// 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. 

<#@ 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.Subjects;
using System.Threading.Tasks;

namespace System.Reactive.Linq
{
    // REVIEW: Consider if these are worth retaining in the async space.

    partial class AsyncObservable
    {
<#
for (var i = 0; i <= 16; i++)
{
    var args = Enumerable.Range(1, i).Select(j => "T" + j).Concat(new[] { "IAsyncObservable<TResult>" });
    var ret = "Func<" + string.Join(", ", args) + ">";

    var genArgs = string.Join(", ", Enumerable.Range(1, i).Select(j => "T" + j).Concat(new[] { "TResult" }));
    var pars = string.Join(", ", Enumerable.Range(1, i).Select(j => "arg" + j));

    var type = "Func<" + string.Join(", ", Enumerable.Range(1, i).Select(j => "T" + j).Concat(new[] { "TResult" })) + ">";

    var invokeArgs = pars;

    if (i > 0)
    {
        invokeArgs = ", " + invokeArgs;
    }
#>
        public static <#=ret#> ToAsync<<#=genArgs#>>(<#=type#> function)
        {
            if (function == null)
                throw new ArgumentNullException(nameof(function));

            return ToAsync(function, TaskPoolAsyncScheduler.Default);
        }

        public static <#=ret#> ToAsync<<#=genArgs#>>(<#=type#> function, IAsyncScheduler scheduler)
        {
            if (function == null)
                throw new ArgumentNullException(nameof(function));
            if (scheduler == null)
                throw new ArgumentNullException(nameof(scheduler));

            return (<#=pars#>) =>
            {
                var subject = new SequentialAsyncAsyncSubject<TResult>();

                AsyncObserver.ToAsync(subject, function<#=invokeArgs#>); // NB: We don't do anything with the result of scheduling the action; it can't be cancelled.

                return subject.AsAsyncObservable();
            };
        }

<#
}
#>
<#
for (var i = 0; i <= 16; i++)
{
    var args = Enumerable.Range(1, i).Select(j => "T" + j).Concat(new[] { "IAsyncObservable<Unit>" });
    var ret = "Func<" + string.Join(", ", args) + ">";

    var genArgs = string.Join(", ", Enumerable.Range(1, i).Select(j => "T" + j));
    var pars = string.Join(", ", Enumerable.Range(1, i).Select(j => "arg" + j));

    var type = "Action";

    if (genArgs != "")
    {
        genArgs = "<" + genArgs + ">";
        type += genArgs;
    }

    var invokeArgs = pars;

    if (i > 0)
    {
        invokeArgs = ", " + invokeArgs;
    }
#>
        public static <#=ret#> ToAsync<#=genArgs#>(<#=type#> action)
        {
            if (action == null)
                throw new ArgumentNullException(nameof(action));

            return ToAsync(action, TaskPoolAsyncScheduler.Default);
        }

        public static <#=ret#> ToAsync<#=genArgs#>(<#=type#> action, IAsyncScheduler scheduler)
        {
            if (action == null)
                throw new ArgumentNullException(nameof(action));
            if (scheduler == null)
                throw new ArgumentNullException(nameof(scheduler));

            return (<#=pars#>) =>
            {
                var subject = new SequentialAsyncAsyncSubject<Unit>();

                AsyncObserver.ToAsync(subject, action<#=invokeArgs#>); // NB: We don't do anything with the result of scheduling the action; it can't be cancelled.

