using System;
using System.Collections.Concurrent;
using System.Numerics;
using DatReaderWriter;
using DatParticleEmitter = DatReaderWriter.DBObjs.ParticleEmitter;
using DatEmitterType = DatReaderWriter.Enums.EmitterType;
using DatParticleType = DatReaderWriter.Enums.ParticleType;

namespace AcDream.Core.Vfx;

/// <summary>
/// Resolves retail <c>ParticleEmitterInfo</c> dat records
/// (<c>0x32xxxxxx</c>) into acdream runtime descriptors.
/// </summary>
public sealed class EmitterDescRegistry
{
    private const uint FallbackEmitterId = 0xFFFFFFFFu;

    private readonly Func<uint, DatParticleEmitter?>? _resolver;
    private readonly ConcurrentDictionary<uint, EmitterDesc> _byId = new();

    public EmitterDescRegistry()
        : this((Func<uint, DatParticleEmitter?>?)null)
    {
    }

    public EmitterDescRegistry(DatCollection dats)
        : this(id => SafeGet(dats, id))
    {
    }

    public EmitterDescRegistry(Func<uint, DatParticleEmitter?>? resolver)
    {
        _resolver = resolver;
        Register(BuildFallback());
    }

    public void Register(EmitterDesc desc)
    {
        ArgumentNullException.ThrowIfNull(desc);
        _byId[desc.DatId] = desc;
    }

    public EmitterDesc Get(uint emitterId)
    {
        if (_byId.TryGetValue(emitterId, out var desc))
            return desc;

        if (_resolver is not null)
        {
            var dat = _resolver(emitterId);
            if (dat is not null)
            {
                desc = FromDat(emitterId, dat);
                _byId[emitterId] = desc;
                return desc;
            }
        }

        if (_byId.TryGetValue(FallbackEmitterId, out var fallback))
            return fallback;

        throw new InvalidOperationException("No default emitter registered in registry.");
    }

    public int Count => _byId.Count;

    public static EmitterDesc FromDat(uint emitterId, DatParticleEmitter dat)
    {
        ArgumentNullException.ThrowIfNull(dat);

        float birthrate = MathF.Max(0f, (float)dat.Birthrate);
        float lifespan = MathF.Max(0f, (float)dat.Lifespan);
        float lifespanRand = MathF.Abs((float)dat.LifespanRand);
        float lifetimeMin = MathF.Max(0f, lifespan - lifespanRand);
        float lifetimeMax = MathF.Max(lifetimeMin, lifespan + lifespanRand);

        // ParticleEmitterInfo has no "additive" field; retail derives blend
        // state from the particle GfxObj surface material.
        var flags = EmitterFlags.Billboard | EmitterFlags.FaceCamera;
        if (dat.IsParentLocal)
            flags |= EmitterFlags.AttachLocal;

        // ParticleEmitterInfo stores translucency, not opacity. Retail feeds
        // StartTrans/FinalTrans to PhysicsPart::SetTranslucency; the GL path
        // uses the complement as source alpha.
        float startOpacity = 1f - Math.Clamp((float)dat.StartTrans, 0f, 1f);
        float endOpacity = 1f - Math.Clamp((float)dat.FinalTrans, 0f, 1f);

