using DatReaderWriter;
using DatReaderWriter.Enums;
using DatReaderWriter.Lib.IO;
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Diagnostics.CodeAnalysis;

namespace AcDream.Content;

/// <summary>
/// THE <see cref="DatCollection"/> → <see cref="IDatReaderWriter"/> adapter,
/// shared by all three consumers: ObjectMeshManager (AcDream.App, via
/// WbMeshAdapter), acdream-bake (AcDream.Bake.BakeRunner), and the pak
/// equivalence suite (AcDream.Content.Tests). MP1b's review found the
/// original App-internal copy had silently forked into three near-identical
/// versions — drift between them is exactly what the live-vs-pak equivalence
/// suite CANNOT detect (both sides would drift together only if they share
/// one implementation), so unification here is load-bearing, not cosmetic.
/// GL-free (DatReaderWriter only), hence Content is the right home
/// (established in MP1a alongside <see cref="IDatReaderWriter"/>).
///
/// <para>History: O-D7 originally introduced this adapter (App-internal)
/// because ObjectMeshManager had 26 <c>_dats.X</c> call sites, letting it
/// stay byte-identical to the WB original while routing all DAT I/O through
/// the single DatCollection.</para>
///
/// <para>Iteration properties return the REAL dat iterations (the App copy
/// hardcoded 0 — a stub nothing read; the bake tool stamps iterations into
/// the pak header from DatCollection directly, and any future consumer of
/// these properties should get truth, so the unification intentionally
/// keeps the real values).</para>
/// </summary>
public sealed class DatCollectionAdapter : IDatReaderWriter {
    private readonly DatCollection _dats;
    private readonly DatDatabaseWrapper _portal;
    private readonly DatDatabaseWrapper _cell;
    private readonly DatDatabaseWrapper _highRes;
    private readonly DatDatabaseWrapper _language;
    private readonly ReadOnlyDictionary<uint, IDatDatabase> _cellRegions;

    public DatCollectionAdapter(DatCollection dats) {
        ArgumentNullException.ThrowIfNull(dats);
        _dats = dats;
        _portal = new DatDatabaseWrapper(dats.Portal);
        _cell = new DatDatabaseWrapper(dats.Cell);
        _highRes = new DatDatabaseWrapper(dats.HighRes);
        _language = new DatDatabaseWrapper(dats.Local);

        // DatCollection has a single Cell, not multiple cell regions.
        // Expose it as region 0 to satisfy callers that iterate CellRegions.
        var regions = new Dictionary<uint, IDatDatabase> { [0u] = _cell };
        _cellRegions = new ReadOnlyDictionary<uint, IDatDatabase>(regions);
    }

    /// <summary>Source directory of the underlying DatCollection.</summary>
    public string SourceDirectory => _dats.Options.DatDirectory ?? string.Empty;

    public IDatDatabase Portal => _portal;
    public ReadOnlyDictionary<uint, IDatDatabase> CellRegions => _cellRegions;
    public IDatDatabase HighRes => _highRes;
    public IDatDatabase Language => _language;

    // RegionFileMap is used by some WB internals but not by any acdream consumer.
    public ReadOnlyDictionary<uint, uint> RegionFileMap =>
        new ReadOnlyDictionary<uint, uint>(new Dictionary<uint, uint>());

    public int PortalIteration => _portal.Iteration;
    public int CellIteration => _cell.Iteration;
    public int HighResIteration => _highRes.Iteration;
    public int LanguageIteration => _language.Iteration;

    public bool TryGetFileBytes(uint regionId, uint fileId, ref byte[] bytes, out int bytesRead) {
        // Route to cell db (the only region we expose)
        return _dats.Cell.TryGetFileBytes(fileId, ref bytes, out bytesRead);
    }

