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import type { Metadata } from "./file.ts";import { CacheError } from "./cache.ts";import { exists, fromFileUrl } from "./deps.ts";
async function protocolFile(url: URL, dest: string): Promise<Metadata> {  const path = fromFileUrl(url);  try {    if (!(await exists(path))) {      throw new CacheError(`${path} does not exist on the local system.`);    }  } catch {    throw new CacheError(`${path} is not valid.`);  }  await Deno.copyFile(path, dest);  return {    url: url.href,  };}
async function protocolHttp(url: URL, dest: string): Promise<Metadata> {  const download = await fetch(url);  if (!download.ok) {    throw new CacheError(download.statusText);  }  const source = await download.arrayBuffer();  await Deno.writeFile(dest, new Uint8Array(source));
  const headers: { [key: string]: string } = {};  for (const [key, value] of download.headers) {    headers[key] = value;  }  return {    url: url.href,    headers,  };}
export async function fetchFile(url: URL, dest: string): Promise<Metadata> {  switch (url.protocol) {    case "file:":      return await protocolFile(url, dest);
    case "http:":    case "https:":      return await protocolHttp(url, dest);
    default:      throw new CacheError(`unsupported protocol ("${url}")`);  }}