using MrGameEng.Core;
using Xunit;

namespace MrGameEng.Core.Tests;

public class GameSpeedTests
{
    [Fact]
    public void Constructor_DefaultSteps_RunsAtFirstStep()
    {
        var clock = new GameClock();

        var speed = new GameSpeed(clock);

        Assert.Equal(new[] { 1f, 3f, 6f }, speed.Steps);
        Assert.False(speed.IsPaused);
        Assert.Equal(1f, speed.CurrentSpeed);
        Assert.Equal(1f, clock.TimeScale);
    }

    [Fact]
    public void Constructor_NonPositiveStep_Throws()
    {
        Assert.Throws<ArgumentOutOfRangeException>(() => new GameSpeed(new GameClock(), 1f, 0f));
    }

    [Fact]
    public void Pause_SetsClockToZero_ResumeRestoresStep()
    {
        var clock = new GameClock();
        var speed = new GameSpeed(clock, 1f, 3f, 6f);
        speed.SetStep(2);

        speed.Pause();

        Assert.True(speed.IsPaused);
        Assert.Equal(0f, clock.TimeScale);
        Assert.Equal(0f, speed.CurrentSpeed);

        speed.Resume();

        Assert.False(speed.IsPaused);
        Assert.Equal(6f, clock.TimeScale);
        Assert.Equal(2, speed.StepIndex);
    }

    [Fact]
    public void SetStep_OutOfRange_Clamps()
    {
        var clock = new GameClock();
        var speed = new GameSpeed(clock, 1f, 3f, 6f);

        speed.SetStep(99);
        Assert.Equal(2, speed.StepIndex);
        Assert.Equal(6f, clock.TimeScale);

        speed.SetStep(-5);
        Assert.Equal(0, speed.StepIndex);
        Assert.Equal(1f, clock.TimeScale);
    }

    [Fact]
    public void FasterAndSlower_ClampAtEnds_AndUnpause()
    {
        var clock = new GameClock();
        var speed = new GameSpeed(clock, 1f, 3f, 6f);

        speed.Faster();
        Assert.Equal(1, speed.StepIndex);
        speed.Faster();
        speed.Faster(); // clamps at fastest
        Assert.Equal(2, speed.StepIndex);

        speed.Pause();
        speed.Slower(); // unpauses and steps down
        Assert.False(speed.IsPaused);
        Assert.Equal(1, speed.StepIndex);
    }

    [Fact]
    public void Cycle_GoesPauseThroughStepsBackToPause()
    {
        var clock = new GameClock();
        var speed = new GameSpeed(clock, 1f, 3f, 6f);
        speed.Pause();

        speed.Cycle(); // -> step 0
        Assert.False(speed.IsPaused);
        Assert.Equal(0, speed.StepIndex);

        speed.Cycle(); // -> step 1
        Assert.Equal(1, speed.StepIndex);

        speed.Cycle(); // -> step 2 (fastest)
        Assert.Equal(2, speed.StepIndex);

        speed.Cycle(); // -> pause
        Assert.True(speed.IsPaused);
    }

    [Fact]
    public void Changed_FiresOnTransitions()
    {
        var clock = new GameClock();
        var speed = new GameSpeed(clock, 1f, 3f, 6f);
        var count = 0;
        speed.Changed += () => count++;

        speed.Pause();
        speed.Resume();
        speed.Faster();

        Assert.Equal(3, count);
    }
}