// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.

using System.Reactive.Concurrency;
using System.Reactive.Disposables;
using System.Reactive.Subjects;

#if !NO_TPL
using System.Reactive.Threading.Tasks;
using System.Threading;
using System.Threading.Tasks;
#endif

namespace System.Reactive.Linq
{
    internal partial class QueryLanguage
    {
        #region FromAsyncPattern

        #region Func

        public virtual Func<IObservable<TResult>> FromAsyncPattern<TResult>(Func<AsyncCallback, object, IAsyncResult> begin, Func<IAsyncResult, TResult> end)
        {
            return () =>
            {
                var subject = new AsyncSubject<TResult>();
                try
                {
                    begin(iar =>
                    {
                        // Note: Even if the callback completes synchronously, outgoing On* calls
                        //       cannot throw in user code since there can't be any subscribers
                        //       to the AsyncSubject yet. Therefore, there is no need to protect
                        //       against exceptions that'd be caught below and sent (incorrectly)
                        //       into the Observable.Throw sequence being constructed.
                        TResult result;
                        try
                        {
                            result = end(iar);
                        }
                        catch (Exception exception)
                        {
                            subject.OnError(exception);
                            return;
                        }
                        subject.OnNext(result);
                        subject.OnCompleted();
                    }, null);
                }
                catch (Exception exception)
                {
                    return Observable.Throw<TResult>(exception, SchedulerDefaults.AsyncConversions);
                }
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, IObservable<TResult>> FromAsyncPattern<T1, TResult>(Func<T1, AsyncCallback, object, IAsyncResult> begin, Func<IAsyncResult, TResult> end)
        {
            return x =>
            {
                var subject = new AsyncSubject<TResult>();
                try
                {
                    begin(x, iar =>
                    {
                        // See remark on FromAsyncPattern<TResult>.
                        TResult result;
                        try
                        {
                            result = end(iar);
                        }
                        catch (Exception exception)
                        {
                            subject.OnError(exception);
                            return;
                        }
                        subject.OnNext(result);
                        subject.OnCompleted();
                    }, null);
                }
                catch (Exception exception)
                {
                    return Observable.Throw<TResult>(exception, SchedulerDefaults.AsyncConversions);
                }
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, IObservable<TResult>> FromAsyncPattern<T1, T2, TResult>(Func<T1, T2, AsyncCallback, object, IAsyncResult> begin, Func<IAsyncResult, TResult> end)
        {
            return (x, y) =>
            {
                var subject = new AsyncSubject<TResult>();
                try
                {
                    begin(x, y, iar =>
                    {
                        // See remark on FromAsyncPattern<TResult>.
                        TResult result;
                        try
                        {
                            result = end(iar);
                        }
                        catch (Exception exception)
                        {
                            subject.OnError(exception);
                            return;
                        }
                        subject.OnNext(result);
                        subject.OnCompleted();
                    }, null);
                }
                catch (Exception exception)
                {
                    return Observable.Throw<TResult>(exception, SchedulerDefaults.AsyncConversions);
                }
                return subject.AsObservable();
            };
        }

