using System.Collections.Concurrent;
using CursorLang.Agent.Services;
using CursorLang.Core.Models;
using CursorLang.Tests.Shared;

namespace CursorLang.Agent.Tests.Services;

/// <summary>
/// Making sense of Caps Lock presses: a short one differs from a long one only
/// by when the key was released.
/// </summary>
public sealed class CapsLockHotkeyServiceTests
{
    private const int CapsLock = 0x14;
    private const int LetterA = 0x41;

    [Fact]
    public void A_Caps_Lock_press_is_not_passed_on()
    {
        using var harness = Harness.Create(holdMilliseconds: 10_000);

        Assert.True(Pump.Run(() => harness.Service.HandleKeyEvent(CapsLock, isKeyDown: true)));
        Assert.True(Pump.Run(() => harness.Service.HandleKeyEvent(CapsLock, isKeyDown: false)));
    }

    [Fact]
    public void The_other_keys_go_through_as_usual()
    {
        using var harness = Harness.Create(holdMilliseconds: 10_000);

        Assert.False(Pump.Run(() => harness.Service.HandleKeyEvent(LetterA, isKeyDown: true)));
        Assert.False(Pump.Run(() => harness.Service.HandleKeyEvent(LetterA, isKeyDown: false)));
        Assert.Empty(harness.Events);
    }

    [Fact]
    public void A_short_press_yields_a_single_event()
    {
        using var harness = Harness.Create(holdMilliseconds: 10_000);

        harness.Press();
        harness.Release();

        Pump.WaitFor(() => harness.Events.Count == 1, "the short press event arrived");
        Assert.Equal(["tap"], harness.Events);
    }

    [Fact]
    public void A_hold_is_announced_once_the_threshold_is_past()
    {
        using var harness = Harness.Create(holdMilliseconds: 20);

        harness.Press();

        Pump.WaitFor(() => harness.Events.Contains("hold-start"), "the hold threshold was passed");
        Assert.Equal(["hold-start"], harness.Events);
    }

    [Fact]
    public void A_release_after_a_hold_yields_an_end_rather_than_a_press()
    {
        using var harness = Harness.Create(holdMilliseconds: 20);

        harness.Press();
        Pump.WaitFor(() => harness.Events.Contains("hold-start"), "the hold threshold was passed");

        harness.Release();

        Pump.WaitFor(() => harness.Events.Count == 2, "the end of the hold arrived");
        Assert.Equal(["hold-start", "hold-end"], harness.Events);
    }

    // While the key is held down Windows repeats the press: the count runs from the first one
    [Fact]
    public void Auto_repeat_does_not_reset_the_countdown()
    {
        using var harness = Harness.Create(holdMilliseconds: 60);

        harness.Press();

        for (int i = 0; i < 10; i++)
        {
            Pump.Pause(TimeSpan.FromMilliseconds(10));
            harness.Press();
        }

        Pump.WaitFor(() => harness.Events.Contains("hold-start"), "the hold was announced despite the repeats");
    }

    [Fact]
    public void A_quick_press_does_not_count_as_a_hold()
    {
        using var harness = Harness.Create(holdMilliseconds: 300);

        harness.Press();
        harness.Release();

        Pump.Pause(TimeSpan.FromMilliseconds(400));

        Assert.Equal(["tap"], harness.Events);
    }

    // The interception may be removed with the key still down — by unticking
    // the setting, for one. The tooltip has to go away in that case
    [Fact]
    public void Removing_the_interception_during_a_hold_announces_its_end()
    {
        using var harness = Harness.Create(holdMilliseconds: 20);

        harness.Press();
        Pump.WaitFor(() => harness.Events.Contains("hold-start"), "the hold threshold was passed");

        Pump.Run(harness.Service.Stop);

        Pump.WaitFor(() => harness.Events.Count == 2, "the end of the hold was announced");
        Assert.Equal(["hold-start", "hold-end"], harness.Events);
    }

    [Fact]
    public void Removing_the_interception_without_a_hold_yields_no_events()
    {
        using var harness = Harness.Create(holdMilliseconds: 10_000);

        harness.Press();
        Pump.Run(harness.Service.Stop);
        Pump.Pause(TimeSpan.FromMilliseconds(50));

        Assert.Empty(harness.Events);
    }

    // After the interception is removed the hold countdown must not keep running
    [Fact]
    public void Removing_the_interception_stops_the_countdown()
    {
        using var harness = Harness.Create(holdMilliseconds: 40);

        harness.Press();
        Pump.Run(harness.Service.Stop);

        Pump.Pause(TimeSpan.FromMilliseconds(120));

        Assert.Empty(harness.Events);
    }

    [Fact]
    public void After_the_interception_is_removed_presses_count_from_scratch()
    {
        using var harness = Harness.Create(holdMilliseconds: 10_000);

        harness.Press();
        Pump.Run(harness.Service.Stop);

        harness.Press();
        harness.Release();

