whistle/lib/util/replace-pattern-transform.js

HTTP, HTTPS, Websocket debugging proxy

var Transform = require('pipestream').Transform;
var util = require('util');
var LENGTH = 5120;

function ReplacePatternTransform(pattern, value) {
  Transform.call(this);
  this._pattern = pattern;
  this._value = value == null ? '' : value + '';
  this._rest = '';
}

util.inherits(ReplacePatternTransform, Transform);

var proto = ReplacePatternTransform.prototype;
proto._transform = function(chunk, encoding, callback) {
  if (chunk != null) {
    chunk = this._rest + chunk;
    var index = 0;
    var value = this._value;
    var result = chunk.replace(this._pattern, function() {
      var matcher = replace(value, arguments);
      var lastIndex = arguments.length - 1;
      index = arguments[lastIndex - 1] + arguments[lastIndex].length;
      return matcher;
    });
    index = Math.max(index, chunk.length + 1 - LENGTH);
    this._rest = chunk.substring(index);
    chunk = result.substring(0, result.length - this._rest.length);
  } else if (this._rest) {
    chunk = this._rest.replace(this._pattern, function() {
      return replace(this._value, arguments);
    });
  }

  callback(null, chunk);
};

function replace(replacement, args) {
  return replacement ? replacement.replace(/(^|.)?(\$[1-9])/g,
function(matched, $1, $2) {
  return $1 == '\\' ? $2 : ($1 || '') + (args[$2.substring(1)] || '');
}) : '';
}

module.exports = ReplacePatternTransform;