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

using System;
using System.Linq;
using System.Threading;
using Xunit;

public partial class TimerFiringTests
{
    internal const int MaxPositiveTimeoutInMs = 30000;

    [Fact]
    public void Timer_Fires_After_DueTime_Ellapses()
    {
        AutoResetEvent are = new AutoResetEvent(false);

        using (var t = new Timer(new TimerCallback((object s) =>
        {
            are.Set();
        }), null, TimeSpan.FromMilliseconds(250), TimeSpan.FromMilliseconds(Timeout.Infinite) /* not relevant */))
        {
            Assert.True(are.WaitOne(TimeSpan.FromMilliseconds(MaxPositiveTimeoutInMs)));
        }
    }

    [Fact]
    public void Timer_Fires_AndPassesStateThroughCallback()
    {
        AutoResetEvent are = new AutoResetEvent(false);

        object state = new object();
        using (var t = new Timer(new TimerCallback((object s) =>
        {
            Assert.Same(s, state);
            are.Set();
        }), state, TimeSpan.FromMilliseconds(100), TimeSpan.FromMilliseconds(Timeout.Infinite) /* not relevant */))
        {
            Assert.True(are.WaitOne(TimeSpan.FromMilliseconds(MaxPositiveTimeoutInMs)));
        }
    }

    [Fact]
    public void Timer_Fires_AndPassesNullStateThroughCallback()
    {
        AutoResetEvent are = new AutoResetEvent(false);

        using (var t = new Timer(new TimerCallback((object s) =>
        {
            Assert.Null(s);
            are.Set();
        }), null, TimeSpan.FromMilliseconds(100), TimeSpan.FromMilliseconds(Timeout.Infinite) /* not relevant */))
        {
            Assert.True(are.WaitOne(TimeSpan.FromMilliseconds(MaxPositiveTimeoutInMs)));
        }
    }

    [Fact]
    public void Timer_Fires_After_DueTime_AndOn_Period()
    {
        int count = 0;
        AutoResetEvent are = new AutoResetEvent(false);

        using (var t = new Timer(new TimerCallback((object s) =>
        {
            if (Interlocked.Increment(ref count) >= 2)
            {
                are.Set();
            }
        }), null, TimeSpan.FromMilliseconds(250), TimeSpan.FromMilliseconds(50)))
        {
            Assert.True(are.WaitOne(TimeSpan.FromMilliseconds(MaxPositiveTimeoutInMs)));
        }
    }

    [Fact]
    public void Timer_FiresOnlyOnce_OnDueTime_With_InfinitePeriod()
    {
        int count = 0;
        AutoResetEvent are = new AutoResetEvent(false);

        using (var t = new Timer(new TimerCallback((object s) =>
        {
            if (Interlocked.Increment(ref count) >= 2)
            {
                are.Set();
            }
        }), null, TimeSpan.FromMilliseconds(100), TimeSpan.FromMilliseconds(Timeout.Infinite) /* not relevant */))
        {
            Assert.False(are.WaitOne(TimeSpan.FromMilliseconds(250 /*enough for 2 fires + buffer*/)));
        }
    }

    [Fact]
    public void Timer_CanDisposeSelfInCallback()
    {
        Timer t = null;
        AutoResetEvent are = new AutoResetEvent(false);
        TimerCallback tc = new TimerCallback((object o) =>
        {
            t.Dispose();
            are.Set();
        });
        t = new Timer(tc, null, -1, -1);
        t.Change(1, -1);
        Assert.True(are.WaitOne(MaxPositiveTimeoutInMs));
        GC.KeepAlive(t);
    }

    [Fact]
    public void Timer_CanBeDisposedMultipleTimes()
    {
        // There's nothing to validate besides that we don't throw an exception, so rely on xunit 
        // to catch any exception that would be thrown and signal a test failure
        TimerCallback tc = new TimerCallback((object o) => { });
        var t = new Timer(tc, null, 100, -1);
        for (int i = 0; i < 10; i++)
            t.Dispose();
    }

    [Fact]
    public void NonRepeatingTimer_ThatHasAlreadyFired_CanChangeAndFireAgain()
    {
        AutoResetEvent are = new AutoResetEvent(false);
        TimerCallback tc = new TimerCallback((object o) => are.Set());
        using (var t = new Timer(tc, null, 1, Timeout.Infinite))
        {
            Assert.True(are.WaitOne(MaxPositiveTimeoutInMs), "Should have received first timer event");
            Assert.False(are.WaitOne(500), "Should not have received a second timer event");
            t.Change(10, Timeout.Infinite);
            Assert.True(are.WaitOne(MaxPositiveTimeoutInMs), "Should have received a second timer event after changing it");
        }
    }

    [Fact]
    public void Running_Timer_CanBeFinalizedAndStopsFiring()
    {
        AutoResetEvent are = new AutoResetEvent(false);
        TimerCallback tc = new TimerCallback((object o) => are.Set());
        var t = new Timer(tc, null, 1, 500);
        Assert.True(are.WaitOne(MaxPositiveTimeoutInMs), "Failed to get first timer fire");
        t = null; // Remove our refence so the timer can be GC'd 
        GC.Collect();
        GC.WaitForPendingFinalizers();
        GC.Collect();
        Assert.False(are.WaitOne(500), "Should not have received a timer fire after it was collected");
    }

    [Fact]
    public void MultpleTimers_PeriodicTimerIsntBlockedByBlockedCallback()
    {
        int callbacks = 2;
        Barrier b = new Barrier(callbacks + 1);
        Timer t = null;
        t = new Timer(_ =>
        {
            if (Interlocked.Decrement(ref callbacks) >= 0)
            {
                Assert.True(b.SignalAndWait(MaxPositiveTimeoutInMs));
            }
            t.Dispose();
        }, null, -1, -1);
        t.Change(1, 50);

        Assert.True(b.SignalAndWait(MaxPositiveTimeoutInMs));
        GC.KeepAlive(t);
    }

    [Fact]
    public void ManyTimers_EachTimerDoesFire()
    {
        int maxTimers = 10000;
        CountdownEvent ce = new CountdownEvent(maxTimers);
        Timer[] timers = System.Linq.Enumerable.Range(0, maxTimers).Select(_ => new Timer(s => ce.Signal(), null, 100 /* enough time to wait on the are */, -1)).ToArray();
        try
        {
            Assert.True(ce.Wait(MaxPositiveTimeoutInMs), String.Format("Not all timers fired, {0} left of {1}", ce.CurrentCount, maxTimers));
        }
        finally
        {
            foreach (Timer t in timers)
                t.Dispose();
        }
    }
}