Connected.Components/Components/DropZone/DropZone.razor.cs

// Copyright (c) MudBlazor 2021
// MudBlazor licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using Connected.Annotations;
using Connected.Utilities;
using Microsoft.AspNetCore.Components;
using Microsoft.JSInterop;

namespace Connected.Components;

public partial class DropZone<T> : UIComponent, IDisposable
{
	private bool _containerIsInitialized = false;
	private bool _canDrop = false;
	private bool _dragInProgress = false;
	private bool _disposedValue = false;
	private Guid _id = Guid.NewGuid();

	private Dictionary<T, int> _indicies = new();

	[Inject] private IJSRuntime JsRuntime { get; set; }

	[CascadingParameter]
	protected DropContainer<T> Container { get; set; }

	/// <summary>
	/// Child content of component
	/// </summary>
	[Parameter]
	[Category(CategoryTypes.DropZone.Appearance)]
	public RenderFragment ChildContent { get; set; }

	/// <summary>
	/// The unique identifier of this drop zone. It is used within transaction to 
	/// </summary>
	[Parameter]
	[Category(CategoryTypes.DropZone.Appearance)]
	public string Identifier { get; set; }

	/// <summary>
	/// The render fragment (template) that should be used to render the items within a drop zone. Overrides value provided by drop container
	/// </summary>
	[Parameter]
	[Category(CategoryTypes.DropZone.Items)]
	public RenderFragment<T> ItemRenderer { get; set; }

	/// <summary>
	/// The method is used to determinate if an item can be dropped within a drop zone. Overrides value provided by drop container
	/// </summary>
	[Parameter]
	[Category(CategoryTypes.DropZone.Items)]
	public Func<T, bool> ItemsSelector { get; set; }

	/// <summary>
	/// The method is used to determinate if an item can be dropped within a drop zone. Overrides value provided by drop container
	/// </summary>
	[Parameter]
	[Category(CategoryTypes.DropZone.DropRules)]
	public Func<T, bool> CanDrop { get; set; }

	/// <summary>
	/// The CSS class(es), that is applied to drop zones that are a valid target for drag and drop transaction. Overrides value provided by drop container
	/// </summary>
	[Parameter]
	[Category(CategoryTypes.DropZone.DropRules)]
	public string CanDropClass { get; set; }

	/// <summary>
	/// The CSS class(es), that is applied to drop zones that are NOT valid target for drag and drop transaction. Overrides value provided by drop container
	/// </summary>
	[Parameter]
	[Category(CategoryTypes.DropZone.DropRules)]
	public string NoDropClass { get; set; }

	/// <summary>
	/// If true, drop classes CanDropClass <see cref="CanDropClass"/>  or NoDropClass <see cref="NoDropClass"/> or applied as soon, as a transaction has started. Overrides value provided by drop container
	/// </summary>
	[Parameter]
	[Category(CategoryTypes.DropZone.DropRules)]
	public bool? ApplyDropClassesOnDragStarted { get; set; }

	/// <summary>
	/// The method is used to determinate if an item should be disabled for dragging. Defaults to allow all items. Overrides value provided by drop container
	/// </summary>
	[Parameter]
	[Category(CategoryTypes.DropZone.Disabled)]
	public Func<T, bool> ItemIsDisabled { get; set; }

	/// <summary>
	/// If a drop item is disabled (determinate by <see cref="ItemIsDisabled"/>). This class is applied to the element. Overrides value provided by drop container
	/// </summary>
	[Parameter]
	[Category(CategoryTypes.DropZone.Disabled)]
	public string DisabledClass { get; set; }

	/// <summary>
	/// An additional class that is applied to the drop zone where a drag operation started
	/// </summary>
	[Parameter]
	[Category(CategoryTypes.DropZone.DraggingClass)]
	public string DraggingClass { get; set; }

	/// <summary>
	/// An additional class that is applied to an drop item, when it is dragged
	/// </summary>
	[Parameter]
	[Category(CategoryTypes.DropZone.DraggingClass)]
	public string ItemDraggingClass { get; set; }

	[Parameter]
	[Category(CategoryTypes.DropZone.Behavior)]
	public bool AllowReorder { get; set; }

	/// <summary>
	/// If true, will only act as a dropable zone and not render any items.
	/// </summary>
	[Parameter]
	[Category(CategoryTypes.DropZone.Behavior)]
	public bool OnlyZone { get; set; }

