:button{ text = "Cancel" }
            d:show()
            if d.data.ok then
                local name = d.data.name
                if name and name ~= "" and not S.anims[name] then
                    table.insert(S.animNames, name)
                    S.anims[name] = {}
                    -- Re-sort alphabetically
                    table.sort(S.animNames, function(a, b) return a:lower() < b:lower() end)
                    for i, n in ipairs(S.animNames) do
                        if n == name then S.currentAnim = i; break end
                    end
                    saveAll()
                    dlg:close()
                    openMainDialog()
                end
            end
        end
    }

    dlg:button{
        id = "btnDelAnim",
        text = "-",
        onclick = function()
            local name = currentAnimName()
            if not name then return end
            local result = app.alert{
                title = "Delete Animation",
                text = "Delete animation '" .. name .. "'?",
                buttons = { "Delete", "Cancel" }
            }
            if result ~= 1 then return end
            S.anims[name] = nil
            table.remove(S.animNames, S.currentAnim)
            S.currentAnim = math.min(S.currentAnim, math.max(1, #S.animNames))
            S.selectedFrame = 0
            saveAll()
            dlg:close()
            openMainDialog()
        end
    }

    dlg:button{
        id = "btnRenameAnim",
        text = "Rename",
        onclick = function()
            local name = currentAnimName()
            if not name then return end
            local d = Dialog{ title = "Rename Animation" }
            d:entry{ id = "newName", label = "New name:", text = name }
            d:button{ id = "ok", text = "OK" }
            d:button{ text = "Cancel" }
            d:show()
            if d.data.ok then
                local newName = d.data.newName
                if newName and newName ~= "" and newName ~= name and not S.anims[newName] then
                    -- Transfer animation data
                    S.anims[newName] = S.anims[name]
                    S.anims[name] = nil
                    S.animNames[S.currentAnim] = newName
                    -- Re-sort alphabetically
                    table.sort(S.animNames, function(a, b) return a:lower() < b:lower() end)
                    for i, n in ipairs(S.animNames) do
                        if n == newName then S.currentAnim = i; break end
                    end
                    saveAll()
                    dlg:close()
                    openMainDialog()
                end
            end
        end
    }

    dlg:button{
        id = "btnCloneAnim",
        text = "Clone",
        onclick = function()
            local name = currentAnimName()
            if not name then return end
            local d = Dialog{ title = "Clone Animation" }
            d:entry{ id = "cloneName", label = "Name:", text = name .. "_clone" }
            d:check{ id = "flipX", text = "Flip X", selected = true }
            d:button{ id = "ok", text = "OK" }
            d:button{ text = "Cancel" }
            d:show()
            if d.data.ok then
                local cloneName = d.data.cloneName
                if cloneName and cloneName ~= "" and not S.anims[cloneName] then
                    local srcFrames = S.anims[name] or {}
                    local newFrames = {}
                    for _, fr in ipairs(srcFrames) do
                        local nf = { x = fr.x, y = fr.y, flipped = fr.flipped, flippedV = fr.flippedV, offX = fr.offX or 0, offY = fr.offY or 0 }
                        if d.data.flipX then
                            nf.flipped = not nf.flipped
                        end
                        table.insert(newFrames, nf)
                    end
                    table.insert(S.animNames, cloneName)
                    S.anims[cloneName] = newFrames
                    -- Re-sort alphabetically
                    table.sort(S.animNames, function(a, b) return a:lower() < b:lower() end)
                    for i, n in ipairs(S.animNames) do
                        if n == cloneName then S.currentAnim = i; break end
                    end
                    saveAll()
                    dlg:close()
                    openMainDialog()
                end
            end
        end
    }

    ----------------------------------------------------------------
    -- Source canvas (L-click=add, R-click=add flipped)
    ----------------------------------------------------------------
    dlg:separator{ id = "sepSource", text = "Source (L-click=add, R-click=flip add)  ||  Frames (L-click=select, R-click=remove, drag=move)" }

    dlg:canvas{
        id = "canvasSource",
        width = viewW,
        height = viewH,
        autoscaling = false,
        onpaint = function(ev)
            local gc = ev.context
            local cW, cH = getSourceContentSize()
            local vw = math.min(cW, SOURCE_VIEWPORT_W)
            local vh = math.min(cH, SOURCE_VIEWPORT_H)

            drawCheckerboard(gc, vw, vh, S.sourceZoom)

            if S.sourceImage then
                local srcW = S.sourceImage.width
                local srcH = S.sourceImage.height
                gc:drawImage(
                    S.sourceImage,
                    Rectangle(0, 0, srcW, srcH),
                    Rectangle(-S.scrollX, -S.scrollY, srcW * S.sourceZoom, srcH * S.sourceZoom)
                )
            end

            -- Draw grid
            if S.sourceImage then
                local imgW = S.sourceImage.width
                local imgH = S.sourceImage.height
                gc.color = Color(255, 255, 255, 40)
                for col = 0, math.floor(imgW / S.tileW) do
                    local lx = col * S.tileW * S.sourceZoom - S.scrollX
                    if lx >= 0 and lx < vw then
                        gc:fillRect(Rectangle(lx, 0, 1, vh))
                    end
                end
                for row = 0, math.floor(imgH / S.tileH) do
                    local ly = row * S.tileH * S.sourceZoom - S.scrollY
                    if ly >= 0 and ly < vh then
                        gc:fillRect(Rectangle(0, ly, vw, 1))
                    end
                end

