const fs = require('fs');
// const path = require('path');
const axios = require('axios');
const dayjs = require('dayjs');
const weekOfYear = require('dayjs/plugin/weekOfYear');
const handlebars = require('handlebars');

dayjs.extend(weekOfYear);

(async function () {

  const campaignId = 'b03de6fc-ff95-40a0-8707-c0706b3c0b31';
  const from = { name: 'Mitja Felicijan', email: 'weekly@mitjafelicijan.com' };

  const headers = {
    'Authorization': 'Bearer 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',
    'Content-Type': 'application/json',
  };

  // gets current week
  let campaign = null;
  try {
    campaign = require(`./campaigns/${dayjs().format('YYYY')}-${dayjs().week()}.json`);
  } catch (err) {
    console.error(err);
    process.exit(1);
  }

  // gets list subscribers
  const personalizations = [];
  const contacts = await axios.get('https://api.sendgrid.com/v3/marketing/contacts', { headers: headers }).catch(error => { console.log(error) });
  if (contacts) {
    for (const contact of contacts.data.result) {
      if (contact.list_ids.includes(campaignId)) {
        personalizations.push({ to: [{ email: contact.email }] });
      }
    }
  }

  // gets handlebars template contents
  let template = null;
  try {
    template = handlebars.compile(fs.readFileSync('template.hbs', 'utf8'));
    template = template(campaign);
  } catch (e) {
    console.error(err);
    process.exit(1);
  }

  // send actual emails
  await axios.post('https://api.sendgrid.com/v3/mail/send', {
    from,
    subject: `Week #${dayjs().week()} Links`,
    personalizations,
    content: [{
      type: 'text/html',
      value: template
    }]
  }, { headers: headers }).catch(error => { console.log(error) });

  // report
  console.log(`Emailing sent to ${personalizations.length} subscribers:`)
  for (const subscriber of personalizations) {
    console.log(' - ', subscriber.to[0].email)
  }

}());