	#region view helper

	private int GetItemIndex(T item)
	{
		if (_indicies.ContainsKey(item) == false)
		{
			_indicies.Add(item, _indicies.Count);
		}

		return _indicies[item];
	}

	private IEnumerable<T> GetItems()
	{
		Func<T, bool> predicate = (item) => Container.ItemsSelector(item, Identifier ?? string.Empty);
		if (ItemsSelector != null)
		{
			predicate = ItemsSelector;
		}

		return (Container?.Items ?? Array.Empty<T>()).Where(predicate).OrderBy(x => GetItemIndex(x)).ToArray();
	}

	private RenderFragment<T> GetItemTemplate() => ItemRenderer ?? Container?.ItemRenderer;

	private string GetDragginClass()
	{
		if (string.IsNullOrEmpty(DraggingClass) == true)
		{
			return Container?.DraggingClass ?? string.Empty;
		}

		return DraggingClass;
	}

	private string GetItemDraggingClass()
	{
		if (string.IsNullOrEmpty(ItemDraggingClass) == false)
		{
			return ItemDraggingClass;
		}

		return Container?.ItemDraggingClass ?? string.Empty;
	}

	private bool GetApplyDropClassesOnDragStarted() => (ApplyDropClassesOnDragStarted ?? Container?.ApplyDropClassesOnDragStarted) ?? false;

	private bool GetItemDisabledStatus(T item)
	{
		var result = false;
		var predicate = ItemIsDisabled ?? Container?.ItemIsDisabled;
		if (predicate != null)
		{
			result = predicate(item);
		}

		return result;
	}

	protected string Classname =>
		new CssBuilder("mud-drop-zone")
			//.AddClass("mud-drop-zone-drag-block", Container?.TransactionInProgress() == true && Container.GetTransactionOrignZoneIdentiifer() != Identifier)
			.AddClass(CanDropClass ?? Container?.CanDropClass, Container?.TransactionInProgress() == true && Container.GetTransactionOrignZoneIdentiifer() != Identifier && _canDrop == true && (_dragCounter > 0 || GetApplyDropClassesOnDragStarted() == true))
			.AddClass(NoDropClass ?? Container?.NoDropClass, Container?.TransactionInProgress() == true && Container.GetTransactionOrignZoneIdentiifer() != Identifier && _canDrop == false && (_dragCounter > 0 || GetApplyDropClassesOnDragStarted() == true))
			.AddClass(GetDragginClass(), _dragInProgress == true)
			.AddClass(Class)
			.Build();

	protected string PlaceholderClassname =>
		new CssBuilder("border-2 mud-border-primary border-dashed mud-chip-text mud-chip-color-primary pa-4 mud-dropitem-placeholder")
			.AddClass("d-none", AllowReorder == false || (Container?.TransactionInProgress() == false || Container.GetTransactionCurrentZoneIdentiifer() != Identifier))
			.Build();

	#endregion

	#region helper

	private (T, bool) ItemCanBeDropped()
	{
		if (Container == null || Container.TransactionInProgress() == false)
		{
			return (default(T), false);
		}

		var item = Container.GetTransactionItem();

		var result = true;
		if (CanDrop != null)
		{
			result = CanDrop(item);
		}
		else if (Container.CanDrop != null)
		{
			result = Container.CanDrop(item, Identifier);
		}

		return (item, result);
	}

	private bool IsOrign(int index) => Container.IsOrign(index, Identifier);

	#endregion

	#region container event handling

	private void Container_TransactionEnded(object sender, DragAndDropTransactionFinishedEventArgs<T> e)
	{
		_dragCounter = 0;

		if (GetApplyDropClassesOnDragStarted() == true)
		{
			_canDrop = false;
		}

		if (e.Success == true)
		{
			if (e.OriginatedDropzoneIdentifier == Identifier && e.DestinationDropzoneIdentifier != e.OriginatedDropzoneIdentifier)
			{
				_indicies.Remove(e.Item);
			}

			if (e.OriginatedDropzoneIdentifier == Identifier || e.DestinationDropzoneIdentifier == Identifier)
			{
				int index = 0;

				foreach (var item in _indicies.OrderBy(x => x.Value).ToArray())
				{
					_indicies[item.Key] = index++;
				}
			}
		}

