const { MongoClient } = require("mongodb");
const express = require('express');
const minio = require('minio');

/*============== VARIABLE DECLARATION ==============*/
// Mongo set-up variables
const mongoCollection = process.env.MONGO_COLLECTION || 'eventlog';
const mongoUri = process.env.MONGO_URI || 'mongodb://127.0.0.1:27017/default?replicaSet=rs0';

// Minio set-up variables
const minioURI = new URL(process.env.MINIO_URI || 'http://kspace-mugshot:2mSI6HdbJ8@127.0.0.1:9000/kspace-mugshot');
const minioBucket = minioURI.pathname.substring(1);
const historyNumber = parseInt(process.env.HISTORY_AMOUNT) || 1000;

// Stream set-up variables
let changeStream;
const options = { fullDocument: "updateLookup" };
const pipeline = [];
const PORT = process.env.PORT || 3002;

// Create Mongo client
const mongoClient = new MongoClient(mongoUri);


/*============== CODE ==============*/
async function run() {

  console.log('server.js has been launched');
  const app = express();

  await mongoClient.connect();
  const collection = mongoClient.db().collection(mongoCollection);

  let eventArray = [];

  changeStream = collection.watch(pipeline, options);
  console.log("Started watching changes in database");

  // Triggers on GET at /event route
  app.get('/events', async function (request, response) {
    let minioClient = new minio.Client({
      endPoint: minioURI.hostname,
      port: parseInt(minioURI.port) || (minioURI.protocol == 'https' ? 443 : 80),
      useSSL: minioURI.protocol == 'https',
      accessKey: minioURI.username,
      secretKey: minioURI.password
    });

    // Notify SSE to React
    const header = { 'Content-Type': 'text/event-stream', 'Connection': 'keep-alive' };
    response.writeHead(200, "OK", header);
    response.write('Connection established \n\n');

    const historyCursor = collection.find({}).sort({$natural : -1}).limit(historyNumber);

    historyCursor.forEach((document) => {
      const stringFormat = JSON.stringify(document);
      eventArray = [stringFormat, ...eventArray];
    })
    response.write(`event: events, data: [${[...eventArray]}]\n\n`)

    changeStream.on("change", data => {

      let document = JSON.stringify(data.fullDocument);
      eventArray = [document];

      if (data.fullDocument.screenshot_count) {

        for (let i = 1; i <= data.fullDocument.screenshot_count ; i++) {
          minioClient.presignedUrl('GET', minioBucket, `${data.fullDocument.camera}/${data.fullDocument._id}/${i}.jpg`, 60 * 60, (err, presignedUrl) => {
            if (err) { return console.log(err) };
            const realURL = JSON.stringify({ picUrl: presignedUrl });
            eventArray = [realURL, ...eventArray];
          })
        }

      };

      response.write(`data: [${[...eventArray]}]\n\n`);

    });
  });

  app.listen(PORT);
  console.log(`Server listening at 127.0.0.1:${PORT}`);
}

run().catch(console.dir);