#if !NO_LARGEARITY
        public virtual Func<T1, T2, T3, IObservable<TResult>> FromAsyncPattern<T1, T2, T3, TResult>(Func<T1, T2, T3, AsyncCallback, object, IAsyncResult> begin, Func<IAsyncResult, TResult> end)
        {
            return (x, y, z) =>
            {
                var subject = new AsyncSubject<TResult>();
                try
                {
                    begin(x, y, z, iar =>
                    {
                        // See remark on FromAsyncPattern<TResult>.
                        TResult result;
                        try
                        {
                            result = end(iar);
                        }
                        catch (Exception exception)
                        {
                            subject.OnError(exception);
                            return;
                        }
                        subject.OnNext(result);
                        subject.OnCompleted();
                    }, null);
                }
                catch (Exception exception)
                {
                    return Observable.Throw<TResult>(exception, SchedulerDefaults.AsyncConversions);
                }
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, IObservable<TResult>> FromAsyncPattern<T1, T2, T3, T4, TResult>(Func<T1, T2, T3, T4, AsyncCallback, object, IAsyncResult> begin, Func<IAsyncResult, TResult> end)
        {
            return (x, y, z, a) =>
            {
                var subject = new AsyncSubject<TResult>();
                try
                {
                    begin(x, y, z, a, iar =>
                    {
                        // See remark on FromAsyncPattern<TResult>.
                        TResult result;
                        try
                        {
                            result = end(iar);
                        }
                        catch (Exception exception)
                        {
                            subject.OnError(exception);
                            return;
                        }
                        subject.OnNext(result);
                        subject.OnCompleted();
                    }, null);
                }
                catch (Exception exception)
                {
                    return Observable.Throw<TResult>(exception, SchedulerDefaults.AsyncConversions);
                }
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, IObservable<TResult>> FromAsyncPattern<T1, T2, T3, T4, T5, TResult>(Func<T1, T2, T3, T4, T5, AsyncCallback, object, IAsyncResult> begin, Func<IAsyncResult, TResult> end)
        {
            return (x, y, z, a, b) =>
            {
                var subject = new AsyncSubject<TResult>();
                try
                {
                    begin(x, y, z, a, b, iar =>
                    {
                        // See remark on FromAsyncPattern<TResult>.
                        TResult result;
                        try
                        {
                            result = end(iar);
                        }
                        catch (Exception exception)
                        {
                            subject.OnError(exception);
                            return;
                        }
                        subject.OnNext(result);
                        subject.OnCompleted();
                    }, null);
                }
                catch (Exception exception)
                {
                    return Observable.Throw<TResult>(exception, SchedulerDefaults.AsyncConversions);
                }
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, IObservable<TResult>> FromAsyncPattern<T1, T2, T3, T4, T5, T6, TResult>(Func<T1, T2, T3, T4, T5, T6, AsyncCallback, object, IAsyncResult> begin, Func<IAsyncResult, TResult> end)
        {
            return (x, y, z, a, b, c) =>
            {
                var subject = new AsyncSubject<TResult>();
                try
                {
                    begin(x, y, z, a, b, c, iar =>
                    {
                        // See remark on FromAsyncPattern<TResult>.
                        TResult result;
                        try
                        {
                            result = end(iar);
                        }
                        catch (Exception exception)
                        {
                            subject.OnError(exception);
                            return;
                        }
                        subject.OnNext(result);
                        subject.OnCompleted();
                    }, null);
                }
                catch (Exception exception)
                {
                    return Observable.Throw<TResult>(exception, SchedulerDefaults.AsyncConversions);
                }
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, IObservable<TResult>> FromAsyncPattern<T1, T2, T3, T4, T5, T6, T7, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, AsyncCallback, object, IAsyncResult> begin, Func<IAsyncResult, TResult> end)
        {
            return (x, y, z, a, b, c, d) =>
            {
                var subject = new AsyncSubject<TResult>();
                try
                {
                    begin(x, y, z, a, b, c, d, iar =>
                    {
                        // See remark on FromAsyncPattern<TResult>.
                        TResult result;
                        try
                        {
                            result = end(iar);
                        }
                        catch (Exception exception)
                        {
                            subject.OnError(exception);
                            return;
                        }
                        subject.OnNext(result);
                        subject.OnCompleted();
                    }, null);
                }
                catch (Exception exception)
                {
                    return Observable.Throw<TResult>(exception, SchedulerDefaults.AsyncConversions);
                }
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, IObservable<TResult>> FromAsyncPattern<T1, T2, T3, T4, T5, T6, T7, T8, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, T8, AsyncCallback, object, IAsyncResult> begin, Func<IAsyncResult, TResult> end)
        {
            return (x, y, z, a, b, c, d, e) =>
            {
                var subject = new AsyncSubject<TResult>();
                try
                {
                    begin(x, y, z, a, b, c, d, e, iar =>
                    {
                        // See remark on FromAsyncPattern<TResult>.
                        TResult result;
                        try
                        {
                            result = end(iar);
                        }
                        catch (Exception exception)
                        {
                            subject.OnError(exception);
                            return;
                        }
                        subject.OnNext(result);
                        subject.OnCompleted();
                    }, null);
                }
                catch (Exception exception)
                {
                    return Observable.Throw<TResult>(exception, SchedulerDefaults.AsyncConversions);
                }
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, IObservable<TResult>> FromAsyncPattern<T1, T2, T3, T4, T5, T6, T7, T8, T9, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, AsyncCallback, object, IAsyncResult> begin, Func<IAsyncResult, TResult> end)
