using JetBrains.Annotations;
using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.ComponentModel;
using System.Runtime.CompilerServices;

namespace Microsoft.Win32.TaskScheduler
{
	/// <summary>Provides information and control for a collection of folders that contain tasks.</summary>
	public sealed class TaskFolderCollection : ICollection<TaskFolder>, IDisposable, INotifyCollectionChanged, INotifyPropertyChanged
	{
		private const string IndexerName = "Item[]";
		private readonly TaskFolder parent;
		private readonly TaskFolder[] v1FolderList;
		private readonly V2Interop.ITaskFolderCollection v2FolderList;

		internal TaskFolderCollection() => v1FolderList = new TaskFolder[0];

		internal TaskFolderCollection([NotNull] TaskFolder folder, [NotNull] V2Interop.ITaskFolderCollection iCollection)
		{
			parent = folder;
			v2FolderList = iCollection;
		}

		/// <summary>Occurs when a collection changes.</summary>
		public event NotifyCollectionChangedEventHandler CollectionChanged;

		/// <summary>Occurs when a property value changes.</summary>
		public event PropertyChangedEventHandler PropertyChanged;

		/// <summary>Gets the number of items in the collection.</summary>
		public int Count => v2FolderList?.Count ?? v1FolderList.Length;

		/// <summary>Gets a value indicating whether the <see cref="ICollection{T}"/> is read-only.</summary>
		bool ICollection<TaskFolder>.IsReadOnly => false;

		/// <summary>Gets the specified folder from the collection.</summary>
		/// <param name="index">The index of the folder to be retrieved.</param>
		/// <returns>A TaskFolder instance that represents the requested folder.</returns>
		public TaskFolder this[int index]
		{
			get
			{
				if (v2FolderList != null)
					return new TaskFolder(parent.TaskService, v2FolderList[++index]);
				return v1FolderList[index];
			}
		}

		/// <summary>Gets the specified folder from the collection.</summary>
		/// <param name="path">The path of the folder to be retrieved.</param>
		/// <returns>A TaskFolder instance that represents the requested folder.</returns>
		public TaskFolder this[[NotNull] string path]
		{
			get
			{
				try
				{
					if (v2FolderList != null)
						return parent.GetFolder(path);
					if (v1FolderList != null && v1FolderList.Length > 0 && (path == string.Empty || path == "\\"))
						return v1FolderList[0];
				}
				catch { }
				throw new ArgumentException(@"Path not found", nameof(path));
			}
		}

		/// <summary>Adds an item to the <see cref="ICollection{T}"/>.</summary>
		/// <param name="item">The object to add to the <see cref="ICollection{T}"/>.</param>
		/// <exception cref="System.NotImplementedException">
		/// This action is technically unfeasible due to limitations of the underlying library. Use the <see
		/// cref="TaskFolder.CreateFolder(string, string, bool)"/> instead.
		/// </exception>
		public void Add([NotNull] TaskFolder item) => throw new NotImplementedException();

		/// <summary>Removes all items from the <see cref="ICollection{T}"/>.</summary>
		public void Clear()
		{
			if (v2FolderList != null)
			{
				for (var i = v2FolderList.Count; i > 0; i--)
					parent.DeleteFolder(v2FolderList[i].Name, false);
				OnNotifyPropertyChanged(nameof(Count));
				OnNotifyPropertyChanged(IndexerName);
				CollectionChanged?.Invoke(this, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
			}
		}

		/// <summary>Determines whether the <see cref="ICollection{T}"/> contains a specific value.</summary>
		/// <param name="item">The object to locate in the <see cref="ICollection{T}"/>.</param>
		/// <returns>true if <paramref name="item"/> is found in the <see cref="ICollection{T}"/>; otherwise, false.</returns>
		public bool Contains([NotNull] TaskFolder item)
		{
			if (v2FolderList != null)
			{
				for (var i = v2FolderList.Count; i > 0; i--)
					if (string.Equals(item.Path, v2FolderList[i].Path, StringComparison.CurrentCultureIgnoreCase))
						return true;
			}
			else
				return item.Path == "\\";
			return false;
		}

