node-task idea: concat

concat.js

var when = require('when');
var fs = require('fs');
var _ = require('lodash');

var nodefn = require('when/node/function');
var readFile = nodefn.bind(fs.readFile);
var writeFile = nodefn.bind(fs.writeFile);

// Listen for events here.
var concat = new (require('events').EventEmitter);

// Internal helper for getting options.
var normalizeOptions = function(o) {
  concat.emit('debug', 'options', o);
  return _.defaults({}, o, {
    separator: '',
    banner: '',
    footer: '',
  });
};

// Concat one file.
concat.each = function(src, dest, o) {
  o = normalizeOptions(o);
  concat.emit('debug', 'src', src);
  concat.emit('debug', 'dest', dest);
  return when.map(src, readFile).then(function(contents) {
    return o.banner + contents.join(o.separator) + o.footer;
  }).then(writeFile.bind(fs, dest));
};

// Concat many files.
concat.all = function(files, o) {
  o = normalizeOptions(o);
  return when.map(files, function(f) {
    return concat.each(f.src, f.dest, o);
  });
};

// Standard "node task" interface.
concat.run = function(o) {
  if (!o) { o = {}; }
  return concat.all(o.files || [], o);
};

module.exports = concat;

usage.js

concat.on('status', console.log.bind(console, 'status'));
concat.on('warn', console.log.bind(console, 'warn'));
concat.on('debug', console.log.bind(console, 'debug'));

concat.each(
  ['test/fixtures/concat/a.txt', 'test/fixtures/concat/b.txt', 'test/fixtures/concat/c.txt'],
  'tmp/each-abc.txt',
  {separator: ';each;', banner: '/* EACH */\n', footer: '\n\n'}
).then(console.log, console.error)

concat.all(
  [
    {src: ['test/fixtures/concat/a.txt', 'test/fixtures/concat/b.txt', 'test/fixtures/concat/c.txt'], dest: 'tmp/all-abc.txt'},
    {src: ['test/fixtures/concat/d.txt', 'test/fixtures/concat/e.txt', 'test/fixtures/concat/f.txt'], dest: 'tmp/all-def.txt'},
    {src: ['test/fixtures/concat/g.txt', 'test/fixtures/concat/h.txt', 'test/fixtures/concat/i.txt'], dest: 'tmp/all-ghi.txt'},
  ],
  {separator: ';all;', banner: '/* ALL */\n', footer: '\n\n'}
).then(console.log, console.error);

concat.run({
  files: [
    {src: ['test/fixtures/concat/a.txt', 'test/fixtures/concat/b.txt', 'test/fixtures/concat/c.txt'], dest: 'tmp/run-abc.txt'},
    {src: ['test/fixtures/concat/d.txt', 'test/fixtures/concat/e.txt', 'test/fixtures/concat/f.txt'], dest: 'tmp/run-def.txt'},
    {src: ['test/fixtures/concat/g.txt', 'test/fixtures/concat/h.txt', 'test/fixtures/concat/i.txt'], dest: 'tmp/run-ghi.txt'},
  ],
  separator: ';run;',
  banner: '/* RUN */\n',
  footer: '\n\n',
}).then(console.log, console.error);