namespace LivingVillage.Desktop

open System
open Microsoft.Xna.Framework
open Microsoft.Xna.Framework.Graphics
open LivingVillage.Kernel

/// P47 场景细节渲染层：把 `SceneDetail` 的纯函数结果落成画面。
/// 倒影为每个光源正下方一条暖色垂直光柱（核心 + 外晕，离光源越远越淡），
/// 岸芦苇/漂浮元素用既有瓦片精灵与原创点阵图集，近景屋顶按统一光源分受光面/背光面。
/// 全部只读，不改瓦片/可达性。
module SceneDetailRender =

    let private tileX (camera: Vector2) (x: int) = x * Sim.tilePixels - int camera.X
    let private tileY (camera: Vector2) (y: int) = y * Sim.tilePixels - int camera.Y

    /// 河道倒影：每个光源在正下方水面格画一段暖色垂直光柱（外晕 20px + 核心 10px），
    /// alpha 随离光源距离递减、逐格 ±1px 微抖，连成一条可辨认的暖色垂直条纹
    /// （明显区别于蓝灰横向波纹）。
    let private drawReflections
        (spriteBatch: SpriteBatch)
        (pixel: Texture2D)
        (camera: Vector2)
        (map: MapGen.Result)
        (tick: int64) =
        for (x, y, alpha, _) in SceneDetail.reflectionStreaks map do
            let wobble = SceneDetail.reflectionWobbleAt tick x y
            let cx = tileX camera x
            let cy = tileY camera y
            let halo = VillageArt.premultiply 255 150 70 (alpha * 3 / 5)
            let core = VillageArt.premultiply 255 208 120 alpha
            spriteBatch.Draw(pixel, Rectangle(cx + 4 + wobble, cy, 24, Sim.tilePixels), halo)
            spriteBatch.Draw(pixel, Rectangle(cx + 10 + wobble, cy, 12, Sim.tilePixels), core)

    /// 岸边芦苇加密度：用既有芦苇精灵补绘一层贴水芦苇。
    let private drawBankReeds (spriteBatch: SpriteBatch) (textures: VillageArt.ArtTextures) (camera: Vector2) (map: MapGen.Result) =
        match textures.Cc0TileAtlas with
        | Some cc0 ->
            for (x, y) in SceneDetail.bankReedTiles map do
                spriteBatch.Draw(cc0, Rectangle(tileX camera x, tileY camera y, Sim.tilePixels, Sim.tilePixels), Nullable(VillageArt.cc0TileRect VillageArt.cc0TileIndexReeds), Color.White)
        | None ->
            let source = VillageArt.atlasTileRectangle 18
            for (x, y) in SceneDetail.bankReedTiles map do
                spriteBatch.Draw(textures.TileAtlas, Rectangle(tileX camera x, tileY camera y, Sim.tilePixels, Sim.tilePixels), Nullable(source), Color.White)

    /// 漂浮元素：原创点阵鸭/叶，按 tick 慢漂移。
    let private drawFloaters (spriteBatch: SpriteBatch) (textures: VillageArt.ArtTextures) (camera: Vector2) (map: MapGen.Result) (tick: int64) =
        for (x, y, kind) in SceneDetail.floatingProps map do
            let seed = x * 31 + y * 7
            let dx, dy = SceneDetail.floatDrift tick seed
            let frame = SceneDetail.floatFrame tick seed
            let kindIndex =
                match kind with
                | SceneDetail.DuckFloat -> FloaterArt.duckIndex
                | SceneDetail.FallenLeaf -> FloaterArt.leafIndex
            let source = FloaterArt.sourceRectangle kindIndex frame
            spriteBatch.Draw(
                textures.FloaterAtlas,
                Rectangle(tileX camera x + dx + (Sim.tilePixels - FloaterArt.cellWidth) / 2, tileY camera y + dy + (Sim.tilePixels - FloaterArt.cellHeight) / 2, FloaterArt.cellWidth, FloaterArt.cellHeight),
                Nullable(source),
                Color.White)

