using System.Threading;
using System;
using Implab.Diagnostics;
using System.Collections.Generic;
using System.Linq;

namespace Implab {
    public static class PromiseExtensions {
        public static IPromise<T> DispatchToCurrentContext<T>(this IPromise<T> that) {
            Safe.ArgumentNotNull(that, "that");
            var context = SynchronizationContext.Current;
            if (context == null)
                return that;

            var p = new SyncContextPromise<T>(context);
            p.CancellationRequested(that.Cancel);

            that.On(
                p.Resolve,
                p.Reject,
                p.CancelOperation
            );
            return p;
        }

        public static IPromise<T> DispatchToContext<T>(this IPromise<T> that, SynchronizationContext context) {
            Safe.ArgumentNotNull(that, "that");
            Safe.ArgumentNotNull(context, "context");

            var p = new SyncContextPromise<T>(context);
            p.CancellationRequested(that.Cancel);

            that.On(
                p.Resolve,
                p.Reject,
                p.CancelOperation
            );
            return p;
        }

        /// <summary>
        /// Ensures the dispatched.
        /// </summary>
        /// <returns>The dispatched.</returns>
        /// <param name="that">That.</param>
        /// <param name="head">Head.</param>
        /// <param name="cleanup">Cleanup.</param>
        /// <typeparam name="TPromise">The 1st type parameter.</typeparam>
        /// <typeparam name="T">The 2nd type parameter.</typeparam>
        public static TPromise EnsureDispatched<TPromise, T>(this TPromise that, IPromise<T> head, Action<T> cleanup) where TPromise : IPromise {
            Safe.ArgumentNotNull(that, "that");
            Safe.ArgumentNotNull(head, "head");

            that.On(() => head.On(cleanup), PromiseEventType.Cancelled);

            return that;
        }

        /// <summary>
        /// Adds a cancellation point to the chain of promises. When a cancellation request reaches the cancellation point the operation is
        /// cancelled immediatelly, and the request is passed towards. If the operation at the higher level can not be cancelled is't result
        /// will be collected with <paramref name="cleanup"/> callback.
        /// </summary>
        /// <typeparam name="T">The type of the promise result.</typeparam>
        /// <param name="that">The promise to which the cancellation point should be attached.</param>
        /// <param name="cleanup">The callback which is used to cleanup the result of the operation if the cancellation point is cancelled already.</param>
        /// <returns>The promise</returns>
        public static IPromise<T> CancellationPoint<T>(this IPromise<T> that, Action<T> cleanup) {
            var meduim = new Promise<T>();

            that.On(meduim.Resolve, meduim.Reject, meduim.CancelOperation);

            meduim.CancellationRequested(that.Cancel);
            meduim.CancellationRequested(meduim.CancelOperation);

            if (cleanup != null)
                meduim.On((Action<T>)null, null, (e) => {
                    that.On(cleanup);
                });

            return meduim;
        }

        public static AsyncCallback AsyncCallback<T>(this Promise<T> that, Func<IAsyncResult, T> callback) {
            Safe.ArgumentNotNull(that, "that");
            Safe.ArgumentNotNull(callback, "callback");
            var op = TraceContext.Instance.CurrentOperation;
            return ar => {
                TraceContext.Instance.EnterLogicalOperation(op, false);
                try {
                    that.Resolve(callback(ar));
                } catch (Exception err) {
                    that.Reject(err);
                } finally {
                    TraceContext.Instance.Leave();
                }
            };
        }

        static void CancelByTimeoutCallback(object cookie) {
            ((ICancellable)cookie).Cancel(new TimeoutException());
        }

