using System;
using System.Collections.Generic;
using System.Threading;
using AcDream.UI.Abstractions.Input;
using Silk.NET.Input;

namespace AcDream.UI.Abstractions.Tests.Input;

/// <summary>
/// Tests for double-click detection added to <see cref="InputDispatcher.OnMouseDown"/>
/// in Phase B.4b. The dispatcher tracks the most-recent mouse-down button +
/// timestamp; a same-button press within DoubleClickThresholdMs (500 ms)
/// additionally fires <see cref="ActivationType.DoubleClick"/> for the matching
/// binding on top of the normal <see cref="ActivationType.Press"/>.
/// </summary>
public class InputDispatcherDoubleClickTests
{
    /// <summary>
    /// Build a dispatcher wired with LMB Press → SelectLeft,
    /// LMB DoubleClick → SelectDblLeft, and RMB Press → SelectRight.
    /// </summary>
    private static (InputDispatcher dispatcher, FakeMouseSource mouse, List<(InputAction, ActivationType)> fired)
        Build()
    {
        var kb = new FakeKeyboardSource();
        var mouse = new FakeMouseSource();
        var bindings = new KeyBindings();

        var lmbChord = new KeyChord(InputDispatcher.MouseButtonToKey(MouseButton.Left),  ModifierMask.None, Device: 1);
        var rmbChord = new KeyChord(InputDispatcher.MouseButtonToKey(MouseButton.Right), ModifierMask.None, Device: 1);

        bindings.Add(new Binding(lmbChord, InputAction.SelectLeft));
        bindings.Add(new Binding(lmbChord, InputAction.SelectDblLeft, ActivationType.DoubleClick));
        bindings.Add(new Binding(rmbChord, InputAction.SelectRight));

        var dispatcher = new InputDispatcher(kb, mouse, bindings);
        var fired = new List<(InputAction, ActivationType)>();
        dispatcher.Fired += (a, t) => fired.Add((a, t));
        return (dispatcher, mouse, fired);
    }

    /// <summary>
    /// Two LMB clicks in rapid succession (~10 ms) → Press fires twice AND
    /// DoubleClick fires once (on the second click).
    /// </summary>
    [Fact]
    public void SecondClick_WithinThreshold_FiresDoubleClick()
    {
        var (_, mouse, fired) = Build();

        mouse.EmitMouseDown(MouseButton.Left, ModifierMask.None);
        Thread.Sleep(10);
        mouse.EmitMouseDown(MouseButton.Left, ModifierMask.None);

        // Two SelectLeft Press events (one per click).
        Assert.Equal(2, fired.FindAll(e => e == (InputAction.SelectLeft, ActivationType.Press)).Count);

        // One SelectDblLeft DoubleClick event on the second click.
        Assert.Single(fired, e => e == (InputAction.SelectDblLeft, ActivationType.DoubleClick));
    }

    /// <summary>
    /// Two LMB clicks 600 ms apart → Press fires twice but NO DoubleClick
    /// (interval exceeds the 500 ms threshold).
    /// </summary>
    [Fact]
    public void SecondClick_BeyondThreshold_DoesNotFireDoubleClick()
    {
        var (_, mouse, fired) = Build();

        mouse.EmitMouseDown(MouseButton.Left, ModifierMask.None);
        Thread.Sleep(600);
        mouse.EmitMouseDown(MouseButton.Left, ModifierMask.None);

        Assert.Equal(2, fired.FindAll(e => e == (InputAction.SelectLeft, ActivationType.Press)).Count);
        Assert.Empty(fired.FindAll(e => e.Item2 == ActivationType.DoubleClick));
    }

    /// <summary>
    /// LMB then RMB in rapid succession → no DoubleClick (different buttons).
    /// </summary>
    [Fact]
    public void DifferentButtons_DoNotFireDoubleClick()
    {
        var (_, mouse, fired) = Build();

        mouse.EmitMouseDown(MouseButton.Left,  ModifierMask.None);
        Thread.Sleep(10);
        mouse.EmitMouseDown(MouseButton.Right, ModifierMask.None);

        Assert.Empty(fired.FindAll(e => e.Item2 == ActivationType.DoubleClick));
    }

    /// <summary>
    /// Three rapid LMB clicks → exactly one DoubleClick (between clicks 1 and 2).
    /// The third click resets the pair-state, so it acts as the "first click" of
    /// a new potential double-click rather than firing a second DoubleClick.
    /// </summary>
    [Fact]
    public void ThirdClick_AfterDoubleClick_RequiresFreshPair()
    {
        var (_, mouse, fired) = Build();

        mouse.EmitMouseDown(MouseButton.Left, ModifierMask.None); // click 1
        Thread.Sleep(10);
        mouse.EmitMouseDown(MouseButton.Left, ModifierMask.None); // click 2 → DoubleClick fires, state reset
        Thread.Sleep(10);
        mouse.EmitMouseDown(MouseButton.Left, ModifierMask.None); // click 3 → no DoubleClick (fresh pair started)

        // Three Press events total.
        Assert.Equal(3, fired.FindAll(e => e == (InputAction.SelectLeft, ActivationType.Press)).Count);

        // Exactly one DoubleClick (between clicks 1 and 2).
        Assert.Single(fired.FindAll(e => e == (InputAction.SelectDblLeft, ActivationType.DoubleClick)));
    }
}