var exec = require('child_process').exec;
var chalk = require('chalk');
var path = require('path');
var _ = require('underscore');
var fs = require('fs-extra');

module.exports = function(grunt) {
  
  var getModuleKeys = function(data) {
    var list = [];
    _.each(data, function(dep, key){
      if (!dep.extraneous) {
        list.push(key);
        if (dep.dependencies) {
          list = list.concat(getModuleKeys(dep.dependencies));
        }
      }
    });
    return list;
  }
  
  grunt.registerTask('copy-modules', "Copy node modules", function(){
    var done = this.async();
    
    // get a JSON structured list of all of our production dependencies
    exec('npm list --production --json', {maxBuffer: 2000*1024}, function(err, stdout){
      var modules = JSON.parse(stdout);
      
      // extract the module names of all dependencies and sub-dependencies
      var dependencies = getModuleKeys(modules.dependencies);
      
      // filter to only modules that are currently in the root, this allows us 
      // to continue using NPM2 without problems
      dependencies = _.intersection(dependencies, fs.readdirSync('node_modules'));
      
      // copy only these directories over to the production app. We need to do
      // this as NPM3 will put all dependencies in the root of node_modules
      // instead of nesting them (currently using on Windows).
      _.each(dependencies, function(key){
        fs.copySync('node_modules/' + key, 'cache/app/node_modules/' + key);
        grunt.verbose.writeln('Copied ' + chalk.cyan(key));
      });

      grunt.log.writeln('Copied ' + chalk.cyan(dependencies.length) + ' modules');
      done();
    });
  }); 
}