using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using UnityEngine;
using UnityEngine.UI;
using Debug = UnityEngine.Debug;

namespace XUI {
    public class UIStack : UIPool {
        [Tooltip("是否为每个组创建一个物体")]
        public bool CreateGroupGameObject = true;

        public bool CreateCanvasPerObject = true;

        private int CanvasSortOffset = 20;
        private Canvas ThisCanvas;

        [System.NonSerialized]
        public Stack<UIPage> Pages = new Stack<UIPage>();

        protected override void Awake() {
            base.Awake();
            this.ThisCanvas = GetComponent<Canvas>();
        }

        /// <summary>
        /// 叠加一个组
        /// </summary>
        /// <param name="prefabs"></param>
        public UIGroup Overlay(IEnumerable<GameObject> prefabs, params object[] args) {
            if (this.Pages.Count == 0) {
                this.Pages.Push(new UIPage());
            }
            var page = this.Pages.Peek();
            var lastGroup = page.Last;
            if (lastGroup != null) {
                lastGroup.Value.SendBeenOverlay();
            }
            var group = new UIGroup(this, prefabs);

            page.AddLast(group);
            UpdateCanvasOrder();
            group.SendEnterStack(args);
            return group;
        }

        /// <summary>
        /// 覆盖一个组
        /// </summary>
        /// <param name="prefabs"></param>
        /// <param name="destroyBefore"></param>
        public UIGroup Cover(IEnumerable<GameObject> prefabs, bool destroyBefore, params object[] args) {
            //关闭底下的界面
            if (this.Pages.Count > 0) {
                var lastPage = this.Pages.Peek();
                lastPage.SendBeenCover();
                foreach (var @group in lastPage) {
                    foreach (var uiPageItem in @group) {
                        uiPageItem.Instance.SetActive(false);
//						Despawn(uiPageItem.Instance, destroyBefore);//这里不使用回收，为了避免复用之后，退回该界面状态丢失
                    }
                }
            }
            //生成新层
            UIPage newPage = new UIPage();
            this.Pages.Push(newPage);

            var newGroup = new UIGroup(this, prefabs);
            newPage.AddLast(newGroup);
            UpdateCanvasOrder();
            newGroup.SendEnterStack(args);
            return newGroup;
        }

        /// <summary>
        /// 退回到上一界面
        /// </summary>
        public virtual void Back(bool destroy = true) {
            if (this.Pages.Count == 0) {
                UnityEngine.Debug.LogError("没有任何界面可以回退");
                return;
            }
            //回收最前面的界面
            var lastPage = this.Pages.Peek();
            var lastGroup = lastPage.Last.Value;
            lastPage.RemoveLast();
            lastGroup.SendLeaveStack();
            lastGroup.Despawn(destroy);
            //显示上一个界面，如果当前页面还有组，则只需通知，如果当前页面没有组了,则需要把下一页全部显示出来
            if (lastPage.Count == 0) {
                this.Pages.Pop();
                if (this.Pages.Count == 0) {
                    return;
                }
                lastPage = this.Pages.Peek();
                foreach (var g in lastPage) {
                    foreach (var i in g) {
                        i.Instance.SetActive(true);
                    }
//					g.Spawn();
                }
                lastPage.SendDeCover(); //注意：这里要先spawn在发消息
            } else {
                lastPage.Last.Value.SendDeOverlay();
            }
            UpdateCanvasOrder();
        }

        /// <summary>
        /// 移除指定的group
        /// </summary>
        /// <param name="group"></param>
        /// <param name="destroy"></param>
        public void BackSpecified(UIGroup @group, bool destroy = true)
        {
            if (this.Pages.Count == 0) {
                UnityEngine.Debug.LogError("fail");
                return;
            }

            var lastPage = this.Pages.Peek();
            var lastGroup = lastPage.Last.Value;

            var tmpPage = new Stack<UIPage>();
            var tmpStack = new Stack<UIGroup>();
            
            while (lastGroup != group) { //查找，直到指定界面
                tmpStack.Push(lastGroup);
                lastPage.RemoveLast();
                if (lastPage.Count == 0)
                {
                    var tmpPopPage = this.Pages.Pop();
                    tmpPage.Push(tmpPopPage);
                    //将推出的页面重新入栈
                    while (tmpStack.Count > 0)
                    {
                        tmpPopPage.AddLast(tmpStack.Pop());
                    }
                    if (this.Pages.Count == 0) {
                        return;
                    }
                    lastPage = this.Pages.Peek();
                }
                lastGroup = lastPage.Last.Value;
            }

            //回收指定的界面
            lastPage = this.Pages.Peek();
            lastGroup = lastPage.Last.Value;
            lastPage.RemoveLast();
            lastGroup.SendLeaveStack();
            lastGroup.Despawn(destroy);
            
            //将退出的页面重新入栈
            while (tmpStack.Count > 0)
            {
                lastPage.AddLast(tmpStack.Pop());
            }

            while (tmpPage.Count > 0)
            {
                this.Pages.Push(tmpPage.Pop());
            }
            
            UpdateCanvasOrder();
        }

        /// <summary>
        /// 退回到指定界面Group
        /// </summary>
        public void BackTo(UIGroup group, bool destroy = true) {
            if (this.Pages.Count == 0) {
                UnityEngine.Debug.LogError("fail");
                return;
            }
            var lastPage = this.Pages.Peek();
            var lastGroup = lastPage.Last.Value;
            bool decover = false;
            bool deoverlay = false;
            while (lastGroup != group) { //一直回收，直到指定界面
                lastPage.RemoveLast();
                lastGroup.SendLeaveStack();
                lastGroup.Despawn(destroy);
                deoverlay = true;
                if (lastPage.Count == 0) {
                    this.Pages.Pop();
                    if (this.Pages.Count == 0) {
                        return;
                    }
                    lastPage = this.Pages.Peek();
                    decover = true;
                    deoverlay = false;
                }
                lastGroup = lastPage.Last.Value;
            }
            //达到指定页面
            if (decover) { //如果经历过翻页，需要生成它
//				lastGroup.Spawn();
                foreach (var i in lastGroup) {
                    i.Instance.SetActive(true);
                }
                lastPage.SendDeCover(); //注意：这里要先spawn在发消息
            }
            if (deoverlay) { //如果被叠加过，需要发送反叠加消息
                lastGroup.SendDeOverlay();
            }
            UpdateCanvasOrder();
        }

        public void UpdateCanvasOrder() {
            if (!this.CreateCanvasPerObject) {
                return;
            }
            var page = this.Pages.Peek();
            if (page == null) {
                return;
            }
            int i = 0;
            foreach (var group in page) {
                foreach (var item in @group) {
                    if (item.Instance.activeSelf) {
                        item.InstanceCanvas.overrideSorting = true;
                        item.InstanceCanvas.sortingLayerID = this.ThisCanvas.sortingLayerID;
                        item.InstanceCanvas.sortingOrder = i * this.CanvasSortOffset + this.ThisCanvas.sortingOrder;
                        i++;
                    }
                }
            }
        }

        internal UIItem PrefabToUIItem(GameObject prefab, GameObject parent) {
            var ins = Spawn(prefab);
            if (parent != null) {
                ins.transform.SetParent(parent.transform);
            }
            Canvas canvas = null;
            if (this.CreateCanvasPerObject) {
                canvas = ins.GetOrAddComponent<Canvas>();
                ins.GetOrAddComponent<GraphicRaycaster>();
            }
            return new UIItem(prefab, ins, canvas);
        }

        public virtual void OnUIGroupCreated(UIGroup uiGroup) {
        }
    }
}