/**
 * Handles requests for static files.
 * @module
 */

import * as path from '@std/path';
import * as media_types from '@std/media-types';

/**
 * Handles requests for static files.
 *
 * @param request The incoming HTTP request
 * @returns Either a response (a static file was requested and returned properly) or undefined if unhandled.
 */
export default async function handle_static_files(request: Request): Promise<Response | undefined> {
	const url = new URL(request.url);
	const normalized_path = path.resolve(path.normalize(url.pathname).replace(/^\/+/, ''));
	if (!normalized_path.startsWith(Deno.cwd())) {
		return;
	}

	try {
		const stat = await Deno.stat(normalized_path);

		if (stat.isDirectory) {
			const extensions: string[] = media_types.allExtensions('text/html') ?? ['html', 'htm'];

			for (const extension of extensions) {
				const index_path = path.join(normalized_path, `index.${extension}`);
				const index_stat = await Deno.stat(index_path);
				if (index_stat.isFile) {
					return new Response(await Deno.readFile(index_path), {
						headers: {
							'Content-Type': 'text/html'
						}
					});
				}
			}

			return;
		}

		if (stat.isFile) {
			const extension = path.extname(normalized_path)?.slice(1)?.toLowerCase() ?? '';

			const content_type = media_types.contentType(extension) ?? 'application/octet-stream';
			return new Response(await Deno.readFile(normalized_path), {
				headers: {
					'Content-Type': content_type
				}
			});
		}
	} catch (error) {
		if (error instanceof Deno.errors.NotFound) {
			return;
		}

		if (error instanceof Deno.errors.PermissionDenied) {
			return new Response('Permission Denied', {
				status: 400,
				headers: {
					'Content-Type': 'text/plain'
				}
			});
		}

		throw error;
	}
}