using System;
using AcDream.Core.Vfx;
using AcDream.Core.World;

namespace AcDream.App.Rendering.Vfx;

/// <summary>
/// Fires <c>Setup.DefaultScript</c> through <see cref="PhysicsScriptRunner"/>
/// when a server-spawned <see cref="WorldEntity"/> enters the world, so static
/// objects (portals, chimneys, fireplaces, building details) emit their
/// retail-faithful persistent particle effects automatically. Stops the
/// scripts and live emitters when the entity despawns.
///
/// <para>
/// Wires alongside <c>EntitySpawnAdapter</c> in <c>GpuWorldState</c>: the
/// adapter handles meshes + animation state, the activator handles scripts +
/// particles. Both are render-thread-only.
/// </para>
///
/// <para>
/// Retail oracle: <c>play_script_internal(setup.DefaultScript)</c> is what
/// retail's <c>CPhysicsObj</c> invokes at object load (see Phase C.1 plan §C.1
/// and <c>memory/project_sky_pes_port.md</c>). C.1 already shipped the runner;
/// this class adds the missing fire-on-spawn call site.
/// </para>
/// </summary>
public sealed class EntityScriptActivator
{
    private readonly PhysicsScriptRunner _scriptRunner;
    private readonly ParticleHookSink _particleSink;
    private readonly Func<WorldEntity, uint> _defaultScriptResolver;

    /// <param name="scriptRunner">Already-shipped runner from C.1. Owns the
    /// (scriptId, entityId) instance table and schedules hooks at their
    /// <c>StartTime</c> offsets.</param>
    /// <param name="particleSink">Already-shipped hook sink from C.1. The
    /// activator only calls its <see cref="ParticleHookSink.StopAllForEntity"/>
    /// to drop any per-entity emitter handles on despawn.</param>
    /// <param name="defaultScriptResolver">Returns
    /// <c>entity.SourceGfxObjOrSetupId</c>'s <c>Setup.DefaultScript.DataId</c>,
    /// or <c>0</c> on miss / dat throw / missing field. Production lambda hits
    /// <see cref="DatReaderWriter.DatCollection"/>; tests pass a hand-rolled
    /// stub.</param>
    public EntityScriptActivator(
        PhysicsScriptRunner scriptRunner,
        ParticleHookSink particleSink,
        Func<WorldEntity, uint> defaultScriptResolver)
    {
        ArgumentNullException.ThrowIfNull(scriptRunner);
        ArgumentNullException.ThrowIfNull(particleSink);
        ArgumentNullException.ThrowIfNull(defaultScriptResolver);
        _scriptRunner = scriptRunner;
        _particleSink = particleSink;
        _defaultScriptResolver = defaultScriptResolver;
    }

    /// <summary>
    /// Resolve the entity's <c>Setup.DefaultScript</c> and fire it through
    /// the script runner. No-op if the entity has no DefaultScript
    /// (resolver returns 0) or if the entity has no server guid
    /// (atlas-tier entities are out of scope for this activator).
    /// </summary>
    public void OnCreate(WorldEntity entity)
    {
        ArgumentNullException.ThrowIfNull(entity);
        if (entity.ServerGuid == 0) return;

        uint scriptId = _defaultScriptResolver(entity);
        if (scriptId == 0) return;

        // Seed the sink's per-entity rotation so CreateParticleHook.Offset.Origin
        // (in entity-local frame) transforms correctly to world space when the
        // hook fires. Without this, the sink falls through to Quaternion.Identity
        // and the offset gets applied in world axes — visual symptom for portals:
        // swirl oriented along world XYZ instead of the portal's facing, partially
        // buried because the local-Z lift becomes a world-axis offset.
        _particleSink.SetEntityRotation(entity.ServerGuid, entity.Rotation);

        _scriptRunner.Play(scriptId, entity.ServerGuid, entity.Position);
    }

    /// <summary>
    /// Stop every script instance the runner is tracking for this entity, and
    /// kill every live emitter the sink has attributed to it. Idempotent for
    /// unknown guids (both calls no-op).
    /// </summary>
    public void OnRemove(uint serverGuid)
    {
        if (serverGuid == 0) return;
        _scriptRunner.StopAllForEntity(serverGuid);
        _particleSink.StopAllForEntity(serverGuid, fadeOut: false);
    }
}