using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;
using static SimpleInventorySystem.InventorySystem;

namespace SimpleInventorySystem
{
    [RequireComponent(typeof (GridLayoutGroup))]
    public class GridUI : MonoBehaviour
    {
        private LayoutElement layoutElement;
        private GridLayoutGroup gridLayout;
        public GameObject CellPrefab;
        public bool generateCells; // will autopopulate grid
        public SlotUI[] slots;
        [HideInInspector] public ItemUI associatedItemUI;
        [SerializeField] public Size gridSize;

        internal void ChangeGridLayoutSize(int rows, int columns)
        {
            gridSize.Width = rows;
            gridSize.Height = columns;
        }

        private Cell[,] cells;
        [HideInInspector] public GameObject testItem;
        [HideInInspector] public GameObject[] testItems;
        [HideInInspector] public List<ItemUI> itemsOnGrid;
        private Size cellSize;
        public Size CellSize { get { return cellSize; } }
        private Vector2 nextAvailableCellCoords;

        private void Awake()
        {
            if(cells == null)
            {
                SetUpCellsArray();
            }
        }
        private bool cellsInitialized;

        public void SetAssociatedItemUI(ItemUI itemUI)
        {
            associatedItemUI = itemUI;
        }

        public bool IsAssociatedItem(ItemUI itemUI)
        {
            return associatedItemUI == itemUI;
        }

        void SetUpCellsArray()
        {
            gridLayout = GetComponent<GridLayoutGroup>();

            if (gridSize.Width == 0 && gridLayout.constraint == GridLayoutGroup.Constraint.FixedColumnCount)
            {
                gridSize.Width = gridLayout.constraintCount;
            }
            else if (gridSize.Height == 0 && gridLayout.constraint == GridLayoutGroup.Constraint.FixedRowCount)
            {
                gridSize.Height = gridLayout.constraintCount;
            }

            if (gridSize.Width == 0 || gridSize.Height == 0)
            {
                Debug.LogError("GridUI needs a defined width and height, or width or height needs to be constrained through the GridLayoutGroup component.");
            }

            //Debug.Log("GridUI: GridSize: " + gridSize.Width + ", " + gridSize.Height);

            cells = new Cell[gridSize.Height, gridSize.Width];
        }

        void GenerateCells()
        {
            SetUpCellsArray();

            if (CellPrefab != null)
            {
                /*foreach(Transform child in transform)
                {
                    // TODO: make sure to unequip items currently in the grid
                    Destroy(child);
                }*/

                //Debug.Log(gridSize.Width + ", " + gridSize.Height);


                for (int y = 0; y < gridSize.Height; y++)
                {
                    for (int x = 0; x < gridSize.Width; x++)
                    {
                        // TODO: load inventory from data here upon intialization
                        GameObject cell = GameObject.Instantiate(CellPrefab, this.transform);
                        cell.transform.localScale = new Vector3(1f, 1f, 1f);
                        SlotUI slot = cell.GetComponentInChildren<SlotUI>();
                        // WARNING: All cell prefabs must now have a slot
                        //if (cell.GetComponentInChildren<SlotUI>() != null)
                        //{
                        slot.grid = this;
                        slot.AllowedItemTags = new List<ItemTags>();
                        slot.AllowedItemTags.Add(ItemTags.Any);
                        cells[y, x] = new Cell(x, y, slot, false);
                        //cells[y, x].GetSlot().SetCell(cells[y, x]);
                        //Debug.Log("Foo: " + (slot == null));
                        //Debug.Log("Bar: " + (cells[y, x].GetSlot().cell == null));
                        //cells[y, x].inUse = false;
                        //}
                    }
                }
                cellsInitialized = true;

                /*if (cells != null && cells[0, 0] != null && testItem != null)
                {
                    Debug.Log("Add item");
                    Cell cell = cells[0, 0];
                    GameObject item = Instantiate(testItem);
                    cell.slot.DropOntoSlot(item);
                    //item.transform.SetParent(.gameObject.transform);
                }*/

                /*if (testItems != null)
                {
                    int i = 0;
                    int x = 0, y = 0;
                    int lootCount = 1;
                    foreach (GameObject testItem in testItems)
                    {
                        bool dropped = false;
                        GameObject item = null;
                        try
                        {
                            do
                            {
                                x = i % gridSize.Width;
                                y = i / gridSize.Width;

