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

namespace AppleHills.UI.CardSystem
{
    /// <summary>
    /// Manages UI page transitions and maintains a stack of active pages.
    /// Pages are pushed onto a stack for navigation and popped when going back.
    /// </summary>
    public class UIPageController : MonoBehaviour
    {
        private static UIPageController _instance;
        public static UIPageController Instance => _instance;

        private Stack<UIPage> _pageStack = new Stack<UIPage>();
        public UIPage CurrentPage => _pageStack.Count > 0 ? _pageStack.Peek() : null;
        
        // Event fired when the page stack changes
        public event Action<UIPage> OnPageChanged;

        private void Awake()
        {
            if (_instance != null && _instance != this)
            {
                Destroy(gameObject);
                return;
            }

            _instance = this;
        }

        /// <summary>
        /// Pushes a new page onto the stack, hiding the current page and showing the new one.
        /// </summary>
        public void PushPage(UIPage page)
        {
            if (page == null) return;
            
            // Hide current page if there is one
            if (_pageStack.Count > 0)
            {
                UIPage currentPage = _pageStack.Peek();
                currentPage.TransitionOut();
            }
            
            // Push and show new page
            _pageStack.Push(page);
            page.TransitionIn();
            
            OnPageChanged?.Invoke(page);
            Logging.Debug($"[UIPageController] Pushed page: {page.PageName}");
        }

        /// <summary>
        /// Pops the current page from the stack and shows the previous page.
        /// </summary>
        public void PopPage()
        {
            if (_pageStack.Count <= 0) return;
            
            // Hide and pop current page
            UIPage currentPage = _pageStack.Pop();
            currentPage.TransitionOut();
            
            // Show previous page if there is one
            if (_pageStack.Count > 0)
            {
                UIPage previousPage = _pageStack.Peek();
                previousPage.TransitionIn();
                OnPageChanged?.Invoke(previousPage);
                Logging.Debug($"[UIPageController] Popped to previous page: {previousPage.PageName}");
            }
            else
            {
                OnPageChanged?.Invoke(null);
                Logging.Debug("[UIPageController] Popped last page, no pages left in stack");
            }
        }

        /// <summary>
        /// Clears all pages from the stack.
        /// </summary>
        public void ClearStack()
        {
            if (_pageStack.Count <= 0) return;
            
            // Hide current page
            UIPage currentPage = _pageStack.Peek();
            currentPage.TransitionOut();
            
            // Clear stack
            _pageStack.Clear();
            OnPageChanged?.Invoke(null);
            Logging.Debug("[UIPageController] Cleared page stack");
        }

        /// <summary>
        /// Handles back button input and navigates to the previous page if possible.
        /// </summary>
        private void Update()
        {
            if (UnityEngine.Input.GetKeyDown(KeyCode.Escape) && _pageStack.Count > 0)
            {
                _pageStack.Peek().OnBackPressed();
            }
        }
    }
}