        /// <summary>
        /// Cancells promise after the specified timeout is elapsed.
        /// </summary>
        /// <param name="that">The promise to cancel on timeout.</param>
        /// <param name="milliseconds">The timeout in milliseconds.</param>
        /// <typeparam name="TPromise">The 1st type parameter.</typeparam>
        public static TPromise Timeout<TPromise>(this TPromise that, int milliseconds) where TPromise : IPromise {
            Safe.ArgumentNotNull(that, "that");
            var timer = new Timer(CancelByTimeoutCallback, that, milliseconds, -1);
            that.On(timer.Dispose, PromiseEventType.All);
            return that;
        }

        public static IPromise PromiseAll(this IEnumerable<IPromise> that) {
            Safe.ArgumentNotNull(that, "that");
            return PromiseAll(that.ToList());
        }

        public static IPromise<T[]> PromiseAll<T>(this IEnumerable<IPromise<T>> that) {
            return PromiseAll(that, null);
        }

        public static IPromise<T[]> PromiseAll<T>(this IEnumerable<IPromise<T>> that, Action<T> cleanup) {
            Safe.ArgumentNotNull(that, "that");
            return PromiseAll(that.ToList(), cleanup);
        }

        public static IPromise PromiseAll(this ICollection<IPromise> that) {
            Safe.ArgumentNotNull(that, "that");

            int count = that.Count;
            int errors = 0;
            var medium = new Promise();

            if (count == 0) {
                medium.Resolve();
                return medium;
            }

            medium.On(() => {
                foreach (var p2 in that)
                    p2.Cancel();
            }, PromiseEventType.ErrorOrCancel);

            foreach (var p in that)
                p.On(
                    () => {
                        if (Interlocked.Decrement(ref count) == 0)
                            medium.Resolve();
                    },
                    error => {
                        if (Interlocked.Increment(ref errors) == 1)
                            medium.Reject(
                                new Exception("The dependency promise is failed", error)
                            );
                    },
                    reason => {
                        if (Interlocked.Increment(ref errors) == 1)
                            medium.Cancel(
                                new Exception("The dependency promise is cancelled")
                            );
                    }
                );

            return medium;
        }

        public static IPromise<T[]> PromiseAll<T>(this ICollection<IPromise<T>> that) {
            return PromiseAll(that, null);
        }

        /// <summary>
        /// Creates a new promise which will be satisfied when all promises are satisfied.
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="that"></param>
        /// <param name="cleanup">A callback used to cleanup already resolved promises in case of an error</param>
        /// <returns></returns>
        public static IPromise<T[]> PromiseAll<T>(this ICollection<IPromise<T>> that, Action<T> cleanup) {
            Safe.ArgumentNotNull(that, "that");

            int count = that.Count;

            if (count == 0)
                return Promise<T[]>.FromResult(new T[0]);

            int errors = 0;
            var medium = new Promise<T[]>();
            var results = new T[that.Count];

            medium.On(() => {
                foreach (var p2 in that) {
                    p2.Cancel();
                    if (cleanup != null)
                        p2.On(cleanup);
                }
            }, PromiseEventType.ErrorOrCancel);

            int i = 0;
            foreach (var p in that) {
                var idx = i;
                p.On(
                    x => {
                        results[idx] = x;
                        if (Interlocked.Decrement(ref count) == 0)
                            medium.Resolve(results);
                    },
                    error => {
                        if (Interlocked.Increment(ref errors) == 1)
                            medium.Reject(
                                new Exception("The dependency promise is failed", error)
                            );
                    },
                    reason => {
                        if (Interlocked.Increment(ref errors) == 1)
                            medium.Cancel(
                                new Exception("The dependency promise is cancelled", reason)
                            );
                    }
                );
                i++;
            }

            return medium;
        }

        public static IPromise Then(this IPromise that, Action success, Action<Exception> error, Action<Exception> cancel) {
            Safe.ArgumentNotNull(that, "that");

            var d = new ActionTask(success, error, cancel, false);
            that.On(d.Resolve, d.Reject, d.CancelOperation);
            d.CancellationRequested(that.Cancel);
            return d;
        }

        public static IPromise Then(this IPromise that, Action success, Action<Exception> error) {
            return Then(that, success, error, null);
        }

        public static IPromise Then(this IPromise that, Action success) {
            return Then(that, success, null, null);
        }