    /// 近景楼层层错落：屏幕空间前景屋顶带。统一光源来自左上，故每段屋顶
    /// 左半受光（暖亮）、右半背光（压暗），并整体投影到右下（shadowOffsetPx）。
    let private drawForeground (spriteBatch: SpriteBatch) (textures: VillageArt.ArtTextures) (pixel: Texture2D) (viewportWidth: int) (viewportHeight: int) (tick: int64) =
        let ridgeSource = VillageArt.atlasTileRectangle 8
        let eaveSource = VillageArt.atlasTileRectangle 9
        let shadowColor = VillageArt.premultiply 8 12 18 120
        let litColor = VillageArt.premultiply 255 236 196 46
        let darkColor = VillageArt.premultiply 6 10 18 110
        let dx, dy = SceneDetail.shadowOffsetPx
        for (x, y, w) in SceneDetail.foregroundRooftops viewportWidth viewportHeight tick do
            // 统一方向的投影：先把 eave 的暗色镜像平移一份到右下，再画本体。
            spriteBatch.Draw(textures.TileAtlas, Rectangle(x + dx, y + dy, w, Sim.tilePixels), Nullable(eaveSource), shadowColor)
            spriteBatch.Draw(textures.TileAtlas, Rectangle(x, y - Sim.tilePixels, w, Sim.tilePixels), Nullable(ridgeSource), Color.White)
            spriteBatch.Draw(textures.TileAtlas, Rectangle(x, y, w, Sim.tilePixels), Nullable(eaveSource), Color.White)
            // 受光面 / 背光面：左半加暖亮、右半压暗，形成两档以上 luma 差。
            let half = max 1 (w / 2)
            spriteBatch.Draw(pixel, Rectangle(x, y - Sim.tilePixels, half, 2 * Sim.tilePixels), litColor)
            spriteBatch.Draw(pixel, Rectangle(x + half, y - Sim.tilePixels, w - half, 2 * Sim.tilePixels), darkColor)

    /// P78 炊烟：生成器世界每户屋顶脊上方一缕，帧号驱动升腾/摇曳，夜帧更醒目。
    /// 复用江南图集的 22-24 三相位烟精灵，只读、不改瓦片。
    let private drawSmoke
        (spriteBatch: SpriteBatch)
        (textures: VillageArt.ArtTextures)
        (camera: Vector2)
        (map: MapGen.Result)
        (tick: int64)
        (nightStrength: float32) =
        let alpha = SceneDetail.smokeAlphaAt nightStrength
        let size = SceneDetail.smokeCellSize nightStrength
        let source = VillageArt.atlasTileRectangle (22 + SceneDetail.smokeFrame tick)
        let color =
            if nightStrength > 0.5f then VillageArt.premultiply 238 230 214 alpha
            else VillageArt.premultiply 222 226 228 alpha
        for (x, y) in SceneDetail.smokeSourceTiles map do
            let seed = x * 29 + y * 11
            let dx, dy = SceneDetail.smokeDrift tick seed
            let cx = tileX camera x + (Sim.tilePixels - size) / 2 + dx
            let cy = tileY camera y + (Sim.tilePixels - size) / 2 + dy
            spriteBatch.Draw(textures.TileAtlas, Rectangle(cx, cy, size, size), source, color)

    /// P78 夜帧水面逐格微光斑：帧号驱动、位置确定性，暗部因此有两档以上层次而非整片死黑。
    let private drawNightWater
        (spriteBatch: SpriteBatch)
        (pixel: Texture2D)
        (camera: Vector2)
        (map: MapGen.Result)
        (tick: int64)
        (nightStrength: float32) =
        for (x, y) in SceneDetail.waterGlintTiles map do
            let alpha = SceneDetail.waterGlintAlpha nightStrength (SceneDetail.waterGlintPhase tick x y)
            if alpha > 0 then
                let wobble = SceneDetail.waterGlintOffset tick x y
                let cx = tileX camera x
                let cy = tileY camera y
                let soft = VillageArt.premultiply 150 190 232 (alpha / 3)
                let cool = VillageArt.premultiply 198 224 255 alpha
                spriteBatch.Draw(pixel, Rectangle(cx + 6 + wobble, cy + 12, 20, 4), soft)
                spriteBatch.Draw(pixel, Rectangle(cx + 10 + wobble, cy + 13, 11, 2), cool)

    /// P78 桥头灯柱窄光晕：只围灯柱一圈（半径 1 tile），夜里给灯柱一圈暖光而不铺满河面。
    let private drawBridgeHalos
        (spriteBatch: SpriteBatch)
        (pixel: Texture2D)
        (camera: Vector2)
        (map: MapGen.Result)
        (nightStrength: float32) =
        let peak = int (78.0f * max 0.0f (min 1.0f nightStrength))
        if peak > 0 then
            let half = Sim.tilePixels / 2
            let radius = SceneDetail.bridgeHaloRadiusTiles * Sim.tilePixels
            for (x, y) in SceneDetail.bridgeLanternTiles map do
                let cx = tileX camera x + half
                let cy = tileY camera y + half
                for (rect, color) in VillageArt.lanternGlowLayers cx cy radius 5 255 214 150 peak do
                    spriteBatch.Draw(pixel, rect, color)

