using System.Collections.ObjectModel;
using System.Diagnostics.CodeAnalysis;
using AcDream.App.Rendering;
using AcDream.App.Rendering.Gpu;
using AcDream.App.Tests.Rendering;
using AcDream.App.Tests.Rendering.Gpu;
using AcDream.App.UI;
using AcDream.Content;
using AcDream.Core.Items;
using DatReaderWriter;
using DatReaderWriter.Lib.IO;
using DatReaderWriter.Options;
using Xunit;

namespace AcDream.App.Tests.UI;

/// <summary>
/// Hermetic companions to <see cref="RetailMarkupIconResolverInstalledDatTests"/>,
/// split into their own untagged (no <c>Lane=InstalledDat</c>) class so CI's
/// portable filter (<c>.gitea/workflows/ci.yml</c>, <c>Lane!=InstalledDat</c>)
/// actually runs them: unlike the rest of that class, these two never touch a
/// real DAT — the property under test is DAT-probe call COUNT via a
/// bare-bones fake <see cref="IDatReaderWriter"/>/<see cref="IDatDatabase"/>,
/// not decode correctness, so no installed retail DAT directory is required.
/// </summary>
public sealed class RetailMarkupIconResolverMemoizationTests
{
    /// <summary>
    /// A Decal-habit "add the block prefix again" mistake applied to an
    /// already-full DID: <c>0x06000165</c> (Melee Defense's real installed
    /// icon, <c>SampleData.cs:69</c>) plus another <c>0x06000000</c> lands at
    /// <c>0x0C000165</c> — a value almost certainly absent from both Portal
    /// and HighRes.
    /// </summary>
    private const uint DecalHabitDoubleNormalizedId = 0x0C000165u;

    /// <summary>
    /// Residual round finding N4 (perf): <see cref="RetailMarkupIconResolver.ResolveDid"/>
    /// used to probe the DAT (two cache misses + two B-tree lookups under
    /// <c>DatDatabaseWrapper</c>'s database lock) on EVERY call for an
    /// unresolvable id — including once per frame from a draw-time icon
    /// source, forever. These two tests use a bare-bones fake
    /// <see cref="IDatReaderWriter"/>/<see cref="IDatDatabase"/> that counts
    /// <c>TryGet</c> calls directly, rather than the InstalledDat lane
    /// on <see cref="RetailMarkupIconResolverInstalledDatTests"/> — the
    /// property under test is call COUNT, not decode correctness, so no real
    /// DAT files are needed here.
    /// </summary>
    [Fact]
    public void ResolveDid_RepeatedUnresolvableId_ProbesTheDatExactlyOnce()
    {
        var dats = new CountingDatReaderWriter();
        var device = new RecordingGpuDevice();
        using var cache = new TextureCache(device, dats);
        var icons = new IconComposer(dats, cache);
        var objects = new ClientObjectTable();
        var resolver = new RetailMarkupIconResolver(dats, icons, objects);

        (uint tex1, int w1, int h1) = resolver.ResolveDid(DecalHabitDoubleNormalizedId);
        (uint tex2, int w2, int h2) = resolver.ResolveDid(DecalHabitDoubleNormalizedId);
        (uint tex3, int w3, int h3) = resolver.ResolveDid(DecalHabitDoubleNormalizedId);

        Assert.Equal((0u, 0, 0), (tex1, w1, h1));
        Assert.Equal((0u, 0, 0), (tex2, w2, h2));
        Assert.Equal((0u, 0, 0), (tex3, w3, h3));

        // Without memoization this would be 3 (one probe pair per call);
        // with it, the miss is cached after the first resolve.
        Assert.Equal(1, dats.Portal.TryGetCallCount);
        Assert.Equal(1, dats.HighRes.TryGetCallCount);
    }

    [Fact]
    public void ResolveDid_DifferentIds_ProbeIndependently()
    {
        // A per-id cache must not collapse distinct ids into one entry.
        var dats = new CountingDatReaderWriter();
        var device = new RecordingGpuDevice();
        using var cache = new TextureCache(device, dats);
        var icons = new IconComposer(dats, cache);
        var objects = new ClientObjectTable();
        var resolver = new RetailMarkupIconResolver(dats, icons, objects);

        resolver.ResolveDid(0x06000001u);
        resolver.ResolveDid(0x06000002u);
        resolver.ResolveDid(0x06000001u);

        Assert.Equal(2, dats.Portal.TryGetCallCount);
        Assert.Equal(2, dats.HighRes.TryGetCallCount);
    }

    /// <summary>
    /// <see cref="RetailMarkupIconResolver"/>'s MISS cache is bounded
    /// (<c>MaxCachedMisses</c> = 256, FIFO eviction) so a plugin markup
    /// binding a different bogus/unresolvable DID every frame cannot grow it
    /// without bound — unlike HIT entries, which are left uncapped because
    /// that population is bounded by the DAT's own real surface count. Fills
    /// the cache with 256 distinct misses, proves the oldest is STILL served
    /// from cache (no re-probe) right up to the cap, then proves a 257th
    /// distinct miss evicts it — a repeat of the evicted id must re-probe
    /// the DAT (the call count rises again) rather than serve a stale hit.
    /// </summary>
    [Fact]
    public void ResolveDid_TwoHundredFiftySeventhDistinctMiss_EvictsTheFirst()
    {
        var dats = new CountingDatReaderWriter();
        var device = new RecordingGpuDevice();
        using var cache = new TextureCache(device, dats);
        var icons = new IconComposer(dats, cache);
        var objects = new ClientObjectTable();
        var resolver = new RetailMarkupIconResolver(dats, icons, objects);

