// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the Apache 2.0 License.
// See the LICENSE file in the project root for more information. 

using System.Collections.Generic;

namespace System.Reactive
{
    /// <summary>
    /// Represents a .NET event invocation consisting of the weakly typed object that raised the event and the data that was generated by the event.
    /// </summary>
    /// <typeparam name="TEventArgs">The type of the event data generated by the event.</typeparam>
    public class EventPattern<TEventArgs> : EventPattern<object, TEventArgs>
#if !NO_EVENTARGS_CONSTRAINT
        where TEventArgs : EventArgs
#endif
    {
        /// <summary>
        /// Creates a new data representation instance of a .NET event invocation with the given sender and event data.
        /// </summary>
        /// <param name="sender">The sender object that raised the event.</param>
        /// <param name="e">The event data that was generated by the event.</param>
        public EventPattern(object sender, TEventArgs e)
            : base(sender, e)
        {
        }
    }

    /// <summary>
    /// Represents a .NET event invocation consisting of the strongly typed object that raised the event and the data that was generated by the event.
    /// </summary>
    /// <typeparam name="TSender">The type of the sender that raised the event.</typeparam>
    /// <typeparam name="TEventArgs">The type of the event data generated by the event.</typeparam>
    public class EventPattern<TSender, TEventArgs> : IEquatable<EventPattern<TSender, TEventArgs>>, IEventPattern<TSender, TEventArgs>
#if !NO_EVENTARGS_CONSTRAINT
        where TEventArgs : EventArgs
#endif
    {
        /// <summary>
        /// Creates a new data representation instance of a .NET event invocation with the given sender and event data.
        /// </summary>
        /// <param name="sender">The sender object that raised the event.</param>
        /// <param name="e">The event data that was generated by the event.</param>
        public EventPattern(TSender sender, TEventArgs e)
        {
            Sender = sender;
            EventArgs = e;
        }

        /// <summary>
        /// Gets the sender object that raised the event.
        /// </summary>
        public TSender Sender { get; private set; }

        /// <summary>
        /// Gets the event data that was generated by the event.
        /// </summary>
        public TEventArgs EventArgs { get; private set; }

        /// <summary>
        /// Determines whether the current EventPattern&lt;TSender, TEventArgs&gt; object represents the same event as a specified EventPattern&lt;TSender, TEventArgs&gt; object.
        /// </summary>
        /// <param name="other">An object to compare to the current EventPattern&lt;TSender, TEventArgs&gt; object.</param>
        /// <returns>true if both EventPattern&lt;TSender, TEventArgs&gt; objects represent the same event; otherwise, false.</returns>
        public bool Equals(EventPattern<TSender, TEventArgs> other)
        {
            if (object.ReferenceEquals(null, other))
                return false;
            if (object.ReferenceEquals(this, other))
                return true;

            return EqualityComparer<TSender>.Default.Equals(Sender, other.Sender) && EqualityComparer<TEventArgs>.Default.Equals(EventArgs, other.EventArgs);
        }

        /// <summary>
        /// Determines whether the specified System.Object is equal to the current EventPattern&lt;TSender, TEventArgs&gt;.
        /// </summary>
        /// <param name="obj">The System.Object to compare with the current EventPattern&lt;TSender, TEventArgs&gt;.</param>
        /// <returns>true if the specified System.Object is equal to the current EventPattern&lt;TSender, TEventArgs&gt;; otherwise, false.</returns>
        public override bool Equals(object obj)
        {
            return Equals(obj as EventPattern<TSender, TEventArgs>);
        }

        /// <summary>
        /// Returns the hash code for the current EventPattern&lt;TSender, TEventArgs&gt; instance.
        /// </summary>
        /// <returns>A hash code for the current EventPattern&lt;TSender, TEventArgs&gt; instance.</returns>
        public override int GetHashCode()
        {
            var x = EqualityComparer<TSender>.Default.GetHashCode(Sender);
            var y = EqualityComparer<TEventArgs>.Default.GetHashCode(EventArgs);
            return (x << 5) + (x ^ y);
        }

        /// <summary>
        /// Determines whether two specified EventPattern&lt;TSender, TEventArgs&gt; objects represent the same event.
        /// </summary>
        /// <param name="first">The first EventPattern&lt;TSender, TEventArgs&gt; to compare, or null.</param>
        /// <param name="second">The second EventPattern&lt;TSender, TEventArgs&gt; to compare, or null.</param>
        /// <returns>true if both EventPattern&lt;TSender, TEventArgs&gt; objects represent the same event; otherwise, false.</returns>
        public static bool operator ==(EventPattern<TSender, TEventArgs> first, EventPattern<TSender, TEventArgs> second)
        {
            return object.Equals(first, second);
        }

        /// <summary>
        /// Determines whether two specified EventPattern&lt;TSender, TEventArgs&gt; objects represent a different event.
        /// </summary>
        /// <param name="first">The first EventPattern&lt;TSender, TEventArgs&gt; to compare, or null.</param>
        /// <param name="second">The second EventPattern&lt;TSender, TEventArgs&gt; to compare, or null.</param>
        /// <returns>true if both EventPattern&lt;TSender, TEventArgs&gt; objects don't represent the same event; otherwise, false.</returns>
        public static bool operator !=(EventPattern<TSender, TEventArgs> first, EventPattern<TSender, TEventArgs> second)
        {
            return !object.Equals(first, second);
        }
    }
}