        {
            return (x, y, z, a, b, c, d, e, f) =>
            {
                var subject = new AsyncSubject<TResult>();
                try
                {
                    begin(x, y, z, a, b, c, d, e, f, iar =>
                    {
                        // See remark on FromAsyncPattern<TResult>.
                        TResult result;
                        try
                        {
                            result = end(iar);
                        }
                        catch (Exception exception)
                        {
                            subject.OnError(exception);
                            return;
                        }
                        subject.OnNext(result);
                        subject.OnCompleted();
                    }, null);
                }
                catch (Exception exception)
                {
                    return Observable.Throw<TResult>(exception, SchedulerDefaults.AsyncConversions);
                }
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, IObservable<TResult>> FromAsyncPattern<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, AsyncCallback, object, IAsyncResult> begin, Func<IAsyncResult, TResult> end)
        {
            return (x, y, z, a, b, c, d, e, f, g) =>
            {
                var subject = new AsyncSubject<TResult>();
                try
                {
                    begin(x, y, z, a, b, c, d, e, f, g, iar =>
                    {
                        // See remark on FromAsyncPattern<TResult>.
                        TResult result;
                        try
                        {
                            result = end(iar);
                        }
                        catch (Exception exception)
                        {
                            subject.OnError(exception);
                            return;
                        }
                        subject.OnNext(result);
                        subject.OnCompleted();
                    }, null);
                }
                catch (Exception exception)
                {
                    return Observable.Throw<TResult>(exception, SchedulerDefaults.AsyncConversions);
                }
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, IObservable<TResult>> FromAsyncPattern<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, AsyncCallback, object, IAsyncResult> begin, Func<IAsyncResult, TResult> end)
        {
            return (x, y, z, a, b, c, d, e, f, g, h) =>
            {
                var subject = new AsyncSubject<TResult>();
                try
                {
                    begin(x, y, z, a, b, c, d, e, f, g, h, iar =>
                    {
                        // See remark on FromAsyncPattern<TResult>.
                        TResult result;
                        try
                        {
                            result = end(iar);
                        }
                        catch (Exception exception)
                        {
                            subject.OnError(exception);
                            return;
                        }
                        subject.OnNext(result);
                        subject.OnCompleted();
                    }, null);
                }
                catch (Exception exception)
                {
                    return Observable.Throw<TResult>(exception, SchedulerDefaults.AsyncConversions);
                }
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, IObservable<TResult>> FromAsyncPattern<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, AsyncCallback, object, IAsyncResult> begin, Func<IAsyncResult, TResult> end)
        {
            return (x, y, z, a, b, c, d, e, f, g, h, i) =>
            {
                var subject = new AsyncSubject<TResult>();
                try
                {
                    begin(x, y, z, a, b, c, d, e, f, g, h, i, iar =>
                    {
                        // See remark on FromAsyncPattern<TResult>.
                        TResult result;
                        try
                        {
                            result = end(iar);
                        }
                        catch (Exception exception)
                        {
                            subject.OnError(exception);
                            return;
                        }
                        subject.OnNext(result);
                        subject.OnCompleted();
                    }, null);
                }
                catch (Exception exception)
                {
                    return Observable.Throw<TResult>(exception, SchedulerDefaults.AsyncConversions);
                }
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, IObservable<TResult>> FromAsyncPattern<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, AsyncCallback, object, IAsyncResult> begin, Func<IAsyncResult, TResult> end)
        {
            return (x, y, z, a, b, c, d, e, f, g, h, i, j) =>
            {
                var subject = new AsyncSubject<TResult>();
                try
                {
                    begin(x, y, z, a, b, c, d, e, f, g, h, i, j, iar =>
                    {
                        // See remark on FromAsyncPattern<TResult>.
                        TResult result;
                        try
                        {
                            result = end(iar);
                        }
                        catch (Exception exception)
                        {
                            subject.OnError(exception);
                            return;
                        }
                        subject.OnNext(result);
                        subject.OnCompleted();
                    }, null);
                }
                catch (Exception exception)
                {
                    return Observable.Throw<TResult>(exception, SchedulerDefaults.AsyncConversions);
                }
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, IObservable<TResult>> FromAsyncPattern<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, AsyncCallback, object, IAsyncResult> begin, Func<IAsyncResult, TResult> end)
        {
            return (x, y, z, a, b, c, d, e, f, g, h, i, j, k) =>
            {
                var subject = new AsyncSubject<TResult>();
                try
                {
                    begin(x, y, z, a, b, c, d, e, f, g, h, i, j, k, iar =>
                    {
                        // See remark on FromAsyncPattern<TResult>.
                        TResult result;
                        try
                        {
                            result = end(iar);
                        }
                        catch (Exception exception)
                        {
                            subject.OnError(exception);
                            return;
                        }
                        subject.OnNext(result);
                        subject.OnCompleted();
                    }, null);
                }
                catch (Exception exception)
                {
                    return Observable.Throw<TResult>(exception, SchedulerDefaults.AsyncConversions);
                }
                return subject.AsObservable();
            };
        }
#endif

