using ProjectM.Simulation;
using Rukhanka;                  // FastAnimatorParameter, AnimatorParametersAspect, ParameterValue,
                                 // AnimatorControllerParameterComponent, AnimatorControllerParameterIndexTableComponent,
                                 // RukhankaAnimationSystemGroup
using Unity.Burst;
using Unity.Collections;
using Unity.Entities;
using Unity.Mathematics;
using Unity.Transforms;          // LocalTransform

namespace ProjectM.Client
{
    /// <summary>
    /// Client-only animation driver for Husk ENEMIES. OBSERVES replicated state and writes Rukhanka animator
    /// blend params; never mutates the sim (presentation-only). The enemy mirror of the REMOTE path of
    /// <see cref="PlayerAnimationDriveSystem"/>: a Husk is an OWNERLESS INTERPOLATED ghost (server-moved by
    /// EnemyAISystem, position+rotation via stock LocalTransform replication, no KinematicCharacterBody on the
    /// client) — structurally identical to a remote player — so planar velocity is derived from replicated
    /// <see cref="LocalTransform.Position"/> frame-deltas, facing from the replicated <see cref="LocalTransform.Rotation"/>
    /// (the server faces the target each tick), and the run-blend normalizer from the baked-on-both-worlds
    /// <see cref="EnemyStats.MoveSpeed"/>. The attack telegraph rides the already-replicated
    /// <see cref="AttackWindup"/> [GhostField] (non-zero for the ~0.3s wind-up) — no new [GhostField], no server
    /// change (Rukhanka is stripped server-side by ServerStripAnimationSystem), no ghost-hash change. See DR-023.
    /// <para>
    /// Runs in SimulationSystemGroup via [UpdateBefore(RukhankaAnimationSystemGroup)] so params are set before
    /// Rukhanka's same-frame controller eval (no 1-tick lag) — the same documented exception to the
    /// "all juice = PresentationSystemGroup" rule the player driver uses. Observe-only, never in the predicted loop.
    /// </para>
    /// <para>
    /// NOTE: deliberately NOT [RequireMatchingQueriesForUpdate]. Husks despawn far more often than players, so the
    /// per-frame prevPos prune must run EVERY frame (even with zero live Husks) to reclaim the cache entry of a
    /// just-killed Husk — otherwise one NativeParallelHashMap entry would leak per kill.
    /// </para>
    /// </summary>
    [WorldSystemFilter(WorldSystemFilterFlags.LocalSimulation | WorldSystemFilterFlags.ClientSimulation)]
    [UpdateBefore(typeof(RukhankaAnimationSystemGroup))]
    public partial class EnemyAnimationDriveSystem : SystemBase
    {
        // Perfect-hash keys, built once. Names MUST match AC_EnemyTopDown.controller parameter names exactly.
        static readonly FastAnimatorParameter k_MoveX       = new FastAnimatorParameter("MoveX");
        static readonly FastAnimatorParameter k_MoveZ       = new FastAnimatorParameter("MoveZ");
        static readonly FastAnimatorParameter k_Speed       = new FastAnimatorParameter("Speed");
        static readonly FastAnimatorParameter k_IsAttacking = new FastAnimatorParameter("IsAttacking");

        // prevPos cache (per Husk Entity). Pruned every frame (a vanished Husk = a server-authoritative death).
        NativeParallelHashMap<Entity, float3> _prevPos;

        protected override void OnCreate()
        {
            _prevPos = new NativeParallelHashMap<Entity, float3>(64, Allocator.Persistent);
        }

        protected override void OnDestroy()
        {
            if (_prevPos.IsCreated) _prevPos.Dispose();
        }

        protected override void OnUpdate()
        {
            float dt = SystemAPI.Time.DeltaTime; // wall-frame delta is correct for presentation
            if (dt < 1e-5f) dt = 1e-5f;

            var seen = new NativeParallelHashSet<Entity>(64, Allocator.TempJob);
            var job = new EnemyDriveJob
            {
                moveX = k_MoveX, moveZ = k_MoveZ, speed = k_Speed, isAttacking = k_IsAttacking,
                dt = dt,
                prevPos = _prevPos,
                seen = seen,
            };
            Dependency = job.Schedule(Dependency); // .Schedule (not parallel): mutates _prevPos
            // Prune stale entries (despawned Husks) AFTER the job, on the main thread.
            Dependency.Complete();
            PruneCache(seen);
            seen.Dispose();
        }

        void PruneCache(NativeParallelHashSet<Entity> seen)
        {
            using var keys = _prevPos.GetKeyArray(Allocator.Temp);
            for (int i = 0; i < keys.Length; i++)
                if (!seen.Contains(keys[i])) _prevPos.Remove(keys[i]);
        }

        // Husks are ownerless interpolated ghosts: no local/remote split, no Dead enableable. Velocity from
        // LocalTransform.Position delta; facing from LocalTransform.Rotation (server-faced); IsAttacking from the
        // replicated AttackWindup telegraph. The Rukhanka param components match only rigged ghosts.
        [BurstCompile]
        [WithAll(typeof(EnemyTag))]
        partial struct EnemyDriveJob : IJobEntity
        {
            public FastAnimatorParameter moveX, moveZ, speed, isAttacking;
            public float dt;
            public NativeParallelHashMap<Entity, float3> prevPos;
            public NativeParallelHashSet<Entity> seen;

            void Execute(
                Entity e,
                AnimatorControllerParameterIndexTableComponent indexTable,
                DynamicBuffer<AnimatorControllerParameterComponent> parametersArr,
                in LocalTransform xform,
                in EnemyStats stats,
                in AttackWindup windup)
            {
                seen.Add(e);
                float3 cur = xform.Position;
                float3 vel = float3.zero;
                if (prevPos.TryGetValue(e, out var prev))
                    vel = (cur - prev) / dt;
                prevPos[e] = cur;

                float2 facing = AnimParamMath.PlanarForward(xform.Rotation);
                float3 p = AnimParamMath.LocomotionParams(vel, facing, stats.MoveSpeed);
                bool attacking = windup.WindUpUntilTick != 0;

                var a = new AnimatorParametersAspect(parametersArr, indexTable);
                if (a.HasParameter(moveX))       a.SetParameterValue(moveX, p.x);
                if (a.HasParameter(moveZ))       a.SetParameterValue(moveZ, p.y);
                if (a.HasParameter(speed))       a.SetParameterValue(speed, p.z);
                if (a.HasParameter(isAttacking)) a.SetParameterValue(isAttacking, attacking);
            }
        }
    }
}