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import { posix } from "../deps/path.ts";import { contentType } from "../deps/media_types.ts";
import type { Middleware, Site } from "../core.ts";
export type Router = (url: URL) => string | undefined;
export interface Options {  site: Site;  router?: Router;}
/** Render pages on demand */export default function onDemand(options: Options): Middleware {  const site = options.site;  let router = options.router;
  return async (request, next) => {    const response = await next(request);
    if (response.status !== 404) {      return response;    }
    if (!router) {      router = await createDefaultRouter(site.src("_routes.json"));    }
    const url = new URL(request.url);    const file = router(url);
    if (!file) {      return response;    }
    const page = await site.renderPage(file);
    if (!page || !page.outputPath) {      return response;    }
    // Redirect /example to /example/    const pageUrl = page.data.url as string;    if (!url.pathname.endsWith("/") && pageUrl.endsWith("/")) {      return new Response(null, {        status: 301,        headers: {          "location": posix.join(url.pathname, "/"),        },      });    }
    const pageResponse = new Response(      page.content,      { status: 200 },    );
    const type = contentType(posix.extname(page.outputPath));
    if (type) {      pageResponse.headers.set("content-type", type);    }
    return pageResponse;  };}
async function createDefaultRouter(file: string): Promise<Router> {  const routes: Record<string, string> = JSON.parse(    await Deno.readTextFile(file),  );  return getRouter(new Map(Object.entries(routes)));}
export function getRouter(routes: Map<string, string>): Router {  return function match(url: URL): string | undefined {    const { pathname } = url;    const path = routes.get(pathname);
    // Handle urls like /example as /example/    if (!path && !pathname.endsWith("/")) {      return routes.get(pathname + "/");    }
    return path;  };}