using System;
using System.Collections.Generic;
using System.IO;
using AcDream.App.UI;
using DatReaderWriter;
using DatReaderWriter.DBObjs;
using DatReaderWriter.Options;
using DatReaderWriter.Types;
using SysEnv = System.Environment;

namespace AcDream.App.Tests.UI;

/// <summary>
/// Pins <c>Font.NumHorizontalBorderPixels</c>/<c>NumVerticalBorderPixels</c>
/// (<c>Font::Serialize @0x00443650</c>) against the real installed DAT, and the
/// <see cref="UiDatFont"/> plumbing that carries them from
/// <see cref="UiDatFont.Load"/> onto <see cref="UiDatFont.BorderX"/>/
/// <see cref="UiDatFont.BorderY"/> — the field this project's font reader
/// dropped entirely before Campaign CH round 4
/// (<c>docs/research/2026-08-10-retail-ui-text-style.md</c> §1.4). A repo-wide
/// grep for <c>BorderPixel</c> returned zero hits before this fix; these tests
/// are the regression guard against that gap reappearing.
///
/// <para>
/// The live-dat tests follow <see cref="AcDream.App.Tests.UI.RetailCursorCatalogTests"/>'s
/// pattern: skip (not fail) when the real dats aren't present, so the suite stays
/// green in environments without the installed game.
/// </para>
/// </summary>
public sealed class UiDatFontBorderPixelTests
{
    // Measured values — docs/research/2026-08-10-retail-ui-text-style.md §1.3.
    [Theory]
    [InlineData(0x40000000u, 4u, 4u)]   // 16px bold serif — chat transcript face
    [InlineData(0x40000001u, 4u, 4u)]   // 18px bold serif — SpewBox face (round 4)
    [InlineData(0x40000002u, 3u, 3u)]   // 14px bold serif
    [InlineData(0x40000025u, 3u, 3u)]   // 11px — the pre-round-4 SpewBox placeholder face
    public void RealDatFont_HasExpectedBorderPixels(uint fontId, uint expectedHorizontal, uint expectedVertical)
    {
        string? datDir = ResolveDatDir();
        if (datDir is null)
            return;

        using var dats = new DatCollection(datDir, DatAccessType.Read);
        Assert.True(dats.TryGet<Font>(fontId, out Font? font), $"Font 0x{fontId:X8} not found");
        Assert.NotNull(font);
        Assert.Equal(expectedHorizontal, font!.NumHorizontalBorderPixels);
        Assert.Equal(expectedVertical, font.NumVerticalBorderPixels);
    }

    [Fact]
    public void RealDatFont_EveryFontWithABackgroundAtlas_HasANonZeroBorder()
    {
        // docs/research/2026-08-10-retail-ui-text-style.md §1.2: "every font that
        // has a background atlas has border >= 3, and every font without one has
        // border == 0" — the data-driven dispatch DrawStringDat's outline pass
        // relies on (background plane vs 8-neighbour fallback) is exactly this
        // correlation. Sweep the documented populated range (0x40000000-0x40000032).
        string? datDir = ResolveDatDir();
        if (datDir is null)
            return;

        using var dats = new DatCollection(datDir, DatAccessType.Read);
        int checkedCount = 0;
        for (uint id = 0x40000000u; id <= 0x40000032u; id++)
        {
            if (!dats.TryGet<Font>(id, out Font? font) || font is null)
                continue;
            checkedCount++;

            bool hasBackground = font.BackgroundSurfaceDataId != 0;
            bool hasBorder = font.NumHorizontalBorderPixels > 0 || font.NumVerticalBorderPixels > 0;
            Assert.True(
                hasBackground == hasBorder,
                $"Font 0x{id:X8}: hasBackground={hasBackground} but hasBorder={hasBorder}");
        }

        Assert.True(checkedCount > 10, "expected the documented font sweep to find multiple populated fonts");
    }

    /// <summary>
    /// Pure plumbing check — no dat, no GL: the <see cref="UiDatFont"/> ctor
    /// stores <paramref name="borderX"/>/<paramref name="borderY"/> verbatim onto
    /// <see cref="UiDatFont.BorderX"/>/<see cref="UiDatFont.BorderY"/>, and existing
    /// callers that omit them (pre-round-4 test fixtures) still default to zero.
    /// </summary>
    [Theory]
    [InlineData(4, 4)]
    [InlineData(3, 3)]
    [InlineData(0, 0)]
    public void Ctor_StoresBorderPixelsVerbatim(int borderX, int borderY)
    {
        var font = new UiDatFont(
            fgTex: 1, fgW: 64, fgH: 64,
            bgTex: 2, bgW: 64, bgH: 64,
            lineHeight: 16f, baselineOffset: 12f,
            glyphs: new Dictionary<char, FontCharDesc>(),
            borderX: borderX, borderY: borderY);

        Assert.Equal(borderX, font.BorderX);
        Assert.Equal(borderY, font.BorderY);
    }

    [Fact]
    public void Ctor_OmittedBorderPixels_DefaultToZero()
    {
        // Pins backward compatibility for the existing UiDatFontTests/SpewBoxControllerTests
        // call sites that construct UiDatFont without borderX/borderY.
        var font = new UiDatFont(
            fgTex: 0, fgW: 0, fgH: 0,
            bgTex: 0, bgW: 0, bgH: 0,
            lineHeight: 16f, baselineOffset: 12f,
            glyphs: new Dictionary<char, FontCharDesc>());

        Assert.Equal(0, font.BorderX);
        Assert.Equal(0, font.BorderY);
    }

    private static string? ResolveDatDir()
    {
        string? fromEnv = SysEnv.GetEnvironmentVariable("ACDREAM_DAT_DIR");
        if (!string.IsNullOrWhiteSpace(fromEnv) && Directory.Exists(fromEnv))
            return fromEnv;

        string defaultDir = Path.Combine(
            SysEnv.GetFolderPath(SysEnv.SpecialFolder.UserProfile),
            "Documents",
            "Asheron's Call");
        return Directory.Exists(defaultDir) ? defaultDir : null;
    }
}