/// <summary>
///     Loads theme templates, CSS, JS, and assets from the theme directory.
///     Supports both embedded default theme and custom theme directories.
/// </summary>
public sealed class ThemeLoader(IFileSystem fileSystem, ILogger<ThemeLoader> logger)
{
    /// <summary>
    ///     Loads a theme render context from the specified theme directory.
    /// </summary>
    /// <param name = "themePath">Absolute path to the theme directory.</param>
    /// <returns>The loaded theme context with templates, partials, and asset lists.</returns>
    public ThemeRenderContext Load(string themePath)
    {
        var templates = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
        var partials = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
        var cssFiles = new List<string>();
        var jsFiles = new List<string>();
        // Load layout templates
        string layoutsDir = fileSystem.Path.Combine(themePath, "layouts");
        if (fileSystem.Directory.Exists(layoutsDir))
        {
            foreach (string file in fileSystem.Directory.GetFiles(layoutsDir, "*.html"))
            {
                string name = fileSystem.Path.GetFileNameWithoutExtension(file);
                templates[name] = fileSystem.File.ReadAllText(file);
                logger.LogDebug("Loaded layout: {Name}", name);
            }
        }

        // Load partials
        string partialsDir = fileSystem.Path.Combine(themePath, "partials");
        if (fileSystem.Directory.Exists(partialsDir))
        {
            foreach (string file in fileSystem.Directory.GetFiles(partialsDir, "*.html"))
            {
                string name = fileSystem.Path.GetFileNameWithoutExtension(file);
                partials[name] = fileSystem.File.ReadAllText(file);
                logger.LogDebug("Loaded partial: {Name}", name);
            }
        }

        // Discover CSS files
        string cssDir = fileSystem.Path.Combine(themePath, "css");
        if (fileSystem.Directory.Exists(cssDir))
        {
            cssFiles = fileSystem.Directory.GetFiles(cssDir, "*.css", SearchOption.AllDirectories).Select(f => "/_theme/" + fileSystem.Path.GetRelativePath(themePath, f).Replace('\\', '/')).OrderBy(f => f) // main.css first via alphabetical
            .ToList();
        }

        // Discover JS files
        string jsDir = fileSystem.Path.Combine(themePath, "js");
        if (fileSystem.Directory.Exists(jsDir))
        {
            jsFiles = fileSystem.Directory.GetFiles(jsDir, "*.js").Select(f => "/_theme/" + fileSystem.Path.GetRelativePath(themePath, f).Replace('\\', '/')).OrderBy(f => f).ToList();
        }

        logger.LogInformation("Loaded theme: {Layouts} layouts, {Partials} partials, {Css} CSS, {Js} JS", templates.Count, partials.Count, cssFiles.Count, jsFiles.Count);
        return new ThemeRenderContext
        {
            Config = null!, // Will be set by the render phase
            Templates = templates,
            Partials = partials,
            CssFiles = cssFiles,
            JsFiles = jsFiles
        };
    }

    /// <summary>
    ///     Copies all theme static assets (CSS, JS, fonts, icons) to the output directory.
    /// </summary>
    /// <param name = "themePath">Source theme directory.</param>
    /// <param name = "outputDir">Target output directory.</param>
    public void CopyAssets(string themePath, string outputDir)
    {
        string themeOutputDir = fileSystem.Path.Combine(outputDir, "_theme");
        string[] assetDirs = new[]
        {
            "css",
            "js",
            "assets"
        };
        foreach (string dir in assetDirs)
        {
            string sourceDir = fileSystem.Path.Combine(themePath, dir);
            if (!fileSystem.Directory.Exists(sourceDir))
            {
                continue;
            }

            string[] files = fileSystem.Directory.GetFiles(sourceDir, "*.*", SearchOption.AllDirectories);
            foreach (string file in files)
            {
                string relativePath = fileSystem.Path.GetRelativePath(themePath, file);
                string destPath = fileSystem.Path.Combine(themeOutputDir, relativePath);
                string destDir = fileSystem.Path.GetDirectoryName(destPath)!;
                fileSystem.Directory.CreateDirectory(destDir);
                fileSystem.File.Copy(file, destPath, true);
            }
        }

        logger.LogInformation("Copied theme assets to {Path}", themeOutputDir);
    }
}