using System;
using System.IO;
using AcDream.App.UI;
using AcDream.Core.Items;
using DatReaderWriter;
using DatReaderWriter.Options;

namespace AcDream.App.Tests.UI;

public class IconComposerTests
{
    private static byte[] Solid(int w, int h, byte r, byte g, byte b, byte a)
    {
        var px = new byte[w * h * 4];
        for (int i = 0; i < w * h; i++) { px[i*4]=r; px[i*4+1]=g; px[i*4+2]=b; px[i*4+3]=a; }
        return px;
    }

    [Fact]
    public void Compose_alphaOver_topOpaqueLayerWins()
    {
        var bottom = (Solid(2, 2, 255, 0, 0, 255), 2, 2); // red, opaque
        var top    = (Solid(2, 2, 0, 0, 255, 255), 2, 2); // blue, opaque
        var (rgba, w, h) = IconComposer.Compose(new[] { bottom, top });
        Assert.Equal(2, w); Assert.Equal(2, h);
        Assert.Equal(0,   rgba[0]); // R
        Assert.Equal(0,   rgba[1]); // G
        Assert.Equal(255, rgba[2]); // B — top layer won
        Assert.Equal(255, rgba[3]); // A
    }

    [Fact]
    public void Compose_alphaOver_transparentTopKeepsBottom()
    {
        var bottom = (Solid(1, 1, 255, 0, 0, 255), 1, 1);
        var top    = (Solid(1, 1, 0, 0, 255, 0), 1, 1); // fully transparent blue
        var (rgba, _, _) = IconComposer.Compose(new[] { bottom, top });
        Assert.Equal(255, rgba[0]); // bottom red preserved
        Assert.Equal(0,   rgba[2]);
    }

    /// <summary>
    /// Dat-free: when an opaque type-default underlay is prepended as layer 0,
    /// Compose yields a fully-opaque result even when the base icon is semi-transparent.
    /// This validates the bottom-up ordering that makes filled toolbar slots non-transparent
    /// (retail IconData::RenderIcons 407524: underlay is OPAQUE Blit_Normal first).
    /// </summary>
    [Fact]
    public void Compose_opaqueUnderlayFirst_resultIsFullyOpaque()
    {
        var underlay  = (Solid(2, 2, 128, 64, 32, 255), 2, 2); // opaque tawny
        var baseIcon  = (Solid(2, 2,   0,  0,  0, 128), 2, 2); // semi-transparent black
        var (rgba, w, h) = IconComposer.Compose(new[] { underlay, baseIcon });
        Assert.Equal(2, w); Assert.Equal(2, h);
        // All pixels fully opaque: underlay A=255, baseIcon blends over it.
        for (int i = 0; i < w * h; i++)
            Assert.Equal(255, rgba[i * 4 + 3]);
    }

    // ── Dat-gated golden tests ────────────────────────────────────────────────
    // These tests open the real Asheron's Call dats (ACDREAM_DAT_DIR or the default
    // Documents path) and verify the EnumIDMap 0x10000004 resolve chain against the
    // known golden DIDs from the dat (confirmed 2026-06-17 research).
    // Golden values: IconData::RenderIcons 0058d214 + DBCache::GetDIDFromEnum 0x413940.

    private static string? ResolveDatDir()
    {
        var fromEnv = Environment.GetEnvironmentVariable("ACDREAM_DAT_DIR");
        if (!string.IsNullOrWhiteSpace(fromEnv) && Directory.Exists(fromEnv))
            return fromEnv;
        var def = Path.Combine(
            Environment.GetFolderPath(Environment.SpecialFolder.UserProfile),
            "Documents", "Asheron's Call");
        return Directory.Exists(def) ? def : null;
    }

    [Fact]
    public void ResolveUnderlayDid_goldenValues_matchDat()
    {
        var datDir = ResolveDatDir();
        if (datDir is null)
            return;  // dats absent (CI) — skip cleanly

        using var dats = new DatCollection(datDir, DatAccessType.Read);
        // TextureCache is not needed for the resolve path; pass a null-safe stub
        // via IconComposer — the underlay-resolve methods only touch _dats.
        // We cannot construct TextureCache without GL, so use a bare IconComposer
        // with a null cache guard: ResolveUnderlayDid is internal and pure-dat.
        var composer = new IconComposer(dats, null!);

        // Golden values confirmed against C:/Users/erikn/Documents/Asheron's Call
        // (IconData::RenderIcons decomp 407524; DBCache::GetDIDFromEnum 0x413940):
        //   MeleeWeapon  (0x1)  → index 1  → 0x060011CB
        //   Armor        (0x2)  → index 2  → 0x060011CF
        //   Clothing     (0x4)  → index 3  → 0x060011F3
        //   Jewelry      (0x8)  → index 4  → 0x060011D5
        //   None         (0x0)  → index 0x21 (fallback) → 0x060011D4
        Assert.Equal(0x060011CBu, composer.ResolveUnderlayDid(ItemType.MeleeWeapon));
        Assert.Equal(0x060011CFu, composer.ResolveUnderlayDid(ItemType.Armor));
        Assert.Equal(0x060011F3u, composer.ResolveUnderlayDid(ItemType.Clothing));
        Assert.Equal(0x060011D5u, composer.ResolveUnderlayDid(ItemType.Jewelry));
        Assert.Equal(0x060011D4u, composer.ResolveUnderlayDid(ItemType.None));
    }

