index.js

/*!
 * content-disposition
 * Copyright(c) 2014 Douglas Christopher Wilson
 * MIT Licensed
 */

'use strict'

/**
 * Module exports.
 */

module.exports = contentDisposition
module.exports.parse = parse

/**
 * Module dependencies.
 */

var basename = require('path').basename

/**
 * RegExp to match non attr-char, *after* encodeURIComponent (i.e. not including "%")
 */

var ENCODE_URL_ATTR_CHAR_REGEXP = /[\x00-\x20"'()*,/:;<=>?@[\\\]{}\x7f]/g // eslint-disable-line no-control-regex

/**
 * RegExp to match percent encoding escape.
 */

var HEX_ESCAPE_REGEXP = /%[0-9A-Fa-f]{2}/
var HEX_ESCAPE_REPLACE_REGEXP = /%([0-9A-Fa-f]{2})/g

/**
 * RegExp to match non-latin1 characters.
 */

var NON_LATIN1_REGEXP = /[^\x20-\x7e\xa0-\xff]/g

/**
 * RegExp to match quoted-pair in RFC 2616
 *
 * quoted-pair = "\" CHAR
 * CHAR        = <any US-ASCII character (octets 0 - 127)>
 */

var QESC_REGEXP = /\\([\u0000-\u007f])/g

/**
 * RegExp to match chars that must be quoted-pair in RFC 2616
 */

var QUOTE_REGEXP = /([\\"])/g

/**
 * RegExp for various RFC 2616 grammar
 *
 * parameter     = token "=" ( token | quoted-string )
 * token         = 1*<any CHAR except CTLs or separators>
 * separators    = "(" | ")" | "<" | ">" | "@"
 *               | "," | ";" | ":" | "\" | <">
 *               | "/" | "[" | "]" | "?" | "="
 *               | "{" | "}" | SP | HT
 * quoted-string = ( <"> *(qdtext | quoted-pair ) <"> )
 * qdtext        = <any TEXT except <">>
 * quoted-pair   = "\" CHAR
 * CHAR          = <any US-ASCII character (octets 0 - 127)>
 * TEXT          = <any OCTET except CTLs, but including LWS>
 * LWS           = [CRLF] 1*( SP | HT )
 * CRLF          = CR LF
 * CR            = <US-ASCII CR, carriage return (13)>
 * LF            = <US-ASCII LF, linefeed (10)>
 * SP            = <US-ASCII SP, space (32)>
 * HT            = <US-ASCII HT, horizontal-tab (9)>
 * CTL           = <any US-ASCII control character (octets 0 - 31) and DEL (127)>
 * OCTET         = <any 8-bit sequence of data>
 */

var PARAM_REGEXP = /;[\x09\x20]*([!#$%&'*+.0-9A-Z^_`a-z|~-]+)[\x09\x20]*=[\x09\x20]*("(?:[\x20!\x23-\x5b\x5d-\x7e\x80-\xff]|\\[\x20-\x7e])*"|[!#$%&'*+.0-9A-Z^_`a-z|~-]+)[\x09\x20]*/g // eslint-disable-line no-control-regex
var TEXT_REGEXP = /^[\x20-\x7e\x80-\xff]+$/
var TOKEN_REGEXP = /^[!#$%&'*+.0-9A-Z^_`a-z|~-]+$/

/**
 * RegExp for various RFC 5987 grammar
 *
 * ext-value     = charset  "'" [ language ] "'" value-chars
 * charset       = "UTF-8" / "ISO-8859-1" / mime-charset
 * mime-charset  = 1*mime-charsetc
 * mime-charsetc = ALPHA / DIGIT
 *               / "!" / "#" / "$" / "%" / "&"
 *               / "+" / "-" / "^" / "_" / "`"
 *               / "{" / "}" / "~"
 * language      = ( 2*3ALPHA [ extlang ] )
 *               / 4ALPHA
 *               / 5*8ALPHA
 * extlang       = *3( "-" 3ALPHA )
 * value-chars   = *( pct-encoded / attr-char )
 * pct-encoded   = "%" HEXDIG HEXDIG
 * attr-char     = ALPHA / DIGIT
 *               / "!" / "#" / "$" / "&" / "+" / "-" / "."
 *               / "^" / "_" / "`" / "|" / "~"
 */

