'use strict';

const opentelemetry = require('@opentelemetry/core');
const config = require('./setup');
/**
 * The trace instance needs to be initialized first, if you want to enable
 * automatic tracing for built-in plugins (HTTP and MySQL in this case).
 */
config.setupTracerAndExporters('http-mysql-server-service');

const mysql = require('mysql');
const http = require('http');

const tracer = opentelemetry.getTracer('example-mysql-http-server');

const pool = mysql.createPool({
  host     : 'localhost',
  user     : 'root',
  password : 'secret',
  database : 'my_db',
});

const connection = mysql.createConnection({
  host     : 'localhost',
  user     : 'root',
  password : 'secret',
  database : 'my_db',
});

const cluster = mysql.createPoolCluster();

cluster.add({
  host     : 'localhost',
  user     : 'root',
  password : 'secret',
  database : 'my_db',
})

/** Starts a HTTP server that receives requests on sample server port. */
function startServer (port) {
  // Creates a server
  const server = http.createServer(handleRequest);
  // Starts the server
  server.listen(port, err => {
    if (err) {
      throw err;
    }
    console.log(`Node HTTP listening on ${port}`);
  });
}

/** A function which handles requests and send response. */
function handleRequest (request, response) {
  const currentSpan = tracer.getCurrentSpan();
  // display traceid in the terminal
  const {traceId} = currentSpan.context();
  console.log(`traceid: ${traceId}`);
  console.log(`Jaeger URL: http://localhost:16686/trace/${traceId}`)
  console.log(`Zipkin URL: http://localhost:9411/zipkin/traces/${traceId}`)
  try {
    let body = [];
    request.on('error', err => console.log(err));
    request.on('data', chunk => body.push(chunk));
    request.on('end', () => {
      if (request.url === "/connection/query") {
        handleConnectionQuery(response);
      } else if (request.url === "/pool/query") {
        handlePoolQuery(response);
      } else if (request.url === "/cluster/query") {
        handleClusterQuery(response);
      } else {
        handleNotFound(response);
      }
    });
  } catch (err) {
    console.log(err);
  }
}

startServer(8080);

function handlePoolQuery(response) {
  const query = "SELECT 1 + 1 as pool_solution";
  pool.getConnection((err, conn) => {
    conn.query(query, (err, results, fields) => {
      tracer.getCurrentSpan().addEvent("results");
      if (err) {
        console.log("Error code:", err.code);
        response.end(err.message);
      }
      else {
        response.end(`${query}: ${results[0].pool_solution}`);
      }
    });
  })
}

function handleConnectionQuery(response) {
  const query = "SELECT 1 + 1 as solution";
  connection.query(query, (err, results, fields) => {
    if (err) {
      console.log("Error code:", err.code);
      response.end(err.message);
    }
    else {
      response.end(`${query}: ${results[0].solution}`);
    }
  });
}

function handleClusterQuery(response) {
  const query = "SELECT 1 + 1 as cluster_solution";
  cluster.getConnection((err, conn) => {
    conn.query(query, (err, results, fields) => {
      tracer.getCurrentSpan().addEvent("results");
      if (err) {
        console.log("Error code:", err.code);
        response.end(err.message);
      }
      else {
        response.end(`${query}: ${results[0].cluster_solution}`);
      }
    });
  })
}

function handleNotFound(response) {
  response.end("not found");
}