        #endregion

        #region Action

        public virtual Func<IObservable<Unit>> FromAsyncPattern(Func<AsyncCallback, object, IAsyncResult> begin, Action<IAsyncResult> end)
        {
            return FromAsyncPattern(begin, iar =>
            {
                end(iar);
                return Unit.Default;
            });
        }

        public virtual Func<T1, IObservable<Unit>> FromAsyncPattern<T1>(Func<T1, AsyncCallback, object, IAsyncResult> begin, Action<IAsyncResult> end)
        {
            return FromAsyncPattern(begin, iar =>
            {
                end(iar);
                return Unit.Default;
            });
        }

        public virtual Func<T1, T2, IObservable<Unit>> FromAsyncPattern<T1, T2>(Func<T1, T2, AsyncCallback, object, IAsyncResult> begin, Action<IAsyncResult> end)
        {
            return FromAsyncPattern(begin, iar =>
            {
                end(iar);
                return Unit.Default;
            });
        }

#if !NO_LARGEARITY
        public virtual Func<T1, T2, T3, IObservable<Unit>> FromAsyncPattern<T1, T2, T3>(Func<T1, T2, T3, AsyncCallback, object, IAsyncResult> begin, Action<IAsyncResult> end)
        {
            return FromAsyncPattern(begin, iar =>
            {
                end(iar);
                return Unit.Default;
            });
        }

        public virtual Func<T1, T2, T3, T4, IObservable<Unit>> FromAsyncPattern<T1, T2, T3, T4>(Func<T1, T2, T3, T4, AsyncCallback, object, IAsyncResult> begin, Action<IAsyncResult> end)
        {
            return FromAsyncPattern(begin, iar =>
            {
                end(iar);
                return Unit.Default;
            });
        }

        public virtual Func<T1, T2, T3, T4, T5, IObservable<Unit>> FromAsyncPattern<T1, T2, T3, T4, T5>(Func<T1, T2, T3, T4, T5, AsyncCallback, object, IAsyncResult> begin, Action<IAsyncResult> end)
        {
            return FromAsyncPattern(begin, iar =>
            {
                end(iar);
                return Unit.Default;
            });
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, IObservable<Unit>> FromAsyncPattern<T1, T2, T3, T4, T5, T6>(Func<T1, T2, T3, T4, T5, T6, AsyncCallback, object, IAsyncResult> begin, Action<IAsyncResult> end)
        {
            return FromAsyncPattern(begin, iar =>
            {
                end(iar);
                return Unit.Default;
            });
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, IObservable<Unit>> FromAsyncPattern<T1, T2, T3, T4, T5, T6, T7>(Func<T1, T2, T3, T4, T5, T6, T7, AsyncCallback, object, IAsyncResult> begin, Action<IAsyncResult> end)
        {
            return FromAsyncPattern(begin, iar =>
            {
                end(iar);
                return Unit.Default;
            });
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, IObservable<Unit>> FromAsyncPattern<T1, T2, T3, T4, T5, T6, T7, T8>(Func<T1, T2, T3, T4, T5, T6, T7, T8, AsyncCallback, object, IAsyncResult> begin, Action<IAsyncResult> end)
        {
            return FromAsyncPattern(begin, iar =>
            {
                end(iar);
                return Unit.Default;
            });
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, IObservable<Unit>> FromAsyncPattern<T1, T2, T3, T4, T5, T6, T7, T8, T9>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, AsyncCallback, object, IAsyncResult> begin, Action<IAsyncResult> end)
        {
            return FromAsyncPattern(begin, iar =>
            {
                end(iar);
                return Unit.Default;
            });
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, IObservable<Unit>> FromAsyncPattern<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, AsyncCallback, object, IAsyncResult> begin, Action<IAsyncResult> end)
        {
            return FromAsyncPattern(begin, iar =>
            {
                end(iar);
                return Unit.Default;
            });
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, IObservable<Unit>> FromAsyncPattern<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, AsyncCallback, object, IAsyncResult> begin, Action<IAsyncResult> end)
        {
            return FromAsyncPattern(begin, iar =>
            {
                end(iar);
                return Unit.Default;
            });
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, IObservable<Unit>> FromAsyncPattern<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, AsyncCallback, object, IAsyncResult> begin, Action<IAsyncResult> end)
        {
            return FromAsyncPattern(begin, iar =>
            {
                end(iar);
                return Unit.Default;
            });
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, IObservable<Unit>> FromAsyncPattern<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, AsyncCallback, object, IAsyncResult> begin, Action<IAsyncResult> end)
        {
            return FromAsyncPattern(begin, iar =>
            {
                end(iar);
                return Unit.Default;
            });
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, IObservable<Unit>> FromAsyncPattern<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, AsyncCallback, object, IAsyncResult> begin, Action<IAsyncResult> end)
        {
            return FromAsyncPattern(begin, iar =>
            {
                end(iar);
                return Unit.Default;
            });
        }
#endif

        #endregion

        #endregion

        #region Start[Async]

        #region Func

        public virtual IObservable<TSource> Start<TSource>(Func<TSource> function)
        {
            return ToAsync(function)();
        }

        public virtual IObservable<TSource> Start<TSource>(Func<TSource> function, IScheduler scheduler)
        {
            return ToAsync(function, scheduler)();
        }

#if !NO_TPL
        public virtual IObservable<TSource> StartAsync<TSource>(Func<Task<TSource>> functionAsync)
        {
            var task = default(Task<TSource>);
            try
            {
                task = functionAsync();
            }
            catch (Exception exception)
            {
                return Throw<TSource>(exception);
            }

            return task.ToObservable();
        }

        public virtual IObservable<TSource> StartAsync<TSource>(Func<CancellationToken, Task<TSource>> functionAsync)
        {
            var cancellable = new CancellationDisposable();

            var task = default(Task<TSource>);
            try
            {
                task = functionAsync(cancellable.Token);
            }
            catch (Exception exception)
            {
                return Throw<TSource>(exception);
            }

            var result = task.ToObservable();

            return new AnonymousObservable<TSource>(observer =>
            {
                //
                // [OK] Use of unsafe Subscribe: result is an AsyncSubject<TSource>.
                //
                var subscription = result.Subscribe/*Unsafe*/(observer);
                return new CompositeDisposable(cancellable, subscription);
            });
        }
#endif

        #endregion

        #region Action

        public virtual IObservable<Unit> Start(Action action)
        {
            return ToAsync(action, SchedulerDefaults.AsyncConversions)();
        }

        public virtual IObservable<Unit> Start(Action action, IScheduler scheduler)
        {
            return ToAsync(action, scheduler)();
        }

