Website/node_modules/form-data/lib/form_data.js

var CombinedStream = require('combined-stream');
var util = require('util');
var path = require('path');
var http = require('http');
var https = require('https');
var parseUrl = require('url').parse;
var fs = require('fs');
var mime = require('mime-types');
var async = require('async');

module.exports = FormData;
function FormData() {
  this._overheadLength = 0;
  this._valueLength = 0;
  this._lengthRetrievers = [];

  CombinedStream.call(this);
}
util.inherits(FormData, CombinedStream);

FormData.LINE_BREAK = '\r\n';
FormData.DEFAULT_CONTENT_TYPE = 'application/octet-stream';

FormData.prototype.append = function(field, value, options) {
  options = (typeof options === 'string')
    ? { filename: options }
    : options || {};

  var append = CombinedStream.prototype.append.bind(this);

  // all that streamy business can't handle numbers
  if (typeof value == 'number') value = ''+value;

  // https://github.com/felixge/node-form-data/issues/38
  if (util.isArray(value)) {
    // Please convert your array into string
    // the way web server expects it
    this._error(new Error('Arrays are not supported.'));
    return;
  }

  var header = this._multiPartHeader(field, value, options);
  var footer = this._multiPartFooter(field, value, options);

  append(header);
  append(value);
  append(footer);

  // pass along options.knownLength
  this._trackLength(header, value, options);
};

FormData.prototype._trackLength = function(header, value, options) {
  var valueLength = 0;

  // used w/ getLengthSync(), when length is known.
  // e.g. for streaming directly from a remote server,
  // w/ a known file a size, and not wanting to wait for
  // incoming file to finish to get its size.
  if (options.knownLength != null) {
    valueLength += +options.knownLength;
  } else if (Buffer.isBuffer(value)) {
    valueLength = value.length;
  } else if (typeof value === 'string') {
    valueLength = Buffer.byteLength(value);
  }

  this._valueLength += valueLength;

  // @check why add CRLF? does this account for custom/multiple CRLFs?
  this._overheadLength +=
    Buffer.byteLength(header) +
    FormData.LINE_BREAK.length;

  // empty or either doesn't have path or not an http response
  if (!value || ( !value.path && !(value.readable && value.hasOwnProperty('httpVersion')) )) {
    return;
  }

  // no need to bother with the length
  if (!options.knownLength)
  this._lengthRetrievers.push(function(next) {

    if (value.hasOwnProperty('fd')) {

      // take read range into a account
      // `end` = Infinity –> read file till the end
      //
      // TODO: Looks like there is bug in Node fs.createReadStream
      // it doesn't respect `end` options without `start` options
      // Fix it when node fixes it.
      // https://github.com/joyent/node/issues/7819
      if (value.end != undefined && value.end != Infinity && value.start != undefined) {

        // when end specified
        // no need to calculate range
        // inclusive, starts with 0
        next(null, value.end+1 - (value.start ? value.start : 0));

      // not that fast snoopy
      } else {
        // still need to fetch file size from fs
        fs.stat(value.path, function(err, stat) {

          var fileSize;

          if (err) {
            next(err);
            return;
          }

          // update final size based on the range options
          fileSize = stat.size - (value.start ? value.start : 0);
          next(null, fileSize);
        });
      }

    // or http response
    } else if (value.hasOwnProperty('httpVersion')) {
      next(null, +value.headers['content-length']);

    // or request stream http://github.com/mikeal/request
    } else if (value.hasOwnProperty('httpModule')) {
      // wait till response come back
      value.on('response', function(response) {
        value.pause();
        next(null, +response.headers['content-length']);
      });
      value.resume();

    // something else
    } else {
      next('Unknown stream');
    }
  });
};

FormData.prototype._multiPartHeader = function(field, value, options) {
  // custom header specified (as string)?
  // it becomes responsible for boundary
  // (e.g. to handle extra CRLFs on .NET servers)
  if (options.header != null) {
    return options.header;
  }

  var contents = '';
  var headers  = {
    'Content-Disposition': ['form-data', 'name="' + field + '"'],
    'Content-Type': []
  };

  // fs- and request- streams have path property
  // or use custom filename and/or contentType
  // TODO: Use request's response mime-type
  if (options.filename || value.path) {
    headers['Content-Disposition'].push(
      'filename="' + path.basename(options.filename || value.path) + '"'
    );
    headers['Content-Type'].push(
      options.contentType ||
      mime.lookup(options.filename || value.path) ||
      FormData.DEFAULT_CONTENT_TYPE
    );
  // http response has not
  } else if (value.readable && value.hasOwnProperty('httpVersion')) {
    headers['Content-Disposition'].push(
      'filename="' + path.basename(value.client._httpMessage.path) + '"'
    );
    headers['Content-Type'].push(
      options.contentType ||
      value.headers['content-type'] ||
      FormData.DEFAULT_CONTENT_TYPE
    );
  } else if (Buffer.isBuffer(value)) {
    headers['Content-Type'].push(
      options.contentType ||
      FormData.DEFAULT_CONTENT_TYPE
    );
  } else if (options.contentType) {
    headers['Content-Type'].push(options.contentType);
  }

  for (var prop in headers) {
    if (headers[prop].length) {
      contents += prop + ': ' + headers[prop].join('; ') + FormData.LINE_BREAK;
    }
  }
  
  return '--' + this.getBoundary() + FormData.LINE_BREAK + contents + FormData.LINE_BREAK;
};