        // Fill the 256-entry miss cache with distinct ids (starting at 1;
        // did == 0 short-circuits before ever touching the DAT).
        for (uint id = 1; id <= 256; id++)
            resolver.ResolveDid(id);

        Assert.Equal(256, dats.Portal.TryGetCallCount);
        Assert.Equal(256, dats.HighRes.TryGetCallCount);

        // Still cached at the cap: a repeat of the OLDEST id must not re-probe.
        resolver.ResolveDid(1u);
        Assert.Equal(256, dats.Portal.TryGetCallCount);
        Assert.Equal(256, dats.HighRes.TryGetCallCount);

        // A 257th DISTINCT miss pushes the cache over its cap, evicting the
        // oldest entry (id 1).
        resolver.ResolveDid(257u);
        Assert.Equal(257, dats.Portal.TryGetCallCount);
        Assert.Equal(257, dats.HighRes.TryGetCallCount);

        // id 1 was evicted: asking again must re-probe the DAT (the call
        // count rises again), rather than serve the now-gone cache entry.
        resolver.ResolveDid(1u);
        Assert.Equal(258, dats.Portal.TryGetCallCount);
        Assert.Equal(258, dats.HighRes.TryGetCallCount);
    }

    /// <summary>Always misses (<c>TryGet</c> returns <see langword="false"/>),
    /// counting how many times it was asked.</summary>
    private sealed class CountingDatDatabase : IDatDatabase
    {
        public int TryGetCallCount { get; private set; }

        public DatDatabase Db => throw new NotImplementedException();
        public int Iteration => 0;

        public IEnumerable<uint> GetAllIdsOfType<T>() where T : IDBObj =>
            throw new NotImplementedException();

        public bool TryGet<T>(uint fileId, [MaybeNullWhen(false)] out T value)
            where T : IDBObj
        {
            TryGetCallCount++;
            value = default;
            return false;
        }

        public bool TryGetFileBytes(uint fileId, [MaybeNullWhen(false)] out byte[] value) =>
            throw new NotImplementedException();

        public bool TryGetFileBytes(uint fileId, ref byte[] bytes, out int bytesRead) =>
            throw new NotImplementedException();

        public bool TrySave<T>(T obj, int iteration = 0) where T : IDBObj =>
            throw new NotImplementedException();

        public void Dispose() { }
    }

    /// <summary>
    /// Only <see cref="Portal"/>/<see cref="HighRes"/> are exercised by
    /// <see cref="RetailMarkupIconResolver.ResolveDid"/>'s miss path — every
    /// other member throws if a future change starts touching it, so this
    /// fake fails loudly rather than silently returning nonsense.
    /// </summary>
    private sealed class CountingDatReaderWriter : IDatReaderWriter
    {
        public CountingDatDatabase Portal { get; } = new();
        public CountingDatDatabase HighRes { get; } = new();

        IDatDatabase IDatReaderWriter.Portal => Portal;
        IDatDatabase IDatReaderWriter.HighRes => HighRes;

        public string SourceDirectory => string.Empty;
        public IDatDatabase Cell => throw new NotImplementedException();
        public ReadOnlyDictionary<uint, IDatDatabase> CellRegions => throw new NotImplementedException();
        public IDatDatabase Language => throw new NotImplementedException();
        public IDatDatabase Local => throw new NotImplementedException();
        public ReadOnlyDictionary<uint, uint> RegionFileMap => throw new NotImplementedException();
        public int PortalIteration => 0;
        public int CellIteration => 0;
        public int HighResIteration => 0;
        public int LanguageIteration => 0;

        public bool TryGetFileBytes(uint regionId, uint fileId, ref byte[] bytes, out int bytesRead) =>
            throw new NotImplementedException();

        public IEnumerable<uint> GetAllIdsOfType<T>() where T : IDBObj =>
            throw new NotImplementedException();

        public bool TrySave<T>(T obj, int iteration = 0) where T : IDBObj =>
            throw new NotImplementedException();

        public bool TrySave<T>(uint regionId, T obj, int iteration = 0) where T : IDBObj =>
            throw new NotImplementedException();

        public IEnumerable<IDatReaderWriter.IdResolution> ResolveId(uint id) =>
            throw new NotImplementedException();

        [return: MaybeNull]
        public T Get<T>(uint fileId) where T : IDBObj =>
            throw new NotImplementedException();

        public bool TryGet<T>(uint fileId, [MaybeNullWhen(false)] out T value)
            where T : IDBObj =>
            throw new NotImplementedException();

        public void Dispose() { }
    }
}