using GameCli;
using Xunit;

namespace GameCli.Tests;

public class RewardTests
{
    [Fact]
    public void AtTarget_ZeroVel_ZeroAngle_Noop_HasZeroReward()
    {
        var ship = new ShipState(0.5f, 0.5f, 0f, 0f, 0f, 0f);
        float r = Reward.Compute(ship, target: (0.5f, 0.5f), action: 0);
        Assert.Equal(0f, r, precision: 5);
    }

    [Fact]
    public void FarFromTarget_HasLargerNegativeThanNear()
    {
        var near = new ShipState(0.5f, 0.5f, 0f, 0f, 0f, 0f);
        var far  = new ShipState(0.9f, 0.9f, 0f, 0f, 0f, 0f);
        float rNear = Reward.Compute(near, target: (0.5f, 0.5f), action: 0);
        float rFar  = Reward.Compute(far,  target: (0.5f, 0.5f), action: 0);
        Assert.True(rFar < rNear, $"far reward {rFar} should be < near reward {rNear}");
    }

    [Fact]
    public void HighVelocity_PenalizesReward()
    {
        var stopped = new ShipState(0.5f, 0.5f, 0f, 0f, 0f, 0f);
        var moving  = new ShipState(0.5f, 0.5f, 1f, 1f, 0f, 0f);
        float rStop = Reward.Compute(stopped, target: (0.5f, 0.5f), action: 0);
        float rMove = Reward.Compute(moving,  target: (0.5f, 0.5f), action: 0);
        Assert.True(rMove < rStop, $"moving reward {rMove} should be < stopped reward {rStop}");
    }

    [Fact]
    public void Tilted_PenalizesReward()
    {
        var upright = new ShipState(0.5f, 0.5f, 0f, 0f, 0f, 0f);
        var tilted  = new ShipState(0.5f, 0.5f, 0f, 0f, 0.8f, 0f);
        float rUp = Reward.Compute(upright, target: (0.5f, 0.5f), action: 0);
        float rTi = Reward.Compute(tilted,  target: (0.5f, 0.5f), action: 0);
        Assert.True(rTi < rUp, $"tilted reward {rTi} should be < upright reward {rUp}");
    }

    [Fact]
    public void FiringEngine_PenalizesReward()
    {
        var ship = new ShipState(0.5f, 0.5f, 0f, 0f, 0f, 0f);
        float rNoop  = Reward.Compute(ship, target: (0.5f, 0.5f), action: 0);
        float rMain  = Reward.Compute(ship, target: (0.5f, 0.5f), action: 2);
        float rLeft  = Reward.Compute(ship, target: (0.5f, 0.5f), action: 1);
        Assert.True(rMain < rNoop, "firing main should be worse than noop");
        Assert.True(rLeft < rNoop, "firing left should be worse than noop");
    }

    [Fact]
    public void AngleWrap_FullRevolutionsProduceSameReward()
    {
        // Physically identical poses (angle differs by 2π) must produce the same reward.
        // Otherwise a spinning ship accumulates unbounded angle penalty.
        var upright   = new ShipState(0.5f, 0.5f, 0f, 0f, 0f, 0f);
        var oneSpin   = new ShipState(0.5f, 0.5f, 0f, 0f,  2f * MathF.PI, 0f);
        var fiveSpins = new ShipState(0.5f, 0.5f, 0f, 0f, 10f * MathF.PI, 0f);
        float r0 = Reward.Compute(upright,   target: (0.5f, 0.5f), action: 0);
        float r1 = Reward.Compute(oneSpin,   target: (0.5f, 0.5f), action: 0);
        float r5 = Reward.Compute(fiveSpins, target: (0.5f, 0.5f), action: 0);
        Assert.Equal(r0, r1, precision: 4);
        Assert.Equal(r0, r5, precision: 4);
    }
}