// (c) Copyright Microsoft Corporation.
// This source is subject to the Microsoft Public License (Ms-PL).
// Please see http://go.microsoft.com/fwlink/?LinkID=131993 for details.
// All other rights reserved.

using System.Collections;
using System.Diagnostics;
using Avalonia.Controls;

namespace AtomUI.Desktop.Controls;

internal class DataGridSelectedItemsCollection : IList
{
    #region 公共属性定义

    public bool IsFixedSize => false;
    public bool IsReadOnly => false;
    public int Count => _selectedSlotsTable.IndexCount;
    public bool IsSynchronized => false;
    public object SyncRoot => this;

    #endregion

    internal DataGrid OwningGrid { get; private set; }

    internal List<object> SelectedItemsCache
    {
        get => _selectedItemsCache;

        set
        {
            _selectedItemsCache = value;
            UpdateIndexes();
        }
    }

    private List<object> _oldSelectedItemsCache;
    private IndexToValueTable<bool> _oldSelectedSlotsTable;
    private List<object> _selectedItemsCache;
    private IndexToValueTable<bool> _selectedSlotsTable;

    public DataGridSelectedItemsCollection(DataGrid owningGrid)
    {
        OwningGrid             = owningGrid;
        _oldSelectedItemsCache = new List<object>();
        _oldSelectedSlotsTable = new IndexToValueTable<bool>();
        _selectedItemsCache    = new List<object>();
        _selectedSlotsTable    = new IndexToValueTable<bool>();
    }

    public object? this[int index]
    {
        get
        {
            if (index < 0 || index >= _selectedSlotsTable.IndexCount)
            {
                throw DataGridError.DataGrid.ValueMustBeBetween("index", "Index", 0, true,
                    _selectedSlotsTable.IndexCount, false);
            }
            
            int slot = _selectedSlotsTable.GetNthIndex(index);
            Debug.Assert(slot > -1);
            return OwningGrid.DataConnection.GetDataItem(OwningGrid.RowIndexFromSlot(slot));
        }

        set => throw new NotSupportedException();
    }

    public int Add(object? dataItem)
    {
        if (OwningGrid.SelectionMode == DataGridSelectionMode.Single || OwningGrid.SelectionMode == DataGridSelectionMode.None)
        {
            throw DataGridError.DataGridSelectedItemsCollection.CannotChangeSelectedItemsCollectionInSingleMode();
        }
        
        int itemIndex = OwningGrid.DataConnection.IndexOf(dataItem);
        if (itemIndex == -1)
        {
            throw DataGridError.DataGrid.ItemIsNotContainedInTheItemsSource("dataItem");
        }
        
        Debug.Assert(itemIndex >= 0);
        
        int slot = OwningGrid.SlotFromRowIndex(itemIndex);
        if (_selectedSlotsTable.RangeCount == 0)
        {
            OwningGrid.SelectedItem = dataItem;
        }
        else
        {
            OwningGrid.SetRowSelection(slot, true /*isSelected*/, false /*setAnchorSlot*/);
        }

        return _selectedSlotsTable.IndexOf(slot);
    }

    public void Clear()
    {
        if (OwningGrid.SelectionMode == DataGridSelectionMode.Single || OwningGrid.SelectionMode == DataGridSelectionMode.None)
        {
            throw DataGridError.DataGridSelectedItemsCollection.CannotChangeSelectedItemsCollectionInSingleMode();
        }
        
        if (_selectedSlotsTable.RangeCount > 0)
        {
            // Clearing the selection does not reset the potential current cell.
            if (!OwningGrid.CommitEdit(DataGridEditingUnit.Row, true /*exitEditing*/))
            {
                // Edited value couldn't be committed or aborted
                return;
            }
        
            OwningGrid.ClearRowSelection(true /*resetAnchorSlot*/);
        }
    }

    public bool Contains(object? dataItem)
    {
        int itemIndex = OwningGrid.DataConnection.IndexOf(dataItem);
        if (itemIndex == -1)
        {
            return false;
        }
        
