using Xunit;

namespace MrGameEng.Mods.Tests;

public sealed class ModLoaderTests : IDisposable
{
    private readonly string _root = Directory.CreateTempSubdirectory("mrge-mods-tests-").FullName;

    private string ModsRoot => Path.Combine(_root, "Mods");

    public void Dispose() => Directory.Delete(_root, recursive: true);

    /// <summary>Создаёт мод с About.json; зависимости — id модов, которые должны грузиться раньше.</summary>
    private void WriteMod(string id, params string[] dependencies)
    {
        var aboutDir = Path.Combine(ModsRoot, id, "About");
        Directory.CreateDirectory(aboutDir);
        var deps = string.Join(", ", dependencies.Select(d => $"\"{d}\""));
        File.WriteAllText(
            Path.Combine(aboutDir, "About.json"),
            $$"""{ "id": "{{id}}", "name": "{{id}} mod", "version": "1.0", "dependencies": [{{deps}}] }"""
        );
    }

    [Fact]
    public void Load_OrdersDependenciesFirst_ThenAlphabetically()
    {
        WriteMod("zebra", "Core");
        WriteMod("apple", "Core");
        WriteMod("Core");

        var mods = ModLoader.Load(ModsRoot);

        Assert.Equal(["Core", "apple", "zebra"], mods.Select(m => m.Id));
    }

    [Fact]
    public void Load_MissingDependency_Throws()
    {
        WriteMod("orphan", "NoSuchMod");

        var exception = Assert.Throws<InvalidDataException>(() => ModLoader.Load(ModsRoot));
        Assert.Contains("NoSuchMod", exception.Message);
    }

    [Fact]
    public void Load_CyclicDependency_Throws()
    {
        WriteMod("a", "b");
        WriteMod("b", "a");

        var exception = Assert.Throws<InvalidDataException>(() => ModLoader.Load(ModsRoot));
        Assert.Contains("Cyclic", exception.Message);
    }

    [Fact]
    public void Load_ActiveSubset_LoadsOnlyRequested()
    {
        WriteMod("Core");
        WriteMod("extra", "Core");
        WriteMod("unused");

        var mods = ModLoader.Load(ModsRoot, ["extra", "Core"]);

        Assert.Equal(["Core", "extra"], mods.Select(m => m.Id));
    }

    [Fact]
    public void Load_IgnoresDirectoriesWithoutAbout()
    {
        WriteMod("Core");
        Directory.CreateDirectory(Path.Combine(ModsRoot, "not-a-mod"));

        var mod = Assert.Single(ModLoader.Load(ModsRoot));
        Assert.Equal("Core", mod.Id);
        Assert.Equal("Core mod", mod.Info.Name);
    }

    [Fact]
    public void FindModsRoot_WalksUpFromNestedDirectory()
    {
        WriteMod("Core");
        var nested = Path.Combine(_root, "bin", "Debug", "net8.0");
        Directory.CreateDirectory(nested);

        Assert.Equal(ModsRoot, ModLoader.FindModsRoot(nested));
    }

    [Fact]
    public void ContentTree_LaterMod_OverridesSameRelativePath()
    {
        WriteMod("Core");
        WriteMod("patch", "Core");
        File.WriteAllText(CreateContentFile("Core", "Textures", "things/rock.png"), "core");
        File.WriteAllText(CreateContentFile("Core", "Textures", "things/tree.png"), "core");
        File.WriteAllText(CreateContentFile("patch", "Textures", "things/rock.png"), "patched");

        var mods = ModLoader.Load(ModsRoot);
        var tree = ModContentTree.Build(mods, "Textures", ".png");

        Assert.Equal(2, tree.Files.Count);
        Assert.True(tree.TryGet("things/rock.png", out var rock));
        Assert.Equal("patch", rock.Mod.Id);
        Assert.Equal("patched", File.ReadAllText(rock.FullPath));
        Assert.True(tree.TryGet("things/tree.png", out var oak));
        Assert.Equal("Core", oak.Mod.Id);
    }

    private string CreateContentFile(string modId, string folder, string relativePath)
    {
        var fullPath = Path.Combine(ModsRoot, modId, folder, relativePath);
        Directory.CreateDirectory(Path.GetDirectoryName(fullPath)!);
        return fullPath;
    }
}