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/*! * Adapted directly from forwarded-parse at https://github.com/lpinca/forwarded-parse * which is licensed as follows: * * Copyright(c) 2015 Luigi Pinca * Copyright(c) 2023 the oak authors * MIT Licensed */
/** * Provides utilities for parsing and validating the `Forwarded` header. * * @module */
import { assert } from "./util.ts";
/** * Unescape a string. * * @param str The string to unescape. * @returns A new unescaped string. */function decode(value: string): string {  return value.replace(/\\(.)/g, "$1");}
/** * Check if a character is a delimiter as defined in section 3.2.6 of RFC 7230. * * @param code The code of the character to check. * @returns `true` if the character is a delimiter, else `false`. */function isDelimiter(code: number): boolean {  return code === 0x22 || // '"'    code === 0x28 || // '('    code === 0x29 || // ')'    code === 0x2C || // ','    code === 0x2F || // '/'    code >= 0x3A && code <= 0x40 || // ':', ';', '<', '=', '>', '?' '@'    code >= 0x5B && code <= 0x5D || // '[', '\', ']'    code === 0x7B || // '{'    code === 0x7D; // '}'}
/** * Check if a character is an extended ASCII character. * * @param code The code of the character to check. * @returns `true` if `code` is in the %x80-FF range, else `false`. */function isExtended(code: number): boolean {  return code >= 0x80 && code <= 0xFF;}
/** * Check if a character is a printable ASCII character. * * @param code The code of the character to check. * @returns `true` if `code` is in the %x20-7E range, else `false`. */function isPrint(code: number): boolean {  return code >= 0x20 && code <= 0x7E;}
/** * Check if a character is allowed in a token as defined in section 3.2.6 * of RFC 7230. * * @param code The code of the character to check. * @returns `true` if the character is allowed, else `false`. */function isTokenChar(code: number): boolean {  return code === 0x21 || // '!'    code >= 0x23 && code <= 0x27 || // '#', '$', '%', '&', '''    code === 0x2A || // '*'    code === 0x2B || // '+'    code === 0x2D || // '-'    code === 0x2E || // '.'    code >= 0x30 && code <= 0x39 || // 0-9    code >= 0x41 && code <= 0x5A || // A-Z    code >= 0x5E && code <= 0x7A || // '^', '_', '`', a-z    code === 0x7C || // '|'    code === 0x7E; // '~'}
/** * Parse the `Forwarded` header field value into an array of objects. If the * value is not parsable, `undefined` is returned. * * @param value The header field value. */export function parse(value: string): Record<string, string>[] | undefined {  let parameter: undefined | string;  let start = -1;  let end = -1;  let isEscaping = false;  let inQuotes = false;  let mustUnescape = false;
  let code;  let forwarded: Record<string, string> = {};  const output: Record<string, string>[] = [];  let i;
  for (i = 0; i < value.length; i++) {    code = value.charCodeAt(i);
    if (parameter === undefined) {      if (i !== 0 && start === -1 && (code === 0x20 || code === 0x09)) {        continue;      }
      if (isTokenChar(code)) {        if (start === -1) {          start = i;        }      } else if (code === 0x3D && start !== -1) {        parameter = value.slice(start, i).toLowerCase();        start = -1;      } else {        return undefined;      }    } else {      if (        isEscaping && (code === 0x09 || isPrint(code) || isExtended(code))      ) {        isEscaping = false;      } else if (isTokenChar(code)) {        if (end !== -1) {          return undefined;        }        if (start === -1) {          start = i;        }      } else if (isDelimiter(code) || isExtended(code)) {        if (inQuotes) {          if (code === 0x22) {            inQuotes = false;            end = i;          } else if (code === 0x5C) {            if (start === -1) {              start = i;            }            isEscaping = mustUnescape = true;          } else if (start === -1) {            start = i;          }        } else if (code === 0x22 && value.charCodeAt(i - 1) === 0x3D) {          inQuotes = true;        } else if (          (code === 0x2C || code === 0x3B) && (start !== -1 || end !== -1)        ) {          assert(parameter, "Variable 'parameter' not defined.");          if (start !== -1) {            if (end === -1) {              end = i;            }
            forwarded[parameter] = mustUnescape              ? decode(value.slice(start, end))              : value.slice(start, end);          } else {            forwarded[parameter] = "";          }
          if (code === 0x2C) {            output.push(forwarded);            forwarded = {};          }
          parameter = undefined;          start = end = -1;        } else {          return undefined;        }      } else if (code === 0x20 || code === 0x09) {        if (end !== -1) {          continue;        }
        if (inQuotes) {          if (start === -1) {            start = i;          }        } else if (start !== -1) {          end = i;        } else {          return undefined;        }      } else {        return undefined;      }    }  }
  if (    parameter === undefined || inQuotes || (start === -1 && end === -1) ||    code === 0x20 || code === 0x09  ) {    return undefined;  }
  if (start !== -1) {    if (end === -1) {      end = i;    }    forwarded[parameter] = mustUnescape      ? decode(value.slice(start, end))      : value.slice(start, end);  } else {    forwarded[parameter] = "";  }
  output.push(forwarded);  return output;}