#!/usr/bin/env node

if (process.argv.length < 3) {
  console.error('get-latest-ami-id.js <role>');
  console.error('Simply specify a Role value as the only argument.');
  console.error('Output is just the AMI ID.');
  console.error('If none match, the exit code will be 2.');
  process.exit(1);
}

var aws = require('aws-sdk');
aws.config.update({region: process.env.AWS_REGION || 'us-east-1'});
var ec2 = new aws.EC2();

var params = {
  Filters: [
    { Name: 'tag:Role', Values: process.argv.slice(2) },
    { Name: 'state', Values: ['available'] },
  ],
};
ec2.describeImages(params, function(err, data) {
  if (err) {
    console.error('Error listing EC2 AMIs:');
    console.error(err.message);
    return console.error();
  }

  data.Images.map(function(image) {
    return {
      date: new Date(image.CreationDate),
      id: image.ImageId,
    };
  }).sort(function(a, b) {
    return b.date - a.date;
  }).slice(0, 1).forEach(function(image) {
    console.log(image.id);
    process.exit();
  });

  // no instances, fail
  process.exit(2);
});