                -- Highlight tiles assigned to current animation
                local name = currentAnimName()
                if name and S.anims[name] then
                    for _, fr in ipairs(S.anims[name]) do
                        local rx = fr.x * S.sourceZoom - S.scrollX
                        local ry = fr.y * S.sourceZoom - S.scrollY
                        local rw = S.tileW * S.sourceZoom
                        local rh = S.tileH * S.sourceZoom
                        if rx + rw > 0 and rx < vw and ry + rh > 0 and ry < vh then
                            gc.color = fr.flipped
                                and Color(255, 160, 0, 160)
                                or Color(100, 200, 255, 160)
                            gc:fillRect(Rectangle(rx, ry, rw, 2))
                            gc:fillRect(Rectangle(rx, ry + rh - 2, rw, 2))
                            gc:fillRect(Rectangle(rx, ry, 2, rh))
                            gc:fillRect(Rectangle(rx + rw - 2, ry, 2, rh))
                        end
                    end
                end
            end
        end,
        onmousedown = function(ev)
            if ev.button == MouseButton.LEFT then
                S.srcClickX = ev.x
                S.srcClickY = ev.y
                S.srcIsDrag = false
                S.dragging = true
                S.dragLastX = ev.x
                S.dragLastY = ev.y
            elseif ev.button == MouseButton.RIGHT then
                local pixelX = math.floor((ev.x + S.scrollX) / S.sourceZoom)
                local pixelY = math.floor((ev.y + S.scrollY) / S.sourceZoom)
                captureCell(pixelX, pixelY, true)
            end
        end,
        onmousemove = function(ev)
            if S.dragging then
                local dx = math.abs(ev.x - S.srcClickX)
                local dy = math.abs(ev.y - S.srcClickY)
                if dx > 3 or dy > 3 then
                    S.srcIsDrag = true
                end
                if S.srcIsDrag then
                    S.scrollX = S.scrollX + (S.dragLastX - ev.x)
                    S.scrollY = S.scrollY + (S.dragLastY - ev.y)
                    clampScroll()
                end
                S.dragLastX = ev.x
                S.dragLastY = ev.y
            end
        end,
        onmouseup = function(ev)
            if S.dragging and not S.srcIsDrag then
                local pixelX = math.floor((S.srcClickX + S.scrollX) / S.sourceZoom)
                local pixelY = math.floor((S.srcClickY + S.scrollY) / S.sourceZoom)
                captureCell(pixelX, pixelY, false)
            end
            S.dragging = false
            S.srcIsDrag = false
        end,
        onwheel = function(ev)
            local dz = ev.deltaY < 0 and 1 or -1
            S.sourceZoom = math.max(1, math.min(10, S.sourceZoom + dz))
            clampScroll()
            dlg:repaint()
        end
    }

    ----------------------------------------------------------------
    -- Frame strip for current animation
    ----------------------------------------------------------------
    local STRIP_TOTAL_W = SOURCE_VIEWPORT_W
    local STRIP_CELL    = THUMB_SIZE + 1
    local STRIP_H       = STRIP_CELL * 2 + 4

    dlg:canvas{
        id = "canvasStrips",
        width = STRIP_TOTAL_W,
        height = STRIP_H,
        autoscaling = false,
        onpaint = function(ev)
            local gc = ev.context
            local name = currentAnimName()
            local frames = name and S.anims[name] or {}
            local cnt = #frames

            gc.color = Color(30, 30, 30)
            gc:fillRect(Rectangle(0, 0, STRIP_TOTAL_W, STRIP_H))

            if cnt == 0 then
                gc.color = Color(60, 60, 60)
                gc:fillRect(Rectangle(4, 4, THUMB_SIZE, THUMB_SIZE))
                return
            end

            local thumbsPerRow = math.max(1, math.floor(STRIP_TOTAL_W / STRIP_CELL))
            for i = 1, cnt do
                local col = (i - 1) % thumbsPerRow
                local row = math.floor((i - 1) / thumbsPerRow)
                local tx = col * STRIP_CELL
                local ty = 2 + row * STRIP_CELL

                -- Checkerboard bg
                local cs = 2
                for cy = 0, THUMB_SIZE - 1, cs do
                    for cx = 0, THUMB_SIZE - 1, cs do
                        local parity = (math.floor(cx / cs) + math.floor(cy / cs)) % 2
                        gc.color = (parity == 0) and Color(50, 50, 50) or Color(70, 70, 70)
                        gc:fillRect(Rectangle(tx + cx, ty + cy, cs, cs))
                    end
                end

                local fimg = getFrameImage(name, i)
                if fimg then
                    -- Pixel-perfect integer scaling
                    local intScale = math.max(1, math.floor(math.min(THUMB_SIZE / S.tileW, THUMB_SIZE / S.tileH)))
                    local dw = S.tileW * intScale
                    local dh = S.tileH * intScale
                    local dx = tx + math.floor((THUMB_SIZE - dw) / 2)
                    local dy = ty + math.floor((THUMB_SIZE - dh) / 2)
                    gc:drawImage(
                        fimg,
                        Rectangle(0, 0, S.tileW, S.tileH),
                        Rectangle(dx, dy, dw, dh)
                    )
                end

                -- Flipped indicator (orange dot)
                if frames[i].flipped then
                    gc.color = Color(255, 160, 0, 220)
                    gc:fillRect(Rectangle(tx + THUMB_SIZE - 4, ty, 4, 4))
                end

                -- Flip V indicator (green dot)
                if frames[i].flippedV then
                    gc.color = Color(0, 200, 0, 220)
                    gc:fillRect(Rectangle(tx, ty, 4, 4))
                end

                -- Offset indicator (cyan dot, bottom-left)
                if (frames[i].offX or 0) ~= 0 or (frames[i].offY or 0) ~= 0 then
                    gc.color = Color(0, 200, 255, 220)
                    gc:fillRect(Rectangle(tx, ty + THUMB_SIZE - 4, 4, 4))
                end

                -- Current playback frame indicator
                if cnt > 0 and ((S.animFrame % cnt)) == (i - 1) then
                    gc.color = Color(100, 200, 255, 200)
                    gc:fillRect(Rectangle(tx, ty - 1, THUMB_SIZE, 2))
                end

                -- Selected frame highlight (yellow border)
                if S.selectedFrame == i then
                    gc.color = Color(255, 255, 0, 220)
                    gc:fillRect(Rectangle(tx, ty, THUMB_SIZE, 2))
                    gc:fillRect(Rectangle(tx, ty + THUMB_SIZE - 2, THUMB_SIZE, 2))
                    gc:fillRect(Rectangle(tx, ty, 2, THUMB_SIZE))
                    gc:fillRect(Rectangle(tx + THUMB_SIZE - 2, ty, 2, THUMB_SIZE))
                end
            end

