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

<#@ template debug="false" hostspecific="false" language="C#" #>
<#@ assembly name="System.Core" #>
<#@ import namespace="System.Linq" #>
<#@ import namespace="System.Text" #>
<#@ import namespace="System.Collections.Generic" #>
<#@ output extension=".cs" #>
using System.Reactive.Concurrency;
using System.Reactive.Disposables;
using System.Threading.Tasks;

namespace System.Reactive.Linq
{
    public partial class AsyncObservable
    {
<#
for (var i = 2; i <= 16; i++)
{
    var tuple = "(" + string.Join(", ", Enumerable.Range(1, i).Select(j => "T" + j + " arg" + j)) + ")";
    var genArgs = string.Join(", ", Enumerable.Range(1, i).Select(j => "T" + j));
    var pars = string.Join(", ", Enumerable.Range(1, i).Select(j => "arg" + j));
#>
        public static IAsyncObservable<<#=tuple#>> FromEvent<<#=genArgs#>>(Action<Action<<#=genArgs#>>> addHandler, Action<Action<<#=genArgs#>>> removeHandler)
        {
            if (addHandler == null)
                throw new ArgumentNullException(nameof(addHandler));
            if (removeHandler == null)
                throw new ArgumentNullException(nameof(removeHandler));

            return FromEventCore<Action<<#=genArgs#>>, <#=genArgs#>>(h => h, addHandler, removeHandler, GetSchedulerForCurrentContext());
        }

        public static IAsyncObservable<<#=tuple#>> FromEvent<<#=genArgs#>>(Action<Action<<#=genArgs#>>> addHandler, Action<Action<<#=genArgs#>>> removeHandler, IAsyncScheduler scheduler)
        {
            if (addHandler == null)
                throw new ArgumentNullException(nameof(addHandler));
            if (removeHandler == null)
                throw new ArgumentNullException(nameof(removeHandler));
            if (scheduler == null)
                throw new ArgumentNullException(nameof(scheduler));

            return FromEventCore<Action<<#=genArgs#>>, <#=genArgs#>>(h => h, addHandler, removeHandler, scheduler);
        }

        public static IAsyncObservable<<#=tuple#>> FromEvent<TDelegate, <#=genArgs#>>(Func<Action<<#=genArgs#>>, TDelegate> conversion, Action<TDelegate> addHandler, Action<TDelegate> removeHandler)
        {
            if (conversion == null)
                throw new ArgumentNullException(nameof(conversion));
            if (addHandler == null)
                throw new ArgumentNullException(nameof(addHandler));
            if (removeHandler == null)
                throw new ArgumentNullException(nameof(removeHandler));

            return FromEventCore<TDelegate, <#=genArgs#>>(conversion, addHandler, removeHandler, GetSchedulerForCurrentContext());
        }

        public static IAsyncObservable<<#=tuple#>> FromEvent<TDelegate, <#=genArgs#>>(Func<Action<<#=genArgs#>>, TDelegate> conversion, Action<TDelegate> addHandler, Action<TDelegate> removeHandler, IAsyncScheduler scheduler)
        {
            if (conversion == null)
                throw new ArgumentNullException(nameof(conversion));
            if (addHandler == null)
                throw new ArgumentNullException(nameof(addHandler));
            if (removeHandler == null)
                throw new ArgumentNullException(nameof(removeHandler));
            if (scheduler == null)
                throw new ArgumentNullException(nameof(scheduler));

            return FromEventCore<TDelegate, <#=genArgs#>>(conversion, addHandler, removeHandler, scheduler);
        }

        private static IAsyncObservable<<#=tuple#>> FromEventCore<TDelegate, <#=genArgs#>>(Func<Action<<#=genArgs#>>, TDelegate> conversion, Action<TDelegate> addHandler, Action<TDelegate> removeHandler, IAsyncScheduler scheduler)
        {
            return
                SynchronizeEvents(
                    Create<<#=tuple#>>(observer =>
                    {
                        var handler = new Action<<#=genArgs#>>((<#=pars#>) =>
                        {
                            observer.OnNextAsync((<#=pars#>)); // REVIEW: Fire-and-forget can lead to out of order processing, and observers may reject these calls as "busy".
                        });

                        var converted = conversion(handler);

                        addHandler(converted);

                        return new ValueTask<IAsyncDisposable>(AsyncDisposable.Create(() =>
                        {
                            removeHandler(converted);

                            return default;
                        }));
                    }),
                    scheduler
                );
        }

<#
}
#>
    }
}