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// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.import { isIterator, isToken, needsEncoding } from "./_util.ts";
/** Serializes the media type and the optional parameters as a media type * conforming to RFC 2045 and RFC 2616. * * The type and parameter names are written in lower-case. * * When any of the arguments results in a standard violation then the return * value will be an empty string (`""`). * * @example * ```ts * import { formatMediaType } from "https://deno.land/std@$STD_VERSION/media_types/format_media_type.ts"; * * formatMediaType("text/plain", { charset: "UTF-8" }); // `text/plain; charset=UTF-8` * ``` */export function formatMediaType(  type: string,  param?: Record<string, string> | Iterable<[string, string]>,): string {  let b = "";  const [major, sub] = type.split("/");  if (!sub) {    if (!isToken(type)) {      return "";    }    b += type.toLowerCase();  } else {    if (!isToken(major) || !isToken(sub)) {      return "";    }    b += `${major.toLowerCase()}/${sub.toLowerCase()}`;  }
  if (param) {    param = isIterator(param) ? Object.fromEntries(param) : param;    const attrs = Object.keys(param);    attrs.sort();
    for (const attribute of attrs) {      if (!isToken(attribute)) {        return "";      }      const value = param[attribute];      b += `; ${attribute.toLowerCase()}`;
      const needEnc = needsEncoding(value);      if (needEnc) {        b += "*";      }      b += "=";
      if (needEnc) {        b += `utf-8''${encodeURIComponent(value)}`;        continue;      }
      if (isToken(value)) {        b += value;        continue;      }      b += `"${value.replace(/["\\]/gi, (m) => `\\${m}`)}"`;    }  }  return b;}