            -- Drag insertion indicator
            if S.frameDragging and S.frameDragTo >= 1 and S.frameDragFrom ~= S.frameDragTo then
                local insertIdx = S.frameDragTo
                local col = (insertIdx - 1) % thumbsPerRow
                local row = math.floor((insertIdx - 1) / thumbsPerRow)
                local lx = col * STRIP_CELL
                local ly = 2 + row * STRIP_CELL
                gc.color = Color(255, 100, 100, 220)
                gc:fillRect(Rectangle(lx - 1, ly, 2, THUMB_SIZE))
            end
        end,
        onmousedown = function(ev)
            local name = currentAnimName()
            if not name then return end
            local frames = S.anims[name]
            if not frames or #frames == 0 then return end
            local thumbsPerRow = math.max(1, math.floor(STRIP_TOTAL_W / STRIP_CELL))
            local col = math.floor(ev.x / STRIP_CELL)
            local row = math.floor((ev.y - 2) / STRIP_CELL)
            local idx = row * thumbsPerRow + col + 1
            if idx >= 1 and idx <= #frames then
                if ev.button == MouseButton.LEFT then
                    -- Click on already-selected frame: deselect
                    if S.selectedFrame == idx then
                        S.selectedFrame = 0
                        dlg:repaint()
                        return  -- don't start drag
                    end
                    S.selectedFrame = idx
                    S.frameDragging = true
                    S.frameDragFrom = idx
                    S.frameDragTo = idx
                    dlg:repaint()
                elseif ev.button == MouseButton.RIGHT then
                    table.remove(frames, idx)
                    if S.selectedFrame > #frames then
                        S.selectedFrame = #frames
                    end
                    if #frames == 0 then S.selectedFrame = 0 end
                    saveAll()
                    dlg:repaint()
                end
            end
        end,
        onmousemove = function(ev)
            if S.frameDragging then
                local name = currentAnimName()
                local frames = name and S.anims[name] or {}
                local thumbsPerRow = math.max(1, math.floor(STRIP_TOTAL_W / STRIP_CELL))
                local col = math.floor(ev.x / STRIP_CELL)
                local row = math.floor((ev.y - 2) / STRIP_CELL)
                local idx = row * thumbsPerRow + col + 1
                S.frameDragTo = clamp(idx, 1, #frames)
                dlg:repaint()
            end
        end,
        onmouseup = function(ev)
            if S.frameDragging then
                local from = S.frameDragFrom
                local to = S.frameDragTo
                if from ~= to then
                    local name = currentAnimName()
                    if name and S.anims[name] then
                        local frames = S.anims[name]
                        local frame = table.remove(frames, from)
                        table.insert(frames, to, frame)
                        S.selectedFrame = to
                        saveAll()
                    end
                end
                S.frameDragging = false
                dlg:repaint()
            end
        end,
        onwheel = function(ev)
            local dz = ev.deltaY < 0 and 1 or -1
            S.sourceZoom = math.max(1, math.min(10, S.sourceZoom + dz))
            clampScroll()
            dlg:repaint()
        end
    }

    ----------------------------------------------------------------
    -- Frame action buttons (no separator - combined into sepSource)
    ----------------------------------------------------------------
    dlg:button{
        id = "btnFlipX",
        text = "FlipX",
        onclick = function()
            local name = currentAnimName()
            if not name or S.selectedFrame < 1 then return end
            local frames = S.anims[name]
            if not frames or S.selectedFrame > #frames then return end
            frames[S.selectedFrame].flipped = not frames[S.selectedFrame].flipped
            saveAll()
            dlg:repaint()
        end
    }

    dlg:button{
        id = "btnFlipY",
        text = "FlipY",
        onclick = function()
            local name = currentAnimName()
            if not name or S.selectedFrame < 1 then return end
            local frames = S.anims[name]
            if not frames or S.selectedFrame > #frames then return end
            frames[S.selectedFrame].flippedV = not frames[S.selectedFrame].flippedV
            saveAll()
            dlg:repaint()
        end
    }

    dlg:button{
        id = "btnMoveLeft",
        text = "<-",
        onclick = function()
            local name = currentAnimName()
            if not name or S.selectedFrame < 2 then return end
            local frames = S.anims[name]
            if not frames then return end
            local idx = S.selectedFrame
            frames[idx], frames[idx - 1] = frames[idx - 1], frames[idx]
            S.selectedFrame = idx - 1
            saveAll()
            dlg:repaint()
        end
    }

    dlg:button{
        id = "btnMoveRight",
        text = "->",
        onclick = function()
            local name = currentAnimName()
            if not name or S.selectedFrame < 1 then return end
            local frames = S.anims[name]
            if not frames or S.selectedFrame >= #frames then return end
            local idx = S.selectedFrame
            frames[idx], frames[idx + 1] = frames[idx + 1], frames[idx]
            S.selectedFrame = idx + 1
            saveAll()
            dlg:repaint()
        end
    }

    dlg:button{
        id = "btnRemoveFrame",
        text = "Del",
        onclick = function()
            local name = currentAnimName()
            if not name then return end
            local frames = S.anims[name]
            if not frames then return end

            if #frames == 0 then
                -- No frames: delete the animation (like Remove Animation)
                local result = app.alert{
                    title = "Delete Animation",
                    text = "Animation '" .. name .. "' has no frames. Delete it?",
                    buttons = { "Delete", "Cancel" }
                }
                if result ~= 1 then return end
                S.anims[name] = nil
                table.remove(S.animNames, S.currentAnim)
                S.currentAnim = math.min(S.currentAnim, math.max(1, #S.animNames))
                S.selectedFrame = 0
                saveAll()
                dlg:close()
                openMainDialog()
                return
            end

            local idx = S.selectedFrame
            if idx < 1 then
                -- No frame selected: remove the last frame
                idx = #frames
            end
            if idx > #frames then return end
            table.remove(frames, idx)
            if S.selectedFrame > #frames then
                S.selectedFrame = #frames
            end
            if #frames == 0 then S.selectedFrame = 0 end
            saveAll()
            dlg:repaint()
        end
    }