                                item = Instantiate(testItem);
                                item.name = item.name + " " + lootCount;
                                dropped = cells[y, x].slot.DropOntoSlot(item);

                                if (!dropped)
                                {
                                    Destroy(item);
                                }
                                else
                                {
                                    lootCount++;
                                    item.transform.localScale = new Vector3(1, 1, 1);
                                }
                                i++;
                            } while (!dropped);
                        }
                        catch (IndexOutOfRangeException err)
                        {
                            Debug.LogWarning("GridUI: " + x + ", " + y);
                        }
                        if (item == null)
                        {
                            Debug.LogWarning("Could not add all test items");
                            break;
                        }

                        // TODO: Make sure this works as expected
                        nextAvailableCellCoords = new Vector2(i % gridSize.Width, i / gridSize.Width);
                    }
                }*/
            }
        }

        public IEnumerator PopulateItemsWithNewInventory(List<ItemUI> items)
        {
            //Debug.Log("Populating Inventory");

            yield return new WaitForFixedUpdate();

            //InitializeCells();

            int i = 0;
            int x = 0, y = 0;
            foreach (ItemUI item in items)
            {
                //Debug.Log(item.itemName);
                bool dropped = false;
                try
                {
                    do
                    {
                        x = i % gridSize.Width;
                        y = i / gridSize.Width;
                        dropped = cells[y, x].slot.DropOntoSlot(item.gameObject);

                        if (!dropped)
                        {
                            //Destroy(item);
                        }
                        else
                        {
                            item.transform.localScale = new Vector3(1, 1, 1);
                        }
                        i++;
                    } while (!dropped);
                }
                catch (IndexOutOfRangeException err)
                {
                    Debug.LogWarning("GridUI: " + x + ", " + y);
                }
                if (item == null)
                {
                    Debug.LogWarning("Could not add all test items");
                    break;
                }

                // TODO: Make sure this works as expected
                nextAvailableCellCoords = new Vector2(i % gridSize.Width, i / gridSize.Width);
            }
        }

        public bool DropItemOnGrid(GameObject item)
        {
            if (item != null)
            {
                int i = 0;
                int limit = 100000;
                int x = (int)nextAvailableCellCoords.x, y = (int)nextAvailableCellCoords.y;
                bool dropped = false;
                try
                {
                    do
                    {
                        x = i % gridSize.Width;
                        y = i / gridSize.Width;

                        if (cells == null)
                        {
                            if (generateCells)
                            {
                                GenerateCells();
                            }
                            else if (!cellsInitialized)
                            {
                                SetUpCellsArray();
                                LocateSlotsForCells();
                            }
                        }
                        //Debug.Log($"GridUI: Is Slot null? {cells[y, x] == null}");

                        dropped = cells[y, x].slot.DropOntoSlot(item);

                        if (!dropped)
                        {
                        }
                        else
                        {
                            item.transform.localScale = new Vector3(1, 1, 1);
                            // TODO: Make sure this works as expected
                            nextAvailableCellCoords = new Vector2(i % gridSize.Width, i / gridSize.Width);
                            return true;
                        }
                        i++;
                        if(i == limit)
                        {
                            //Debug.Log("Limit reached");
                        }
                    } while (!dropped && i < cells.Length && i < limit); // TODO: perhaps add a check to make sure i has not exceeded the total number of slots
                }
                catch (IndexOutOfRangeException err)
                {
                    Debug.LogWarning("GridUI: " + x + ", " + y);
                    return false;
                }

                return false;
            }
            else
            {
                //Debug.LogWarning("GridUI: Could not add item to grid.");
                return false;
            }
        }

        public void AddItemToGrid(ItemUI item)
        {
            if (!itemsOnGrid.Contains(item))
            {
                itemsOnGrid.Add(item.GetComponent<ItemUI>());
            }
        }

        public bool ContainsItemFromGrid(ItemUI item)
        {
            return itemsOnGrid.Contains(item);
        }

        public void RemoveItemFromGrid(ItemUI item)
        {
            if (itemsOnGrid.Contains(item))
            {
                itemsOnGrid.Remove(item.GetComponent<ItemUI>());
            }
        }

