koa.js

const Koa = require('koa');
const Router = require('koa-router');
const { Pool } = require('pg');
const koaBody = require('koa-bodyparser')();
const cors = require('kcors');

// db pool
const pool = new Pool({
  user: 'weather',
  host: 'db',
  database: 'weather_db',
  password: 'weather',
});

// The port that this server will run on, defaults to 9000
const port = process.env.PORT || 9000;
// Instantiate a Koa server
const app = new Koa();
app.use(cors());

// Instantiate routers
const weather = new Router();

// Define API path
const apiPath = '/v1';
const weatherPath = `${apiPath}/weather`;

// async/await - check out a client
weather.get(apiPath, async (ctx) => {
  const client = await pool.connect();
  try {
    const data = await client.query('SELECT NOW() as now');
    client.release();
    // Tell the HTTP response that it contains JSON data encoded in UTF-8
    ctx.type = 'application/json; charset=utf-8';
    ctx.body = data.rows;
  } catch (error) {
    console.error('Error occurred:', error);
    ctx.throw(500, error);
  }
});

// get last 50
weather.get(weatherPath, async (ctx) => {
    const client = await pool.connect();
    try {
      const sql=`SELECT device_id, date_time, data from weather ORDER BY id DESC LIMIT 50`;
      const data = await client.query(sql);
      ctx.type = 'application/json; charset=utf-8';
      ctx.body = data.rows;
    } catch (error) {
      console.error('Error occurred:', error);
      ctx.throw(500, error);
    } finally {
      client.release(); // release client back to pool
    }
  });

  // get lastest
weather.get(`${weatherPath}/latest`, async (ctx) => {
  const client = await pool.connect();
  try {
    const sql=`SELECT device_id, date_time, data from weather ORDER BY id DESC LIMIT 1`;
    const data = await client.query(sql);
    ctx.type = 'application/json; charset=utf-8';
    ctx.body = data.rows;
  } catch (error) {
    console.error('Error occurred:', error);
    ctx.throw(500, error);
  } finally {
    client.release(); // release client back to pool
  }
});

// insert new data
weather.post(weatherPath, koaBody, async (ctx) => {
  const { device_id } = ctx.request.body;
  const data = ctx.request.body.data;

  const sql = 'INSERT INTO weather(device_id, data) VALUES($1, $2)';
  const values = [device_id, data];

  const client = await pool.connect();
  try {
    await client.query(sql, values);
    ctx.type = 'application/json; charset=utf-8';
    ctx.status = 201;
  } catch (error) {
    console.error('Error occurred:', error);
    ctx.throw(500, error);
  } finally {
    client.release(); // release client back to pool
  }
});

app.use(weather.routes());
app.use(weather.allowedMethods());

// Start the server and keep listening on port until stopped
app.listen(port);

console.log(`App listening on port ${port}`);