    ----------------------------------------------------------------
    -- Frame offset buttons
    ----------------------------------------------------------------
    dlg:newrow()
    dlg:button{
        id = "btnFrameUp",
        text = "Up",
        onclick = function()
            local name = currentAnimName()
            if not name or S.selectedFrame < 1 then return end
            local frames = S.anims[name]
            if not frames or S.selectedFrame > #frames then return end
            frames[S.selectedFrame].offY = (frames[S.selectedFrame].offY or 0) - 1
            saveAll()
            dlg:repaint()
        end
    }
    dlg:button{
        id = "btnFrameDown",
        text = "Down",
        onclick = function()
            local name = currentAnimName()
            if not name or S.selectedFrame < 1 then return end
            local frames = S.anims[name]
            if not frames or S.selectedFrame > #frames then return end
            frames[S.selectedFrame].offY = (frames[S.selectedFrame].offY or 0) + 1
            saveAll()
            dlg:repaint()
        end
    }
    dlg:button{
        id = "btnFrameLeft",
        text = "Left",
        onclick = function()
            local name = currentAnimName()
            if not name or S.selectedFrame < 1 then return end
            local frames = S.anims[name]
            if not frames or S.selectedFrame > #frames then return end
            frames[S.selectedFrame].offX = (frames[S.selectedFrame].offX or 0) - 1
            saveAll()
            dlg:repaint()
        end
    }
    dlg:button{
        id = "btnFrameRight",
        text = "Right",
        onclick = function()
            local name = currentAnimName()
            if not name or S.selectedFrame < 1 then return end
            local frames = S.anims[name]
            if not frames or S.selectedFrame > #frames then return end
            frames[S.selectedFrame].offX = (frames[S.selectedFrame].offX or 0) + 1
            saveAll()
            dlg:repaint()
        end
    }
    dlg:button{
        id = "btnFrameReset",
        text = "Reset",
        onclick = function()
            local name = currentAnimName()
            if not name or S.selectedFrame < 1 then return end
            local frames = S.anims[name]
            if not frames or S.selectedFrame > #frames then return end
            frames[S.selectedFrame].offX = 0
            frames[S.selectedFrame].offY = 0
            saveAll()
            dlg:repaint()
        end
    }

    ----------------------------------------------------------------
    -- OPTIMIZE TAB
    ----------------------------------------------------------------
    dlg:separator{ id = "sepGb", text = "Tile Optimizer", visible = false }

    -- Row: Flip + Offset + Silhouette + Compress (reordered)
    dlg:check{
        id = "gbFlipOpt",
        text = "Flip",
        selected = S.gbFlipOpt,
        visible = false,
        onclick = function() S.gbFlipOpt = dlg.data.gbFlipOpt end
    }
    dlg:check{
        id = "gbOffsetOpt",
        text = "Offset",
        selected = S.gbOffsetOpt,
        visible = false,
        onclick = function() S.gbOffsetOpt = dlg.data.gbOffsetOpt end
    }
    dlg:check{
        id = "gbSilhouette",
        text = "Silhouette",
        selected = S.gbSilhouette,
        visible = false,
        onclick = function() S.gbSilhouette = dlg.data.gbSilhouette end
    }
    dlg:check{
        id = "gbCompress",
        text = "Compress",
        selected = S.gbCompress,
        visible = false,
        onclick = function() S.gbCompress = dlg.data.gbCompress end
    }
    dlg:combobox{
        id = "gbAnalyzeMode",
        option = S.gbAnalyzeMode,
        options = {"pixel", "tile"},
        visible = false,
        onchange = function() S.gbAnalyzeMode = dlg.data.gbAnalyzeMode end
    }

    -- Row: Analyze + Find Similars + Threshold
    dlg:button{
        id = "btnAnalyze",
        text = "Analyze",
        visible = false,
        onclick = function()
            if not S.sourceImage then return end
            local usedTileW = S.gbTileW
            local usedTileH = S.gbTileH
            if S.gbAnalyzeMode == "tile" then
                local rtw, rth
                S.gbTiles, S.gbTotalTiles, rtw, rth = analyzeTilesTileMode(app.sprite, app.frame.frameNumber)
                if rtw then usedTileW = rtw end
                if rth then usedTileH = rth end
            else
                S.gbTiles, S.gbTotalTiles = analyzeTiles(S.sourceImage, S.gbFlipOpt, S.gbOffsetOpt, usedTileW, usedTileH)
            end
            S.gbTileW = usedTileW
            S.gbTileH = usedTileH
            S.gbOptImage, S.gbCols = buildOptimizedImage(
                S.sourceImage, S.gbTiles, S.gbCompress,
                S.gbSilhouette, S.gbSilhouetteColor, usedTileW, usedTileH)
            S.gbSelectedTile = 0
            S.gbScrollX = 0
            S.gbScrollY = 0
            local unique = #S.gbTiles
            local total = S.gbTotalTiles
            dlg:modify{ id = "btnAnalyze", text = "Analyze (" .. unique .. "/" .. total .. ")" }
            if S.gbOptImage then
                local z = S.gbZoomOpt
                dlg:modify{ id = "canvasGbOpt",
                    width = math.min(S.gbOptImage.width * z, SOURCE_VIEWPORT_W),
                    height = math.min(S.gbOptImage.height * z, GB_OPT_H) }
            end
            saveAll()
            dlg:repaint()
        end
    }
    dlg:button{
        id = "btnFindSimilar",
        text = "Find similars",
        visible = false,
        onclick = function()
            if #S.gbTiles == 0 then
                app.alert("Run Analyze first.")
                return
            end
            S.gbSimilarPairs = findSimilarTiles(
                S.sourceImage, S.gbTiles, S.gbSimilarThreshold,
                S.gbFlipOpt, S.gbOffsetOpt, S.gbTileW, S.gbTileH)
            dlg:modify{ id = "btnFindSimilar",
                text = "Find similars (" .. #S.gbSimilarPairs .. ")" }
            dlg:repaint()
        end
    }
    dlg:button{
        id = "gbSimilarThreshold",
        text = "Threshold " .. S.gbSimilarThreshold .. "%",
        visible = false,
        onclick = function()
            local d = Dialog{ title = "Similarity Threshold" }
            d:number{ id = "val", label = "% of painted pixels that must match (1-100):",
                text = tostring(S.gbSimilarThreshold), decimals = 0 }
            d:button{ id = "ok", text = "OK" }
            d:button{ text = "Cancel" }
            d:show()
            if d.data.ok then
                local v = d.data.val
                if v < 1 then v = 1 end
                if v > 100 then v = 100 end
                S.gbSimilarThreshold = v
                dlg:modify{ id = "gbSimilarThreshold", text = "Threshold " .. v .. "%" }
            end
        end
    }