        return new EmitterDesc
        {
            DatId = emitterId,
            Type = MapParticleType(dat.ParticleType),
            EmitterKind = MapEmitterKind(dat.EmitterType),
            Flags = flags,
            GfxObjId = dat.GfxObjId.DataId,
            HwGfxObjId = dat.HwGfxObjId.DataId,
            Birthrate = birthrate,
            EmitRate = dat.EmitterType == DatEmitterType.BirthratePerSec && birthrate > 0f
                ? 1f / birthrate
                : 0f,
            MaxParticles = Math.Max(1, dat.MaxParticles),
            InitialParticles = Math.Max(0, dat.InitialParticles),
            TotalParticles = Math.Max(0, dat.TotalParticles),
            TotalDuration = MathF.Max(0f, (float)dat.TotalSeconds),
            Lifespan = lifespan,
            LifespanRand = lifespanRand,
            LifetimeMin = lifetimeMin,
            LifetimeMax = lifetimeMax,
            OffsetDir = dat.OffsetDir,
            MinOffset = dat.MinOffset,
            MaxOffset = dat.MaxOffset,
            SpawnDiskRadius = dat.MaxOffset,
            InitialVelocity = dat.A,
            Gravity = dat.B,
            A = dat.A,
            MinA = dat.MinA,
            MaxA = dat.MaxA,
            B = dat.B,
            MinB = dat.MinB,
            MaxB = dat.MaxB,
            C = dat.C,
            MinC = dat.MinC,
            MaxC = dat.MaxC,
            StartSize = dat.StartScale,
            EndSize = dat.FinalScale,
            ScaleRand = dat.ScaleRand,
            StartAlpha = startOpacity,
            EndAlpha = endOpacity,
            TransRand = dat.TransRand,
        };
    }

    private static DatParticleEmitter? SafeGet(DatCollection dats, uint id)
    {
        if (dats is null)
            return null;
        try
        {
            return dats.Get<DatParticleEmitter>(id);
        }
        catch
        {
            return null;
        }
    }

    private static EmitterDesc BuildFallback() => new()
    {
        DatId = FallbackEmitterId,
        Type = ParticleType.LocalVelocity,
        EmitterKind = ParticleEmitterKind.BirthratePerSec,
        Flags = EmitterFlags.Billboard | EmitterFlags.FaceCamera,
        Birthrate = 0.1f,
        EmitRate = 10f,
        MaxParticles = 32,
        LifetimeMin = 0.6f,
        LifetimeMax = 1.2f,
        Lifespan = 0.9f,
        LifespanRand = 0.3f,
        OffsetDir = new Vector3(0, 0, 1),
        MinOffset = 0f,
        MaxOffset = 0.1f,
        SpawnDiskRadius = 0.1f,
        InitialVelocity = new Vector3(0, 0, 0.5f),
        VelocityJitter = 0.3f,
        A = new Vector3(0, 0, 0.5f),
        MinA = 1f,
        MaxA = 1f,
        B = Vector3.Zero,
        C = Vector3.Zero,
        StartSize = 0.25f,
        EndSize = 0.6f,
        StartAlpha = 0.85f,
        EndAlpha = 0f,
    };

    private static ParticleEmitterKind MapEmitterKind(DatEmitterType type) => type switch
    {
        DatEmitterType.BirthratePerSec => ParticleEmitterKind.BirthratePerSec,
        DatEmitterType.BirthratePerMeter => ParticleEmitterKind.BirthratePerMeter,
        _ => ParticleEmitterKind.Unknown,
    };

    private static ParticleType MapParticleType(DatParticleType type) => type switch
    {
        DatParticleType.Still => ParticleType.Still,
        DatParticleType.LocalVelocity => ParticleType.LocalVelocity,
        DatParticleType.ParabolicLVGA => ParticleType.ParabolicLVGA,
        DatParticleType.ParabolicLVGAGR => ParticleType.ParabolicLVGAGR,
        DatParticleType.Swarm => ParticleType.Swarm,
        DatParticleType.Explode => ParticleType.Explode,
        DatParticleType.Implode => ParticleType.Implode,
        DatParticleType.ParabolicLVLA => ParticleType.ParabolicLVLA,
        DatParticleType.ParabolicLVLALR => ParticleType.ParabolicLVLALR,
        DatParticleType.ParabolicGVGA => ParticleType.ParabolicGVGA,
        DatParticleType.ParabolicGVGAGR => ParticleType.ParabolicGVGAGR,
        DatParticleType.GlobalVelocity => ParticleType.GlobalVelocity,
        _ => ParticleType.Unknown,
    };
}