using Nonemm.Keying;

namespace Nonemm.Session.Tests;

public class AlternatingCqTests
{
    /// A keyer that sends nothing and says it has finished when the test says
    /// so, so the alternation is what is under test rather than a timer.
    private sealed class FakeKeyer : MessageSender
    {
        public bool IsReady => true;

        public bool ReportsCompletion { get; init; } = true;

        public event EventHandler? Finished;

        public void FinishMessage() => Finished?.Invoke(this, EventArgs.Empty);

        public Task SendAsync(string text, CancellationToken cancellation = default) =>
            Task.CompletedTask;

        public Task AbortAsync(CancellationToken cancellation = default) => Task.CompletedTask;

        public Task SetSpeedAsync(int wordsPerMinute, CancellationToken cancellation = default) =>
            Task.CompletedTask;

        public void Dispose()
        {
        }
    }

    private static readonly Func<TimeSpan, CancellationToken, Task> NoWait =
        (_, _) => Task.CompletedTask;

    private static AlternatingCq Driving(FakeKeyer keyer, List<int> called) =>
        new(
            keyer,
            radio =>
            {
                called.Add(radio);
                return Task.CompletedTask;
            },
            TimeSpan.Zero,
            NoWait);

    [Fact]
    public void StartingCallsOnTheRadioItWasGiven()
    {
        FakeKeyer keyer = new();
        List<int> called = [];
        using AlternatingCq cq = Driving(keyer, called);

        cq.Start(2);

        Assert.Equal([2], called);
        Assert.True(cq.IsRunning);
        Assert.Equal(2, cq.RadioNumber);
    }

    [Fact]
    public void TheOtherRadioCallsOnceTheMessageHasGoneOut()
    {
        FakeKeyer keyer = new();
        List<int> called = [];
        using AlternatingCq cq = Driving(keyer, called);

        cq.Start(1);
        keyer.FinishMessage();
        keyer.FinishMessage();
        keyer.FinishMessage();

        Assert.Equal([1, 2, 1, 2], called);
    }

    [Fact]
    public void StoppingLeavesTheKeyerAlone()
    {
        FakeKeyer keyer = new();
        List<int> called = [];
        using AlternatingCq cq = Driving(keyer, called);

        cq.Start(1);
        cq.Stop();
        keyer.FinishMessage();

        Assert.Equal([1], called);
        Assert.False(cq.IsRunning);
    }

    /// The message that was already going out when the operator stopped still
    /// reports itself finished, and that must not start the other radio.
    [Fact]
    public void AMessageFinishingAfterAStopStartsNothing()
    {
        FakeKeyer keyer = new();
        List<int> called = [];
        using AlternatingCq cq = Driving(keyer, called);

        cq.Start(1);
        keyer.FinishMessage();
        cq.Stop();
        keyer.FinishMessage();

        Assert.Equal([1, 2], called);
    }

    /// A message that is not a CQ leaves the CQ where it is, and the next CQ
    /// carries the alternation on. This is what happens while a contact is
    /// worked, and it is N1MM's rule.
    [Fact]
    public void WorkingAStationHoldsTheCqOnOneRadio()
    {
        FakeKeyer keyer = new();
        List<int> called = [];
        using AlternatingCq cq = Driving(keyer, called);

        cq.Start(1);
        cq.Hold();
        keyer.FinishMessage();
        keyer.FinishMessage();

        Assert.Equal([1], called);
        Assert.True(cq.IsRunning);
        Assert.False(cq.CarriesOn);
    }

    /// The CQ that follows a logged contact starts the alternation again,
    /// without the operator switching it back on.
    [Fact]
    public void TheNextCqCarriesTheAlternationOnAgain()
    {
        FakeKeyer keyer = new();
        List<int> called = [];
        using AlternatingCq cq = Driving(keyer, called);

        cq.Start(1);
        cq.Hold();
        keyer.FinishMessage();
        cq.CarryOn();
        keyer.FinishMessage();

        Assert.Equal([1, 2], called);
    }

    [Fact]
    public void AKeyerThatCannotReportCompletionCannotDriveIt()
    {
        FakeKeyer keyer = new() { ReportsCompletion = false };
        List<int> called = [];
        using AlternatingCq cq = Driving(keyer, called);

        Assert.False(cq.IsPossible);
        Assert.Throws<InvalidOperationException>(() => cq.Start(1));
        Assert.Empty(called);
    }

    [Fact]
    public void AKeyerThatHasGoneAwayStopsTheWholeThing()
    {
        FakeKeyer keyer = new();
        List<string> reasons = [];
        using AlternatingCq cq = new(
            keyer,
            _ => throw new InvalidOperationException("could not reach cwdaemon at 127.0.0.1:6789"),
            TimeSpan.Zero,
            NoWait);
        cq.Stopped += (_, reason) => reasons.Add(reason);

        cq.Start(1);

        Assert.False(cq.IsRunning);
        Assert.Equal(["could not reach cwdaemon at 127.0.0.1:6789"], reasons);
    }
}