/// <summary>
///     Scans the project directory for Markdown files, C# projects, and static assets.
/// </summary>
public sealed class FileDiscoveryService(IFileSystem fileSystem, ILogger<FileDiscoveryService> logger)
{
    private static readonly HashSet<string> _assetExtensions = new(StringComparer.OrdinalIgnoreCase)
    {
        ".png",
        ".jpg",
        ".jpeg",
        ".gif",
        ".svg",
        ".webp",
        ".ico",
        ".pdf",
        ".zip",
        ".mp4",
        ".webm",
        ".css",
        ".js",
        ".json",
        ".xml",
        ".woff",
        ".woff2",
        ".ttf",
        ".eot"
    };
    /// <summary>
    ///     Discovers all relevant files based on the site configuration.
    /// </summary>
    public DiscoveryResult Discover(string rootDirectory, SiteConfig config) => Discover(rootDirectory, config, fileSystem);
    /// <summary>
    ///     Discovers all relevant files using a specific filesystem abstraction.
    ///     Used by ASP.NET Core integration to pass the virtual MockFileSystem.
    /// </summary>
    public DiscoveryResult Discover(string rootDirectory, SiteConfig config, IFileSystem fs)
    {
        var result = new DiscoveryResult();
        // Discover Markdown files
        string docsPath = ResolvePath(fs, rootDirectory, config.Content.Docs);
        if (fs.Directory.Exists(docsPath))
        {
            var mdFiles = fs.Directory.GetFiles(docsPath, "*.md", SearchOption.AllDirectories).Select(f => fs.Path.GetRelativePath(docsPath, f)).Order(StringComparer.OrdinalIgnoreCase).ToList();
            result.MarkdownFiles.AddRange(mdFiles);
            logger.LogInformation("Discovered {Count} Markdown files in {Path}", mdFiles.Count, docsPath);
        }
        else
        {
            logger.LogWarning("Documentation directory not found: {Path}", docsPath);
        }

        // Discover C# project files
        foreach (ProjectSource project in config.Content.Projects)
        {
            string projectPath = ResolvePath(fs, rootDirectory, project.Path);
            if (fs.File.Exists(projectPath))
            {
                result.ProjectFiles.Add(projectPath);
                logger.LogInformation("Discovered project: {Path}", projectPath);
            }
            else
            {
                logger.LogWarning("Project file not found: {Path}", projectPath);
            }
        }

        // Discover static assets in docs directory
        if (fs.Directory.Exists(docsPath))
        {
            var assetFiles = fs.Directory.GetFiles(docsPath, "*.*", SearchOption.AllDirectories).Where(f => _assetExtensions.Contains(fs.Path.GetExtension(f))).Select(f => fs.Path.GetRelativePath(docsPath, f)).Order(StringComparer.OrdinalIgnoreCase).ToList();
            result.AssetFiles.AddRange(assetFiles);
            logger.LogInformation("Discovered {Count} asset files", assetFiles.Count);
        }

        return result;
    }

    private static string ResolvePath(IFileSystem fs, string rootDirectory, string relativePath)
    {
        if (fs.Path.IsPathRooted(relativePath))
        {
            return relativePath;
        }

        return fs.Path.GetFullPath(fs.Path.Combine(rootDirectory, relativePath));
    }
}