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import { ensureDir, Logger, path } from "../deps.ts";
export type Cacher = (  request: Request,  response: Response,) => Promise<void> | void;
export type CacheUpdater = (urlOrPathname: string) => unknown;
/** * @alpha */export const cacheResponseBody = (publicDir: string, log: Logger): Cacher => {  const getFilepath = _requestToCacheFilepath(publicDir, log);  return async (request: Request, response: Response) => {    if (request.method === "GET" && response.ok && response.body) {      const filepath = getFilepath(        request.url,        response.headers.get("Content-Type"),      );      // if no file path, don't cache      if (!filepath) return;
      const responseToFile = response.clone();
      await ensureDir(path.dirname(filepath));      const file = await Deno.open(filepath, {        read: false,        write: true,        create: true,      });      responseToFile.body?.pipeTo(file.writable);    }  };};
/** * @alpha */export const updateCache = (  handler: (req: Request) => Promise<Response> | Response,  log: Logger,): CacheUpdater => {  return (urlOrPathname) => {    log?.debug(`Updating cache at ${urlOrPathname}`);    const url = new URL(urlOrPathname, "http://localhost");    handler(new Request(url.toString()));  };};
export const _requestToCacheFilepath = (publicDir: string, log?: Logger) => {  /** Check if segmented path is a directory */  const isDirectory = (segments: string[]): boolean =>    !segments[segments.length - 1];
  return (url: string, contentType?: string | null): string | undefined => {    // split the pathname into parts    const pathSegments = new URL(url).pathname.split("/");    // if this is an html file (very likely), check that we have    // a trailing slash, since this is only smart    // if not, it should not be a directory    if (contentType === "text/html") {      if (!isDirectory(pathSegments)) {        log?.warning(          `Cached HTML responses should have a trailing slash (${url})`,        );        return;      }      pathSegments.push("index.html");    } else if (isDirectory(pathSegments)) {      log?.warning(        `Non-HTML responses ending in slash cannot be cached (${url})`,      );      return;    }    return path.join(publicDir, ...pathSegments);  };};