    ----------------------------------------------------------------
    -- Occurrences in Source canvas (BEFORE Optimized)
    ----------------------------------------------------------------
    dlg:separator{ id = "sepGbSource", text = "Source  ||  Optimized (L-click=check occurrences, R-click=deselect)", visible = false }

    local GB_SRC_W = SOURCE_VIEWPORT_W

    -- Flip colors
    local FLIP_COLORS = {
        none = Color(255, 0, 0, 180),
        h    = Color(255, 160, 0, 180),
        v    = Color(0, 200, 0, 180),
        hv   = Color(255, 255, 0, 180),
    }

    dlg:canvas{
        id = "canvasGbSource",
        width = GB_SRC_W,
        height = GB_SRC_H,
        autoscaling = false,
        visible = false,
        onpaint = function(ev)
            local gc = ev.context
            local tw = S.gbTileW
            local th = S.gbTileH

            gc.color = Color(30, 30, 30)
            gc:fillRect(Rectangle(0, 0, GB_SRC_W, GB_SRC_H))

            if not S.sourceImage then return end

            local z = S.gbZoomSrc
            local srcW = S.sourceImage.width
            local srcH = S.sourceImage.height

            drawCheckerboard(gc, math.min(srcW * z, GB_SRC_W), math.min(srcH * z, GB_SRC_H), z)

            gc:drawImage(
                S.sourceImage,
                Rectangle(0, 0, srcW, srcH),
                Rectangle(-S.gbSrcScrollX, -S.gbSrcScrollY, srcW * z, srcH * z)
            )

            -- Draw tile grid
            gc.color = Color(255, 255, 255, 20)
            for col = 0, math.floor(srcW / tw) do
                local lx = col * tw * z - S.gbSrcScrollX
                if lx >= 0 and lx < GB_SRC_W then
                    gc:fillRect(Rectangle(lx, 0, 1, math.min(srcH * z, GB_SRC_H)))
                end
            end
            for row = 0, math.floor(srcH / th) do
                local ly = row * th * z - S.gbSrcScrollY
                if ly >= 0 and ly < GB_SRC_H then
                    gc:fillRect(Rectangle(0, ly, math.min(srcW * z, GB_SRC_W), 1))
                end
            end

            -- Highlight all occurrences of selected tile
            if S.gbSelectedTile > 0 and S.gbSelectedTile <= #S.gbTiles then
                local tile = S.gbTiles[S.gbSelectedTile]
                for _, pos in ipairs(tile.positions) do
                    local rx = pos.x * z - S.gbSrcScrollX
                    local ry = pos.y * z - S.gbSrcScrollY
                    local rw = tw * z
                    local rh = th * z
                    if rx + rw > 0 and rx < GB_SRC_W and ry + rh > 0 and ry < GB_SRC_H then
                        local c = FLIP_COLORS[pos.flip] or FLIP_COLORS.none
                        gc.color = Color(c.red, c.green, c.blue, 60)
                        gc:fillRect(Rectangle(rx, ry, rw, rh))
                        gc.color = c
                        gc:fillRect(Rectangle(rx, ry, rw, 2))
                        gc:fillRect(Rectangle(rx, ry + rh - 2, rw, 2))
                        gc:fillRect(Rectangle(rx, ry, 2, rh))
                        gc:fillRect(Rectangle(rx + rw - 2, ry, 2, rh))
                    end
                end
            end
        end,
        onmousedown = function(ev)
            if ev.button == MouseButton.LEFT then
                S.gbSrcClickX = ev.x
                S.gbSrcClickY = ev.y
                S.gbSrcIsDrag = false
                S.gbSrcDragging = true
                S.gbSrcDragLastX = ev.x
                S.gbSrcDragLastY = ev.y
            elseif ev.button == MouseButton.RIGHT then
                -- R-click: deselect
                if S.gbSelectedTile > 0 then
                    S.gbSelectedTile = 0
                    dlg:repaint()
                end
            end
        end,
        onmousemove = function(ev)
            if S.gbSrcDragging then
                local dx = math.abs(ev.x - S.gbSrcClickX)
                local dy = math.abs(ev.y - S.gbSrcClickY)
                if dx > 3 or dy > 3 then
                    S.gbSrcIsDrag = true
                end
                if S.gbSrcIsDrag then
                    S.gbSrcScrollX = S.gbSrcScrollX + (S.gbSrcDragLastX - ev.x)
                    S.gbSrcScrollY = S.gbSrcScrollY + (S.gbSrcDragLastY - ev.y)
                    S.gbSrcScrollX = math.max(0, S.gbSrcScrollX)
                    S.gbSrcScrollY = math.max(0, S.gbSrcScrollY)
                end
                S.gbSrcDragLastX = ev.x
                S.gbSrcDragLastY = ev.y
            end
        end,
        onmouseup = function(ev)
            if S.gbSrcDragging and not S.gbSrcIsDrag then
                -- Click: select tile at this position
                local z = S.gbZoomSrc
                local tw = S.gbTileW
                local th = S.gbTileH
                local pixelX = math.floor((S.gbSrcClickX + S.gbSrcScrollX) / z)
                local pixelY = math.floor((S.gbSrcClickY + S.gbSrcScrollY) / z)

                -- Find all tiles whose positions cover this pixel
                local candidates = {}
                for i, tile in ipairs(S.gbTiles) do
                    for _, pos in ipairs(tile.positions) do
                        if pixelX >= pos.x and pixelX < pos.x + tw and
                           pixelY >= pos.y and pixelY < pos.y + th then
                            -- Check if pixel is non-transparent at this position
                            local isOpaque = false
                            if S.sourceImage and pixelX >= 0 and pixelX < S.sourceImage.width
                               and pixelY >= 0 and pixelY < S.sourceImage.height then
                                isOpaque = pc.rgbaA(S.sourceImage:getPixel(pixelX, pixelY)) > 0
                            end
                            table.insert(candidates, { tileIdx = i, opaque = isOpaque })
                        end
                    end
                end

                if #candidates > 0 then
                    -- Sort: opaque tiles first
                    table.sort(candidates, function(a, b)
                        if a.opaque ~= b.opaque then return a.opaque end
                        return a.tileIdx < b.tileIdx
                    end)

