// Messenger.cs v1.0 by Magnus Wolffelt, magnus.wolffelt@gmail.com
// Version 1.4 by Julie Iaccarino, biscuitWizard @ github.com
//
// Inspired by and based on Rod Hyde's Messenger:
// http://www.unifycommunity.com/wiki/index.php?title=CSharpMessenger
//
// See the below wiki for additional documentation / examples:
// http://wiki.unity3d.com/index.php/CSharpMessenger_Extended
//
// This is a C# messenger (notification center). It uses delegates
// and generics to provide type-checked messaging between event producers and
// event consumers, without the need for producers or consumers to be aware of
// each other. The major improvement from Hyde's implementation is that
// there is more extensive error detection, preventing silent bugs.
//
// Usage example:
// Messenger<float>.AddListener("myEvent", MyEventHandler);
// ...
// Messenger<float>.Broadcast("myEvent", 1.0f);
//
// Callback example:
// Messenger<float>.AddListener<string>("myEvent", MyEventHandler);
// private string MyEventHandler(float f1) { return "Test " + f1; }
// ...
// Messenger<float>.Broadcast<string>("myEvent", 1.0f, MyEventCallback);
// private void MyEventCallback(string s1) { Debug.Log(s1"); }

using System;
using System.Collections.Generic;
using System.Linq;

public enum MessengerMode
{
    DONT_REQUIRE_LISTENER,
    REQUIRE_LISTENER,
}

static internal class MessengerInternal
{
    readonly public static Dictionary<string, Delegate> eventTable = new Dictionary<string, Delegate>();
    static public readonly MessengerMode DEFAULT_MODE = MessengerMode.REQUIRE_LISTENER;

    static public void AddListener(string eventType, Delegate callback)
    {
        MessengerInternal.OnListenerAdding(eventType, callback);
        eventTable[eventType] = Delegate.Combine(eventTable[eventType], callback);
    }

    static public void RemoveListener(string eventType, Delegate handler)
    {
        MessengerInternal.OnListenerRemoving(eventType, handler);
        eventTable[eventType] = Delegate.Remove(eventTable[eventType], handler);
        MessengerInternal.OnListenerRemoved(eventType);
    }

    static public T[] GetInvocationList<T>(string eventType)
    {
        Delegate d;
        if (eventTable.TryGetValue(eventType, out d))
        {
            if (d != null)
            {
                return d.GetInvocationList().Cast<T>().ToArray();
            }
            else
            {
                throw MessengerInternal.CreateBroadcastSignatureException(eventType);
            }
        }
        return new T[0];// CJK - Changed this from simply returning 'null.' Returning null would then mean that the function that called
                        // this function would try to iterate over this returned value in a 'foreach' loop. The loop would crash with a null exception.
                        // Returning an array of size zero (0) will ensure that the 'foreach' loop can execute a total of zero times (but won't crash).
    }

    static public void OnListenerAdding(string eventType, Delegate listenerBeingAdded)
    {
        if (!eventTable.ContainsKey(eventType))
        {
            eventTable.Add(eventType, null);
        }

        var d = eventTable[eventType];
        if (d != null && d.GetType() != listenerBeingAdded.GetType())
        {
            throw new ListenerException(string.Format("Attempting to add listener with inconsistent signature for event type {0}. Current listeners have type {1} and listener being added has type {2}", eventType, d.GetType().Name, listenerBeingAdded.GetType().Name));
        }
    }

    static public void OnListenerRemoving(string eventType, Delegate listenerBeingRemoved)
    {
        if (eventTable.ContainsKey(eventType))
        {
            var d = eventTable[eventType];

            if (d == null)
            {
                throw new ListenerException(string.Format("Attempting to remove listener with for event type {0} but current listener is null.", eventType));
            }
            else if (d.GetType() != listenerBeingRemoved.GetType())
            {
                throw new ListenerException(string.Format("Attempting to remove listener with inconsistent signature for event type {0}. Current listeners have type {1} and listener being removed has type {2}", eventType, d.GetType().Name, listenerBeingRemoved.GetType().Name));
            }
        }
        else
        {
            throw new ListenerException(string.Format("Attempting to remove listener for type {0} but Messenger doesn't know about this event type.", eventType));
        }
    }