        Debug.Assert(itemIndex >= 0);
        
        return ContainsSlot(OwningGrid.SlotFromRowIndex(itemIndex));
    }

    public int IndexOf(object? dataItem)
    {
        int itemIndex = OwningGrid.DataConnection.IndexOf(dataItem);
        if (itemIndex == -1)
        {
            return -1;
        }
        
        Debug.Assert(itemIndex >= 0);
        int slot = OwningGrid.SlotFromRowIndex(itemIndex);
        return _selectedSlotsTable.IndexOf(slot);
    }

    public void Insert(int index, object? dataItem)
    {
        throw new NotSupportedException();
    }

    public void Remove(object? dataItem)
    {
        if (OwningGrid.SelectionMode == DataGridSelectionMode.Single || OwningGrid.SelectionMode == DataGridSelectionMode.None)
        {
            throw DataGridError.DataGridSelectedItemsCollection.CannotChangeSelectedItemsCollectionInSingleMode();
        }
        
        int itemIndex = OwningGrid.DataConnection.IndexOf(dataItem);
        if (itemIndex == -1)
        {
            return;
        }
        
        Debug.Assert(itemIndex >= 0);
        
        if (itemIndex == OwningGrid.CurrentSlot &&
            !OwningGrid.CommitEdit(DataGridEditingUnit.Row, true /*exitEditing*/))
        {
            // Edited value couldn't be committed or aborted
            return;
        }
        
        OwningGrid.SetRowSelection(OwningGrid.SlotFromRowIndex(itemIndex), false /*isSelected*/,
            false /*setAnchorSlot*/);
    }

    public void RemoveAt(int index)
    {
        if (OwningGrid.SelectionMode == DataGridSelectionMode.Single || OwningGrid.SelectionMode == DataGridSelectionMode.None)
        {
            throw DataGridError.DataGridSelectedItemsCollection.CannotChangeSelectedItemsCollectionInSingleMode();
        }
        
        if (index < 0 || index >= _selectedSlotsTable.IndexCount)
        {
            throw DataGridError.DataGrid.ValueMustBeBetween("index", "Index", 0, true, _selectedSlotsTable.IndexCount,
                false);
        }
        
        int rowIndex = _selectedSlotsTable.GetNthIndex(index);
        Debug.Assert(rowIndex > -1);
        
        if (rowIndex == OwningGrid.CurrentSlot &&
            !OwningGrid.CommitEdit(DataGridEditingUnit.Row, true /*exitEditing*/))
        {
            // Edited value couldn't be committed or aborted
            return;
        }
        
        OwningGrid.SetRowSelection(rowIndex, false /*isSelected*/, false /*setAnchorSlot*/);
    }

    public void CopyTo(System.Array array, int index)
    {
        throw new NotImplementedException();
    }

    public IEnumerator GetEnumerator()
    {
        Debug.Assert(OwningGrid != null);
        Debug.Assert(OwningGrid.DataConnection != null);
        Debug.Assert(_selectedSlotsTable != null);
        
        foreach (int slot in _selectedSlotsTable.GetIndexes())
        {
            int rowIndex = OwningGrid.RowIndexFromSlot(slot);
            Debug.Assert(rowIndex > -1);
            yield return OwningGrid.DataConnection.GetDataItem(rowIndex);
        }
    }

    internal void ClearRows()
    {
        _selectedSlotsTable.Clear();
        _selectedItemsCache.Clear();
    }

    internal bool ContainsSlot(int slot)
    {
        return _selectedSlotsTable.Contains(slot);
    }

    internal bool ContainsAll(int startSlot, int endSlot)
    {
        int itemSlot = OwningGrid.RowGroupHeadersTable.GetNextGap(startSlot - 1);
        while (itemSlot <= endSlot)
        {
            // Skip over the RowGroupHeaderSlots
            int nextRowGroupHeaderSlot = OwningGrid.RowGroupHeadersTable.GetNextIndex(itemSlot);
            int lastItemSlot = nextRowGroupHeaderSlot == -1 ? endSlot : Math.Min(endSlot, nextRowGroupHeaderSlot - 1);
            if (!_selectedSlotsTable.ContainsAll(itemSlot, lastItemSlot))
            {
                return false;
            }
        
            itemSlot = OwningGrid.RowGroupHeadersTable.GetNextGap(lastItemSlot);
        }

        return true;
    }

    // Called when an item is deleted from the ItemsSource as opposed to just being unselected
    internal void Delete(int slot, object? item)
    {
        if (_oldSelectedSlotsTable.Contains(slot))
        {
            OwningGrid.SelectionHasChanged = true;
        }
        