#if !NO_TPL
        public virtual IObservable<Unit> StartAsync(Func<Task> actionAsync)
        {
            var task = default(Task);
            try
            {
                task = actionAsync();
            }
            catch (Exception exception)
            {
                return Throw<Unit>(exception);
            }

            return task.ToObservable();
        }

        public virtual IObservable<Unit> StartAsync(Func<CancellationToken, Task> actionAsync)
        {
            var cancellable = new CancellationDisposable();

            var task = default(Task);
            try
            {
                task = actionAsync(cancellable.Token);
            }
            catch (Exception exception)
            {
                return Throw<Unit>(exception);
            }

            var result = task.ToObservable();

            return new AnonymousObservable<Unit>(observer =>
            {
                //
                // [OK] Use of unsafe Subscribe: result is an AsyncSubject<TSource>.
                //
                var subscription = result.Subscribe/*Unsafe*/(observer);
                return new CompositeDisposable(cancellable, subscription);
            });
        }
#endif

        #endregion

        #endregion

        #region FromAsync

#if !NO_TPL

        #region Func

        public virtual IObservable<TResult> FromAsync<TResult>(Func<Task<TResult>> functionAsync)
        {
            return Defer(() => StartAsync(functionAsync));
        }

        public virtual IObservable<TResult> FromAsync<TResult>(Func<CancellationToken, Task<TResult>> functionAsync)
        {
            return Defer(() => StartAsync(functionAsync));
        }

        #endregion

        #region Action

        public virtual IObservable<Unit> FromAsync(Func<Task> actionAsync)
        {
            return Defer(() => StartAsync(actionAsync));
        }

        public virtual IObservable<Unit> FromAsync(Func<CancellationToken, Task> actionAsync)
        {
            return Defer(() => StartAsync(actionAsync));
        }

        #endregion

#endif

        #endregion

        #region ToAsync

        #region Func

        public virtual Func<IObservable<TResult>> ToAsync<TResult>(Func<TResult> function)
        {
            return ToAsync(function, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<IObservable<TResult>> ToAsync<TResult>(Func<TResult> function, IScheduler scheduler)
        {
            return () =>
            {
                var subject = new AsyncSubject<TResult>();
                scheduler.Schedule(() =>
                {
                    var result = default(TResult);
                    try
                    {
                        result = function();
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(result);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T, IObservable<TResult>> ToAsync<T, TResult>(Func<T, TResult> function)
        {
            return ToAsync(function, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T, IObservable<TResult>> ToAsync<T, TResult>(Func<T, TResult> function, IScheduler scheduler)
        {
            return (first) =>
            {
                var subject = new AsyncSubject<TResult>();
                scheduler.Schedule(() =>
                {
                    var result = default(TResult);
                    try
                    {
                        result = function(first);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(result);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, IObservable<TResult>> ToAsync<T1, T2, TResult>(Func<T1, T2, TResult> function)
        {
            return ToAsync(function, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, IObservable<TResult>> ToAsync<T1, T2, TResult>(Func<T1, T2, TResult> function, IScheduler scheduler)
        {
            return (first, second) =>
            {
                var subject = new AsyncSubject<TResult>();
                scheduler.Schedule(() =>
                {
                    var result = default(TResult);
                    try
                    {
                        result = function(first, second);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(result);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, IObservable<TResult>> ToAsync<T1, T2, T3, TResult>(Func<T1, T2, T3, TResult> function)
        {
            return ToAsync(function, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, IObservable<TResult>> ToAsync<T1, T2, T3, TResult>(Func<T1, T2, T3, TResult> function, IScheduler scheduler)
        {
            return (first, second, third) =>
            {
                var subject = new AsyncSubject<TResult>();
                scheduler.Schedule(() =>
                {
                    var result = default(TResult);
                    try
                    {
                        result = function(first, second, third);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(result);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, IObservable<TResult>> ToAsync<T1, T2, T3, T4, TResult>(Func<T1, T2, T3, T4, TResult> function)
        {
            return ToAsync(function, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, IObservable<TResult>> ToAsync<T1, T2, T3, T4, TResult>(Func<T1, T2, T3, T4, TResult> function, IScheduler scheduler)
        {
            return (first, second, third, fourth) =>
            {
                var subject = new AsyncSubject<TResult>();
                scheduler.Schedule(() =>
                {
                    var result = default(TResult);
                    try
                    {
                        result = function(first, second, third, fourth);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(result);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