		/// <summary>Copies the elements of the ICollection to an Array, starting at a particular Array index.</summary>
		/// <param name="array">
		/// The one-dimensional Array that is the destination of the elements copied from <see cref="ICollection{T}"/>. The Array must have
		/// zero-based indexing.
		/// </param>
		/// <param name="arrayIndex">The zero-based index in array at which copying begins.</param>
		public void CopyTo(TaskFolder[] array, int arrayIndex)
		{
			if (arrayIndex < 0) throw new ArgumentOutOfRangeException(nameof(arrayIndex));
			if (array == null) throw new ArgumentNullException(nameof(array));
			if (v2FolderList != null)
			{
				if (arrayIndex + Count > array.Length)
					throw new ArgumentException();
				foreach (var f in this)
					array[arrayIndex++] = f;
			}
			else
			{
				if (arrayIndex + v1FolderList.Length > array.Length)
					throw new ArgumentException();
				v1FolderList.CopyTo(array, arrayIndex);
			}
		}

		/// <summary>Releases all resources used by this class.</summary>
		public void Dispose()
		{
			if (v1FolderList != null && v1FolderList.Length > 0)
			{
				v1FolderList[0].Dispose();
				v1FolderList[0] = null;
			}
			if (v2FolderList != null)
				System.Runtime.InteropServices.Marshal.ReleaseComObject(v2FolderList);
		}

		/// <summary>Determines whether the specified folder exists.</summary>
		/// <param name="path">The path of the folder.</param>
		/// <returns>true if folder exists; otherwise, false.</returns>
		public bool Exists([NotNull] string path)
		{
			try
			{
				parent.GetFolder(path);
				return true;
			}
			catch { }
			return false;
		}

		/// <summary>Gets a list of items in a collection.</summary>
		/// <returns>Enumerated list of items in the collection.</returns>
		public IEnumerator<TaskFolder> GetEnumerator()
		{
			if (v2FolderList != null)
				return new System.Runtime.InteropServices.ComEnumerator<TaskFolder, V2Interop.ITaskFolder>(() => v2FolderList.Count, (object o) => v2FolderList[o], o => new TaskFolder(parent.TaskService, o));
			return Array.AsReadOnly(v1FolderList).GetEnumerator();
		}

		/*
		/// <summary>Returns the index of the TaskFolder within the collection.</summary>
		/// <param name="item">TaskFolder to find.</param>
		/// <returns>Index of the TaskFolder; -1 if not found.</returns>
		public int IndexOf(TaskFolder item)
		{
			return IndexOf(item.Path);
		}

		/// <summary>Returns the index of the TaskFolder within the collection.</summary>
		/// <param name="path">Path to find.</param>
		/// <returns>Index of the TaskFolder; -1 if not found.</returns>
		public int IndexOf(string path)
		{
			if (v2FolderList != null)
			{
				for (int i = 0; i < v2FolderList.Count; i++)
				{
					if (v2FolderList[new System.Runtime.InteropServices.VariantWrapper(i)].Path == path)
						return i;
				}
				return -1;
			}
			else
				return (v1FolderList.Length > 0 && (path == string.Empty || path == "\\")) ? 0 : -1;
		}
		*/

		/// <summary>Removes the first occurrence of a specific object from the <see cref="ICollection{T}"/>.</summary>
		/// <param name="item">The object to remove from the <see cref="ICollection{T}"/>.</param>
		/// <returns>
		/// true if <paramref name="item"/> was successfully removed from the <see cref="ICollection{T}"/>; otherwise, false. This method
		/// also returns false if <paramref name="item"/> is not found in the original <see cref="ICollection{T}"/>.
		/// </returns>
		public bool Remove([NotNull] TaskFolder item)
		{
			if (v2FolderList != null)
			{
				for (var i = v2FolderList.Count; i > 0; i--)
				{
					if (string.Equals(item.Path, v2FolderList[i].Path, StringComparison.CurrentCultureIgnoreCase))
					{
						try
						{
							parent.DeleteFolder(v2FolderList[i].Name);
							OnNotifyPropertyChanged(nameof(Count));
							OnNotifyPropertyChanged(IndexerName);
							CollectionChanged?.Invoke(this, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, item, i));
						}
						catch
						{
							return false;
						}
						return true;
					}
				}
			}
			return false;
		}

		System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() => GetEnumerator();

		/// <summary>Called when a property has changed to notify any attached elements.</summary>
		/// <param name="propertyName">Name of the property.</param>
		private void OnNotifyPropertyChanged([CallerMemberName] string propertyName = "") => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
	}
}