    static public void OnListenerRemoved(string eventType)
    {
        if (eventTable[eventType] == null)
        {
            eventTable.Remove(eventType);
        }
    }

    static public void OnBroadcasting(string eventType, MessengerMode mode)
    {
        if (mode == MessengerMode.REQUIRE_LISTENER && !eventTable.ContainsKey(eventType))
        {
            throw new MessengerInternal.BroadcastException(string.Format("Broadcasting message {0} but no listener found.", eventType));
        }
    }

    static public BroadcastException CreateBroadcastSignatureException(string eventType)
    {
        return new BroadcastException(string.Format("Broadcasting message {0} but listeners have a different signature than the broadcaster.", eventType));
    }

    public class BroadcastException : Exception
    {
        public BroadcastException(string msg)
            : base(msg)
        {
        }
    }

    public class ListenerException : Exception
    {
        public ListenerException(string msg)
            : base(msg)
        {
        }
    }
}

// No parameters
static public class Messenger
{
    static public void AddListener(string eventType, Action handler)
    {
        MessengerInternal.AddListener(eventType, handler);
    }

    static public void AddListener<TReturn>(string eventType, Func<TReturn> handler)
    {
        MessengerInternal.AddListener(eventType, handler);
    }

    static public void RemoveListener(string eventType, Action handler)
    {
        MessengerInternal.RemoveListener(eventType, handler);
    }

    static public void RemoveListener<TReturn>(string eventType, Func<TReturn> handler)
    {
        MessengerInternal.RemoveListener(eventType, handler);
    }

    static public void Broadcast(string eventType)
    {
        Broadcast(eventType, MessengerInternal.DEFAULT_MODE);
    }

    static public void Broadcast<TReturn>(string eventType, Action<TReturn> returnCall)
    {
        Broadcast(eventType, returnCall, MessengerInternal.DEFAULT_MODE);
    }

    static public void Broadcast(string eventType, MessengerMode mode)
    {
        MessengerInternal.OnBroadcasting(eventType, mode);
        var invocationList = MessengerInternal.GetInvocationList<Action>(eventType);

        foreach (var callback in invocationList)
        {
            callback.Invoke();
        }
    }

    static public void Broadcast<TReturn>(string eventType, Action<TReturn> returnCall, MessengerMode mode)
    {
        MessengerInternal.OnBroadcasting(eventType, mode);
        var invocationList = MessengerInternal.GetInvocationList<Func<TReturn>>(eventType);

        foreach (var result in invocationList.Select(del => del.Invoke()).Cast<TReturn>())
        {
            returnCall.Invoke(result);
        }
    }
}

// One parameter
static public class Messenger<T>
{
    static public void AddListener(string eventType, Action<T> handler)
    {
        MessengerInternal.AddListener(eventType, handler);
    }

    static public void AddListener<TReturn>(string eventType, Func<T, TReturn> handler)
    {
        MessengerInternal.AddListener(eventType, handler);
    }

    static public void RemoveListener(string eventType, Action<T> handler)
    {
        MessengerInternal.RemoveListener(eventType, handler);
    }

    static public void RemoveListener<TReturn>(string eventType, Func<T, TReturn> handler)
    {
        MessengerInternal.RemoveListener(eventType, handler);
    }

    static public void Broadcast(string eventType, T arg1)
    {
        Broadcast(eventType, arg1, MessengerInternal.DEFAULT_MODE);
    }

    static public void Broadcast<TReturn>(string eventType, T arg1, Action<TReturn> returnCall)
    {
        Broadcast(eventType, arg1, returnCall, MessengerInternal.DEFAULT_MODE);
    }

    static public void Broadcast(string eventType, T arg1, MessengerMode mode)
    {
        MessengerInternal.OnBroadcasting(eventType, mode);
        var invocationList = MessengerInternal.GetInvocationList<Action<T>>(eventType);

        foreach (var callback in invocationList)
            callback.Invoke(arg1);
    }

    static public void Broadcast<TReturn>(string eventType, T arg1, Action<TReturn> returnCall, MessengerMode mode)
    {
        MessengerInternal.OnBroadcasting(eventType, mode);
        var invocationList = MessengerInternal.GetInvocationList<Func<T, TReturn>>(eventType);

        foreach (var result in invocationList.Select(del => del.Invoke(arg1)).Cast<TReturn>())
        {
            returnCall.Invoke(result);
        }
    }
}