        // Start is called before the first frame update
        void Start()
        {
            InitializeCells();
        }

        void InitializeCells()
        {
            if (!generateCells)
            {
                if (!cellsInitialized)
                {
                    LocateSlotsForCells();
                }
            }
            else
            {
                GenerateCells();
            }
        }

        void LocateSlotsForCells()
        {
            //if (slots != null)
            for (int i = 0; i < gridLayout.transform.childCount; i++)
            {
                int x = i % gridSize.Width;
                int y = (i - x) / gridSize.Width;

                if (cells[y, x] != null)
                {
                    continue;
                }

                Transform child = gridLayout.transform.GetChild(i);
                SlotUI slot = child.GetComponentInChildren<SlotUI>();
                if (slot != null)
                {
                    cells[y, x] = new Cell(x, y, slot, true);
                    slot.SetCell(cells[y, x]);
                    slot.grid = this;

                    if (slot.width > 1 || slot.height > 1)
                    {
                        for (int j = 0; j < slot.height; j++)
                        {
                            for (int k = 1; k < slot.width; k++)
                            {
                                cells[y + j, x + k] = new Cell(x + k, y + j, slot, false);
                            }
                        }
                    }

                    //Debug.Log("START: " + (slot.cell == null));
                }
                else
                {
                    cells[y, x] = null;// new Cell(null, false, false); // Setting null so that we can reserve memory
                }
            }
            cellsInitialized = true;
        }

        internal void HideSlotsOfItem(ItemUI itemDrop)
        {
            if(itemDrop != null)
            {
                itemDrop.HideSlots();
            }
        }

        public bool CanMoveInCells(ItemUI item, SlotUI slot, List<Cell> occupiedCells = null)
        {
            if (slot == null || slot.cell == null || (slot.cell.inUse && (slot.GetItemUI() != null && !slot.GetItemUI().Stackable)) || (associatedItemUI == item))
            {
                //Debug.Log("GridUI: CanMoveInCells(): " + slot.gameObject.name + ": A" + (slot.cell == null));
                return false;
            }
            else if (slot.IsSingleCellSlot() && item.IsSingleCellItem() && (!slot.cell.inUse || (slot.StackItemsOnSlot && slot.GetItemUI().name == item.name)))
            {
                //Debug.Log("GridUI: CanMoveInCells(): " + slot.gameObject.name + ": B");
                //if (!slot.cell.inUse)
                return true;
                //else
                //    return false;
            }
            else if  (cells != null)
            {
                List<Cell> oCells = new List<Cell>();
                if(occupiedCells != null)
                {
                    oCells = occupiedCells;
                }
                Size size = item.SizeAfterOrientation();
                // for (int h = 0; h < slot.height; h++){
                //     for (int w = 0; w < slot.width; w++)
                for (int h = 0; h < size.Height; h++)
                {
                    for (int w = 0; w < size.Width; w++)
                    {
                        if(slot.cell.Y + h >= gridSize.Height || slot.cell.X + w >= gridSize.Width)
                        {
                            //Debug.Log("GridUI: CanMoveInCells(): " + slot.gameObject.name + ": D");
                            return false;
                        }
                        Cell cell = cells[slot.cell.Y + h, slot.cell.X + w];
                        if (cell != null && cell.inUse)
                        {
                            //Debug.Log(cell != null);
                            //Debug.Log(cell.inUse);
                            //Debug.Log("GridUI: CanMoveInCells(): " + slot.gameObject.name + ": E");
                            return false;
                        }
                        oCells.Add(cell);
                    }
                }

                //Debug.Log(occupiedCells.Count);
                //Debug.Log("GridUI: CanMoveInCells(): " + slot.gameObject.name + ": F");

                //Debug.Log(oCells.Count);

                return true;
            }
            //Debug.Log("GridUI: CanMoveInCells(): " + slot.gameObject.name + ": G");


            return false;
        }

        // Update is called once per frame
        void Update()
        {

        }

        public class Cell
        {
            protected int x, y;
            public int X { get { return x; } }
            public int Y { get { return y; } }
            public SlotUI slot;
            public bool ownsSlot;
            public bool inUse;
            public ItemUI item;

            public Cell(int x, int y, SlotUI slot, bool ownsSlot)
            {
                this.x = x;
                this.y = y;
                this.slot = slot;
                slot.SetCell(this);
                inUse = false;
                this.ownsSlot = ownsSlot;
            }

            public bool HasSlot()
            {
                return slot != null;
            }

            public SlotUI GetSlot()
            {
                return slot;
            }
        }
    }
}