		StateHasChanged();
	}

	private void Container_TransactionStarted(object sender, DragAndDropItemTransaction<T> e)
	{
		if (GetApplyDropClassesOnDragStarted() == true)
		{
			var dropResult = ItemCanBeDropped();
			_canDrop = dropResult.Item2;
		}

		StateHasChanged();
	}

	private void Container_RefreshRequested(object sender, EventArgs e)
	{
		_indicies.Clear();
		InvokeAsync(StateHasChanged);
	}

	#endregion

	#region handling event callbacks

	private int _dragCounter = 0;

	private void HandleDragEnter()
	{
		_dragCounter++;

		var (context, isValidZone) = ItemCanBeDropped();
		if (context == null)
		{
			return;
		}

		_canDrop = isValidZone;

		Container.UpdateTransactionZone(Identifier);
	}

	private void HandleDragLeave()
	{
		_dragCounter--;

		var (context, _) = ItemCanBeDropped();
		if (context == null)
		{
			return;
		}
	}

	private async Task HandleDrop()
	{
		var (context, isValidZone) = ItemCanBeDropped();
		if (context == null)
		{
			return;
		}

		_dragCounter = 0;

		if (isValidZone == false)
		{
			await Container.CancelTransaction();
			return;
		}

		if (AllowReorder == true)
		{
			if (Container.HasTransactionIndexChanged() == true)
			{
				var newIndex = Container.GetTransactionIndex() + 1;

				if (Container.IsTransactionOriginatedFromInside(this.Identifier) == true)
				{
					var oldIndex = _indicies[context];

					if (Container.IsItemMovedDownwards() == true)
					{
						newIndex -= 1;

						foreach (var item in _indicies.Where(x => x.Value >= oldIndex + 1 && x.Value <= newIndex).ToArray())
						{
							_indicies[item.Key] -= 1;
						}
					}
					else
					{
						foreach (var item in _indicies.Where(x => x.Value >= newIndex && x.Value < oldIndex).ToArray())
						{
							_indicies[item.Key] += 1;
						}
					}

					_indicies[context] = newIndex;
				}
				else
				{
					foreach (var item in _indicies.Where(x => x.Value >= newIndex).ToArray())
					{
						_indicies[item.Key] = item.Value + 1;
					}

					_indicies.Add(context, newIndex);
				}
			}
		}
		else
		{
			_indicies.Clear();
		}

		await Container.CommitTransaction(Identifier, AllowReorder);
	}

	private void FinishedDragOperation() => _dragInProgress = false;
	private void DragOperationStarted() => _dragInProgress = true;

	#endregion

	#region life cycle

	protected override void OnParametersSet()
	{
		if (Container != null && _containerIsInitialized == false)
		{
			_containerIsInitialized = true;
			Container.TransactionStarted += Container_TransactionStarted;
			Container.TransactionEnded += Container_TransactionEnded;
			Container.RefreshRequested += Container_RefreshRequested;
			Container.TransactionIndexChanged += Container_TransactionIndexChanged;
		}

		base.OnParametersSet();
	}

	private void Container_TransactionIndexChanged(object sender, DragAndDropIndexChangedEventArgs e)
	{
		if (e.ZoneIdentifier != Identifier && e.OldZoneIdentifier != Identifier) { return; }

		StateHasChanged();
	}

	protected override async Task OnAfterRenderAsync(bool firstRender)
	{
		if (firstRender == true)
		{
			await JsRuntime.InvokeVoidAsyncWithErrorHandling("mudDragAndDrop.initDropZone", _id.ToString());
		}

		await base.OnAfterRenderAsync(firstRender);
	}

	protected virtual void Dispose(bool disposing)
	{
		if (!_disposedValue)
		{
			if (disposing)
			{
				if (Container != null)
				{
					Container.TransactionStarted -= Container_TransactionStarted;
					Container.TransactionEnded -= Container_TransactionEnded;
					Container.RefreshRequested -= Container_RefreshRequested;
					Container.TransactionIndexChanged -= Container_TransactionIndexChanged;

				}
			}

			_disposedValue = true;
		}
	}

	public void Dispose()
	{
		Dispose(disposing: true);
		GC.SuppressFinalize(this);
	}

	#endregion
}