using System.Numerics;
using AcDream.Core.Vfx;
using DatReaderWriter.Types;
using Xunit;

namespace AcDream.Core.Tests.Vfx;

public sealed class ParticleHookSinkTests
{
    private static EmitterDesc MakeDesc(uint id, bool attachLocal, int totalParticles = 0)
    {
        return new EmitterDesc
        {
            DatId = id,
            Type = ParticleType.Still,
            Flags = EmitterFlags.Billboard | (attachLocal ? EmitterFlags.AttachLocal : 0),
            EmitterKind = ParticleEmitterKind.BirthratePerSec,
            MaxParticles = 4,
            InitialParticles = 1,
            TotalParticles = totalParticles,
            LifetimeMin = 0.05f, LifetimeMax = 0.05f, Lifespan = 0.05f,
            StartSize = 1f, EndSize = 1f,
            StartAlpha = 1f, EndAlpha = 1f,
            Birthrate = 1000f,    // effectively never re-emit
        };
    }

    [Fact]
    public void UpdateEntityAnchor_WithAttachLocal_MovesParticleToLiveAnchor()
    {
        var registry = new EmitterDescRegistry();
        registry.Register(MakeDesc(0x32000010u, attachLocal: true));
        var sys = new ParticleSystem(registry, new System.Random(42));
        var sink = new ParticleHookSink(sys);

        var hook = new CreateParticleHook
        {
            EmitterInfoId = 0x32000010u,
            EmitterId = 0,
            PartIndex = 0,
            Offset = new Frame(),
        };
        // First spawn at world origin.
        sink.OnHook(entityId: 0xCAFEu, entityWorldPosition: Vector3.Zero, hook);
        sys.Tick(0.01f);

        var live1 = System.Linq.Enumerable.Single(sys.EnumerateLive());
        Assert.Equal(Vector3.Zero, live1.Emitter.Particles[live1.Index].Position);

        // Move the parent to (5, 7, 0) — UpdateEntityAnchor must propagate.
        sink.UpdateEntityAnchor(0xCAFEu, new Vector3(5, 7, 0), Quaternion.Identity);
        sys.Tick(0.01f);

        var live2 = System.Linq.Enumerable.Single(sys.EnumerateLive());
        Assert.Equal(new Vector3(5, 7, 0), live2.Emitter.Particles[live2.Index].Position);
    }

    [Fact]
    public void EmitterDied_PrunesPerEntityHandleTracking()
    {
        // M4: ConcurrentBag<int> couldn't drop entries when a particle
        // emitter expired naturally, so per-entity tracking grew without
        // bound. The sink now subscribes to ParticleSystem.EmitterDied
        // and prunes both the (entity,key) map and the per-entity set.
        var registry = new EmitterDescRegistry();
        registry.Register(MakeDesc(0x32000020u, attachLocal: false, totalParticles: 1));
        var sys = new ParticleSystem(registry, new System.Random(42));
        var sink = new ParticleHookSink(sys);

        var hook = new CreateParticleHook
        {
            EmitterInfoId = 0x32000020u,
            EmitterId = 0xABCDu,    // logical key
            PartIndex = 0,
            Offset = new Frame(),
        };
        sink.OnHook(0xCAFEu, Vector3.Zero, hook);
        Assert.Equal(1, sys.ActiveEmitterCount);

        // TotalParticles=1 cap hit immediately by the InitialParticles spawn,
        // so the emitter Finishes once its single particle expires (0.05s
        // lifetime). After this, EmitterDied has fired and tracking is pruned.
        for (int i = 0; i < 5; i++) sys.Tick(0.05f);
        Assert.Equal(0, sys.ActiveEmitterCount);

        // A fresh spawn for the same (entity, key) succeeds and is the only
        // live emitter — i.e., the previous handle was pruned cleanly.
        sink.OnHook(0xCAFEu, Vector3.Zero, hook);
        Assert.Equal(1, sys.ActiveEmitterCount);

        sink.StopAllForEntity(0xCAFEu, fadeOut: false);
        sys.Tick(0.01f);
        Assert.Equal(0, sys.ActiveEmitterCount);
    }
}