#if !NO_LARGEARITY

        public virtual Func<T1, T2, T3, T4, T5, IObservable<TResult>> ToAsync<T1, T2, T3, T4, T5, TResult>(Func<T1, T2, T3, T4, T5, TResult> function)
        {
            return ToAsync(function, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, T5, IObservable<TResult>> ToAsync<T1, T2, T3, T4, T5, TResult>(Func<T1, T2, T3, T4, T5, TResult> function, IScheduler scheduler)
        {
            return (first, second, third, fourth, fifth) =>
            {
                var subject = new AsyncSubject<TResult>();
                scheduler.Schedule(() =>
                {
                    var result = default(TResult);
                    try
                    {
                        result = function(first, second, third, fourth, fifth);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(result);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, IObservable<TResult>> ToAsync<T1, T2, T3, T4, T5, T6, TResult>(Func<T1, T2, T3, T4, T5, T6, TResult> function)
        {
            return ToAsync(function, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, IObservable<TResult>> ToAsync<T1, T2, T3, T4, T5, T6, TResult>(Func<T1, T2, T3, T4, T5, T6, TResult> function, IScheduler scheduler)
        {
            return (first, second, third, fourth, fifth, sixth) =>
            {
                var subject = new AsyncSubject<TResult>();
                scheduler.Schedule(() =>
                {
                    var result = default(TResult);
                    try
                    {
                        result = function(first, second, third, fourth, fifth, sixth);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(result);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, IObservable<TResult>> ToAsync<T1, T2, T3, T4, T5, T6, T7, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, TResult> function)
        {
            return ToAsync(function, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, IObservable<TResult>> ToAsync<T1, T2, T3, T4, T5, T6, T7, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, TResult> function, IScheduler scheduler)
        {
            return (first, second, third, fourth, fifth, sixth, seventh) =>
            {
                var subject = new AsyncSubject<TResult>();
                scheduler.Schedule(() =>
                {
                    var result = default(TResult);
                    try
                    {
                        result = function(first, second, third, fourth, fifth, sixth, seventh);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(result);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, IObservable<TResult>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, T8, TResult> function)
        {
            return ToAsync(function, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, IObservable<TResult>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, T8, TResult> function, IScheduler scheduler)
        {
            return (first, second, third, fourth, fifth, sixth, seventh, eight) =>
            {
                var subject = new AsyncSubject<TResult>();
                scheduler.Schedule(() =>
                {
                    var result = default(TResult);
                    try
                    {
                        result = function(first, second, third, fourth, fifth, sixth, seventh, eight);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(result);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, IObservable<TResult>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, TResult> function)
        {
            return ToAsync(function, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, IObservable<TResult>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, TResult> function, IScheduler scheduler)
        {
            return (first, second, third, fourth, fifth, sixth, seventh, eight, ninth) =>
            {
                var subject = new AsyncSubject<TResult>();
                scheduler.Schedule(() =>
                {
                    var result = default(TResult);
                    try
                    {
                        result = function(first, second, third, fourth, fifth, sixth, seventh, eight, ninth);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(result);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, IObservable<TResult>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, TResult> function)
        {
            return ToAsync(function, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, IObservable<TResult>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, TResult> function, IScheduler scheduler)
        {
            return (first, second, third, fourth, fifth, sixth, seventh, eight, ninth, tenth) =>
            {
                var subject = new AsyncSubject<TResult>();
                scheduler.Schedule(() =>
                {
                    var result = default(TResult);
                    try
                    {
                        result = function(first, second, third, fourth, fifth, sixth, seventh, eight, ninth, tenth);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(result);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, IObservable<TResult>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, TResult> function)
        {
            return ToAsync(function, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, IObservable<TResult>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, TResult> function, IScheduler scheduler)
        {
            return (first, second, third, fourth, fifth, sixth, seventh, eight, ninth, tenth, eleventh) =>
            {
                var subject = new AsyncSubject<TResult>();
                scheduler.Schedule(() =>
                {
                    var result = default(TResult);
                    try
                    {
                        result = function(first, second, third, fourth, fifth, sixth, seventh, eight, ninth, tenth, eleventh);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(result);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, IObservable<TResult>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, TResult> function)
        {
            return ToAsync(function, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, IObservable<TResult>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, TResult> function, IScheduler scheduler)
        {
            return (first, second, third, fourth, fifth, sixth, seventh, eight, ninth, tenth, eleventh, twelfth) =>
            {
                var subject = new AsyncSubject<TResult>();
                scheduler.Schedule(() =>
                {
                    var result = default(TResult);
                    try
                    {
                        result = function(first, second, third, fourth, fifth, sixth, seventh, eight, ninth, tenth, eleventh, twelfth);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(result);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, IObservable<TResult>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, TResult> function)
        {
            return ToAsync(function, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, IObservable<TResult>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, TResult> function, IScheduler scheduler)
        {
            return (first, second, third, fourth, fifth, sixth, seventh, eight, ninth, tenth, eleventh, twelfth, thirteenth) =>
            {
                var subject = new AsyncSubject<TResult>();
                scheduler.Schedule(() =>
                {
                    var result = default(TResult);
                    try
                    {
                        result = function(first, second, third, fourth, fifth, sixth, seventh, eight, ninth, tenth, eleventh, twelfth, thirteenth);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(result);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, IObservable<TResult>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, TResult> function)
        {
            return ToAsync(function, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, IObservable<TResult>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, TResult> function, IScheduler scheduler)
        {
            return (first, second, third, fourth, fifth, sixth, seventh, eight, ninth, tenth, eleventh, twelfth, thirteenth, fourteenth) =>
            {
                var subject = new AsyncSubject<TResult>();
                scheduler.Schedule(() =>
                {
                    var result = default(TResult);
                    try
                    {
                        result = function(first, second, third, fourth, fifth, sixth, seventh, eight, ninth, tenth, eleventh, twelfth, thirteenth, fourteenth);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(result);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, IObservable<TResult>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, TResult> function)
        {
            return ToAsync(function, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, IObservable<TResult>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, TResult> function, IScheduler scheduler)
        {
            return (first, second, third, fourth, fifth, sixth, seventh, eight, ninth, tenth, eleventh, twelfth, thirteenth, fourteenth, fifteenth) =>
            {
                var subject = new AsyncSubject<TResult>();
                scheduler.Schedule(() =>
                {
                    var result = default(TResult);
                    try
                    {
                        result = function(first, second, third, fourth, fifth, sixth, seventh, eight, ninth, tenth, eleventh, twelfth, thirteenth, fourteenth, fifteenth);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(result);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, IObservable<TResult>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, TResult> function)
        {
            return ToAsync(function, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, IObservable<TResult>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, TResult>(Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, TResult> function, IScheduler scheduler)
        {
            return (first, second, third, fourth, fifth, sixth, seventh, eight, ninth, tenth, eleventh, twelfth, thirteenth, fourteenth, fifteenth, sixteenth) =>
            {
                var subject = new AsyncSubject<TResult>();
                scheduler.Schedule(() =>
                {
                    var result = default(TResult);
                    try
                    {
                        result = function(first, second, third, fourth, fifth, sixth, seventh, eight, ninth, tenth, eleventh, twelfth, thirteenth, fourteenth, fifteenth, sixteenth);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(result);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