FormData.prototype._multiPartFooter = function(field, value, options) {
  return function(next) {
    var footer = FormData.LINE_BREAK;

    var lastPart = (this._streams.length === 0);
    if (lastPart) {
      footer += this._lastBoundary();
    }

    next(footer);
  }.bind(this);
};

FormData.prototype._lastBoundary = function() {
  return '--' + this.getBoundary() + '--' + FormData.LINE_BREAK;
};

FormData.prototype.getHeaders = function(userHeaders) {
  var formHeaders = {
    'content-type': 'multipart/form-data; boundary=' + this.getBoundary()
  };

  for (var header in userHeaders) {
    formHeaders[header.toLowerCase()] = userHeaders[header];
  }

  return formHeaders;
}

FormData.prototype.getCustomHeaders = function(contentType) {
    contentType = contentType ? contentType : 'multipart/form-data';

    var formHeaders = {
        'content-type': contentType + '; boundary=' + this.getBoundary(),
        'content-length': this.getLengthSync()
    };

    return formHeaders;
}

FormData.prototype.getBoundary = function() {
  if (!this._boundary) {
    this._generateBoundary();
  }

  return this._boundary;
};

FormData.prototype._generateBoundary = function() {
  // This generates a 50 character boundary similar to those used by Firefox.
  // They are optimized for boyer-moore parsing.
  var boundary = '--------------------------';
  for (var i = 0; i < 24; i++) {
    boundary += Math.floor(Math.random() * 10).toString(16);
  }

  this._boundary = boundary;
};

// Note: getLengthSync DOESN'T calculate streams length
// As workaround one can calculate file size manually
// and add it as knownLength option
FormData.prototype.getLengthSync = function(debug) {
  var knownLength = this._overheadLength + this._valueLength;

  // Don't get confused, there are 3 "internal" streams for each keyval pair
  // so it basically checks if there is any value added to the form
  if (this._streams.length) {
    knownLength += this._lastBoundary().length;
  }

  // https://github.com/felixge/node-form-data/issues/40
  if (this._lengthRetrievers.length) {
    // Some async length retrivers are present
    // therefore synchronous length calculation is false.
    // Please use getLength(callback) to get proper length
    this._error(new Error('Cannot calculate proper length in synchronous way.'));
  }

  return knownLength;
};

FormData.prototype.getLength = function(cb) {
  var knownLength = this._overheadLength + this._valueLength;

  if (this._streams.length) {
    knownLength += this._lastBoundary().length;
  }

  if (!this._lengthRetrievers.length) {
    process.nextTick(cb.bind(this, null, knownLength));
    return;
  }

  async.parallel(this._lengthRetrievers, function(err, values) {
    if (err) {
      cb(err);
      return;
    }

    values.forEach(function(length) {
      knownLength += length;
    });

    cb(null, knownLength);
  });
};

FormData.prototype.submit = function(params, cb) {

  var request
    , options
    , defaults = {
        method : 'post'
    };

  // parse provided url if it's string
  // or treat it as options object
  if (typeof params == 'string') {
    params = parseUrl(params);

    options = populate({
      port: params.port,
      path: params.pathname,
      host: params.hostname
    }, defaults);
  }
  else // use custom params
  {
    options = populate(params, defaults);
    // if no port provided use default one
    if (!options.port) {
      options.port = options.protocol == 'https:' ? 443 : 80;
    }
  }

  // put that good code in getHeaders to some use
  options.headers = this.getHeaders(params.headers);

  // https if specified, fallback to http in any other case
  if (options.protocol == 'https:') {
    request = https.request(options);
  } else {
    request = http.request(options);
  }

  // get content length and fire away
  this.getLength(function(err, length) {

    // TODO: Add chunked encoding when no length (if err)

    // add content length
    request.setHeader('Content-Length', length);

    this.pipe(request);
    if (cb) {
      request.on('error', cb);
      request.on('response', cb.bind(this, null));
    }
  }.bind(this));

  return request;
};

FormData.prototype._error = function(err) {
  if (this.error) return;

  this.error = err;
  this.pause();
  this.emit('error', err);
};

/*
 * Santa's little helpers
 */

// populates missing values
function populate(dst, src) {
  for (var prop in src) {
    if (!dst[prop]) dst[prop] = src[prop];
  }
  return dst;
}