        Pump.WaitFor(() => harness.Events.Count == 1, "a short press after the restart");
        Assert.Equal(["tap"], harness.Events);
    }

    // When the application is shutting down nobody is waiting for events anymore
    [Fact]
    public void Closing_the_service_sends_out_no_events()
    {
        var harness = Harness.Create(holdMilliseconds: 20);

        harness.Press();
        Pump.WaitFor(() => harness.Events.Contains("hold-start"), "the hold threshold was passed");

        Pump.Run(harness.Service.Dispose);
        Pump.Pause(TimeSpan.FromMilliseconds(80));

        Assert.Equal(["hold-start"], harness.Events);
    }

    [Fact]
    public void The_hold_threshold_is_read_on_every_press()
    {
        using var harness = Harness.Create(holdMilliseconds: 10_000);

        harness.Press();
        harness.Release();
        Pump.WaitFor(() => harness.Events.Count == 1, "the first press counted as short");

        harness.Settings.CapsLockHoldMilliseconds = 20;
        harness.Press();

        Pump.WaitFor(() => harness.Events.Contains("hold-start"), "the new threshold took effect");
    }

    [Fact]
    public void Before_the_start_there_is_no_interception()
    {
        using var harness = Harness.Create(holdMilliseconds: 10_000);

        Assert.False(harness.Service.IsRunning);
    }

    // The real system hook is installed and removed on the interface thread
    [Fact]
    public void The_interception_is_installed_and_removed()
    {
        using var harness = Harness.Create(holdMilliseconds: 10_000);
        Pump.Run(() =>
        {
            harness.Service.Start();
            Assert.True(harness.Service.IsRunning);

            // Starting again breaks nothing
            harness.Service.Start();
            Assert.True(harness.Service.IsRunning);

            harness.Service.Stop();
            Assert.False(harness.Service.IsRunning);

            // Nor does stopping again
            harness.Service.Stop();
            Assert.False(harness.Service.IsRunning);
        });
    }

    [Fact]
    public void Closing_removes_the_interception()
    {
        var harness = Harness.Create(holdMilliseconds: 10_000);

        Pump.Run(() =>
        {
            harness.Service.Start();
            harness.Service.Dispose();

            Assert.False(harness.Service.IsRunning);
        });
    }

    /// <summary>
    /// A hold is never announced for a key that has already been let go.
    /// </summary>
    /// <remarks>
    /// The countdown started by the press can still be delivered just after the
    /// release: Windows does not withdraw a WM_TIMER it has already posted. Taken at
    /// face value it turned a tap into a hold — the popup came up showing the layout
    /// the tap was about to change away from, and the switch followed it.
    ///
    /// The tick is driven straight in here rather than waited for, because the point is
    /// the one ordering a real clock will not reproduce on demand.
    /// </remarks>
    [Fact]
    public void A_hold_is_not_announced_after_the_key_has_been_released()
    {
        using var harness = Harness.Create(holdMilliseconds: 10_000);

        harness.Press();
        harness.Release();

        harness.ForceHoldTick();
        Pump.Drain();

        Assert.Equal(["tap"], harness.Events);
    }

    /// <summary>
    /// The service together with its settings and the list of events that happened.
    /// </summary>
    private sealed class Harness : IDisposable
    {
        private Harness(CapsLockHotkeyService service, AppSettings settings)
        {
            Service = service;
            Settings = settings;
        }

        internal CapsLockHotkeyService Service { get; }

        internal AppSettings Settings { get; }

        /// <summary>Events arrive from the interface thread and are read by the test thread.</summary>
        internal ConcurrentQueue<string> Events { get; } = new();

        internal static Harness Create(double holdMilliseconds)
        {
            var settings = new AppSettings { CapsLockHoldMilliseconds = holdMilliseconds };

            // Events reach their subscribers the way they do in the agent: posted back
            // to the message loop, after the hook procedure has returned
            CapsLockHotkeyService service =
                Pump.Run(() => new CapsLockHotkeyService(settings, Pump.Post));
            var harness = new Harness(service, settings);

            service.Tapped += (_, _) => harness.Events.Enqueue("tap");
            service.HoldStarted += (_, _) => harness.Events.Enqueue("hold-start");
            service.HoldEnded += (_, _) => harness.Events.Enqueue("hold-end");

            return harness;
        }

        internal void Press() => Pump.Run(() => Service.HandleKeyEvent(CapsLock, isKeyDown: true));

        internal void Release() => Pump.Run(() => Service.HandleKeyEvent(CapsLock, isKeyDown: false));

        /// <summary>Delivers the hold countdown by hand, the way a late WM_TIMER does.</summary>
        internal void ForceHoldTick() => Pump.Run(Service.HandleHoldElapsed);

        public void Dispose() => Pump.Run(Service.Dispose);
    }
}