                    -- Cycle through candidates if current selection is among them
                    local found = false
                    for ci, cand in ipairs(candidates) do
                        if cand.tileIdx == S.gbSelectedTile then
                            -- Select next candidate
                            local nextIdx = (ci % #candidates) + 1
                            S.gbSelectedTile = candidates[nextIdx].tileIdx
                            found = true
                            break
                        end
                    end
                    if not found then
                        S.gbSelectedTile = candidates[1].tileIdx
                    end
                end
            end
            S.gbSrcDragging = false
            dlg:repaint()
        end,
        onwheel = function(ev)
            local dz = ev.deltaY < 0 and 1 or -1
            local newZoom = math.max(1, math.min(10, S.gbZoomSrc + dz))
            S.gbZoomSrc = newZoom
            S.gbZoomOpt = newZoom
            dlg:repaint()
        end
    }

    ----------------------------------------------------------------
    -- Optimized Spritesheet canvas (L-click=select, R-click=deselect)
    ----------------------------------------------------------------
    local GB_OPT_W = SOURCE_VIEWPORT_W

    dlg:canvas{
        id = "canvasGbOpt",
        width = GB_OPT_W,
        height = GB_OPT_H,
        autoscaling = false,
        visible = false,
        onpaint = function(ev)
            local gc = ev.context
            local z = S.gbZoomOpt
            local tw = S.gbTileW
            local th = S.gbTileH

            gc.color = Color(30, 30, 30)
            gc:fillRect(Rectangle(0, 0, GB_OPT_W, GB_OPT_H))

            if not S.gbOptImage then return end

            local imgW = S.gbOptImage.width
            local imgH = S.gbOptImage.height

            drawCheckerboard(gc, math.min(imgW * z, GB_OPT_W), math.min(imgH * z, GB_OPT_H), z)

            gc:drawImage(
                S.gbOptImage,
                Rectangle(0, 0, imgW, imgH),
                Rectangle(-S.gbScrollX, -S.gbScrollY, imgW * z, imgH * z)
            )

            -- Draw tile grid
            gc.color = Color(255, 255, 255, 30)
            for col = 0, math.floor(imgW / tw) do
                local lx = col * tw * z - S.gbScrollX
                if lx >= 0 and lx < GB_OPT_W then
                    gc:fillRect(Rectangle(lx, 0, 1, math.min(imgH * z, GB_OPT_H)))
                end
            end
            for row = 0, math.floor(imgH / th) do
                local ly = row * th * z - S.gbScrollY
                if ly >= 0 and ly < GB_OPT_H then
                    gc:fillRect(Rectangle(0, ly, math.min(imgW * z, GB_OPT_W), 1))
                end
            end

            -- Helper: get pixel position of tile i in optimized image
            local function tilePos(i)
                if S.gbCompress then
                    local c = (i - 1) % S.gbCols
                    local r = math.floor((i - 1) / S.gbCols)
                    return c * tw, r * th
                else
                    local pos = S.gbTiles[i].positions[1]
                    return pos.x, pos.y
                end
            end

            -- Highlight tiles involved in similar pairs with distinct group colors
            if #S.gbSimilarPairs > 0 then
                local parent = {}
                local function find(x)
                    if not parent[x] then parent[x] = x end
                    while parent[x] ~= x do
                        parent[x] = parent[parent[x]]
                        x = parent[x]
                    end
                    return x
                end
                local function union(a, b)
                    local ra, rb = find(a), find(b)
                    if ra ~= rb then parent[ra] = rb end
                end

                for _, pair in ipairs(S.gbSimilarPairs) do
                    union(pair.i, pair.j)
                end

                local groupColors = {}
                local colorIdx = 0
                local GROUP_HUES = {
                    Color(255, 0, 255, 150),
                    Color(0, 200, 255, 150),
                    Color(255, 128, 0, 150),
                    Color(0, 255, 128, 150),
                    Color(255, 255, 0, 150),
                    Color(128, 0, 255, 150),
                    Color(255, 0, 128, 150),
                    Color(0, 255, 0, 150),
                    Color(0, 128, 255, 150),
                    Color(255, 64, 64, 150),
                    Color(128, 255, 0, 150),
                    Color(255, 0, 64, 150),
                    Color(0, 255, 255, 150),
                    Color(200, 100, 255, 150),
                    Color(255, 200, 0, 150),
                    Color(100, 255, 200, 150),
                }

                local similarSet = {}
                for _, pair in ipairs(S.gbSimilarPairs) do
                    local root = find(pair.i)
                    if not groupColors[root] then
                        colorIdx = colorIdx + 1
                        groupColors[root] = GROUP_HUES[((colorIdx - 1) % #GROUP_HUES) + 1]
                    end
                    similarSet[pair.i] = groupColors[find(pair.i)]
                    similarSet[pair.j] = groupColors[find(pair.j)]
                end

                local rw = tw * z
                local rh = th * z
                for idx, c in pairs(similarSet) do
                    local ttx, tty = tilePos(idx)
                    local srx = ttx * z - S.gbScrollX
                    local sry = tty * z - S.gbScrollY
                    gc.color = Color(c.red, c.green, c.blue, 40)
                    gc:fillRect(Rectangle(srx, sry, rw, rh))
                    gc.color = c
                    gc:fillRect(Rectangle(srx, sry, rw, 1))
                    gc:fillRect(Rectangle(srx, sry + rh - 1, rw, 1))
                    gc:fillRect(Rectangle(srx, sry, 1, rh))
                    gc:fillRect(Rectangle(srx + rw - 1, sry, 1, rh))
                end

                if S.gbSelectedTile > 0 then
                    for _, pair in ipairs(S.gbSimilarPairs) do
                        local partner = nil
                        if pair.i == S.gbSelectedTile then partner = pair.j end
                        if pair.j == S.gbSelectedTile then partner = pair.i end
                        if partner then
                            local ptx, pty = tilePos(partner)
                            local prx = ptx * z - S.gbScrollX
                            local pry = pty * z - S.gbScrollY
                            gc.color = Color(255, 255, 0, 80)
                            gc:fillRect(Rectangle(prx, pry, rw, rh))
                            gc.color = Color(255, 255, 0, 220)
                            gc:fillRect(Rectangle(prx, pry, rw, 2))
                            gc:fillRect(Rectangle(prx, pry + rh - 2, rw, 2))
                            gc:fillRect(Rectangle(prx, pry, 2, rh))
                            gc:fillRect(Rectangle(prx + rw - 2, pry, 2, rh))
                        end
                    end
                end
            end

