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

namespace UI.PanelStack
{
    public class UIPanelStack : MonoBehaviour
    {
        public static UIPanelStack Instance { get; private set; }

        private readonly List<Entry> stack = new List<Entry>();
        private Func<bool> escapeOpenHandler;
        [SerializeField] private bool debugLogs = true;

        private sealed class Entry
        {
            public UIPanelKind kind;
            public GameObject root;
            public Action closeAction;
        }

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

        public void Push(UIPanelKind kind, GameObject root, Action closeAction)
        {
            if (root == null) { return; }

            Remove(root);

            stack.Add(new Entry
            {
                kind = kind,
                root = root,
                closeAction = closeAction
            });
            if (debugLogs) Debug.Log($"[UIPanelStack] Push kind={kind} root={root.name} count={stack.Count}");
        }

        public bool Remove(GameObject root)
        {
            if (root == null) { return false; }

            for (int i = stack.Count - 1; i >= 0; i--)
            {
                if (stack[i].root == root)
                {
                    stack.RemoveAt(i);
                    if (debugLogs) Debug.Log($"[UIPanelStack] Remove root={root.name} count={stack.Count}");
                    return true;
                }
            }

            return false;
        }

        public bool CloseTop()
        {
            CleanupInactive();

            if (stack.Count == 0) { return false; }

            Entry top = stack[stack.Count - 1];
            stack.RemoveAt(stack.Count - 1);

            if (top.root == null) { return false; }

            if (top.closeAction != null)
            {
                if (debugLogs) Debug.Log($"[UIPanelStack] CloseTop via action kind={top.kind} root={top.root.name} remain={stack.Count}");
                top.closeAction.Invoke();
                return true;
            }

            if (debugLogs) Debug.Log($"[UIPanelStack] CloseTop via SetActive(false) kind={top.kind} root={top.root.name} remain={stack.Count}");
            top.root.SetActive(false);
            return true;
        }

        public void SetEscapeOpenHandler(Func<bool> handler)
        {
            escapeOpenHandler = handler;
            if (debugLogs) Debug.Log($"[UIPanelStack] SetEscapeOpenHandler set={(handler!=null)}");
        }

        public void ClearEscapeOpenHandler(Func<bool> handler)
        {
            if (handler == null) { return; }
            if (escapeOpenHandler == handler)
            {
                escapeOpenHandler = null;
            }
        }

        public bool TryOpenOnEscapeWhenEmpty()
        {
            if (escapeOpenHandler == null) { return false; }
            bool result = escapeOpenHandler.Invoke();
            if (debugLogs) Debug.Log($"[UIPanelStack] TryOpenOnEscapeWhenEmpty result={result}");
            return result;
        }

        public bool IsAnyOpen()
        {
            CleanupInactive();
            return stack.Count > 0;
        }

        private void CleanupInactive()
        {
            for (int i = stack.Count - 1; i >= 0; i--)
            {
                if (stack[i].root == null || !stack[i].root.activeInHierarchy)
                {
                    stack.RemoveAt(i);
                }
            }
        }
    }
}