const request = require('request');
const restify = require('restify');
const Handlebars = require('handlebars');
const fs = require('fs');
const path = require('path');
const config = require('indecent');

const { chain, get, indexOf, merge, set, startCase } = require('lodash');

const knownEmails = get(config, 'emails');

const MAILGUN_URL = get(config, 'mailgun.url');
const MAILGUN_API_KEY = get(config, 'mailgun.key');

const FORM_FIELDS = [
  '_from',
  '_subject',
  '_to',
  '_attachment'
];

const PRIVATE_FIELDS = [
  '_fake',
  '_info',
  '_next'
];

const htmlSource = fs.readFileSync(path.join(__dirname, 'html_template.hbs'), { encoding: 'utf8' });
const textSource = fs.readFileSync(path.join(__dirname, 'text_template.hbs'), { encoding: 'utf8' });
const htmlTemplate = Handlebars.compile(htmlSource);
const textTemplate = Handlebars.compile(textSource);

var server = restify.createServer();
server.use(restify.CORS());
server.use(restify.bodyParser());

server.post('/:_to', (req, res, next) => {
  const { formData, fields } = parseRequest(req);

  if (indexOf(knownEmails, get(formData, 'to')) < 0) {
    return next(new Error('Unknown email address'));
  }

  const params = {
    formData,
    auth: {
      user: 'api',
      pass: MAILGUN_API_KEY
    },
    url: MAILGUN_URL,
    method: 'post'
  };

  sendMail(fields, params).then(response => {
    const redirect = get(fields, 'next');
    if (redirect) {
      res.redirect(redirect, next);
    } else {
      res.json(response);
    }

    return next();
  }).catch(error => {
    return next(error);
  });
});

function parseRequest (req) {
  const body = get(req, 'params');

  const formData = chain(body)
    .pick(FORM_FIELDS)
    .mapKeys((value, key) => key.replace('_', ''))
    .value();

  const fields = chain(body)
    .pick(PRIVATE_FIELDS)
    .mapKeys((value, key) => key.replace('_', ''))
    .value();

  const data = chain(body)
    .omit(PRIVATE_FIELDS)
    .omit(FORM_FIELDS)
    .mapKeys((value, key) => startCase(key))
    .map((value, key) => {
      return { key, value };
    })
    .value();

  set(fields, 'data', data);
  set(formData, 'html', htmlTemplate(fields));
  set(formData, 'text', textTemplate(fields));

  const attachment = get(req, 'files._attachment');
  if (attachment) {
    const filePath = get(attachment, 'path');
    const value = get(fields, 'fake') ? filePath : fs.createReadStream(filePath);

    set(formData, 'attachment', {
      value,
      options: {
        filename: get(attachment, 'name'),
        contentType: get(attachment, 'type')
      }
    });
  }

  return { data, fields, formData };
}

function sendMail (fields, params) {
  const fake = get(fields, 'fake');

  if (fake) {
    return Promise.resolve(merge({ message: 'fake response' }, params));
  }

  return new Promise((resolve, reject) => {
    request(params, (error, msg, response) => {
      if (error) {
        return reject(error);
      }

      return resolve(JSON.parse(response));
    });
  });
}

server.listen(8081, () => {
  console.log(`${server.name} listening at ${server.url}`);
});