namespace LivingVillage.Desktop

open System
open System.IO
open Microsoft.Xna.Framework
open Microsoft.Xna.Framework.Graphics

module CjkGlyphAtlas =
    let columns = 16
    let cellPixels = 24

    // Keep this table sorted and stable so the generated PNG has a reproducible layout.
    let private characterTable =
        "×一不业中主乐乡书买事于互交人今从价任传体作使保倍停入关内农准出到前力功务动助单卖南原友取受可同和回围圃土在墙备夜大天夫失好始存完家察对就层居屋工已币帮年庄库应度开式当录待得心必态怒总恼意戏成或打找报拒择挑捕据接提播操收效敌数新方无日时明昏易是晚晨景暂更最有村板林标格档桥歉段民水求江没法清渔游物状理瓦生用留白目石确社离移空竹笑粮精系紧给绝继绪续置翻聊职能范获菜衅行观认讨议记讲论设话询说请读谅谈败货资足跳转过近返还进迫退送选速道郎量金鉴钱门闭闲间闻附零需面项须食饥饿黄黛，："

    let characters = characterTable.ToCharArray()
    let rowCount = (characters.Length + columns - 1) / columns
    let pixelWidth = columns * cellPixels
    let pixelHeight = rowCount * cellPixels
    let assetRelativePath = "Assets/cjk-glyph-atlas.png"
    let manifestRelativePath = "Assets/cjk-glyphs.txt"

    let private indices =
        characters
        |> Array.mapi (fun index character -> character, index)
        |> Map.ofArray

    let contains (character: char) = Map.containsKey character indices

    let sourceRectangle (character: char) =
        indices
        |> Map.tryFind character
        |> Option.map (fun index ->
            Rectangle(
                (index % columns) * cellPixels,
                (index / columns) * cellPixels,
                cellPixels,
                cellPixels))

    let runtimeAssetPath () = Path.Combine(AppContext.BaseDirectory, assetRelativePath)

    let runtimeManifestPath () = Path.Combine(AppContext.BaseDirectory, manifestRelativePath)

    let load (device: GraphicsDevice) : Texture2D =
        let path = runtimeAssetPath ()
        if not (File.Exists path) then
            raise (FileNotFoundException(sprintf "CJK glyph atlas is missing: %s" path, path))

        use stream = File.OpenRead path
        let texture = Texture2D.FromStream(device, stream)
        if texture.Width <> pixelWidth || texture.Height <> pixelHeight then
            texture.Dispose()
            invalidOp (sprintf "CJK glyph atlas has dimensions %dx%d; expected %dx%d." texture.Width texture.Height pixelWidth pixelHeight)
        else
            texture