        public static IPromise<T> Then<T>(this IPromise that, Func<T> success, Func<Exception, T> error, Func<Exception, T> cancel) {
            Safe.ArgumentNotNull(that, "that");

            var d = new FuncTask<T>(success, error, cancel, false);
            that.On(d.Resolve, d.Reject, d.CancelOperation);
            d.CancellationRequested(that.Cancel);
            return d;
        }

        public static IPromise<T> Then<T>(this IPromise that, Func<T> success, Func<Exception, T> error) {
            return Then(that, success, error, null);
        }

        public static IPromise<T> Then<T>(this IPromise that, Func<T> success) {
            return Then(that, success, null, null);
        }

        public static IPromise<T2> Then<T, T2>(this IPromise<T> that, Func<T, T2> success, Func<Exception, T2> error, Func<Exception, T2> cancel) {
            Safe.ArgumentNotNull(that, "that");
            Safe.ArgumentNotNull(success, "success");

            var d = new FuncTask<T, T2>(success, error, cancel, false);
            that.On(d.Resolve, d.Reject, d.CancelOperation);
            d.CancellationRequested(that.Cancel);
            return d;
        }

        public static IPromise<T> Then<T>(this IPromise<T> that, Action<T> success, Func<Exception, T> error, Func<Exception, T> cancel) {
            Safe.ArgumentNotNull(that, "that");
            var d = new FuncTask<T, T>(
                x => {
                    success(x);
                    return x;
                },
                error,
                cancel,
                false
            );
            that.On(d.Resolve, d.Reject, d.CancelOperation);
            d.CancellationRequested(that.Cancel);
            return d;
        }

        public static IPromise<T> Then<T>(this IPromise<T> that, Action<T> success, Func<Exception, T> error) {
            return Then(that, success, error, null);
        }

        public static IPromise<T> Then<T>(this IPromise<T> that, Action<T> success) {
            return Then(that, success, null, null);
        }

        public static IPromise<T2> Then<T, T2>(this IPromise<T> that, Func<T, T2> success, Func<Exception, T2> error) {
            return Then(that, success, error, null);
        }

        public static IPromise<T2> Then<T, T2>(this IPromise<T> that, Func<T, T2> success) {
            return Then(that, success, null, null);
        }

        public static IPromise<T> Always<T>(this IPromise<T> that, Action handler) {
            Func<Exception, T> errorOrCancel;
            if (handler != null)
                errorOrCancel = e => {
                    handler();
                    throw new PromiseTransientException(e);
                };
            else
                errorOrCancel = null;

            return Then(
                that,
                x => {
                    handler();
                    return x;
                },
                errorOrCancel,
                errorOrCancel);
        }

        public static IPromise Always(this IPromise that, Action handler) {
            Action<Exception> errorOrCancel;
            if (handler != null)
                errorOrCancel = e => {
                    handler();
                    throw new PromiseTransientException(e);
                };
            else
                errorOrCancel = null;

            return Then(
                that,
                handler,
                errorOrCancel,
                errorOrCancel);
        }

        public static IPromise Error(this IPromise that, Action<Exception> handler, bool handleCancellation) {
            Action<Exception> errorOrCancel;
            if (handler != null)
                errorOrCancel = e => {
                    handler(e);
                    throw new PromiseTransientException(e);
                };
            else
                errorOrCancel = null;

            return Then(that, null, errorOrCancel, handleCancellation ? errorOrCancel : null);
        }

        public static IPromise Error(this IPromise that, Action<Exception> handler) {
            return Error(that, handler, false);
        }

        public static IPromise<T> Error<T>(this IPromise<T> that, Action<Exception> handler, bool handleCancellation) {
            Func<Exception, T> errorOrCancel;
            if (handler != null)
                errorOrCancel = e => {
                    handler(e);
                    throw new PromiseTransientException(e);
                };
            else
                errorOrCancel = null;

            return Then(that, null, errorOrCancel, handleCancellation ? errorOrCancel : null);
        }

        public static IPromise<T> Error<T>(this IPromise<T> that, Action<Exception> handler) {
            return Error(that, handler, false);
        }

