using System.Collections.Generic;
using UnityEngine;
using BaseGames.Core;
using BaseGames.Core.Events;

namespace BaseGames.UI
{
    [DefaultExecutionOrder(+50)]
    public class UIManager : MonoBehaviour
    {
        [Header("Canvas Roots")]
        [SerializeField] private GameObject _hudRoot;
        [SerializeField] private GameObject _pauseMenuRoot;
        [SerializeField] private GameObject _deathScreenRoot;
        [SerializeField] private GameObject _settingsRoot;
        [SerializeField] private GameObject _mapRoot;
        [SerializeField] private GameObject _shopRoot;

        [Header("Event Channels")]
        [SerializeField] private GameStateEventChannelSO _onGameStateChanged;
        [SerializeField] private VoidEventChannelSO      _onPauseRequested;
        [SerializeField] private VoidEventChannelSO      _onFastTravelOpen;
        [SerializeField] private StringEventChannelSO    _onShopOpen;
        [SerializeField] private VoidEventChannelSO      _onMapOpen;

        private readonly Stack<GameObject> _panelStack = new();

        private void OnEnable()
        {
            if (_onGameStateChanged != null) _onGameStateChanged.OnEventRaised += HandleGameStateChanged;
            if (_onPauseRequested   != null) _onPauseRequested.OnEventRaised   += TogglePause;
            if (_onFastTravelOpen   != null) _onFastTravelOpen.OnEventRaised   += OpenMap;
            if (_onShopOpen         != null) _onShopOpen.OnEventRaised         += OpenShop;
            if (_onMapOpen          != null) _onMapOpen.OnEventRaised          += OpenMap;
        }

        private void OnDisable()
        {
            if (_onGameStateChanged != null) _onGameStateChanged.OnEventRaised -= HandleGameStateChanged;
            if (_onPauseRequested   != null) _onPauseRequested.OnEventRaised   -= TogglePause;
            if (_onFastTravelOpen   != null) _onFastTravelOpen.OnEventRaised   -= OpenMap;
            if (_onShopOpen         != null) _onShopOpen.OnEventRaised         -= OpenShop;
            if (_onMapOpen          != null) _onMapOpen.OnEventRaised          -= OpenMap;
        }

        private void HandleGameStateChanged(GameStateId state)
        {
            // GameStateId 是 struct，用 if/else 而非 switch
            bool showHud = state == GameStates.Gameplay || state == GameStates.BossFight;
            if (_hudRoot != null) _hudRoot.SetActive(showHud);

            if (state == GameStates.Dead)
            {
                if (_deathScreenRoot != null) _deathScreenRoot.SetActive(true);
            }
            else if (state == GameStates.Cutscene)
            {
                if (_hudRoot != null) _hudRoot.SetActive(false);
            }
        }

        public void OpenPanel(GameObject panel)
        {
            if (panel == null) return;
            if (_panelStack.Count > 0) _panelStack.Peek().SetActive(false);
            panel.SetActive(true);
            _panelStack.Push(panel);
        }

        public void CloseTopPanel()
        {
            if (_panelStack.Count == 0) return;
            _panelStack.Pop().SetActive(false);
            if (_panelStack.Count > 0) _panelStack.Peek().SetActive(true);
        }

        private void TogglePause()          => OpenPanel(_pauseMenuRoot);
        private void OpenShop(string _)     => OpenPanel(_shopRoot);
        private void OpenMap()              => OpenPanel(_mapRoot);
    }
}