Method handler

packages/fresh/src/app.ts:391–496

* Create handler function for `Deno.serve` or to be used in * testing.

()

   * testing.
   */
  handler(): (
    request: Request,
    info?: Deno.ServeHandlerInfo,
  ) => Promise<Response> {
    let buildCache = this.#getBuildCache();
    if (buildCache === null) {
      if (
        this.config.mode === "production" &&
        DENO_DEPLOYMENT_ID !== undefined
      ) {
        throw new Error(
          `Could not find _fresh directory. Maybe you forgot to run "deno task build" or maybe you're trying to run "main.ts" directly instead of "_fresh/server.js"?`,
        );
      } else {
        buildCache = new MockBuildCache([], this.config.mode);
      }
    }

    const router = new UrlPatternRouter<Middleware<State>>();

    const { rootHandler } = applyCommands(
      router,
      this.#commands,
      this.config.basePath,
      this.#onError,
    );

    const trustProxy = this.config.trustProxy;

    return async (
      req: Request,
      conn: Deno.ServeHandlerInfo = DEFAULT_CONN_INFO,
    ) => {
      const url = new URL(req.url);
      // Prevent open redirect attacks
      url.pathname = url.pathname.replace(/\/+/g, "/");

      // Apply X-Forwarded-* headers when behind a reverse proxy
      if (trustProxy) {
        const proto = req.headers.get("x-forwarded-proto");
        if (proto) {
          url.protocol = proto + ":";
        }
        const host = req.headers.get("x-forwarded-host");
        if (host) {
          url.host = host;
        }
      }

      const method = req.method.toUpperCase() as Method;
      const matched = router.match(method, url);
      let { params, pattern, item: handler, methodMatch } = matched;

      const span = trace.getActiveSpan();
      if (span && pattern) {
        span.updateName(`${method} ${pattern}`);
        span.setAttribute("http.route", pattern);
      }