mod.ts

/*!
 * Based on https://github.com/jshttp/content-type/blob/master/index.js
 * Copyright(c) 2015 Douglas Christopher Wilson
 * Copyright(c) 2020 Henry Zhuang
 * MIT Licensed
 */

export type Parameters = { [key: string]: string };

export interface ContentType {
  type: string;
  parameters?: Parameters;
}

class ContentTypeImpl implements ContentType {
  constructor(type: string) {
    this.type = type;
    this.parameters = Object.create(null);
  }
  type: string;
  parameters: Parameters;
}

/**
 * RegExp to match *( ";" parameter ) in RFC 7231 sec 3.1.1.1
 *
 * parameter     = token "=" ( token / quoted-string )
 * token         = 1*tchar
 * tchar         = "!" / "#" / "$" / "%" / "&" / "'" / "*"
 *               / "+" / "-" / "." / "^" / "_" / "`" / "|" / "~"
 *               / DIGIT / ALPHA
 *               ; any VCHAR, except delimiters
 * quoted-string = DQUOTE *( qdtext / quoted-pair ) DQUOTE
 * qdtext        = HTAB / SP / %x21 / %x23-5B / %x5D-7E / obs-text
 * obs-text      = %x80-FF
 * quoted-pair   = "\" ( HTAB / SP / VCHAR / obs-text )
 */
const PARAM_REGEXP =
  /; *([!#$%&'*+.^_`|~0-9A-Za-z-]+) *= *("(?:[\u000b\u0020\u0021\u0023-\u005b\u005d-\u007e\u0080-\u00ff]|\\[\u000b\u0020-\u00ff])*"|[!#$%&'*+.^_`|~0-9A-Za-z-]+) */g;
const TEXT_REGEXP = /^[\u000b\u0020-\u007e\u0080-\u00ff]+$/;
const TOKEN_REGEXP = /^[!#$%&'*+.^_`|~0-9A-Za-z-]+$/;

/**
 * RegExp to match quoted-pair in RFC 7230 sec 3.2.6
 *
 * quoted-pair = "\" ( HTAB / SP / VCHAR / obs-text )
 * obs-text    = %x80-FF
 */
const QESC_REGEXP = /\\([\u000b\u0020-\u00ff])/g;

/**
 * RegExp to match chars that must be quoted-pair in RFC 7230 sec 3.2.6
 */
const QUOTE_REGEXP = /([\\"])/g;

/**
 * RegExp to match type in RFC 7231 sec 3.1.1.1
 *
 * media-type = type "/" subtype
 * type       = token
 * subtype    = token
 */
const TYPE_REGEXP =
  /^[!#$%&'*+.^_`|~0-9A-Za-z-]+\/[!#$%&'*+.^_`|~0-9A-Za-z-]+$/;

/**
 * Format ContentType object to media type.
 */
export function format(obj: ContentType): string {
  const parameters = obj.parameters;
  const type = obj.type;

  if (!type || !TYPE_REGEXP.test(type)) {
    throw new TypeError("invalid type");
  }

  let string = type;

  // append parameters
  if (parameters && typeof parameters === "object") {
    let param;
    const params = Object.keys(parameters).sort();

    for (let i = 0; i < params.length; i++) {
      param = params[i];

      if (!TOKEN_REGEXP.test(param)) {
        throw new TypeError("invalid parameter name");
      }

      string += "; " + param + "=" + qstring(parameters[param]);
    }
  }

  return string;
}

/**
 * Parse media type to object.
 */
export function parse(str: string): ContentType {
  let index = str.indexOf(";");
  const type = index !== -1 ? str.substr(0, index).trim() : str.trim();

  if (!TYPE_REGEXP.test(type)) {
    throw new TypeError("invalid media type");
  }

  const obj = new ContentTypeImpl(type.toLowerCase());

  // parse parameters
  if (index !== -1) {
    let key;
    let match;
    let value;

    PARAM_REGEXP.lastIndex = index;

    while ((match = PARAM_REGEXP.exec(str))) {
      if (match.index !== index) {
        throw new TypeError("invalid parameter format");
      }

      index += match[0].length;
      key = match[1].toLowerCase();
      value = match[2];

      if (value[0] === '"') {
        // remove quotes and escapes
        value = value
          .substr(1, value.length - 2)
          .replace(QESC_REGEXP, "$1");
      }

      obj.parameters[key] = value;
    }

    if (index !== str.length) {
      throw new TypeError("invalid parameter format");
    }
  }

  return obj;
}

/**
 * Quote a string if necessary.
 */
function qstring(val: string): string {
  const str = String(val);

  // no need to quote tokens
  if (TOKEN_REGEXP.test(str)) {
    return str;
  }

  if (str.length > 0 && !TEXT_REGEXP.test(str)) {
    throw new TypeError("invalid parameter value");
  }

  return '"' + str.replace(QUOTE_REGEXP, "\\$1") + '"';
}