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.NetCode;             // GhostOwnerIsLocal
using Unity.Transforms;          // LocalTransform
using Unity.CharacterController; // KinematicCharacterBody

namespace ProjectM.Client
{
    /// <summary>
    /// Client-only animation driver. OBSERVES authoritative/replicated state and writes Rukhanka animator
    /// blend params; never mutates the sim (presentation-only). Runs once/frame in the client/local world,
    /// BEFORE Rukhanka evaluates the controller this frame (same-frame, no 1-tick lag). NOTE: this lands in
    /// SimulationSystemGroup (via UpdateBefore the Rukhanka group, which itself has no UpdateInGroup), a
    /// deliberate, documented exception to the project's "all juice = PresentationSystemGroup" rule -- the
    /// params MUST be set before Rukhanka's same-frame controller eval (see DR-022).
    ///
    /// Two paths:
    ///   LOCAL  (owner-predicted, GhostOwnerIsLocal ENABLED): realized CC RelativeVelocity (wall-aware).
    ///   REMOTE (interpolated, GhostOwnerIsLocal DISABLED): KinematicCharacterBody is NOT a [GhostField] and
    ///          the CC processor is owner-only, so RelativeVelocity stays baked-zero on remotes -> derive
    ///          planar velocity from replicated LocalTransform.Position deltas. PlayerFacing.Direction is a
    ///          [GhostField] (valid on remotes); EffectiveCharacterStats.MoveSpeed is derived locally each
    ///          tick by StatRecomputeSystem (present on remotes). Cache prevPos per Entity, prune each frame.
    /// </summary>
    [WorldSystemFilter(WorldSystemFilterFlags.LocalSimulation | WorldSystemFilterFlags.ClientSimulation)]
    [UpdateBefore(typeof(RukhankaAnimationSystemGroup))]
    [RequireMatchingQueriesForUpdate]
    public partial class PlayerAnimationDriveSystem : SystemBase
    {
        // Perfect-hash keys, built once (managed string ctor). Names MUST match AC_PlayerTopDown.controller
        // parameter names exactly. Immutable readonly hashes -> domain-reload safe.
        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_IsDead = new FastAnimatorParameter("IsDead");

        // Remote prevPos cache (per ghost Entity). Pruned every frame (a vanished remote = a despawn).
        NativeParallelHashMap<Entity, float3> _prevPos;

        protected override void OnCreate()
        {
            _prevPos = new NativeParallelHashMap<Entity, float3>(16, 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;

            // --- LOCAL owner (CC velocity) ---
            var localJob = new LocalDriveJob
            {
                moveX = k_MoveX, moveZ = k_MoveZ, speed = k_Speed, isDead = k_IsDead,
            };
            Dependency = localJob.ScheduleParallel(Dependency);

            // --- REMOTE players (position-delta). Single-threaded write to the shared prevPos cache. ---
            var seen = new NativeParallelHashSet<Entity>(16, Allocator.TempJob);
            var remoteJob = new RemoteDriveJob
            {
                moveX = k_MoveX, moveZ = k_MoveZ, speed = k_Speed, isDead = k_IsDead,
                dt = dt,
                prevPos = _prevPos,
                seen = seen,
            };
            Dependency = remoteJob.Schedule(Dependency); // .Schedule (not parallel): mutates _prevPos
            // Prune stale entries (despawned remotes) 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]);
        }

        // LOCAL: GhostOwnerIsLocal ENABLED -> exactly the owned player. WithPresent<Dead> so alive
        // (Dead-disabled) players are visited. NOTE: GhostOwnerIsLocal as a WithAll filter respects the
        // enable bit; do NOT take it as an `in` parameter (that matches on presence -> drives remotes too).
        [BurstCompile]
        [WithAll(typeof(GhostOwnerIsLocal))]
        [WithPresent(typeof(Dead))]
        partial struct LocalDriveJob : IJobEntity
        {
            public FastAnimatorParameter moveX, moveZ, speed, isDead;

            void Execute(
                AnimatorControllerParameterIndexTableComponent indexTable,
                DynamicBuffer<AnimatorControllerParameterComponent> parametersArr,
                in PlayerFacing facing,
                in EffectiveCharacterStats stats,
                in KinematicCharacterBody body,
                EnabledRefRO<Dead> dead)
            {
                var a = new AnimatorParametersAspect(parametersArr, indexTable);
                float3 p = AnimParamMath.LocomotionParams(body.RelativeVelocity, facing.Direction, stats.MoveSpeed);
                Write(ref a, p, dead.ValueRO, moveX, moveZ, speed, isDead);
            }
        }

        // REMOTE: GhostOwnerIsLocal DISABLED -> interpolated teammates. Velocity from LocalTransform.Position
        // delta (KinematicCharacterBody.RelativeVelocity is baked-zero on remotes, non-GhostField, owner-only).
        [BurstCompile]
        [WithDisabled(typeof(GhostOwnerIsLocal))]
        [WithPresent(typeof(Dead))]
        partial struct RemoteDriveJob : IJobEntity
        {
            public FastAnimatorParameter moveX, moveZ, speed, isDead;
            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 PlayerFacing facing,
                in EffectiveCharacterStats stats,
                EnabledRefRO<Dead> dead)
            {
                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;

                var a = new AnimatorParametersAspect(parametersArr, indexTable);
                float3 p = AnimParamMath.LocomotionParams(vel, facing.Direction, stats.MoveSpeed);
                Write(ref a, p, dead.ValueRO, moveX, moveZ, speed, isDead);
            }
        }

        // ParameterValue has implicit float/bool operators -> SetParameterValue(key, float) / (key, bool) compile.
        static void Write(ref AnimatorParametersAspect a, float3 p, bool isDeadVal,
                          FastAnimatorParameter moveX, FastAnimatorParameter moveZ,
                          FastAnimatorParameter speed, FastAnimatorParameter isDead)
        {
            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(isDead)) a.SetParameterValue(isDead, isDeadVal);
        }
    }
}