            -- Highlight selected tile
            if S.gbSelectedTile > 0 and S.gbSelectedTile <= #S.gbTiles then
                local ttx, tty = tilePos(S.gbSelectedTile)
                local rx = ttx * z - S.gbScrollX
                local ry = tty * z - S.gbScrollY
                local rw = tw * z
                local rh = th * z
                gc.color = Color(255, 0, 0, 220)
                gc:fillRect(Rectangle(rx, ry, rw, 2))
                gc:fillRect(Rectangle(rx, ry + rh - 2, rw, 2))
                gc:fillRect(Rectangle(rx, ry, 2, rh))
                gc:fillRect(Rectangle(rx + rw - 2, ry, 2, rh))
            end
        end,
        onmousedown = function(ev)
            if ev.button == MouseButton.LEFT then
                -- Click vs drag detection
                S.gbOptClickX = ev.x
                S.gbOptClickY = ev.y
                S.gbOptIsDrag = false
                S.gbDragging = true
                S.gbDragLastX = ev.x
                S.gbDragLastY = ev.y
            elseif ev.button == MouseButton.RIGHT then
                -- R-click: deselect
                if S.gbSelectedTile > 0 then
                    S.gbSelectedTile = 0
                    dlg:repaint()
                end
            end
        end,
        onmousemove = function(ev)
            if S.gbDragging then
                local dx = math.abs(ev.x - S.gbOptClickX)
                local dy = math.abs(ev.y - S.gbOptClickY)
                if dx > 3 or dy > 3 then
                    S.gbOptIsDrag = true
                end
                if S.gbOptIsDrag then
                    S.gbScrollX = S.gbScrollX + (S.gbDragLastX - ev.x)
                    S.gbScrollY = S.gbScrollY + (S.gbDragLastY - ev.y)
                    S.gbScrollX = math.max(0, S.gbScrollX)
                    S.gbScrollY = math.max(0, S.gbScrollY)
                end
                S.gbDragLastX = ev.x
                S.gbDragLastY = ev.y
            end
        end,
        onmouseup = function(ev)
            if S.gbDragging and not S.gbOptIsDrag then
                -- Click: select tile using candidate-based logic
                if not S.gbOptImage then
                    S.gbDragging = false
                    return
                end
                local z = S.gbZoomOpt
                local tw = S.gbTileW
                local th = S.gbTileH
                local pixelX = math.floor((S.gbOptClickX + S.gbScrollX) / z)
                local pixelY = math.floor((S.gbOptClickY + S.gbScrollY) / z)

                -- Find all tiles whose positions cover the clicked pixel
                local candidates = {}

                if S.gbCompress then
                    -- In compress mode, tiles are laid out in a grid
                    local col = math.floor(pixelX / tw)
                    local row = math.floor(pixelY / th)
                    local idx = row * S.gbCols + col + 1
                    if idx >= 1 and idx <= #S.gbTiles then
                        local isOpaque = false
                        if pixelX >= 0 and pixelX < S.gbOptImage.width
                           and pixelY >= 0 and pixelY < S.gbOptImage.height then
                            isOpaque = pc.rgbaA(S.gbOptImage:getPixel(pixelX, pixelY)) > 0
                        end
                        table.insert(candidates, { tileIdx = idx, opaque = isOpaque })
                    end
                else
                    -- Non-compress mode: candidate-based click like Occurrences canvas
                    for i, tile in ipairs(S.gbTiles) do
                        local pos = tile.positions[1]
                        if pixelX >= pos.x and pixelX < pos.x + tw and
                           pixelY >= pos.y and pixelY < pos.y + th then
                            local isOpaque = false
                            if S.gbOptImage and pixelX >= 0 and pixelX < S.gbOptImage.width
                               and pixelY >= 0 and pixelY < S.gbOptImage.height then
                                isOpaque = pc.rgbaA(S.gbOptImage:getPixel(pixelX, pixelY)) > 0
                            end
                            table.insert(candidates, { tileIdx = i, opaque = isOpaque })
                        end
                    end

                    -- Also check silhouette positions (duplicate tile positions rendered as silhouettes)
                    if S.gbSilhouette then
                        for i, tile in ipairs(S.gbTiles) do
                            for pi = 2, #tile.positions do
                                local pos = tile.positions[pi]
                                if pixelX >= pos.x and pixelX < pos.x + tw and
                                   pixelY >= pos.y and pixelY < pos.y + th then
                                    local isOpaque = false
                                    if S.gbOptImage and pixelX >= 0 and pixelX < S.gbOptImage.width
                                       and pixelY >= 0 and pixelY < S.gbOptImage.height then
                                        isOpaque = pc.rgbaA(S.gbOptImage:getPixel(pixelX, pixelY)) > 0
                                    end
                                    -- Check if not already in candidates
                                    local alreadyIn = false
                                    for _, c in ipairs(candidates) do
                                        if c.tileIdx == i then alreadyIn = true; break end
                                    end
                                    if not alreadyIn then
                                        table.insert(candidates, { tileIdx = i, opaque = isOpaque })
                                    end
                                end
                            end
                        end
                    end
                end

                if #candidates > 0 then
                    -- Sort: opaque tiles first
                    table.sort(candidates, function(a, b)
                        if a.opaque ~= b.opaque then return a.opaque end
                        return a.tileIdx < b.tileIdx
                    end)

                    -- Cycle through candidates if current selection is among them
                    local found = false
                    for ci, cand in ipairs(candidates) do
                        if cand.tileIdx == S.gbSelectedTile then
                            local nextIdx = (ci % #candidates) + 1
                            S.gbSelectedTile = candidates[nextIdx].tileIdx
                            found = true
                            break
                        end
                    end
                    if not found then
                        S.gbSelectedTile = candidates[1].tileIdx
                    end
                end
            end
            S.gbDragging = false
            dlg:repaint()
        end,
        onwheel = function(ev)
            local dz = ev.deltaY < 0 and 1 or -1
            local newZoom = math.max(1, math.min(10, S.gbZoomOpt + dz))
            S.gbZoomOpt = newZoom
            S.gbZoomSrc = newZoom
            dlg:repaint()
        end
    }

