using UnityEngine;
using Unity.Netcode;
using UnityEngine.InputSystem;
using UnityEngine.EventSystems;
using System.Collections.Generic;

public class BuildManager : NetworkBehaviour
{
    public static BuildManager Instance;

    [System.Serializable]
    public struct TurretData
    {
        public string turretName;
        public GameObject finalPrefab;     // NetworkObject 필수
        public GameObject ghostPrefab;     // 로컬 프리뷰용
        public float buildTime;
    }

    [Header("Grid Settings")]
    public float cellSize = 1f;
    public float tunnelHeight = 3f;
    [SerializeField] private float yOffset = 0.5f; // 터널 중심점 오프셋

    [Header("Prefabs & Layers")]
    [SerializeField] private GameObject constructionSitePrefab;
    [SerializeField] private List<TurretData> turretLibrary = new List<TurretData>();
    [SerializeField] private LayerMask groundLayer;
    [SerializeField] private LayerMask playerLayer;

    private int _selectedTurretIndex = 0;
    private bool _isBuildMode = false;
    private GameObject _ghostInstance;
    private Vector3Int _currentGridPos;
    private PlayerInputActions _inputActions;

    // 데이터 레지스트리 (다른 코드에서 참조)
    private Dictionary<Vector3Int, TunnelNode> _tunnelRegistry = new Dictionary<Vector3Int, TunnelNode>();
    private HashSet<Vector3Int> _occupiedNodes = new HashSet<Vector3Int>();

    void Awake()
    {
        if (Instance == null) Instance = this;
        else Destroy(gameObject);

        _inputActions = new PlayerInputActions();
    }

    public override void OnNetworkSpawn()
    {
        // 최신 Action-based 이벤트 바인딩
        _inputActions.Player.ToggleBuild.performed += ctx => ToggleBuildMode();
        _inputActions.Player.Build.performed += ctx => OnBuildRequested();
        _inputActions.Player.Cancel.performed += ctx => ExitBuildMode();

        // 숫자키 슬롯 선택 (Input Action 에셋 설정에 따라 Select1, Select2... 등 사용)
        _inputActions.Player.Select1.performed += ctx => SelectTurret(0);
        _inputActions.Player.Select2.performed += ctx => SelectTurret(1);
        _inputActions.Player.Select3.performed += ctx => SelectTurret(2);

        _inputActions.Enable();

        // 시작 시 씬에 배치된 터널 자동 등록
        RegisterAllExistingTunnels();
    }

    void Update()
    {
        if (!_isBuildMode || _ghostInstance == null) return;
        UpdateGhostPosition();
    }

    #region Selection & Build Logic

    public void SelectTurret(int index)
    {
        if (index < 0 || index >= turretLibrary.Count) return;

        _selectedTurretIndex = index;
        Debug.Log($"타워 선택: {turretLibrary[_selectedTurretIndex].turretName}");

        if (_isBuildMode)
        {
            if (_ghostInstance != null) Destroy(_ghostInstance);
            _ghostInstance = Instantiate(turretLibrary[_selectedTurretIndex].ghostPrefab);
            _ghostInstance.transform.position = GridToWorld(_currentGridPos);
        }
    }

    private void UpdateGhostPosition()
    {
        Ray ray = Camera.main.ScreenPointToRay(Mouse.current.position.ReadValue());
        int tunnelMask = LayerMask.GetMask("Tunnel");

        if (Physics.Raycast(ray, out RaycastHit hit, Mathf.Infinity, groundLayer | tunnelMask))
        {
            Vector3Int gridPos = WorldToGrid3D(hit.point);

            // 터널 조준 시 해당 터널의 한 칸 아래로 스냅
            if (((1 << hit.collider.gameObject.layer) & tunnelMask) != 0)
            {
                gridPos = WorldToGrid3D(hit.collider.transform.position) + Vector3Int.down;
            }

            _currentGridPos = gridPos;
            _ghostInstance.transform.position = GridToWorld(gridPos);
        }
    }

    private void OnBuildRequested()
    {
        if (!_isBuildMode || EventSystem.current.IsPointerOverGameObject()) return;

        // 서버에 건설 가능 여부 확인 및 생성 요청
        RequestBuildRpc(_selectedTurretIndex, _currentGridPos);

        ExitBuildMode();
    }

    [Rpc(SendTo.Server, InvokePermission = RpcInvokePermission.Everyone)]
    private void RequestBuildRpc(int index, Vector3Int gridPos)
    {
        // 서버 측 중복 점유 확인
        if (_occupiedNodes.Contains(gridPos)) return;

        Vector3 spawnPos = GridToWorld(gridPos);

        // 1. 토대 생성 및 네트워크 스폰
        GameObject siteObj = Instantiate(constructionSitePrefab, spawnPos, Quaternion.identity);
        siteObj.GetComponent<NetworkObject>().Spawn();

        // 2. 토대 데이터 초기화
        ConstructionSite site = siteObj.GetComponent<ConstructionSite>();
        if (site != null)
        {
            site.Initialize(index, gridPos);
        }

        _occupiedNodes.Add(gridPos);
    }

    #endregion

    #region Utility Functions (External References)

    // ConstructionSite에서 프리팹 정보를 가져갈 때 사용
    public TurretData GetTurretData(int index) => turretLibrary[index];

    // TunnelNode가 스폰될 때 자신을 등록하기 위해 사용
    public void RegisterTunnel(Vector3Int pos, TunnelNode node)
    {
        if (!_tunnelRegistry.ContainsKey(pos))
        {
            _tunnelRegistry.Add(pos, node);
            _occupiedNodes.Add(pos); // 건설된 구역으로 마킹
        }
    }

    // TunnelNode가 위아래 노드를 찾기 위해 사용
    public TunnelNode GetTunnelAt(Vector3Int pos) => _tunnelRegistry.GetValueOrDefault(pos);

    // 좌표 변환: 월드 -> 격자 인덱스 (0.5 오프셋 반영)
    public Vector3Int WorldToGrid3D(Vector3 worldPos)
    {
        return new Vector3Int(
            Mathf.FloorToInt(worldPos.x / cellSize),
            Mathf.RoundToInt((worldPos.y - yOffset) / tunnelHeight),
            Mathf.FloorToInt(worldPos.z / cellSize)
        );
    }

    // 좌표 변환: 격자 인덱스 -> 월드 (0.5 오프셋 반영)
    public Vector3 GridToWorld(Vector3Int gridPos)
    {
        return new Vector3(
            gridPos.x * cellSize,
            (gridPos.y * tunnelHeight) + yOffset,
            gridPos.z * cellSize
        );
    }

    // 씬에 미리 배치된 터널들을 한꺼번에 등록
    public void RegisterAllExistingTunnels()
    {
        TunnelNode[] nodes = FindObjectsByType<TunnelNode>(FindObjectsSortMode.None);
        foreach (var node in nodes)
        {
            Vector3Int pos = WorldToGrid3D(node.transform.position);
            RegisterTunnel(pos, node);
        }
    }

    #endregion

    #region Mode Switching

    public void ToggleBuildMode() { if (_isBuildMode) ExitBuildMode(); else EnterBuildMode(); }
    private void EnterBuildMode()
    {
        if (turretLibrary.Count == 0) return;
        _isBuildMode = true;
        _ghostInstance = Instantiate(turretLibrary[_selectedTurretIndex].ghostPrefab);
    }
    private void ExitBuildMode()
    {
        _isBuildMode = false;
        if (_ghostInstance) Destroy(_ghostInstance);
    }

    #endregion

    public override void OnNetworkDespawn() => _inputActions.Disable();
}