imgo task for Grunt

imgo.js

/**
 * imgo task for Grunt
 *
 * @author Artem Sapegin (http://sapegin.me)
 */

/*jshint node:true */
module.exports = function(grunt) {
	'use strict';

	var async = grunt.utils.async;

	grunt.registerMultiTask('imgo', 'Optimize images using imgo', function(target) {
		this.requiresConfig('imgo');

		// Build an array of files/tasks objects
		var imgo = grunt.config('imgo'),
			targets = target ? [target] : Object.keys(imgo).filter(function(key) {
      			return typeof imgo[key] !== 'string' && !Array.isArray(imgo[key]);
    		});
		targets = targets.map(function(target) {
			// Fail if any required config properties have been omitted
			target = ['imgo', target];
			this.requiresConfig(target.concat('files'));
			return grunt.config(target);
		}, this);

		// Allow "basic" non-target format
		if (typeof imgo.files === 'string' || Array.isArray(imgo.files)) {
			targets.push({files: imgo.files, options: imgo.options});
		}    		

		// Work
		var done = this.async();
		async.forEachSeries(targets, function(target, nextTarget) {
			var files = grunt.file.expandFiles(target.files);
			async.forEach(files, function(file, nextFile) {
				var args = [file];
				if (target.options) {
					args.unshift(target.options);
				}
				grunt.helper('imgo', {
					args: args,
					done: function(data) {
						if (!data.err && data.compressed) {
							grunt.log.writeln("File '" + file + "': saved " + data.saved + " bytes " +
									"(" + Math.round(data.saved/data.before*100) + "%)");
						}
						nextFile();
					}
				});
			}, function() {
				nextTarget();
			});
		}, function() {
			done();
		});
	});

	grunt.registerHelper('imgo', function(options) {
		return grunt.utils.spawn({
			cmd: 'imgo',
			args: options.args
		}, function(err, result, code) {
			if (!err) {
				var fields = result.split('\n')[0].split(' '),
					before = parseInt(fields[1], 10),
					after = parseInt(fields[3], 10),
					saved = before - after;
				if (!isNaN(saved) && saved > 0) {
					return options.done({
						compressed: true,
						before: before,
						after: before,
						saved: saved
					})
				}
				else {
					return options.done({ compressed: false });
				}
			};

			// Something went horribly wrong
			grunt.verbose.or.writeln();
			grunt.log.write('Running imgo...').error();
			if (code === 127) {  // @todo ???
				grunt.log.errorlns(
					'Please install imgo: https://github.com/imgo/imgo'
				);
				grunt.warn('imgo not found', options.code);
			}
			else {
				result.split('\n').forEach(grunt.log.error, grunt.log);
				grunt.warn('imgo exited unexpectedly with exit code ' + code + '.', options.code);
			}
			options.done({ err: code });
		});
	});
};