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/*! * Based on https://github.com/jshttp/vary/blob/master/index.js * Copyright(c) 2014-2017 Douglas Christopher Wilson * Copyright(c) 2020 Henry Zhuang * MIT Licensed */
/** * RegExp to match field-name in RFC 7230 sec 3.2 * * field-name    = token * token         = 1*tchar * tchar         = "!" / "#" / "$" / "%" / "&" / "'" / "*" *               / "+" / "-" / "." / "^" / "_" / "`" / "|" / "~" *               / DIGIT / ALPHA *               ; any VCHAR, except delimiters */
const FIELD_NAME_REGEXP = /^[!#$%&'*+\-.^_`|~0-9A-Za-z]+$/;
/** * Append a field to a vary header. * * @param {String} header * @param {String|Array} field * @return {String} * @public */
export function append(header: string, field: string | string[]): string {  // if (typeof header !== 'string') {  //   throw new TypeError('header argument is required')  // }
  // if (!field) {  //   throw new TypeError('field argument is required')  // }
  // existing, unspecified vary  if (header === "*") {    return header;  }
  // get fields array  const fields = !Array.isArray(field) ? parse(String(field)) : field;
  // assert on invalid field names  for (let j = 0; j < fields.length; j++) {    if (!FIELD_NAME_REGEXP.test(fields[j])) {      throw new TypeError(        `field argument contains an invalid header name \`${fields[j]}\``,      );    }  }
  // enumerate current values  let val = header;  const vals = parse(header.toLowerCase());
  // unspecified vary  if (fields.indexOf("*") !== -1 || vals.indexOf("*") !== -1) {    return "*";  }
  for (let i = 0; i < fields.length; i++) {    const fld = fields[i].toLowerCase();
    // append value (case-preserving)    if (vals.indexOf(fld) === -1) {      vals.push(fld);      val = val ? val + ", " + fields[i] : fields[i];    }  }
  return val;}
/** * Parse a vary header into an array. * * @param {String} header * @return {Array} * @private */
function parse(header: string): string[] {  let end = 0;  const list = [];  let start = 0;
  // gather tokens  for (let i = 0, len = header.length; i < len; i++) {    switch (header.charCodeAt(i)) {      case 0x20:/*   */        if (start === end) {          start = end = i + 1;        }        break;      case 0x2c:/* , */        list.push(header.substring(start, end));        start = end = i + 1;        break;      default:        end = i + 1;        break;    }  }
  // final token  list.push(header.substring(start, end));
  return list;}
/** * Mark that a request is varied on a header field. * * @param {Headers} header * @param {String|Array} field * @public */
export function vary(header: Headers, field: string | string[]): void {  // get existing header  let val = header.get("vary") || "";
  // set new header  if ((val = append(val, field))) {    header.set("vary", val);  }}