using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Runtime.InteropServices.ComTypes;

namespace Vanara.InteropServices
{
	/// <summary>
	/// Helper class to create an advised COM sink. When this class is constructed, the source is queried for an
	/// <see cref="IConnectionPointContainer"/> reference.
	/// </summary>
	public class ComConnectionPoint : IDisposable
	{
		private readonly List<(IConnectionPoint, int)> connectionPoints = new List<(IConnectionPoint, int)>();

		/// <summary>Initializes a new instance of the <see cref="ComConnectionPoint"/> class.</summary>
		/// <param name="source">The COM object from which to query the <see cref="IConnectionPointContainer"/> reference.</param>
		/// <param name="sink">The object which implements the COM interface or interfaces signaled by an event.</param>
		/// <param name="interfaces">The interfaces supported by <paramref name="source"/> that support events.</param>
		public ComConnectionPoint(object source, object sink, params Type[] interfaces)
		{
			if (source is null) throw new ArgumentNullException(nameof(source));
			if (source is not IConnectionPointContainer connectionPointContainer)
				throw new ArgumentException("The source object must be COM object that supports the IConnectionPointContainer interface.", nameof(source));
			Sink = sink ?? this;
			if (interfaces == null) interfaces = GetComInterfaces(Sink);
			if (interfaces.Length < 1) throw new ArgumentOutOfRangeException(nameof(interfaces));

			// Start the event sink
			foreach (var i in interfaces)
			{
				var comappEventsInterfaceId = i.GUID;
				connectionPointContainer.FindConnectionPoint(ref comappEventsInterfaceId, out var connectionPoint);
				connectionPoint.Advise(Sink, out var cookie);
				connectionPoints.Add((connectionPoint, cookie));
			}
		}

		/// <summary>Initializes a new instance of the <see cref="ComConnectionPoint"/> class.</summary>
		/// <param name="source">The COM object from which to query the <see cref="IConnectionPointContainer"/> reference.</param>
		/// <param name="sink">
		/// The object which implements the COM interface or interfaces signaled by an event. All COM interfaces implemented by this object
		/// will be used to setup the connection points. If this object implements COM interfaces that cannot be used as connection points,
		/// use the constructor that allows for supported interfaces to be specified.
		/// </param>
		public ComConnectionPoint(object source, object sink) : this(source, sink, null) { }

		/// <summary>Gets the sink.</summary>
		/// <value>The sink.</value>
		public object Sink { get; private set; }

		private static Type[] GetComInterfaces(object sink) => 
			sink?.GetType().GetInterfaces().
			Where(i => i.GetCustomAttributes(true).Any(a => a.GetType() == typeof(ComImportAttribute) || a.GetType() == typeof(InterfaceTypeAttribute))).
			ToArray();

		/// <summary>Releases unmanaged and - optionally - managed resources.</summary>
		public void Dispose()
		{
			foreach (var pair in connectionPoints)
			{
				//unhook the event sink
				pair.Item1.Unadvise(pair.Item2);
			}
			connectionPoints.Clear();
			Sink = null;
		}
	}
}