// Copyright 2017 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

'use strict';

// Require process, so we can mock environment variables
const process = require('process');

// [START gae_flex_mysql_app]
const express = require('express');
const Knex = require('knex');
const crypto = require('crypto');

const app = express();
app.enable('trust proxy');

const connect = () => {
  // [START gae_flex_mysql_connect]
  const config = {
    user: process.env.SQL_USER,
    password: process.env.SQL_PASSWORD,
    database: process.env.SQL_DATABASE,
  };

  if (
    process.env.INSTANCE_CONNECTION_NAME &&
    process.env.NODE_ENV === 'production'
  ) {
    config.socketPath = `/cloudsql/${process.env.INSTANCE_CONNECTION_NAME}`;
  }

  // Connect to the database
  const knex = Knex({
    client: 'mysql',
    connection: config,
  });
  // [END gae_flex_mysql_connect]

  return knex;
};

const knex = connect();

/**
 * Insert a visit record into the database.
 *
 * @param {object} knex The Knex connection object.
 * @param {object} visit The visit record to insert.
 * @returns {Promise}
 */
const insertVisit = (knex, visit) => {
  return knex('visits').insert(visit);
};

/**
 * Retrieve the latest 10 visit records from the database.
 *
 * @param {object} knex The Knex connection object.
 * @returns {Promise}
 */
const getVisits = async (knex) => {
  const results = await knex
    .select('timestamp', 'userIp')
    .from('visits')
    .orderBy('timestamp', 'desc')
    .limit(10);

  return results.map(
    (visit) => `Time: ${visit.timestamp}, AddrHash: ${visit.userIp}`
  );
};

app.get('/', async (req, res, next) => {
  // Create a visit record to be stored in the database
  const visit = {
    timestamp: new Date(),
    // Store a hash of the visitor's ip address
    userIp: crypto
      .createHash('sha256')
      .update(req.ip)
      .digest('hex')
      .substr(0, 7),
  };

  try {
    await insertVisit(knex, visit);

    // Query the last 10 visits from the database.
    const visits = await getVisits(knex);
    res
      .status(200)
      .set('Content-Type', 'text/plain')
      .send(`Last 10 visits:\n${visits.join('\n')}`)
      .end();
  } catch (err) {
    next(err);
  }
});

const PORT = process.env.PORT || 8080;
app.listen(PORT, () => {
  console.log(`App listening on port ${PORT}`);
  console.log('Press Ctrl+C to quit.');
});
// [END gae_flex_mysql_app]

module.exports = app;