gulp-insert/index.js

Append or Prepend a string with gulp

var Stream = require('readable-stream');
var StreamQueue = require('streamqueue');

// Helper
function getStreamFromBuffer(string) {
  var stream = new Stream.Readable();
  stream._read = function() {
    stream.push(new Buffer(string));
    stream._read = stream.push.bind(stream, null);
  };
  return stream;
}

// Get string to insert
function getInsertString(arg, file) {
  if(typeof arg === 'function') {
    return arg(file);
  } else {
    return arg;
  }
}

exports.prepend = function(prepend) {
  var stream = new Stream.Transform({objectMode: true});

  stream._transform = function(file, unused, cb) {
    if(file.isNull()) {
      return cb(null, file);
    }
    var prependedBuffer = new Buffer(getInsertString(prepend, file));
    if(file.isStream()) {
      file.contents = new StreamQueue(
        getStreamFromBuffer(prependedBuffer),
        file.contents
      );
      return cb(null, file);
    }
    file.contents = Buffer.concat([prependedBuffer, file.contents],
      prependedBuffer.length + file.contents.length);
    cb(null, file);
  };

  return stream;
};

exports.append = function(append) {
  var stream = new Stream.Transform({objectMode: true});

  stream._transform = function(file, unused, cb) {
    if(file.isNull()) {
      return cb(null, file);
    }
    var appendedBuffer = new Buffer(getInsertString(append, file));
    if(file.isStream()) {
      file.contents = new StreamQueue(
        file.contents,
        getStreamFromBuffer(appendedBuffer)
      );
      return cb(null, file);
    }
    file.contents = Buffer.concat([file.contents, appendedBuffer],
      appendedBuffer.length + file.contents.length);
    cb(null, file);
  };

  return stream;
};

exports.wrap = function(begin, end) {
  var stream = new Stream.Transform({objectMode: true});

  stream._transform = function(file, unused, cb) {
    if(file.isNull()) {
      return cb(null, file);
    }
    var prependedBuffer = new Buffer(getInsertString(begin, file));
    var appendedBuffer = new Buffer(getInsertString(end, file));
    if(file.isStream()) {
      file.contents = new StreamQueue(
        getStreamFromBuffer(prependedBuffer),
        file.contents,
        getStreamFromBuffer(appendedBuffer)
      );
      return cb(null, file);
    }
    file.contents = Buffer.concat([prependedBuffer, file.contents, appendedBuffer],
      appendedBuffer.length + file.contents.length + prependedBuffer.length);
    cb(null, file);
  };

  return stream;
};

exports.transform = function(fn) {
  var stream = new Stream.Transform({objectMode: true});

  stream._transform = function(file, unused, cb) {
    if(file.isNull()) {
      return cb(null, file);
    }
    if(file.isStream()) {
      file.contents = file.contents.pipe(new Stream.Transform());
      file.contents._transform = function(chunk, encoding, cb) {
        cb(null, new Buffer(fn(chunk.toString(), file)))
      };
      return cb(null, file);
    }
    file.contents = new Buffer(fn(file.contents.toString(), file));
    cb(null, file);
  };

  return stream;
};