namespace HSchool.AppHost.Tests;

/// <summary>
/// Same rules as <c>tools/apphost-uptodate.ps1</c>. Keep the two in sync.
/// </summary>
internal static class LaunchBuildStamp
{
    public const string TargetFramework = "net10.0";

    public static readonly string[] InputExtensions = [".cs", ".csproj", ".props"];

    public static readonly string[] NamedInputs =
    [
        "global.json",
        "Directory.Build.props",
        "Directory.Packages.props",
    ];

    public static readonly string[] SkipDirectoryNames = ["bin", "obj", "node_modules"];

    public static readonly string[] OutputProjects = ["HSchool.AppHost", "HSchool.Server"];

    public static bool NeedsBuild(string repoRoot, string configuration = "Debug")
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(repoRoot);
        ArgumentException.ThrowIfNullOrWhiteSpace(configuration);

        DateTime? oldestOutput = null;
        foreach (var project in OutputProjects)
        {
            var dll = Path.Combine(
                repoRoot,
                "src",
                project,
                "bin",
                configuration,
                TargetFramework,
                project + ".dll");
            if (!File.Exists(dll))
            {
                return true;
            }

            var written = File.GetLastWriteTimeUtc(dll);
            if (oldestOutput is null || written < oldestOutput.Value)
            {
                oldestOutput = written;
            }
        }

        if (oldestOutput is null)
        {
            return true;
        }

        var cutoff = oldestOutput.Value;

        foreach (var name in NamedInputs)
        {
            var path = Path.Combine(repoRoot, name);
            if (File.Exists(path) && File.GetLastWriteTimeUtc(path) > cutoff)
            {
                return true;
            }
        }

        var src = Path.Combine(repoRoot, "src");
        return !Directory.Exists(src) || HasNewerInput(src, cutoff);
    }

    private static bool HasNewerInput(string directory, DateTime cutoff)
    {
        foreach (var file in Directory.EnumerateFiles(directory))
        {
            if (!IsInputExtension(Path.GetExtension(file)))
            {
                continue;
            }

            if (File.GetLastWriteTimeUtc(file) > cutoff)
            {
                return true;
            }
        }

        foreach (var child in Directory.EnumerateDirectories(directory))
        {
            var leaf = Path.GetFileName(child);
            if (SkipDirectoryNames.Contains(leaf, StringComparer.OrdinalIgnoreCase))
            {
                continue;
            }

            if (HasNewerInput(child, cutoff))
            {
                return true;
            }
        }

        return false;
    }

    private static bool IsInputExtension(string extension) =>
        InputExtensions.Contains(extension, StringComparer.OrdinalIgnoreCase);
}