#endif

        #endregion

        #region Action

        public virtual Func<IObservable<Unit>> ToAsync(Action action)
        {
            return ToAsync(action, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<IObservable<Unit>> ToAsync(Action action, IScheduler scheduler)
        {
            return () =>
            {
                var subject = new AsyncSubject<Unit>();
                scheduler.Schedule(() =>
                {
                    try
                    {
                        action();
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(Unit.Default);
                    subject.OnCompleted();
                });

                return subject.AsObservable();
            };
        }

        public virtual Func<TSource, IObservable<Unit>> ToAsync<TSource>(Action<TSource> action)
        {
            return ToAsync(action, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<TSource, IObservable<Unit>> ToAsync<TSource>(Action<TSource> action, IScheduler scheduler)
        {
            return (first) =>
            {
                var subject = new AsyncSubject<Unit>();
                scheduler.Schedule(() =>
                {
                    try
                    {
                        action(first);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(Unit.Default);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, IObservable<Unit>> ToAsync<T1, T2>(Action<T1, T2> action)
        {
            return ToAsync(action, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, IObservable<Unit>> ToAsync<T1, T2>(Action<T1, T2> action, IScheduler scheduler)
        {
            return (first, second) =>
            {
                var subject = new AsyncSubject<Unit>();
                scheduler.Schedule(() =>
                {
                    try
                    {
                        action(first, second);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(Unit.Default);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, IObservable<Unit>> ToAsync<T1, T2, T3>(Action<T1, T2, T3> action)
        {
            return ToAsync(action, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, IObservable<Unit>> ToAsync<T1, T2, T3>(Action<T1, T2, T3> action, IScheduler scheduler)
        {
            return (first, second, third) =>
            {
                var subject = new AsyncSubject<Unit>();
                scheduler.Schedule(() =>
                {
                    try
                    {
                        action(first, second, third);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(Unit.Default);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, IObservable<Unit>> ToAsync<T1, T2, T3, T4>(Action<T1, T2, T3, T4> action)
        {
            return ToAsync(action, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, IObservable<Unit>> ToAsync<T1, T2, T3, T4>(Action<T1, T2, T3, T4> action, IScheduler scheduler)
        {
            return (first, second, third, fourth) =>
            {
                var subject = new AsyncSubject<Unit>();
                scheduler.Schedule(() =>
                {
                    try
                    {
                        action(first, second, third, fourth);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(Unit.Default);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

