using MeetingAssistant.Notifications;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging.Abstractions;

namespace MeetingAssistant.Tests;

public sealed class DesktopUserRequestTests
{
    [Fact]
    public async Task OfferedDecisionIsListedAndDeliveredOnce()
    {
        using var lifetime = new TestApplicationLifetime();
        using var store = CreateStore(lifetime);
        var registration = store.Add(Approval(), CancellationToken.None);
        var request = Assert.Single(store.List());
        Assert.Equal(registration.Id, request.Id);
        Assert.Equal("Associate Alpha?", request.Title);
        Assert.Equal(["yes", "no"], request.Actions.Select(action => action.Id));
        Assert.False(registration.Decision.IsCompleted);

        Assert.Equal(DesktopUserRequestRespondResult.Accepted, await store.RespondAsync(request.Id, "yes"));
        Assert.Equal("yes", await registration.Decision);
        Assert.Empty(store.List());
        Assert.Equal(DesktopUserRequestRespondResult.NoLongerPending, await store.RespondAsync(request.Id, "yes"));
    }

    [Fact]
    public async Task UnsupportedActionLeavesDecisionPending()
    {
        using var lifetime = new TestApplicationLifetime();
        using var store = CreateStore(lifetime);
        var registration = store.Add(Approval(), CancellationToken.None);
        Assert.Equal(DesktopUserRequestRespondResult.InvalidAction, await store.RespondAsync(registration.Id, "delete"));
        Assert.Single(store.List());
        Assert.False(registration.Decision.IsCompleted);
        Assert.Equal(DesktopUserRequestRespondResult.Accepted, await store.RespondAsync(registration.Id, "no"));
        Assert.Equal("no", await registration.Decision);
    }

    [Fact]
    public async Task CanceledOriginRemovesDecisionAndRejectsLateResponse()
    {
        using var lifetime = new TestApplicationLifetime();
        using var store = CreateStore(lifetime);
        using var origin = new CancellationTokenSource();
        var invoked = false;
        var registration = store.Add(Approval(), origin.Token, (_, _) =>
        {
            invoked = true;
            return Task.CompletedTask;
        });
        await origin.CancelAsync();
        Assert.Empty(store.List());
        Assert.Null(await registration.Decision.WaitAsync(TimeSpan.FromSeconds(2)));
        Assert.Equal(DesktopUserRequestRespondResult.NoLongerPending, await store.RespondAsync(registration.Id, "yes"));
        Assert.False(invoked);
    }

    [Fact]
    public async Task DeadlineResolvesUnansweredDecisionWithoutPolling()
    {
        using var lifetime = new TestApplicationLifetime();
        var clock = new ManualDesktopRequestTimeProvider();
        using var store = new DesktopUserRequestStore(clock, lifetime, NullLogger<DesktopUserRequestStore>.Instance);
        var registration = store.Add(Approval(), CancellationToken.None);
        Assert.Equal(DateTimeOffset.Parse("2026-10-03T10:10:00Z"), Assert.Single(store.List()).ExpiresAt);
        clock.Advance(TimeSpan.FromMinutes(10));
        Assert.True(registration.Decision.IsCompleted);
        Assert.Null(await registration.Decision);
        Assert.Empty(store.List());
        Assert.Equal(DesktopUserRequestRespondResult.NoLongerPending, await store.RespondAsync(registration.Id, "yes"));
    }

    [Fact]
    public async Task KindWithdrawalPreservesOtherQuestionsAndShutdownRemovesThem()
    {
        using var lifetime = new TestApplicationLifetime();
        using var store = CreateStore(lifetime);
        var approval = store.Add(Approval(), CancellationToken.None);
        var warning = store.Add(Approval() with { Kind = "meeting-inactivity" }, CancellationToken.None);
        store.DismissKind("meeting-inactivity");
        Assert.Equal(approval.Id, Assert.Single(store.List()).Id);
        Assert.Null(await warning.Decision.WaitAsync(TimeSpan.FromSeconds(2)));
        Assert.Equal(DesktopUserRequestRespondResult.NoLongerPending, await store.RespondAsync(warning.Id, "yes"));
        lifetime.StopApplication();
        Assert.Empty(store.List());
        Assert.Null(await approval.Decision.WaitAsync(TimeSpan.FromSeconds(2)));
        Assert.Equal(DesktopUserRequestRespondResult.NoLongerPending, await store.RespondAsync(approval.Id, "yes"));
    }

