all files / lib/offshore/utils/ stream.js

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/**
 * Streams
 *
 * A Streaming API with support for Transformations
 */
 
var util = require('util');
var Stream = require('stream');
var Transformations = require('./transformations');
var _ = require('lodash');
 
var ModelStream = module.exports = function(transformation) {
 
  // Use specified, or otherwise default, JSON transformation
  this.transformation = transformation || Transformations.json;
 
  // Reset write index
  this.index = 0;
 
  // Make stream writable
  this.writable = true;
};
 
util.inherits(ModelStream, Stream);
 
/**
 * Write to stream
 *
 * Extracts args to write and emits them as data events
 *
 * @param {Object} model
 * @param {Function} cb
 */
 
ModelStream.prototype.write = function(model, cb) {
  var self = this;
 
  // Run transformation on this item
  this.transformation.write(model, this.index, function writeToStream(err, transformedModel) {
 
    // Increment index for next time
    self.index++;
 
    // Write transformed model to stream
    self.emit('data', _.clone(transformedModel));
 
    // Inform that we're finished
    Iif (cb) return cb(err);
  });
 
};
 
/**
 * End Stream
 */
 
ModelStream.prototype.end = function(err, cb) {
  var self = this;
 
  Eif (err) {
    this.emit('error', err.message);
    Iif (cb) return cb(err);
    return;
  }
 
  this.transformation.end(function(err, suffix) {
 
    if (err) {
      self.emit('error', err);
      if (cb) return cb(err);
      return;
    }
 
    // Emit suffix if specified
    if (suffix) self.emit('data', suffix);
    self.emit('end');
    if (cb) return cb();
  });
};