using System.Collections.Concurrent;
using System.Collections.Generic;
using DatReaderWriter;
using DatReaderWriter.DBObjs;

namespace AcDream.Core.Audio;

/// <summary>
/// DatCollection-backed cache of decoded waves + SoundTable lookups.
///
/// <para>
/// Lazy-loads each Wave / SoundTable on first request, decodes Wave PCM
/// data via <see cref="WaveDecoder"/>, and memoizes the result. Safe to
/// call from any thread — the inner dicts are
/// <see cref="ConcurrentDictionary{TKey,TValue}"/>.
/// </para>
///
/// <para>
/// Returns <c>null</c> for waves whose format tag isn't PCM (MP3 / ADPCM
/// fall through silently until a compressed-decoder path is wired up).
/// </para>
/// </summary>
public sealed class DatSoundCache
{
    private readonly DatCollection _dats;
    private readonly ConcurrentDictionary<uint, WaveData?> _waves = new();
    private readonly ConcurrentDictionary<uint, SoundTable?> _tables = new();

    public DatSoundCache(DatCollection dats)
    {
        _dats = dats;
    }

    /// <summary>
    /// Retrieve decoded PCM data for a Wave dat id. Returns null if the
    /// wave is missing, malformed, or uses a currently-unsupported format
    /// (MP3 / ADPCM).
    /// </summary>
    public WaveData? GetWave(uint waveId)
    {
        if (_waves.TryGetValue(waveId, out var cached)) return cached;

        var wave = _dats.Get<Wave>(waveId);
        if (wave is null)
        {
            _waves[waveId] = null;
            return null;
        }

        var decoded = WaveDecoder.Decode(wave.Header, wave.Data);
        _waves[waveId] = decoded;
        return decoded;
    }

    /// <summary>
    /// Retrieve a SoundTable by dat id. Returns null if the table is
    /// missing from the dats.
    /// </summary>
    public SoundTable? GetSoundTable(uint soundTableId)
    {
        if (_tables.TryGetValue(soundTableId, out var cached)) return cached;

        var table = _dats.Get<SoundTable>(soundTableId);
        _tables[soundTableId] = table;
        return table;
    }

    /// <summary>
    /// Total number of waves that have been accessed (hit or miss).
    /// Useful for diagnostic overlays.
    /// </summary>
    public int CachedWaveCount => _waves.Count;

    /// <summary>
    /// Total number of SoundTables that have been accessed.
    /// </summary>
    public int CachedSoundTableCount => _tables.Count;
}