    [Fact]
    public void ResolveEffectDid_goldenValues_matchDat()
    {
        var datDir = ResolveDatDir();
        if (datDir is null) return;  // dats absent (CI) — skip cleanly

        using var dats = new DatCollection(datDir, DatAccessType.Read);
        var composer = new IconComposer(dats, null!);

        // Golden values (live dat, MasterMap 0x25000000 → effect submap 0x25000009;
        // index = LowestSetBit(UiEffects)+1, fallback 0x21):
        //   Magical      (0x0001) → idx 1  → 0x060011CA
        //   Poisoned     (0x0002) → idx 2  → 0x060011C6
        //   BoostHealth  (0x0004) → idx 3  → 0x06001B05
        //   BoostStamina (0x0010) → idx 5  → 0x06001B06
        //   Nether       (0x1000) → idx 13 (absent) → fallback 0x21 → 0x060011C5
        //   none         (0x0000) → idx 0  (zero)   → fallback 0x21 → 0x060011C5
        Assert.Equal(0x060011CAu, composer.ResolveEffectDid(0x0001u));
        Assert.Equal(0x060011C6u, composer.ResolveEffectDid(0x0002u));
        Assert.Equal(0x06001B05u, composer.ResolveEffectDid(0x0004u));
        Assert.Equal(0x06001B06u, composer.ResolveEffectDid(0x0010u));
        Assert.Equal(0x060011C5u, composer.ResolveEffectDid(0x1000u));
        Assert.Equal(0x060011C5u, composer.ResolveEffectDid(0x0000u));
    }

    [Fact]
    public void TryGetEffectTile_noEffectBlack_magicalTextured()
    {
        var datDir = ResolveDatDir();
        if (datDir is null) return;  // dats absent (CI) — skip cleanly

        using var dats = new DatCollection(datDir, DatAccessType.Read);
        var composer = new IconComposer(dats, null!);

        // effects==0 → 0x21 fallback → 0x060011C5, a 32x32 SOLID-BLACK tile. Copying it
        // per-pixel blackens an icon's pure-white pixels (retail-faithful no-mana scroll edge).
        Assert.True(composer.TryGetEffectTile(0u, out var black));
        Assert.Equal(32, black.Width);
        Assert.Equal(32, black.Height);
        Assert.True(black.Rgba8[0] <= 8 && black.Rgba8[1] <= 8 && black.Rgba8[2] <= 8);

        // Magical (0x1) → 0x060011CA, a TEXTURED blue tile (NOT a flat color) — this is the
        // gradient retail copies per-pixel into the icon's white pixels (the Energy Crystal
        // blue). Assert the tile is non-uniform so a future flat-color regression fails here.
        Assert.True(composer.TryGetEffectTile(0x1u, out var magic));
        bool uniform = true;
        for (int i = 4; i < magic.Width * magic.Height * 4 && uniform; i += 4)
            if (magic.Rgba8[i] != magic.Rgba8[0] || magic.Rgba8[i + 1] != magic.Rgba8[1] ||
                magic.Rgba8[i + 2] != magic.Rgba8[2])
                uniform = false;
        Assert.False(uniform);  // textured → gradient, not flat
    }

    [Fact]
    public void ReplaceWhiteFromSurface_copiesSourcePixelForPureWhiteOpaque()
    {
        // 2x2 dest: [white-opaque, red-opaque, white-transparent, white-opaque]
        var dst = new byte[]
        {
            255,255,255,255,   // pure white opaque  → takes src(0,0)
            255,  0,  0,255,   // red                → untouched
            255,255,255,  0,   // white but alpha 0  → untouched (not 0xFFFFFFFF)
            255,255,255,255,   // pure white opaque  → takes src(1,1)
        };
        // 2x2 src — distinct per-pixel colors (a "gradient").
        var src = new byte[]
        {
            10, 20, 30,255,    // (0,0)
            40, 50, 60,255,    // (1,0)
            70, 80, 90,255,    // (0,1)
            100,110,120,255,   // (1,1)
        };
        IconComposer.ReplaceWhiteFromSurface(dst, 2, 2, src, 2, 2);
        Assert.Equal(new byte[] { 10, 20, 30, 255 }, dst[0..4]);      // copied src(0,0)
        Assert.Equal(new byte[] { 255, 0, 0, 255 }, dst[4..8]);       // untouched (not white)
        Assert.Equal(new byte[] { 255, 255, 255, 0 }, dst[8..12]);    // untouched (transparent)
        Assert.Equal(new byte[] { 100, 110, 120, 255 }, dst[12..16]); // copied src(1,1) — per-pixel
    }

    [Fact]
    public void TwoStageWithEffect_copiesTilePixelBeforeUnderlay()
    {
        // drag = base (white pixel); copy the effect tile's pixel into the white; then over
        // an opaque tawny underlay. The white pixel must become the tile's pixel in the final.
        var baseIcon  = (new byte[] { 255,255,255,255 }, 1, 1);   // 1x1 white opaque
        var drag = IconComposer.Compose(new[] { baseIcon });
        var tile = new byte[] { 0, 0, 255, 255 };                // 1x1 blue tile pixel
        IconComposer.ReplaceWhiteFromSurface(drag.rgba, drag.w, drag.h, tile, 1, 1);
        var underlay = (new byte[] { 105, 70, 50, 255 }, 1, 1);   // tawny opaque
        var final = IconComposer.Compose(new[] { underlay, (drag.rgba, drag.w, drag.h) });
        Assert.Equal(new byte[] { 0, 0, 255, 255 }, final.rgba);  // tile pixel on top
    }
}