        DeleteSlot(slot);
        if (item != null)
        {
            _selectedItemsCache.Remove(item);
        }
    }

    internal void DeleteSlot(int slot)
    {
        _selectedSlotsTable.RemoveIndex(slot);
        _oldSelectedSlotsTable.RemoveIndex(slot);
    }

    // Returns the inclusive index count between lowerBound and upperBound of all indexes with the given value
    internal int GetIndexCount(int lowerBound, int upperBound)
    {
        return _selectedSlotsTable.GetIndexCount(lowerBound, upperBound, true);
    }

    internal IEnumerable<int> GetIndexes()
    {
        return _selectedSlotsTable.GetIndexes();
    }

    internal IEnumerable<int> GetSlots(int startSlot)
    {
        return _selectedSlotsTable.GetIndexes(startSlot);
    }

    internal SelectionChangedEventArgs GetSelectionChangedEventArgs()
    {
        List<object> addedSelectedItems   = new List<object>();
        List<object> removedSelectedItems = new List<object>();
        
        // Compare the old selected indexes with the current selection to determine which items
        // have been added and removed since the last time this method was called
        foreach (int newSlot in _selectedSlotsTable.GetIndexes())
        {
            object? newItem = OwningGrid.DataConnection.GetDataItem(OwningGrid.RowIndexFromSlot(newSlot));
            Debug.Assert(newItem != null);
            if (_oldSelectedSlotsTable.Contains(newSlot))
            {
                _oldSelectedSlotsTable.RemoveValue(newSlot);
                _oldSelectedItemsCache.Remove(newItem);
            }
            else
            {
                addedSelectedItems.Add(newItem);
            }
        }
        
        foreach (object oldItem in _oldSelectedItemsCache)
        {
            removedSelectedItems.Add(oldItem);
        }
        
        // The current selection becomes the old selection
        _oldSelectedSlotsTable = _selectedSlotsTable.Copy();
        _oldSelectedItemsCache = new List<object>(_selectedItemsCache);
        
        return
            new SelectionChangedEventArgs(DataGrid.SelectionChangedEvent, removedSelectedItems, addedSelectedItems)
            {
                Source = OwningGrid
            };
    }

    internal void InsertIndex(int slot)
    {
        _selectedSlotsTable.InsertIndex(slot);
        _oldSelectedSlotsTable.InsertIndex(slot);
        
        // It's possible that we're inserting an item that was just removed.  If that's the case,
        // and the re-inserted item used to be selected, we want to update the _oldSelectedSlotsTable
        // to include the item's new index within the collection.
        int rowIndex = OwningGrid.RowIndexFromSlot(slot);
        if (rowIndex != -1)
        {
            object? insertedItem = OwningGrid.DataConnection.GetDataItem(rowIndex);
            if (insertedItem != null && _oldSelectedItemsCache.Contains(insertedItem))
            {
                _oldSelectedSlotsTable.AddValue(slot, true);
            }
        }
    }

    internal void SelectSlot(int slot, bool select)
    {
        if (OwningGrid.RowGroupHeadersTable.Contains(slot))
        {
            return;
        }
        
        if (select)
        {
            if (!_selectedSlotsTable.Contains(slot))
            {
                var item = OwningGrid.DataConnection.GetDataItem(OwningGrid.RowIndexFromSlot(slot));
                Debug.Assert(item != null);
                _selectedItemsCache.Add(item);
            }
        