    /// P79 夜帧炊烟增强：烟柱（3 段向上堆叠）+ 外发光。只在夜帧叠加绘制，白天帧不受影响。
    let private drawNightSmoke
        (spriteBatch: SpriteBatch)
        (textures: VillageArt.ArtTextures)
        (pixel: Texture2D)
        (camera: Vector2)
        (map: MapGen.Result)
        (tick: int64)
        (nightStrength: float32) =
        let alpha = SceneDetail.nightSmokeAlphaAt nightStrength
        let glowPeak = SceneDetail.nightSmokeGlowPeakAt nightStrength
        let source = VillageArt.atlasTileRectangle (22 + SceneDetail.smokeFrame tick)
        let cell = SceneDetail.smokeCellSize nightStrength
        for (x, y) in SceneDetail.smokeSourceTiles map do
            let seed = x * 29 + y * 11
            let sway, rise = SceneDetail.smokeDrift tick seed
            let baseX = tileX camera x + (Sim.tilePixels - cell) / 2
            let baseY = tileY camera y + (Sim.tilePixels - cell) / 2
            // 外发光：暖色径向柔光，让烟柱在夜色里浮起。
            for (rect, glowColor) in
                VillageArt.lanternGlowLayers
                    (baseX + cell / 2)
                    (baseY + rise)
                    SceneDetail.nightSmokeGlowRadius
                    4
                    255
                    236
                    200
                    glowPeak do
                spriteBatch.Draw(pixel, rect, glowColor)
            // 烟柱：自屋顶向上堆叠，越上越淡，并在每段叠一枚中性柔光团（外发光），
            // 弥补烟精灵本身 alpha 很低的问题，使夜色里每一缕烟柱都清晰可辨。
            for segment in 0 .. SceneDetail.nightSmokeSegments - 1 do
                let segmentAlpha = max 1 (alpha * (SceneDetail.nightSmokeSegments - segment) / SceneDetail.nightSmokeSegments)
                let segmentColor = VillageArt.premultiply 246 242 232 segmentAlpha
                let sx = baseX + sway * (segment + 1) / 2
                let sy = baseY + rise - segment * SceneDetail.nightSmokeSegmentLift
                spriteBatch.Draw(textures.TileAtlas, Rectangle(sx, sy, cell, cell), source, segmentColor)
                let puffPeak = max 1 (glowPeak * (SceneDetail.nightSmokeSegments - segment) / (SceneDetail.nightSmokeSegments + 1))
                for (rect, puffColor) in
                    VillageArt.lanternGlowLayers (sx + cell / 2) (sy + cell / 2) 12 3 238 242 248 puffPeak do
                    spriteBatch.Draw(pixel, rect, puffColor)

    /// P79 夜景光晕去叠：每个光源最多 2 层（内芯 + 外环）、层间暗隙、半径收紧到 3 tile。
    let private drawNightHalos
        (spriteBatch: SpriteBatch)
        (pixel: Texture2D)
        (camera: Vector2)
        (map: MapGen.Result)
        (includeRoadLanterns: bool)
        (nightStrength: float32) =
        let peak = SceneDetail.nightHaloPeakAlphaAt nightStrength
        if peak > 0 then
            let half = Sim.tilePixels / 2
            let radius = SceneDetail.nightHaloRadiusTiles * Sim.tilePixels
            for (lx, ly) in VillageArt.nightLightTilesWith includeRoadLanterns map do
                let cx = tileX camera lx + half
                let cy = tileY camera ly + half
                for (rect, color) in VillageArt.haloRingLayers cx cy radius peak do
                    spriteBatch.Draw(pixel, rect, color)

    /// P78 夜帧加成层（水面光斑 + 桥头窄光晕）：在 veil 之后调用，故不被夜色乘暗、仍醒目。
    let drawNight
        (spriteBatch: SpriteBatch)
        (textures: VillageArt.ArtTextures)
        (pixel: Texture2D)
        (camera: Vector2)
        (map: MapGen.Result)
        (tick: int64)
        (nightStrength: float32) =
        drawNightWater spriteBatch pixel camera map tick nightStrength
        drawBridgeHalos spriteBatch pixel camera map nightStrength
        drawNightHalos spriteBatch pixel camera map textures.Cc0TileAtlas.IsSome nightStrength
        drawNightSmoke spriteBatch textures pixel camera map tick nightStrength

    /// 一次性绘制全部 P47 场景细节（倒影 → 岸边芦苇 → 漂浮元素 → 近景前景层 → P78 炊烟）。
    let draw
        (spriteBatch: SpriteBatch)
        (textures: VillageArt.ArtTextures)
        (pixel: Texture2D)
        (camera: Vector2)
        (viewportWidth: int)
        (viewportHeight: int)
        (map: MapGen.Result)
        (tick: int64)
        (nightStrength: float32) =
        drawReflections spriteBatch pixel camera map tick
        drawBankReeds spriteBatch textures camera map
        drawFloaters spriteBatch textures camera map tick
        drawForeground spriteBatch textures pixel viewportWidth viewportHeight tick
        drawSmoke spriteBatch textures camera map tick nightStrength