        #region chain traits
        public static IPromise Chain(this IPromise that, Func<IPromise> success, Func<Exception, IPromise> error, Func<Exception, IPromise> cancel) {
            Safe.ArgumentNotNull(that, "that");

            var d = new ActionChainTask(success, error, cancel, false);
            that.On(d.Resolve, d.Reject, d.CancelOperation);
            d.CancellationRequested(that.Cancel);
            return d;
        }

        public static IPromise Chain(this IPromise that, Func<IPromise> success, Func<Exception, IPromise> error) {
            return Chain(that, success, error, null);
        }

        public static IPromise Chain(this IPromise that, Func<IPromise> success) {
            return Chain(that, success, null, null);
        }

        public static IPromise<T> Chain<T>(this IPromise that, Func<IPromise<T>> success, Func<Exception, IPromise<T>> error, Func<Exception, IPromise<T>> cancel) {
            Safe.ArgumentNotNull(that, "that");

            var d = new FuncChainTask<T>(success, error, cancel, false);
            that.On(d.Resolve, d.Reject, d.CancelOperation);
            if (success != null)
                d.CancellationRequested(that.Cancel);
            return d;
        }

        public static IPromise<T> Chain<T>(this IPromise that, Func<IPromise<T>> success, Func<Exception, IPromise<T>> error) {
            return Chain(that, success, error, null);
        }

        public static IPromise<T> Chain<T>(this IPromise that, Func<IPromise<T>> success) {
            return Chain(that, success, null, null);
        }

        public static IPromise<T2> Chain<T, T2>(this IPromise<T> that, Func<T, IPromise<T2>> success, Func<Exception, IPromise<T2>> error, Func<Exception, IPromise<T2>> cancel) {
            Safe.ArgumentNotNull(that, "that");
            var d = new FuncChainTask<T, T2>(success, error, cancel, false);
            that.On(d.Resolve, d.Reject, d.CancelOperation);
            if (success != null)
                d.CancellationRequested(that.Cancel);
            return d;
        }

        public static IPromise<T2> Chain<T, T2>(this IPromise<T> that, Func<T, IPromise<T2>> success, Func<Exception, IPromise<T2>> error) {
            return Chain(that, success, error, null);
        }

        public static IPromise<T2> Chain<T, T2>(this IPromise<T> that, Func<T, IPromise<T2>> success) {
            return Chain(that, success, null, null);
        }

        #endregion

        public static IPromise<T2> Guard<T, T2>(this IPromise<T> that, Func<IPromise<T>, IPromise<T2>> continuation, Action<T> cleanup) {
            Safe.ArgumentNotNull(that, "that");
            Safe.ArgumentNotNull(continuation, "continuation");
            return continuation(that).Error((err) => {
                that.On(cleanup);
            }, true);
        }

#if NET_4_5

        public static PromiseAwaiter<T> GetAwaiter<T>(this IPromise<T> that) {
            Safe.ArgumentNotNull(that, "that");

            return new PromiseAwaiter<T>(that);
        }

        public static PromiseAwaiter GetAwaiter(this IPromise that) {
            Safe.ArgumentNotNull(that, "that");

            return new PromiseAwaiter(that);
        }

        public static IPromise BoundCancellationToken(this IPromise that, CancellationToken ct) {
            Safe.ArgumentNotNull(that, "that");
            ct.Register(that.Cancel);
            return that.Then(null, null, (err) => {
                ct.ThrowIfCancellationRequested();
                throw new PromiseTransientException(err);
            });
        }

        public static IPromise<T> BoundCancellationToken<T>(this IPromise<T> that, CancellationToken ct) {
            Safe.ArgumentNotNull(that, "that");
            ct.Register(that.Cancel);
            return that.Then(null, null, (err) => {
                ct.ThrowIfCancellationRequested();
                throw new PromiseTransientException(err);
            });
        }

#endif
    }
}