var EXT_VALUE_REGEXP = /^([A-Za-z0-9!#$%&+\-^_`{}~]+)'(?:[A-Za-z]{2,3}(?:-[A-Za-z]{3}){0,3}|[A-Za-z]{4,8}|)'((?:%[0-9A-Fa-f]{2}|[A-Za-z0-9!#$&+.^_`|~-])+)$/

/**
 * RegExp for various RFC 6266 grammar
 *
 * disposition-type = "inline" | "attachment" | disp-ext-type
 * disp-ext-type    = token
 * disposition-parm = filename-parm | disp-ext-parm
 * filename-parm    = "filename" "=" value
 *                  | "filename*" "=" ext-value
 * disp-ext-parm    = token "=" value
 *                  | ext-token "=" ext-value
 * ext-token        = <the characters in token, followed by "*">
 */

var DISPOSITION_TYPE_REGEXP = /^([!#$%&'*+.0-9A-Z^_`a-z|~-]+)[\x09\x20]*(?:$|;)/ // eslint-disable-line no-control-regex

/**
 * Create an attachment Content-Disposition header.
 *
 * @param {string} [filename]
 * @param {object} [options]
 * @param {string} [options.type=attachment]
 * @param {string|boolean} [options.fallback=true]
 * @return {string}
 * @api public
 */

function contentDisposition (filename, options) {
  var opts = options || {}

  // get type
  var type = opts.type || 'attachment'

  // get parameters
  var params = createparams(filename, opts.fallback)

  // format into string
  return format(new ContentDisposition(type, params))
}

/**
 * Create parameters object from filename and fallback.
 *
 * @param {string} [filename]
 * @param {string|boolean} [fallback=true]
 * @return {object}
 * @api private
 */

function createparams (filename, fallback) {
  if (filename === undefined) {
    return
  }

  var params = {}

  if (typeof filename !== 'string') {
    throw new TypeError('filename must be a string')
  }

  // fallback defaults to true
  if (fallback === undefined) {
    fallback = true
  }

  if (typeof fallback !== 'string' && typeof fallback !== 'boolean') {
    throw new TypeError('fallback must be a string or boolean')
  }

  if (typeof fallback === 'string' && NON_LATIN1_REGEXP.test(fallback)) {
    throw new TypeError('fallback must be ISO-8859-1 string')
  }

  // restrict to file base name
  var name = basename(filename)

  // determine if name is suitable for quoted string
  var isQuotedString = TEXT_REGEXP.test(name)

  // generate fallback name
  var fallbackName = typeof fallback !== 'string'
    ? fallback && getlatin1(name)
    : basename(fallback)
  var hasFallback = typeof fallbackName === 'string' && fallbackName !== name

  // set extended filename parameter
  if (hasFallback || !isQuotedString || HEX_ESCAPE_REGEXP.test(name)) {
    params['filename*'] = name
  }

  // set filename parameter
  if (isQuotedString || hasFallback) {
    params.filename = hasFallback
      ? fallbackName
      : name
  }

  return params
}

/**
 * Format object to Content-Disposition header.
 *
 * @param {object} obj
 * @param {string} obj.type
 * @param {object} [obj.parameters]
 * @return {string}
 * @api private
 */

function format (obj) {
  var parameters = obj.parameters
  var type = obj.type

  if (!type || typeof type !== 'string' || !TOKEN_REGEXP.test(type)) {
    throw new TypeError('invalid type')
  }

  // start with normalized type
  var string = String(type).toLowerCase()

  // append parameters
  if (parameters && typeof parameters === 'object') {
    var param
    var params = Object.keys(parameters).sort()