// Two parameters
static public class Messenger<T, U>
{
    static public void AddListener(string eventType, Action<T, U> handler)
    {
        MessengerInternal.AddListener(eventType, handler);
    }

    static public void AddListener<TReturn>(string eventType, Func<T, U, TReturn> handler)
    {
        MessengerInternal.AddListener(eventType, handler);
    }

    static public void RemoveListener(string eventType, Action<T, U> handler)
    {
        MessengerInternal.RemoveListener(eventType, handler);
    }

    static public void RemoveListener<TReturn>(string eventType, Func<T, U, TReturn> handler)
    {
        MessengerInternal.RemoveListener(eventType, handler);
    }

    static public void Broadcast(string eventType, T arg1, U arg2)
    {
        Broadcast(eventType, arg1, arg2, MessengerInternal.DEFAULT_MODE);
    }

    static public void Broadcast<TReturn>(string eventType, T arg1, U arg2, Action<TReturn> returnCall)
    {
        Broadcast(eventType, arg1, arg2, returnCall, MessengerInternal.DEFAULT_MODE);
    }

    static public void Broadcast(string eventType, T arg1, U arg2, MessengerMode mode)
    {
        MessengerInternal.OnBroadcasting(eventType, mode);
        var invocationList = MessengerInternal.GetInvocationList<Action<T, U>>(eventType);

        foreach (var callback in invocationList)
            callback.Invoke(arg1, arg2);
    }

    static public void Broadcast<TReturn>(string eventType, T arg1, U arg2, Action<TReturn> returnCall, MessengerMode mode)
    {
        MessengerInternal.OnBroadcasting(eventType, mode);
        var invocationList = MessengerInternal.GetInvocationList<Func<T, U, TReturn>>(eventType);

        foreach (var result in invocationList.Select(del => del.Invoke(arg1, arg2)).Cast<TReturn>())
        {
            returnCall.Invoke(result);
        }
    }
}


// Three parameters
static public class Messenger<T, U, V>
{
    static public void AddListener(string eventType, Action<T, U, V> handler)
    {
        MessengerInternal.AddListener(eventType, handler);
    }

    static public void AddListener<TReturn>(string eventType, Func<T, U, V, TReturn> handler)
    {
        MessengerInternal.AddListener(eventType, handler);
    }

    static public void RemoveListener(string eventType, Action<T, U, V> handler)
    {
        MessengerInternal.RemoveListener(eventType, handler);
    }

    static public void RemoveListener<TReturn>(string eventType, Func<T, U, V, TReturn> handler)
    {
        MessengerInternal.RemoveListener(eventType, handler);
    }

    static public void Broadcast(string eventType, T arg1, U arg2, V arg3)
    {
        Broadcast(eventType, arg1, arg2, arg3, MessengerInternal.DEFAULT_MODE);
    }

    static public void Broadcast<TReturn>(string eventType, T arg1, U arg2, V arg3, Action<TReturn> returnCall)
    {
        Broadcast(eventType, arg1, arg2, arg3, returnCall, MessengerInternal.DEFAULT_MODE);
    }

    static public void Broadcast(string eventType, T arg1, U arg2, V arg3, MessengerMode mode)
    {
        MessengerInternal.OnBroadcasting(eventType, mode);
        var invocationList = MessengerInternal.GetInvocationList<Action<T, U, V>>(eventType);

        foreach (var callback in invocationList)
            callback.Invoke(arg1, arg2, arg3);
    }

    static public void Broadcast<TReturn>(string eventType, T arg1, U arg2, V arg3, Action<TReturn> returnCall, MessengerMode mode)
    {
        MessengerInternal.OnBroadcasting(eventType, mode);
        var invocationList = MessengerInternal.GetInvocationList<Func<T, U, V, TReturn>>(eventType);

        foreach (var result in invocationList.Select(del => del.Invoke(arg1, arg2, arg3)).Cast<TReturn>())
        {
            returnCall.Invoke(result);
        }
    }
}