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// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.import { consumeMediaParam, decode2331Encoding } from "./_util.ts";
/** * Parses the media type and any optional parameters, per * [RFC 1521](https://datatracker.ietf.org/doc/html/rfc1521). Media types are * the values in `Content-Type` and `Content-Disposition` headers. On success * the function returns a tuple where the first element is the media type and * the second element is the optional parameters or `undefined` if there are * none. * * The function will throw if the parsed value is invalid. * * The returned media type will be normalized to be lower case, and returned * params keys will be normalized to lower case, but preserves the casing of * the value. * * @example * ```ts * import { parseMediaType } from "https://deno.land/std@$STD_VERSION/media_types/parse_media_type.ts"; * import { assertEquals } from "https://deno.land/std@$STD_VERSION/testing/asserts.ts"; * * assertEquals( *   parseMediaType("application/JSON"), *   [ *     "application/json", *     undefined *   ] * ); * * assertEquals( *   parseMediaType("text/html; charset=UTF-8"), *   [ *     "application/json", *     { charset: "UTF-8" }, *   ] * ); * ``` */export function parseMediaType(  v: string,): [mediaType: string, params: Record<string, string> | undefined] {  const [base] = v.split(";");  const mediaType = base.toLowerCase().trim();
  const params: Record<string, string> = {};  // Map of base parameter name -> parameter name -> value  // for parameters containing a '*' character.  const continuation = new Map<string, Record<string, string>>();
  v = v.slice(base.length);  while (v.length) {    v = v.trimStart();    if (v.length === 0) {      break;    }    const [key, value, rest] = consumeMediaParam(v);    if (!key) {      if (rest.trim() === ";") {        // ignore trailing semicolons        break;      }      throw new TypeError("Invalid media parameter.");    }
    let pmap = params;    const [baseName, rest2] = key.split("*");    if (baseName && rest2 != null) {      if (!continuation.has(baseName)) {        continuation.set(baseName, {});      }      pmap = continuation.get(baseName)!;    }    if (key in pmap) {      throw new TypeError("Duplicate key parsed.");    }    pmap[key] = value;    v = rest;  }
  // Stitch together any continuations or things with stars  // (i.e. RFC 2231 things with stars: "foo*0" or "foo*")  let str = "";  for (const [key, pieceMap] of continuation) {    const singlePartKey = `${key}*`;    const v = pieceMap[singlePartKey];    if (v) {      const decv = decode2331Encoding(v);      if (decv) {        params[key] = decv;      }      continue;    }
    str = "";    let valid = false;    for (let n = 0;; n++) {      const simplePart = `${key}*${n}`;      let v = pieceMap[simplePart];      if (v) {        valid = true;        str += v;        continue;      }      const encodedPart = `${simplePart}*`;      v = pieceMap[encodedPart];      if (!v) {        break;      }      valid = true;      if (n === 0) {        const decv = decode2331Encoding(v);        if (decv) {          str += decv;        }      } else {        const decv = decodeURI(v);        str += decv;      }    }    if (valid) {      params[key] = str;    }  }
  return Object.keys(params).length    ? [mediaType, params]    : [mediaType, undefined];}