main.ts

type TMethod = "GET" | "POST" | "PUT" | "PATCH" | "DELETE";

type THandler = (
  req: Request,
  match: URLPatternResult | null,
) => Response | Promise<Response>;

class Route {
  constructor(
    private pattern: URLPatternInput,
    private handlers: Partial<Record<TMethod, THandler>>,
  ) {}

  test(pattern: URLPatternInput) {
    return new URLPattern(this.pattern).test(pattern);
  }

  exec(req: Request) {
    const handler = this.handlers[req.method as TMethod];

    if (!handler) {
      throw new Error("Method not allowed");
    }

    return handler(
      req,
      new URLPattern(this.pattern).exec(req.url),
    );
  }
}

function ok(...args: Parameters<typeof String.raw>) {
  return new Response(String.raw(...args), {
    headers: { "Content-Type": "text/html; charset=utf-8" },
    status: 200,
  });
}

function notFound(...args: Parameters<typeof String.raw>) {
  return new Response(String.raw(...args), {
    headers: { "Content-Type": "text/html; charset=utf-8" },
    status: 404,
  });
}

const routes = [
  new Route({ pathname: "/books", search: "{page=:page}?" }, {
    async GET(req, match) {
      return ok`<h1>Books - Page ${match?.search.groups.page ?? 1}</h1>`;
    },
  }),
  new Route({ pathname: "/books/:id" }, {
    async GET(req, match) {
      return ok`<h1>Book ID ${match?.pathname.groups.id}</h1>`;
    },
  }),
];

Deno.serve((req: Request) => {
  const url = new URL(req.url);

  for (const route of routes) {
    if (route.test(url)) {
      return route.exec(req);
    }
  }

  return notFound`<h1>Not found</h1>`;
});