            _selectedSlotsTable.AddValue(slot, true);
        }
        else
        {
            if (_selectedSlotsTable.Contains(slot))
            {
                var item = OwningGrid.DataConnection.GetDataItem(OwningGrid.RowIndexFromSlot(slot));
                Debug.Assert(item != null);
                _selectedItemsCache.Remove(item);
            }
        
            _selectedSlotsTable.RemoveValue(slot);
        }
    }

    internal void SelectSlots(int startSlot, int endSlot, bool select)
    {
        int itemSlot    = OwningGrid.RowGroupHeadersTable.GetNextGap(startSlot - 1);
        int endItemSlot = OwningGrid.RowGroupHeadersTable.GetPreviousGap(endSlot + 1);
        if (select)
        {
            while (itemSlot <= endItemSlot)
            {
                // Add the newly selected item slots by skipping over the RowGroupHeaderSlots
                int nextRowGroupHeaderSlot = OwningGrid.RowGroupHeadersTable.GetNextIndex(itemSlot);
                int lastItemSlot = nextRowGroupHeaderSlot == -1
                    ? endItemSlot
                    : Math.Min(endItemSlot, nextRowGroupHeaderSlot - 1);
                for (int slot = itemSlot; slot <= lastItemSlot; slot++)
                {
                    if (!_selectedSlotsTable.Contains(slot))
                    {
                        var item =
                            OwningGrid.DataConnection.GetDataItem(OwningGrid.RowIndexFromSlot(slot));
                        Debug.Assert(item != null);
                        _selectedItemsCache.Add(item);
                    }
                }
        
                _selectedSlotsTable.AddValues(itemSlot, lastItemSlot - itemSlot + 1, true);
                itemSlot = OwningGrid.RowGroupHeadersTable.GetNextGap(lastItemSlot);
            }
        }
        else
        {
            while (itemSlot <= endItemSlot)
            {
                // Remove the unselected item slots by skipping over the RowGroupHeaderSlots
                int nextRowGroupHeaderSlot = OwningGrid.RowGroupHeadersTable.GetNextIndex(itemSlot);
                int lastItemSlot = nextRowGroupHeaderSlot == -1
                    ? endItemSlot
                    : Math.Min(endItemSlot, nextRowGroupHeaderSlot - 1);
                for (int slot = itemSlot; slot <= lastItemSlot; slot++)
                {
                    if (_selectedSlotsTable.Contains(slot))
                    {
                        var item = OwningGrid.DataConnection.GetDataItem(OwningGrid.RowIndexFromSlot(slot));
                        Debug.Assert(item != null);
                        _selectedItemsCache.Remove(item);
                    }
                }
        
                _selectedSlotsTable.RemoveValues(itemSlot, lastItemSlot - itemSlot + 1);
                itemSlot = OwningGrid.RowGroupHeadersTable.GetNextGap(lastItemSlot);
            }
        }
    }

    internal void UpdateIndexes()
    {
        _oldSelectedSlotsTable.Clear();
        _selectedSlotsTable.Clear();
        
        if (OwningGrid.DataConnection.DataSource == null)
        {
            if (SelectedItemsCache.Count > 0)
            {
                OwningGrid.SelectionHasChanged = true;
                SelectedItemsCache.Clear();
            }
        }
        else
        {
            List<object> tempSelectedItemsCache = new List<object>();
            foreach (object item in _selectedItemsCache)
            {
                int index = OwningGrid.DataConnection.IndexOf(item);
                if (index != -1)
                {
                    tempSelectedItemsCache.Add(item);
                    _selectedSlotsTable.AddValue(OwningGrid.SlotFromRowIndex(index), true);
                }
            }
        
            foreach (object item in _oldSelectedItemsCache)
            {
                int index = OwningGrid.DataConnection.IndexOf(item);
                if (index == -1)
                {
                    OwningGrid.SelectionHasChanged = true;
                }
                else
                {
                    _oldSelectedSlotsTable.AddValue(OwningGrid.SlotFromRowIndex(index), true);
                }
            }
        
            _selectedItemsCache = tempSelectedItemsCache;
        }
    }
}