    /// <summary>
    /// Resolves a DAT id to all databases that contain it, along with the DBObjType.
    /// Mirrors DefaultDatReaderWriter.ResolveId — checks each underlying DatDatabase
    /// via DatDatabase.TypeFromId (which reads the type range tables).
    /// </summary>
    public IEnumerable<IDatReaderWriter.IdResolution> ResolveId(uint id) {
        var results = new List<IDatReaderWriter.IdResolution>();

        void CheckDb(DatDatabaseWrapper wrapper) {
            var rawDb = wrapper.RawDatabase;
            if (rawDb.Tree.TryGetFile(id, out _)) {
                var type = rawDb.TypeFromId(id);
                if (type != DBObjType.Unknown)
                    results.Add(new IDatReaderWriter.IdResolution(wrapper, type));
            }
        }

        // Match DefaultDatReaderWriter ordering: HighRes → Portal → Language → Cell
        CheckDb(_highRes);
        CheckDb(_portal);
        CheckDb(_language);
        CheckDb(_cell);

        return results;
    }

    public bool TrySave<T>(T obj, int iteration = 0) where T : IDBObj =>
        throw new NotSupportedException("DatCollectionAdapter is read-only.");

    public bool TrySave<T>(uint regionId, T obj, int iteration = 0) where T : IDBObj =>
        throw new NotSupportedException("DatCollectionAdapter is read-only.");

    public void Dispose() {
        // The underlying DatCollection is owned by the caller — do not dispose it here.
        // Individual wrapper objects hold no unmanaged resources.
    }
}

/// <summary>
/// Wraps a <see cref="DatDatabase"/> as <see cref="IDatDatabase"/>.
/// Mirrors WorldBuilder.Shared.Services.DefaultDatDatabase (taken into our
/// tree in Phase O; moved here from AcDream.App in the MP1b adapter
/// unification).
/// </summary>
public sealed class DatDatabaseWrapper : IDatDatabase {
    private readonly DatDatabase _db;
    private readonly ConcurrentDictionary<(Type, uint), IDBObj> _cache = new();
    private readonly object _lock = new();

    public DatDatabaseWrapper(DatDatabase db) {
        ArgumentNullException.ThrowIfNull(db);
        _db = db;
    }

    /// <summary>Exposes the raw DatDatabase for ResolveId's Tree.TryGetFile + TypeFromId calls.</summary>
    internal DatDatabase RawDatabase => _db;

    public DatDatabase Db => _db;
    public int Iteration => _db.Iteration?.CurrentIteration ?? 0;

    public IEnumerable<uint> GetAllIdsOfType<T>() where T : IDBObj =>
        _db.GetAllIdsOfType<T>();

    public bool TryGet<T>(uint fileId, [MaybeNullWhen(false)] out T value) where T : IDBObj {
        if (_cache.TryGetValue((typeof(T), fileId), out var cached)) {
            value = (T)cached;
            return true;
        }

        lock (_lock) {
            if (_db.TryGet<T>(fileId, out value)) {
                _cache.TryAdd((typeof(T), fileId), value);
                return true;
            }

            // TEMP diagnostic (dat-race investigation 2026-06-09, strip with fix):
            // a miss for an id whose BTree entry EXISTS is always an anomaly —
            // either Unpack returned false or the lookup flickered transiently.
            // Legit not-found probes (e.g. Portal→HighRes fallback) stay silent.
            // Kept through the MP1b unification — the tripwire now covers the
            // bake tool and the equivalence suite too, not just the client.
            if (_db.Tree.TryGetFile(fileId, out _)) {
                Console.WriteLine(
                    $"[dat-miss] {typeof(T).Name} 0x{fileId:X8} entry EXISTS but TryGet failed " +
                    $"(thread={Environment.CurrentManagedThreadId})");
            }
        }

        return false;
    }

    public bool TryGetFileBytes(uint fileId, [MaybeNullWhen(false)] out byte[] value) {
        lock (_lock) {
            return _db.TryGetFileBytes(fileId, out value);
        }
    }

    public bool TryGetFileBytes(uint fileId, ref byte[] bytes, out int bytesRead) {
        lock (_lock) {
            return _db.TryGetFileBytes(fileId, ref bytes, out bytesRead);
        }
    }

    public bool TrySave<T>(T obj, int iteration = 0) where T : IDBObj =>
        throw new NotSupportedException("DatDatabaseWrapper is read-only.");

    public void Dispose() {
        // The underlying DatDatabase is owned by DatCollection — do not dispose here.
    }
}