index.js

var fs = require('fs'),
	path = require('path'),
	EventEmitter = require('events').EventEmitter,
	Q = require('q'),
	shell = require('shelljs'),
	getProjectRoot = require('cordova-common').CordovaCheck.findProjectRoot,
	ConfigParser = require('cordova-common').ConfigParser;
/**
 * Given a PhoneGap project, pin Cordova as a dependency. Installation is not verified if dependency already exists.
 *
 * 1) Verify that projectDir is a valid project; get root
 * 2) Create package.json from config.xml if it does not exist
 * 3) If cordova is not a dependency, use npm to install and save it to package.json
 *
 *  
 * @param  {Path[String]} projectDir [Path to anywhere within the PhoneGap project being modified]
 * @param  {EventEmitter|False} extEvents   [Used for events emitting. If undefined, 'log' and 'warn' will log to console. If false, will silence logging] (optional) 
 * @return {Promise|Error}            [Returns the project root path or a cordova error.]
 */
module.exports.exec = function (projectDir, extEvents) {
	extEvents = extEvents ? extEvents : ConsoleEmitter(extEvents);
	var PROJECTROOT;
	return Q()
	.then(function(){
		var project = getProjectRoot(projectDir);
		if (!project) {
			return Q.reject(new Error('"'+projectDir+'" ' + 'does not point to a valid PhoneGap project'));
		} else {
			PROJECTROOT = project;
			return project;
		}
	}).then(function(projectRoot){
		shell.cd(projectRoot);
		var config,
			pkgJson,
			pkgJsonPath = path.resolve(projectRoot, 'package.json');

		if (!fs.existsSync(pkgJsonPath)) {
			extEvents.emit('warn', 'No package.json was found for your project. Creating one from config.xml');		
			config = new ConfigParser(path.resolve(projectRoot, 'config.xml'));
			pkgJson = {};
            pkgJson.name = (config.name() || path.basename(projectRoot)).toLowerCase().replace(' ',''); 
            pkgJson.version = config.version() || '1.0.0';
            fs.writeFileSync(pkgJsonPath, JSON.stringify(pkgJson, null, 4), 'utf8');
            return pkgJsonPath;
		} else {
			return pkgJsonPath;
		}
	}).then(function(pkgJsonPath){
		pkgJson = './' + path.relative(__dirname, pkgJsonPath);
		pkgJson = require(pkgJson);
		
		//Does not have cordova dependency in package.json
		if (!pkgJson.dependencies || !pkgJson.dependencies.hasOwnProperty('cordova')) {
			if(!shell.which('npm')) {
		        return Q.reject(new Error('"npm" command line tool is not installed: make sure it is accessible on your PATH.'));
		    }
		    var deferred = Q.defer();

		    // Find the latest version of Cordova published and install it
	        var cordovaCommand= 'npm install cordova --save';
	        extEvents.emit('log', 'Adding Cordova dependency with: "' +  cordovaCommand +'"');
	        /* OR Find the system version of Cordova installed //To/Do: handle dev version case
	        *  var cordovaVersionCommand = 'cordova -v'
	        *  var cordovaVersion = ... use shell.exec
	        *  var cordovaCommand = 'npm install --save cordova@'+ cordovaVersion 
	        */
	        var child = shell.exec(cordovaCommand, {silent:true}, function(code, stdout, stderr) {
	            if (code != 0) {
	                e = new Error('Error from npm: '+ stdout.replace('\n',''));
	                e.exitCode = code;
	                deferred.reject(e);
	            } else {
	            	//ToDo: @carynbear progress bar is needed to show npm status
	                extEvents.emit('verbose', 'Project is using Cordova '+ stdout.replace('\n',''))
	                deferred.resolve(stdout.replace('\n',''));
	            }
	        });

	        child.stdout.on('data', function(data) {
	            extEvents.emit('raw', data.toString('utf8').replace('\n',''));
	        });

	        child.stderr.on('data', function(data) {
				extEvents.emit('raw', data.toString('utf8').replace('\n',''));
	        });
	        return deferred.promise;
		} else {
			extEvents.emit('verbose', 'Found Cordova dependency in package.json');
		}	
	}).then(function(){
		return PROJECTROOT;
	});
}

function ConsoleEmitter(arg) {
	if (arg != false) {
		var emitter = new EventEmitter();
		emitter.on('log', function(msg){
			console.log('[LOG]: '+ msg);
		})
		emitter.on('warn', function(msg){
			console.log('[WARN]: '+ msg);
		})
	}
	return emitter;
}