using System.IO;
using Backend;
using Xunit;

namespace Backend.Tests;

public class PolicyRunnerTests
{
    private static string LocateOnnxModel()
    {
        var dir = AppContext.BaseDirectory;
        while (dir is not null)
        {
            var candidate = Path.Combine(dir, "models", "ppo_lander.onnx");
            if (File.Exists(candidate)) return candidate;
            var parent = Directory.GetParent(dir);
            if (parent is null) break;
            dir = parent.FullName;
        }
        throw new FileNotFoundException(
            "models/ppo_lander.onnx not found — run `python Training/export_onnx.py ...`");
    }

    [Fact]
    public void LoadsWithoutError()
    {
        using var runner = new PolicyRunner(LocateOnnxModel());
    }

    [Fact]
    public void SelectAction_ReturnsValidActionForZeroObs()
    {
        using var runner = new PolicyRunner(LocateOnnxModel());
        var obs = new float[7];  // all zeros
        int action = runner.SelectAction(obs);
        Assert.InRange(action, 0, 3);
    }

    [Fact]
    public void SelectAction_IsDeterministicForSameInput()
    {
        using var runner = new PolicyRunner(LocateOnnxModel());
        var obs = new float[] { 0.1f, -0.2f, 0.05f, 0.0f, 0.0f, 1.0f, 0.0f };
        int a1 = runner.SelectAction(obs);
        int a2 = runner.SelectAction(obs);
        Assert.Equal(a1, a2);
    }

    [Fact]
    public void SelectAction_ThrowsIfObsLengthWrong()
    {
        using var runner = new PolicyRunner(LocateOnnxModel());
        Assert.Throws<ArgumentException>(() => runner.SelectAction(new float[3]));
    }
}