import { WebSocketServer } from 'ws';
import { ObjectId } from 'mongodb';

let wss;
let connections = [];

function replaceIdInFilter (filter) {
  if (filter) {
    for (const key in filter) {
      if (key == '_id' && typeof filter[key] == 'string') {
        filter[key] = new ObjectId(filter[key]);
      } else if (typeof filter[key] == 'object') {
        filter[key] = replaceIdInFilter(filter[key]);
      }
    }
  }
  return filter;
}

export function init(cfg, db) {
  wss = new WebSocketServer(cfg);

  wss.on('connection', ws => {
    connections.push(ws);

    ws.on('error', console.error);
    ws.on('close', (e) => {
      connections.splice(connections.indexOf(ws), 1);
    });
    ws.on('message', (data, isBinary) => {
      try {
        let message = JSON.parse(data);

        switch (message.action) {
          case "set":
            db.persist(
              message.subject,
              replaceIdInFilter(message.filter),
              message.field,
              message.value
            );
            break;
          case "subscribe":
            db.subscribe(
              message.subject,
              replaceIdInFilter(message.filter)
            ).then(r => ws.send(
              JSON.stringify({
                subject: message.subject,
                field: message.field,
                filter: message.filter,
                value: r.map(v => v[message.field]),
              })
            ));
            break;
          default:
            throw 'invalid action "' + message.action + '"';
        }
      } catch (e) {
        console.error(e);
      }
    });
  });
  return wss;
}