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import { join } from "https://deno.land/std@0.136.0/path/mod.ts";import { existsDir, existsFile } from "./fs.ts";import log from "./log.ts";import util from "./util.ts";
type Meta = {  url: string;  headers: Record<string, string>;  now: {    secs_since_epoch: number;    nanos_since_epoch: number;  };};
const memoryCache = new Map<string, [content: Uint8Array, meta: Meta]>();const reloaded = new Set<string>();
/** fetch and cache remote contents */export default async function cache(  url: string,  options?: { forceRefresh?: boolean; retryTimes?: number; userAgent?: string },): Promise<Response> {  const { protocol, hostname, port, pathname, search } = new URL(url);  const isLocalhost = ["localhost", "0.0.0.0", "127.0.0.1"].includes(hostname);  const modulesCacheDir = Deno.env.get("MODULES_CACHE_DIR");  const hashname = isLocalhost ? "" : await util.computeHash("sha-256", pathname + search + (options?.userAgent || ""));
  let cacheDir = "";  let metaFilepath = "";  let contentFilepath = "";  if (modulesCacheDir) {    cacheDir = join(modulesCacheDir, util.trimSuffix(protocol, ":"), hostname + (port ? "_PORT" + port : ""));    contentFilepath = join(cacheDir, hashname);    metaFilepath = join(cacheDir, hashname + ".metadata.json");  }
  if (!options?.forceRefresh && !isLocalhost) {    if (modulesCacheDir) {      if (await existsFile(contentFilepath) && await existsFile(metaFilepath)) {        const reload = Deno.env.get("ALEPH_RELOAD_FLAG");        if (!reload || reloaded.has(url)) {          const [content, metaJSON] = await Promise.all([            Deno.readFile(contentFilepath),            Deno.readTextFile(metaFilepath),          ]);          try {            const meta = JSON.parse(metaJSON);            if (!isExpired(meta)) {              return new Response(content, { headers: { ...meta.headers, "cache-hit": "true" } });            }          } catch (_e) {            log.debug(`skip cache of ${url}: invalid cache metadata file`);          }        } else {          reloaded.add(url);        }      }    } else if (memoryCache.has(hashname)) {      const [content, meta] = memoryCache.get(hashname)!;      if (!isExpired(meta)) {        return new Response(content, { headers: { ...meta.headers, "cache-hit": "true" } });      }    }  }
  const retryTimes = options?.retryTimes ?? 3;  let finalRes = new Response("Server Error", { status: 500 });  for (let i = 0; i < retryTimes; i++) {    if (i === 0) {      if (!isLocalhost) {        log.debug("Download", url);      }    } else {      log.warn(`Download ${url} failed, retrying...`);    }
    const res = await fetch(url, { headers: options?.userAgent ? { "User-Agent": options?.userAgent } : undefined });    if (res.status >= 500) {      finalRes = res;      continue;    }
    if (res.ok && !isLocalhost) {      const buffer = await res.arrayBuffer();      const content = new Uint8Array(buffer);      const meta: Meta = {        url,        headers: {},        now: {          secs_since_epoch: Math.round(Date.now() / 1000),          nanos_since_epoch: 0,        },      };      res.headers.forEach((val, key) => {        meta.headers[key] = val;      });      if (modulesCacheDir) {        if (!(await existsDir(cacheDir))) {          await Deno.mkdir(cacheDir, { recursive: true });        }        await Promise.all([          Deno.writeFile(contentFilepath, content),          Deno.writeTextFile(metaFilepath, JSON.stringify(meta, undefined, 2)),        ]);      } else {        memoryCache.set(hashname, [content, meta]);      }      return new Response(content, { headers: res.headers });    }
    return res;  }
  return finalRes;}
function isExpired(meta: Meta) {  const cc = meta.headers["cache-control"];  const dataCacheTtl = cc && cc.includes("max-age=") ? parseInt(cc.split("max-age=")[1]) : undefined;  if (dataCacheTtl) {    const now = Date.now();    const expireTime = (meta.now.secs_since_epoch + dataCacheTtl) * 1000;    if (now > expireTime) {      return true;    }  }  return false;}