                return subject.AsAsyncObservable();
            };
        }

<#
}
#>
    }

    partial class AsyncObserver
    {
<#
for (var i = 0; i <= 16; i++)
{
    var args = Enumerable.Range(1, i).Select(j => "T" + j).Concat(new[] { "IAsyncObservable<TResult>" });
    var ret = "Func<" + string.Join(", ", args) + ">";

    var genArgs = string.Join(", ", Enumerable.Range(1, i).Select(j => "T" + j).Concat(new[] { "TResult" }));
    var pars = string.Join(", ", Enumerable.Range(1, i).Select(j => "arg" + j));

    var type = "Func<" + string.Join(", ", Enumerable.Range(1, i).Select(j => "T" + j).Concat(new[] { "TResult" })) + ">";

    var invokePars = string.Join(", ", Enumerable.Range(1, i).Select(j => "T" + j + " arg" + j));
    var invokeArgs = pars;
    if (i > 0)
    {
        invokePars = ", " + invokePars;
        invokeArgs += ", ";
    }
#>
        public static Task<IAsyncDisposable> ToAsync<<#=genArgs#>>(IAsyncObserver<TResult> observer, <#=type#> function<#=invokePars#>)
        {
            if (observer == null)
                throw new ArgumentNullException(nameof(observer));
            if (function == null)
                throw new ArgumentNullException(nameof(function));

            return ToAsync(observer, function, <#=invokeArgs#>TaskPoolAsyncScheduler.Default);
        }

        public static Task<IAsyncDisposable> ToAsync<<#=genArgs#>>(IAsyncObserver<TResult> observer, <#=type#> function<#=invokePars#>, IAsyncScheduler scheduler)
        {
            if (observer == null)
                throw new ArgumentNullException(nameof(observer));
            if (function == null)
                throw new ArgumentNullException(nameof(function));
            if (scheduler == null)
                throw new ArgumentNullException(nameof(scheduler));

            return scheduler.ScheduleAsync(async ct =>
            {
                TResult res;
                try
                {
                    res = function(<#=pars#>);
                }
                catch (Exception ex)
                {
                    await observer.OnErrorAsync(ex).RendezVous(scheduler, ct);
                    return;
                }

                await observer.OnNextAsync(res).RendezVous(scheduler, ct);
                await observer.OnCompletedAsync().RendezVous(scheduler, ct);
            });
        }

<#
}
#>
<#
for (var i = 0; i <= 16; i++)
{
    var args = Enumerable.Range(1, i).Select(j => "T" + j).Concat(new[] { "IAsyncObservable<Unit>" });
    var ret = "Func<" + string.Join(", ", args) + ">";

    var genArgs = string.Join(", ", Enumerable.Range(1, i).Select(j => "T" + j));
    var pars = string.Join(", ", Enumerable.Range(1, i).Select(j => "arg" + j));

    var type = "Action";

    if (genArgs != "")
    {
        genArgs = "<" + genArgs + ">";
        type += genArgs;
    }

    var invokePars = string.Join(", ", Enumerable.Range(1, i).Select(j => "T" + j + " arg" + j));
    var invokeArgs = pars;
    if (i > 0)
    {
        invokePars = ", " + invokePars;
        invokeArgs += ", ";
    }
#>
        public static Task<IAsyncDisposable> ToAsync<#=genArgs#>(IAsyncObserver<Unit> observer, <#=type#> action<#=invokePars#>)
        {
            if (observer == null)
                throw new ArgumentNullException(nameof(observer));
            if (action == null)
                throw new ArgumentNullException(nameof(action));

            return ToAsync(observer, action, <#=invokeArgs#>TaskPoolAsyncScheduler.Default);
        }

        public static Task<IAsyncDisposable> ToAsync<#=genArgs#>(IAsyncObserver<Unit> observer, <#=type#> action<#=invokePars#>, IAsyncScheduler scheduler)
        {
            if (observer == null)
                throw new ArgumentNullException(nameof(observer));
            if (action == null)
                throw new ArgumentNullException(nameof(action));
            if (scheduler == null)
                throw new ArgumentNullException(nameof(scheduler));

            return scheduler.ScheduleAsync(async ct =>
            {
                try
                {
                    action(<#=pars#>);
                }
                catch (Exception ex)
                {
                    await observer.OnErrorAsync(ex).RendezVous(scheduler, ct);
                    return;
                }

                await observer.OnNextAsync(Unit.Default).RendezVous(scheduler, ct);
                await observer.OnCompletedAsync().RendezVous(scheduler, ct);
            });
        }

<#
}
#>
    }
}