#if !NO_LARGEARITY

        public virtual Func<T1, T2, T3, T4, T5, IObservable<Unit>> ToAsync<T1, T2, T3, T4, T5>(Action<T1, T2, T3, T4, T5> action)
        {
            return ToAsync(action, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, T5, IObservable<Unit>> ToAsync<T1, T2, T3, T4, T5>(Action<T1, T2, T3, T4, T5> action, IScheduler scheduler)
        {
            return (first, second, third, fourth, fifth) =>
            {
                var subject = new AsyncSubject<Unit>();
                scheduler.Schedule(() =>
                {
                    try
                    {
                        action(first, second, third, fourth, fifth);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(Unit.Default);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, IObservable<Unit>> ToAsync<T1, T2, T3, T4, T5, T6>(Action<T1, T2, T3, T4, T5, T6> action)
        {
            return ToAsync(action, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, IObservable<Unit>> ToAsync<T1, T2, T3, T4, T5, T6>(Action<T1, T2, T3, T4, T5, T6> action, IScheduler scheduler)
        {
            return (first, second, third, fourth, fifth, sixth) =>
            {
                var subject = new AsyncSubject<Unit>();
                scheduler.Schedule(() =>
                {
                    try
                    {
                        action(first, second, third, fourth, fifth, sixth);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(Unit.Default);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, IObservable<Unit>> ToAsync<T1, T2, T3, T4, T5, T6, T7>(Action<T1, T2, T3, T4, T5, T6, T7> action)
        {
            return ToAsync(action, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, IObservable<Unit>> ToAsync<T1, T2, T3, T4, T5, T6, T7>(Action<T1, T2, T3, T4, T5, T6, T7> action, IScheduler scheduler)
        {
            return (first, second, third, fourth, fifth, sixth, seventh) =>
            {
                var subject = new AsyncSubject<Unit>();
                scheduler.Schedule(() =>
                {
                    try
                    {
                        action(first, second, third, fourth, fifth, sixth, seventh);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(Unit.Default);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, IObservable<Unit>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8>(Action<T1, T2, T3, T4, T5, T6, T7, T8> action)
        {
            return ToAsync(action, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, IObservable<Unit>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8>(Action<T1, T2, T3, T4, T5, T6, T7, T8> action, IScheduler scheduler)
        {
            return (first, second, third, fourth, fifth, sixth, seventh, eight) =>
            {
                var subject = new AsyncSubject<Unit>();
                scheduler.Schedule(() =>
                {
                    try
                    {
                        action(first, second, third, fourth, fifth, sixth, seventh, eight);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(Unit.Default);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, IObservable<Unit>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9>(Action<T1, T2, T3, T4, T5, T6, T7, T8, T9> action)
        {
            return ToAsync(action, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, IObservable<Unit>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9>(Action<T1, T2, T3, T4, T5, T6, T7, T8, T9> action, IScheduler scheduler)
        {
            return (first, second, third, fourth, fifth, sixth, seventh, eighth, ninth) =>
            {
                var subject = new AsyncSubject<Unit>();
                scheduler.Schedule(() =>
                {
                    try
                    {
                        action(first, second, third, fourth, fifth, sixth, seventh, eighth, ninth);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(Unit.Default);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, IObservable<Unit>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10> action)
        {
            return ToAsync(action, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, IObservable<Unit>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10> action, IScheduler scheduler)
        {
            return (first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth) =>
            {
                var subject = new AsyncSubject<Unit>();
                scheduler.Schedule(() =>
                {
                    try
                    {
                        action(first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(Unit.Default);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, IObservable<Unit>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11> action)
        {
            return ToAsync(action, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, IObservable<Unit>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11> action, IScheduler scheduler)
        {
            return (first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh) =>
            {
                var subject = new AsyncSubject<Unit>();
                scheduler.Schedule(() =>
                {
                    try
                    {
                        action(first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(Unit.Default);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, IObservable<Unit>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12> action)
        {
            return ToAsync(action, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, IObservable<Unit>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12> action, IScheduler scheduler)
        {
            return (first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth) =>
            {
                var subject = new AsyncSubject<Unit>();
                scheduler.Schedule(() =>
                {
                    try
                    {
                        action(first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(Unit.Default);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, IObservable<Unit>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13>(Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13> action)
        {
            return ToAsync(action, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, IObservable<Unit>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13>(Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13> action, IScheduler scheduler)
        {
            return (first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth, thirteenth) =>
            {
                var subject = new AsyncSubject<Unit>();
                scheduler.Schedule(() =>
                {
                    try
                    {
                        action(first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth, thirteenth);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(Unit.Default);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, IObservable<Unit>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14>(Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14> action)
        {
            return ToAsync(action, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, IObservable<Unit>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14>(Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14> action, IScheduler scheduler)
        {
            return (first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth, thirteenth, fourteenth) =>
            {
                var subject = new AsyncSubject<Unit>();
                scheduler.Schedule(() =>
                {
                    try
                    {
                        action(first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth, thirteenth, fourteenth);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(Unit.Default);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, IObservable<Unit>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15>(Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15> action)
        {
            return ToAsync(action, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, IObservable<Unit>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15>(Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15> action, IScheduler scheduler)
        {
            return (first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth, thirteenth, fourteenth, fifteenth) =>
            {
                var subject = new AsyncSubject<Unit>();
                scheduler.Schedule(() =>
                {
                    try
                    {
                        action(first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth, thirteenth, fourteenth, fifteenth);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(Unit.Default);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, IObservable<Unit>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16>(Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16> action)
        {
            return ToAsync(action, SchedulerDefaults.AsyncConversions);
        }

        public virtual Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, IObservable<Unit>> ToAsync<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16>(Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16> action, IScheduler scheduler)
        {
            return (first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth, thirteenth, fourteenth, fifteenth, sixteenth) =>
            {
                var subject = new AsyncSubject<Unit>();
                scheduler.Schedule(() =>
                {
                    try
                    {
                        action(first, second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, twelfth, thirteenth, fourteenth, fifteenth, sixteenth);
                    }
                    catch (Exception exception)
                    {
                        subject.OnError(exception);
                        return;
                    }
                    subject.OnNext(Unit.Default);
                    subject.OnCompleted();
                });
                return subject.AsObservable();
            };
        }

#endif

        #endregion

        #endregion
    }
}