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

      var val = param.substr(-1) === '*'
        ? ustring(parameters[param])
        : qstring(parameters[param])

      string += '; ' + param + '=' + val
    }
  }

  return string
}

/**
 * Decode a RFC 6987 field value (gracefully).
 *
 * @param {string} str
 * @return {string}
 * @api private
 */

function decodefield (str) {
  var match = EXT_VALUE_REGEXP.exec(str)

  if (!match) {
    throw new TypeError('invalid extended field value')
  }

  var charset = match[1].toLowerCase()
  var encoded = match[2]
  var value

  // to binary string
  var binary = encoded.replace(HEX_ESCAPE_REPLACE_REGEXP, pdecode)

  switch (charset) {
    case 'iso-8859-1':
      value = getlatin1(binary)
      break
    case 'utf-8':
      value = new Buffer(binary, 'binary').toString('utf8')
      break
    default:
      throw new TypeError('unsupported charset in extended field')
  }

  return value
}

/**
 * Get ISO-8859-1 version of string.
 *
 * @param {string} val
 * @return {string}
 * @api private
 */

function getlatin1 (val) {
  // simple Unicode -> ISO-8859-1 transformation
  return String(val).replace(NON_LATIN1_REGEXP, '?')
}

/**
 * Parse Content-Disposition header string.
 *
 * @param {string} string
 * @return {object}
 * @api private
 */

function parse (string) {
  if (!string || typeof string !== 'string') {
    throw new TypeError('argument string is required')
  }

  var match = DISPOSITION_TYPE_REGEXP.exec(string)

  if (!match) {
    throw new TypeError('invalid type format')
  }

  // normalize type
  var index = match[0].length
  var type = match[1].toLowerCase()

  var key
  var names = []
  var params = {}
  var value

  // calculate index to start at
  index = PARAM_REGEXP.lastIndex = match[0].substr(-1) === ';'
    ? index - 1
    : index

  // match parameters
  while ((match = PARAM_REGEXP.exec(string))) {
    if (match.index !== index) {
      throw new TypeError('invalid parameter format')
    }

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

    if (names.indexOf(key) !== -1) {
      throw new TypeError('invalid duplicate parameter')
    }

    names.push(key)

    if (key.indexOf('*') + 1 === key.length) {
      // decode extended value
      key = key.slice(0, -1)
      value = decodefield(value)

      // overwrite existing value
      params[key] = value
      continue
    }

    if (typeof params[key] === 'string') {
      continue
    }

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

    params[key] = value
  }

  if (index !== -1 && index !== string.length) {
    throw new TypeError('invalid parameter format')
  }

  return new ContentDisposition(type, params)
}

/**
 * Percent decode a single character.
 *
 * @param {string} str
 * @param {string} hex
 * @return {string}
 * @api private
 */

function pdecode (str, hex) {
  return String.fromCharCode(parseInt(hex, 16))
}

/**
 * Percent encode a single character.
 *
 * @param {string} char
 * @return {string}
 * @api private
 */

function pencode (char) {
  var hex = String(char)
    .charCodeAt(0)
    .toString(16)
    .toUpperCase()
  return hex.length === 1
    ? '%0' + hex
    : '%' + hex
}

/**
 * Quote a string for HTTP.
 *
 * @param {string} val
 * @return {string}
 * @api private
 */

function qstring (val) {
  var str = String(val)

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

/**
 * Encode a Unicode string for HTTP (RFC 5987).
 *
 * @param {string} val
 * @return {string}
 * @api private
 */

function ustring (val) {
  var str = String(val)

  // percent encode as UTF-8
  var encoded = encodeURIComponent(str)
    .replace(ENCODE_URL_ATTR_CHAR_REGEXP, pencode)

  return 'UTF-8\'\'' + encoded
}

/**
 * Class for parsed Content-Disposition header for v8 optimization
 */

function ContentDisposition (type, parameters) {
  this.type = type
  this.parameters = parameters
}