    -- Save as Layer button
    dlg:button{
        id = "btnGbSaveLayer",
        text = "Save as Layer",
        visible = false,
        onclick = function()
            if not S.gbOptImage then
                app.alert("Run Analyze first.")
                return
            end
            local sp = app.sprite
            if not sp then return end

            local layerName = S.gbLayerName
            if not layerName or layerName == "" then layerName = "auto-optimized-tiles" end

            local existingLayer = nil
            for i, layer in ipairs(sp.layers) do
                if layer.name == layerName then
                    existingLayer = layer
                    break
                end
            end

            local imgConverted = Image(S.gbOptImage.width, S.gbOptImage.height, sp.colorMode)
            imgConverted:clear()
            imgConverted:drawImage(S.gbOptImage, Point(0, 0))
            app.transaction("Save Optimized Layer", function()
                if existingLayer then
                    if S.gbAlwaysOverwrite then
                        existingLayer.isEditable = true
                        for _, cel in ipairs(existingLayer.cels) do
                            sp:deleteCel(cel)
                        end
                        sp:newCel(existingLayer, app.frame, imgConverted, Point(0, 0))
                        existingLayer.isEditable = false
                    else
                        local suffix = 2
                        local newName = layerName .. "-" .. suffix
                        local nameExists = true
                        while nameExists do
                            nameExists = false
                            for _, layer in ipairs(sp.layers) do
                                if layer.name == newName then
                                    nameExists = true
                                    suffix = suffix + 1
                                    newName = layerName .. "-" .. suffix
                                    break
                                end
                            end
                        end
                        local newLayer = sp:newLayer()
                        newLayer.name = newName
                        sp:newCel(newLayer, app.frame, imgConverted, Point(0, 0))
                        newLayer.isEditable = false
                    end
                else
                    local newLayer = sp:newLayer()
                    newLayer.name = layerName
                    sp:newCel(newLayer, app.frame, imgConverted, Point(0, 0))
                    newLayer.isEditable = false
                end
            end)
        end
    }

    -- Copy to clipboard button (preserves transparency)
    dlg:button{
        id = "btnGbCopyClipboard",
        text = "Copy to Clipboard",
        visible = false,
        onclick = function()
            if not S.gbOptImage then
                app.alert("Run Analyze first.")
                return
            end
            local optW = S.gbOptImage.width
            local optH = S.gbOptImage.height
            local tmpSprite = Sprite(optW, optH, ColorMode.RGB)
            app.command.LayerFromBackground()
            local layer = tmpSprite.layers[1]
            for _, c in ipairs(layer.cels) do tmpSprite:deleteCel(c) end
            tmpSprite:newCel(layer, 1, S.gbOptImage:clone(), Point(0, 0))
            app.command.MaskAll()
            app.command.Copy()
            tmpSprite:close()
        end
    }

    -- Save PNG button
    dlg:button{
        id = "btnGbSave",
        text = "Save PNG",
        visible = false,
        onclick = function()
            if not S.gbOptImage then
                app.alert("Run Analyze first.")
                return
            end

            local defaultFile = "tileset_optimized.png"
            if S.gbLastSavePath ~= "" then
                defaultFile = S.gbLastSavePath
            end

            local saveDlg = Dialog{ title = "Save Optimized Tileset" }
            saveDlg:file{
                id = "path",
                save = true,
                filename = defaultFile,
                filetypes = { "png" },
            }
            saveDlg:button{ id = "ok", text = "Save" }
            saveDlg:button{ text = "Cancel" }
            saveDlg:show()

            if not saveDlg.data.ok then return end
            local path = saveDlg.data.path
            if not path or path == "" then return end

            S.gbLastSavePath = path
            saveAll()

            local optW = S.gbOptImage.width
            local optH = S.gbOptImage.height
            local tmpSprite = Sprite(optW, optH, ColorMode.RGB)
            local cel = tmpSprite.cels[1]
            cel.image:drawImage(S.gbOptImage)
            tmpSprite:saveCopyAs(path)
            tmpSprite:close()
            app.alert("Saved: " .. path)
        end
    }

    ----------------------------------------------------------------
    -- Timers for main dialog
    ----------------------------------------------------------------
    mainAnimTimer = Timer{
        interval = S.animSpeed / 1000.0,
        ontick = function()
            S.animFrame = S.animFrame + 1
            pcall(function() dlg:repaint() end)
        end
    }
    mainAnimTimer:start()

    local gbRefreshCounter = 0
    mainRefreshTimer = Timer{
        interval = 0.5,
        ontick = function()
            local isDragging = S.dragging or S.gbDragging or S.gbSrcDragging
            if S.currentTab == "Optimize" and not isDragging then
                gbRefreshCounter = gbRefreshCounter + 1
                if gbRefreshCounter >= 4 then
                    gbRefreshCounter = 0
                    refreshSource()
                end
                pcall(function() dlg:repaint() end)
            else
                gbRefreshCounter = 0
                if not isDragging then
                    refreshSource()
                end
                pcall(function() dlg:repaint() end)
            end

            -- Auto-detect file change (also in main dialog timer)
            local currentFile = app.sprite and app.sprite.filename or ""
            if currentFile ~= lastSpriteFilename then
                lastSpriteFilename = currentFile
                local presetForFile = filePresetMap[currentFile] or "Default"
                if presetForFile ~= S.currentPreset then
                    loadPreset(presetForFile)
                    S.currentPreset = presetForFile
                    pcall(function() dlg:close() end)
                    openMainDialog()
                end
            end
        end
    }
    mainRefreshTimer:start()

    startAnimTimer()
    switchTab(S.currentTab)
    dlg:show{ wait = false }
end

----------------------------------------------------------------------
-- Entry point
----------------------------------------------------------------------
local function run()
    if not app.sprite then
        app.alert("No sprite is open.")
        return
    end
    -- Check if already running via lock file
    local lockF = io.open(LOCK_FILE, "r")
    if lockF then
        lockF:close()
        app.alert("AniPhallow is already running.")
        return
    end
    -- Create lock file
    local lf = io.open(LOCK_FILE, "w")
    if lf then lf:write("running"); lf:close() end

    S.currentTab = "Animations"
    refreshSource()
    -- Always open preview window on launch
    openPreviewWindow()
end

run()