    [Fact]
    public async Task FailedActionIsConsumedAndReportedWithoutReplayingWork()
    {
        using var lifetime = new TestApplicationLifetime();
        using var store = CreateStore(lifetime);
        var registration = store.Add(Approval(), CancellationToken.None,
            (_, _) => throw new InvalidOperationException("Test action could not finish."));
        Assert.Equal(DesktopUserRequestRespondResult.Failed, await store.RespondAsync(registration.Id, "yes"));
        Assert.Null(await registration.Decision);
        Assert.Empty(store.List());
        Assert.Equal(DesktopUserRequestRespondResult.NoLongerPending, await store.RespondAsync(registration.Id, "yes"));
    }

    [Fact]
    public async Task PendingListExcludesDeadlinesBeforeTimerDispatch()
    {
        using var lifetime = new TestApplicationLifetime();
        var clock = new ManualDesktopRequestTimeProvider();
        using var store = new DesktopUserRequestStore(clock, lifetime, NullLogger<DesktopUserRequestStore>.Instance);
        var registration = store.Add(Approval(), CancellationToken.None);
        clock.Advance(TimeSpan.FromMinutes(10), fireTimers: false);
        Assert.Empty(store.List());
        Assert.Null(await registration.Decision);
        Assert.Equal(DesktopUserRequestRespondResult.NoLongerPending, await store.RespondAsync(registration.Id, "yes"));
    }

    [Fact]
    public async Task SimultaneousPresentationsUseTheOriginLifetimeAndPerformOneAction()
    {
        using var lifetime = new TestApplicationLifetime();
        using var origin = new CancellationTokenSource();
        using var store = CreateStore(lifetime);
        var started = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
        var finish = new TaskCompletionSource(TaskCreationOptions.RunContinuationsAsynchronously);
        var actionCount = 0;
        CancellationToken observedToken = default;
        var registration = store.Add(Approval(), origin.Token, async (_, token) =>
        {
            Interlocked.Increment(ref actionCount);
            observedToken = token;
            started.TrySetResult();
            await finish.Task.WaitAsync(token);
        });
        var firstResponse = store.RespondAsync(registration.Id, "yes");
        await started.Task.WaitAsync(TimeSpan.FromSeconds(2));
        Assert.Equal(DesktopUserRequestRespondResult.NoLongerPending, await store.RespondAsync(registration.Id, "no"));
        Assert.Equal(origin.Token, observedToken);
        finish.SetResult();
        Assert.Equal(DesktopUserRequestRespondResult.Accepted, await firstResponse);
        Assert.Equal("yes", await registration.Decision);
        Assert.Equal(1, actionCount);
    }

    private static DesktopUserRequestSpec Approval() => new(
        "agent-approval", "Associate Alpha?", "The meeting discusses Alpha.", TimeSpan.FromMinutes(10),
        [new("yes", "Yes"), new("no", "No")]);

    private static DesktopUserRequestStore CreateStore(TestApplicationLifetime lifetime) => new(
        TimeProvider.System, lifetime, NullLogger<DesktopUserRequestStore>.Instance);
}

internal sealed class TestApplicationLifetime : IHostApplicationLifetime, IDisposable
{
    private readonly CancellationTokenSource stopping = new();
    public CancellationToken ApplicationStarted => CancellationToken.None;
    public CancellationToken ApplicationStopping => stopping.Token;
    public CancellationToken ApplicationStopped => stopping.Token;
    public void StopApplication() => stopping.Cancel();
    public void Dispose() => stopping.Dispose();
}

internal sealed class ManualDesktopRequestTimeProvider : TimeProvider
{
    private DateTimeOffset now = DateTimeOffset.Parse("2026-10-03T10:00:00Z");
    private readonly List<ManualTimer> timers = [];
    public override DateTimeOffset GetUtcNow() => now;
    public override ITimer CreateTimer(TimerCallback callback, object? state, TimeSpan dueTime, TimeSpan period)
    {
        var timer = new ManualTimer(this, callback, state);
        timers.Add(timer);
        timer.Change(dueTime, period);
        return timer;
    }
    public void Advance(TimeSpan elapsed, bool fireTimers = true)
    {
        now += elapsed;
        if (!fireTimers) return;
        foreach (var timer in timers.ToArray()) timer.FireIfDue();
    }
    private sealed class ManualTimer(ManualDesktopRequestTimeProvider owner, TimerCallback callback, object? state) : ITimer
    {
        private DateTimeOffset due;
        private bool disposed;
        public bool Change(TimeSpan dueTime, TimeSpan period)
        {
            due = dueTime == Timeout.InfiniteTimeSpan ? DateTimeOffset.MaxValue : owner.now + dueTime;
            return !disposed;
        }
        public void FireIfDue()
        {
            if (disposed || due > owner.now) return;
            due = DateTimeOffset.MaxValue;
            callback(state);
        }
        public void Dispose() => disposed = true;
        public ValueTask DisposeAsync() { Dispose(); return ValueTask.CompletedTask; }
    }
}