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");
        static readonly FastAnimatorParameter k_IsDead      = new FastAnimatorParameter("IsDead"); // B3: the controller's Death state existed but was never driven
        static readonly FastAnimatorParameter k_IsHit       = new FastAnimatorParameter("IsHit");      // 07-21 hit-react (G5): pulsed off replicated Health-drop edges
        static readonly FastAnimatorParameter k_IsHitHeavy  = new FastAnimatorParameter("IsHitHeavy"); // heavy tier -> HitStagger (aligns with the server's B2 poise break)

        /// <summary>07-21: per-Husk anim cache -- position (velocity derivation), Health (the hit-react damage
        /// edge), and the active flinch pulse. Pruned every frame (a vanished Husk = a server-authoritative death).</summary>
        struct EnemyAnimCache
        {
            public float3 Pos;
            public float Hp;
            public float ReactUntil; // wall-clock ElapsedTime the flinch pulse ends (0 = none)
            public bool Heavy;       // this pulse is the stagger tier
        }

        NativeParallelHashMap<Entity, EnemyAnimCache> _prevPos;

        protected override void OnCreate()
        {
            _prevPos = new NativeParallelHashMap<Entity, EnemyAnimCache>(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, isDead = k_IsDead,
                isHit = k_IsHit, isHitHeavy = k_IsHitHeavy,
                // 07-21 hit-react knobs (read main-thread, passed by value -- never FeelConfig inside Burst)
                el = (float)SystemAPI.Time.ElapsedTime,
                reactSeconds = math.max(0f, FeelConfig.HitReactSeconds),
                staggerSeconds = math.max(0f, FeelConfig.HitStaggerSeconds),
                staggerDamage = math.max(1f, FeelConfig.HitReactStaggerDamage),
                dt = dt,
                prevPos = _prevPos,
                seen = seen,
                isLunging = SystemAPI.GetComponentLookup<IsLunging>(true),

            };
            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, isDead, isHit, isHitHeavy;
            public float el, reactSeconds, staggerSeconds, staggerDamage; // 07-21 hit-react (reactSeconds 0 = off)
            [Unity.Collections.ReadOnly] public ComponentLookup<IsLunging> isLunging; // A7: a lunge has no AttackWindup; OR it in so the boss/Charger attack anim plays during the committed lunge

            public float dt;
            public NativeParallelHashMap<Entity, EnemyAnimCache> prevPos;
            public NativeParallelHashSet<Entity> seen;

            void Execute(
                Entity e,
                AnimatorControllerParameterIndexTableComponent indexTable,
                DynamicBuffer<AnimatorControllerParameterComponent> parametersArr,
                in LocalTransform xform,
                in EnemyStats stats,
                in AttackWindup windup,
                in Health health)
            {
                seen.Add(e);
                float3 cur = xform.Position;
                float3 vel = float3.zero;
                var cache = new EnemyAnimCache { Pos = cur, Hp = health.Current };
                if (prevPos.TryGetValue(e, out var prev))
                {
                    vel = (cur - prev.Pos) / dt;
                    cache.ReactUntil = prev.ReactUntil;
                    cache.Heavy = prev.Heavy;
                    // 07-21 hit-react (G5): a replicated Health DROP on a living Husk = the flinch edge. The heavy
                    // tier (>= staggerDamage, e.g. the finisher) plays the stagger -- aligned with the server's B2
                    // poise break, so the anim never claims an interrupt the sim didn't make.
                    float drop = prev.Hp - health.Current;
                    if (drop > 0.01f && health.Current > 0f && reactSeconds > 0f)
                    {
                        cache.Heavy = drop >= staggerDamage;
                        cache.ReactUntil = el + (cache.Heavy ? staggerSeconds : reactSeconds);
                    }
                }
                prevPos[e] = cache;

                float2 facing = AnimParamMath.PlanarForward(xform.Rotation);
                float3 p = AnimParamMath.LocomotionParams(vel, facing, stats.MoveSpeed);
                bool attacking = windup.WindUpUntilTick != 0 || (isLunging.HasComponent(e) && isLunging.IsComponentEnabled(e)); // A7: the committed lunge (which zeroes AttackWindup) still animates as an attack

                // B3: the corpse window — Health.Current is replicated, so <=0 IS the death read. A corpse
                // plays the Death state and nothing else (no jog, no frozen attack).
                bool dead = health.Current <= 0f;
                if (dead) { p = float3.zero; attacking = false; }

                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);
                if (a.HasParameter(isDead))      a.SetParameterValue(isDead, dead);
                // 07-21 hit-react pulse (a corpse never flinches; the controller adds the windup-honesty gate).
                bool hitActive = !dead && cache.ReactUntil > 0f && el < cache.ReactUntil;
                if (a.HasParameter(isHit))       a.SetParameterValue(isHit, hitActive);
                if (a.HasParameter(isHitHeavy))  a.SetParameterValue(isHitHeavy, hitActive && cache.Heavy);
            }
        }
    }
}