// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System.Diagnostics;
using System.IO.Pipelines;
using System.Runtime.CompilerServices;

namespace System.Threading.Tasks
{
    public static class TaskExtensions
    {
        private const int DefaultTimeout = 5000;

        public static Task OrTimeout(this Task task, int milliseconds = DefaultTimeout, [CallerMemberName] string memberName = null, [CallerFilePath] string filePath = null, [CallerLineNumber] int? lineNumber = null)
        {
            return OrTimeout(task, new TimeSpan(0, 0, 0, 0, milliseconds), memberName, filePath, lineNumber);
        }

        public static async Task OrTimeout(this Task task, TimeSpan timeout, [CallerMemberName] string memberName = null, [CallerFilePath] string filePath = null, [CallerLineNumber] int? lineNumber = null)
        {
            if (task.IsCompleted)
            {
                await task;
                return;
            }

            var cts = new CancellationTokenSource();
            var completed = await Task.WhenAny(task, Task.Delay(Debugger.IsAttached ? Timeout.InfiniteTimeSpan : timeout, cts.Token));
            if (completed != task)
            {
                throw new TimeoutException(GetMessage(memberName, filePath, lineNumber));
            }
            cts.Cancel();

            await task;
        }

        public static Task<T> OrTimeout<T>(this Task<T> task, int milliseconds = DefaultTimeout, [CallerMemberName] string memberName = null, [CallerFilePath] string filePath = null, [CallerLineNumber] int? lineNumber = null)
        {
            return OrTimeout(task, new TimeSpan(0, 0, 0, 0, milliseconds), memberName, filePath, lineNumber);
        }

        public static async Task<T> OrTimeout<T>(this Task<T> task, TimeSpan timeout, [CallerMemberName] string memberName = null, [CallerFilePath] string filePath = null, [CallerLineNumber] int? lineNumber = null)
        {
            if (task.IsCompleted)
            {
                return await task;
            }

            var cts = new CancellationTokenSource();
            var completed = await Task.WhenAny(task, Task.Delay(Debugger.IsAttached ? Timeout.InfiniteTimeSpan : timeout, cts.Token));
            if (completed != task)
            {
                throw new TimeoutException(GetMessage(memberName, filePath, lineNumber));
            }
            cts.Cancel();

            return await task;
        }

        public static async Task OrThrowIfOtherFails(this Task task, Task otherTask)
        {
            var completed = await Task.WhenAny(task, otherTask);
            if(completed == otherTask && otherTask.IsFaulted)
            {
                // Manifest the exception
                otherTask.GetAwaiter().GetResult();
                throw new Exception("Unreachable code");
            }
            else
            {
                // Await the task we were asked to await. Either it's finished, or the otherTask finished successfully, and it's not our job to check that
                await task;
            }
        }

        public static async Task<T> OrThrowIfOtherFails<T>(this Task<T> task, Task otherTask)
        {
            await OrThrowIfOtherFails((Task)task, otherTask);

            // If we get here, 'task' is finished and succeeded.
            return task.GetAwaiter().GetResult();
        }

        private static string GetMessage(string memberName, string filePath, int? lineNumber)
        {
            if (!string.IsNullOrEmpty(memberName))
            {
                return $"Operation in {memberName} timed out at {filePath}:{lineNumber}";
            }
            else
            {
                return "Operation timed out";
            }
        }
    }
}