'use strict';

require('dotenv').config();
const line = require('@line/bot-sdk');
const Datastore = require('@google-cloud/datastore');

const config = {
  channelAccessToken: process.env.CHANNEL_ACCESS_TOKEN,
  channelSecret: process.env.CHANNEL_SECRET,
};

const datastore = Datastore();
const client = new line.Client(config);

function handleEvent(event) {
  console.log(event);
  var message = '';

  const query = datastore.createQuery(event.message.type);
  return datastore.runQuery(query).then((results) => {
    const messages = results[0];
    message = messages[Math.floor(Math.random() * messages.length)].text;

    const echo = { type: 'text', text: message };
    return client.replyMessage(event.replyToken, echo);
  });
}

exports.handler = function echoBot (req, res) {
  const signature = req.get('x-line-signature');

  if (!signature) {
    throw new line.SignatureValidationFailed("no signature");
  }

  if (!line.validateSignature(req.rawBody, config.channelSecret, signature)) {
    throw new line.SignatureValidationFailed("signature validation failed", signature);
  }

  Promise
    .all(req.body.events.map(handleEvent))
    .then(result => res.status(200).send(`Success: ${result}`))
    .catch(err => res.status(400).send(err.toString()));
};