using Unity.Burst;
using Unity.Collections;
using Unity.Entities;
using Unity.Mathematics;
using Unity.Transforms;
using Unity.NetCode;
using EE2Clone.Components;
using EE2Clone.Core;

namespace EE2Clone.Systems
{
    /// <summary>
    /// Server-side: processes GatherCommandRpc — assigns a gather target to citizens.
    /// </summary>
    [BurstCompile]
    [WorldSystemFilter(WorldSystemFilterFlags.ServerSimulation)]
    public partial struct GatherCommandSystem : ISystem
    {
        [BurstCompile]
        public void OnUpdate(ref SystemState state)
        {
            var ecb = new EntityCommandBuffer(Allocator.Temp);

            foreach (var (cmd, source, entity) in
                     SystemAPI.Query<RefRO<GatherCommandRpc>, RefRO<ReceiveRpcCommandRequest>>()
                         .WithEntityAccess())
            {
                var citizen = cmd.ValueRO.CitizenEntity;
                var node = cmd.ValueRO.ResourceNodeEntity;

                if (state.EntityManager.Exists(citizen) && state.EntityManager.Exists(node) &&
                    state.EntityManager.HasComponent<CitizenStateComponent>(citizen) &&
                    state.EntityManager.HasComponent<ResourceNode>(node))
                {
                    state.EntityManager.SetComponentData(citizen, new GatherTarget { Target = node });
                    state.EntityManager.SetComponentData(citizen, new CitizenStateComponent { Value = CitizenState.MovingToGather });

                    // Set move target to the resource node's position
                    var nodePos = state.EntityManager.GetComponentData<LocalTransform>(node).Position;
                    state.EntityManager.SetComponentData(citizen, new MoveTarget
                    {
                        Position = nodePos,
                        IsActive = true
                    });
                }

                ecb.DestroyEntity(entity);
            }

            ecb.Playback(state.EntityManager);
            ecb.Dispose();
        }
    }

    /// <summary>
    /// Server-side: citizen gathering state machine.
    /// Handles: MovingToGather → Gathering → MovingToDropoff → Depositing → repeat.
    /// </summary>
    [BurstCompile]
    [WorldSystemFilter(WorldSystemFilterFlags.ServerSimulation)]
    [UpdateAfter(typeof(GatherCommandSystem))]
    public partial struct GatheringSystem : ISystem
    {
        private float _gatherTimer;

        public void OnCreate(ref SystemState state)
        {
            _gatherTimer = 0f;
        }

        [BurstCompile]
        public void OnUpdate(ref SystemState state)
        {
            float dt = SystemAPI.Time.DeltaTime;
            _gatherTimer += dt;
            bool gatherTick = _gatherTimer >= GameConstants.GatherTickInterval;
            if (gatherTick) _gatherTimer -= GameConstants.GatherTickInterval;

            foreach (var (citizenState, gatherTarget, carried, transform, moveTarget, owner) in
                     SystemAPI.Query<RefRW<CitizenStateComponent>, RefRW<GatherTarget>,
                             RefRW<CarriedResource>, RefRO<LocalTransform>, RefRW<MoveTarget>, RefRO<OwnerPlayer>>()
                         .WithAll<CitizenTag>())
            {
                switch (citizenState.ValueRO.Value)
                {
                    case CitizenState.MovingToGather:
                        // Check if arrived (MoveTarget will be deactivated by movement system)
                        if (!moveTarget.ValueRO.IsActive)
                        {
                            citizenState.ValueRW.Value = CitizenState.Gathering;
                        }
                        break;

                    case CitizenState.Gathering:
                        if (!gatherTick) break;

                        var targetEntity = gatherTarget.ValueRO.Target;
                        if (targetEntity == Entity.Null || !state.EntityManager.Exists(targetEntity))
                        {
                            citizenState.ValueRW.Value = CitizenState.Idle;
                            break;
                        }

                        var node = state.EntityManager.GetComponentData<ResourceNode>(targetEntity);
                        if (node.RemainingAmount <= 0)
                        {
                            citizenState.ValueRW.Value = CitizenState.Idle;
                            gatherTarget.ValueRW.Target = Entity.Null;
                            break;
                        }

                        // Gather one unit
                        int gatherAmount = math.min(1, node.RemainingAmount);
                        gatherAmount = math.min(gatherAmount, carried.ValueRO.MaxCarryCapacity - carried.ValueRO.Amount);

                        if (gatherAmount > 0)
                        {
                            node.RemainingAmount -= gatherAmount;
                            state.EntityManager.SetComponentData(targetEntity, node);

                            carried.ValueRW.Amount += gatherAmount;
                            carried.ValueRW.Type = node.Type;
                        }

                        // If carrying capacity full, go to dropoff
                        if (carried.ValueRO.Amount >= carried.ValueRO.MaxCarryCapacity)
                        {
                            citizenState.ValueRW.Value = CitizenState.MovingToDropoff;
                            // TODO: Find nearest dropoff building and set as move target
                            // For now, move back toward origin as placeholder
                            moveTarget.ValueRW = new MoveTarget
                            {
                                Position = float3.zero,
                                IsActive = true
                            };
                        }
                        break;

                    case CitizenState.MovingToDropoff:
                        if (!moveTarget.ValueRO.IsActive)
                        {
                            citizenState.ValueRW.Value = CitizenState.Depositing;
                        }
                        break;

                    case CitizenState.Depositing:
                        // Deposit resources into player economy
                        // TODO: Find PlayerResourcesComponent for this owner and add resources
                        carried.ValueRW.Amount = 0;

                        // Go back to gather if the node still exists
                        if (gatherTarget.ValueRO.Target != Entity.Null &&
                            state.EntityManager.Exists(gatherTarget.ValueRO.Target))
                        {
                            var nodePos = state.EntityManager.GetComponentData<LocalTransform>(gatherTarget.ValueRO.Target).Position;
                            moveTarget.ValueRW = new MoveTarget
                            {
                                Position = nodePos,
                                IsActive = true
                            };
                            citizenState.ValueRW.Value = CitizenState.MovingToGather;
                        }
                        else
                        {
                            citizenState.ValueRW.Value = CitizenState.Idle;
                        }
                        break;
                }
            }
        }
    }
}