using Unity.Burst;
using Unity.Collections;
using Unity.Jobs;
using Unity.Mathematics;

namespace SepCore.Simulation
{
    internal static class EnemyMovementSystem
    {
        // 读写集：R EnemyTransform / EnemyMoveInput / EnemyAttack；W EnemyTransform / EnemyBehavior
        public static JobHandle Schedule(EnemyStore enemies, float deltaTime, float3 playerPosition,
            JobHandle dependency)
        {
            int enemyCount = enemies.Count;
            if (enemyCount == 0)
            {
                return dependency;
            }

            EnemyMovementJob job = new EnemyMovementJob
            {
                Transforms = enemies.Transform.Data.AsArray(),
                MoveInputs = enemies.MoveInput.Data.AsArray(),
                Attacks = enemies.Attack.Data.AsArray(),
                Behaviors = enemies.Behavior.Data.AsArray(),
                DeltaTime = deltaTime,
                PlayerPosition = playerPosition
            };
            return job.Schedule(enemyCount, 64, dependency);
        }
    }

    [BurstCompile]
    internal struct EnemyMovementJob : IJobParallelFor
    {
        public NativeArray<EnemyTransformSim> Transforms;
        [ReadOnly] public NativeArray<EnemyMoveInputSim> MoveInputs;
        [ReadOnly] public NativeArray<EnemyAttackSim> Attacks;
        public NativeArray<EnemyBehaviorSim> Behaviors;
        public float DeltaTime;
        public float3 PlayerPosition;

        public void Execute(int index)
        {
            EnemyMoveInputSim moveInput = MoveInputs[index];
            EnemyAttackSim attack = Attacks[index];
            EnemyTransformSim transform = Transforms[index];

            float attackRange = attack.AttackRange > 0f ? attack.AttackRange : EnemyAttackSim.DefaultAttackRange;
            float attackRangeSqr = attackRange * attackRange;

            float3 currentPosition = transform.Position;
            float3 horizontalPosition = new float3(currentPosition.x, 0f, currentPosition.z);
            float3 toPlayer = PlayerPosition - horizontalPosition;
            float sqrDistance = math.lengthsq(toPlayer);
            bool isInAttackRange = sqrDistance <= attackRangeSqr;
            bool canChase = !isInAttackRange && moveInput.Speed > 0f && sqrDistance > float.Epsilon;

            float3 forward = transform.Forward;
            float3 desiredPosition = currentPosition;
            quaternion rotation = transform.Rotation;

            if (canChase)
            {
                forward = math.normalizesafe(toPlayer, forward);
                desiredPosition = currentPosition + forward * moveInput.Speed * DeltaTime;
                if (math.lengthsq(forward) > float.Epsilon)
                {
                    rotation = quaternion.LookRotationSafe(forward, math.up());
                }
            }

            int nextState;
            if (isInAttackRange)
            {
                nextState = EnemyBehaviorSim.StateInAttackRange;
            }
            else if (canChase)
            {
                nextState = EnemyBehaviorSim.StateChasing;
            }
            else
            {
                nextState = EnemyBehaviorSim.StateIdle;
            }

            transform.Position = desiredPosition;
            transform.Forward = forward;
            transform.Rotation = rotation;
            Transforms[index] = transform;
            Behaviors[index] = new EnemyBehaviorSim { State = nextState };
        }
    }
}