import { WebSocketServer } from "ws";
import { MongoClient, ObjectId } from "mongodb";

const mongo = new MongoClient(process.env.MONGO_CONN_STR);
const db = mongo.db();
const collections = {};

const wss = new WebSocketServer({ port: 7130 });
const connections = [];
const subscriptions = [];

async function executeSet(message, ws) {
  let subject = collections[message.subject];
  if (!subject) {
    subject = collections[message.subject] = db.collection(message.subject);
  }
  let newValue = { $set: {} };
  newValue.$set[message.field + ".modifiedAt"] = Date.now();
  newValue.$set[message.field + ".modifiedBy"] = "anonymous";
  newValue.$set[message.field + ".transientValue"] = message.value;

  await subject.updateMany(message.filter, newValue, { upsert: true });
}

wss.on("connection", function connection(ws) {
  connections.push(ws);
  console.log("accepted new connection");

  ws.on("error", console.error);
  ws.on("close", (e) => {
    console.log("closed a connection");
    connections.splice(connections.indexOf(ws), 1);
  });

  ws.on("message", function message(data, isBinary) {
    console.log("received a new message");

    try {
      let message = JSON.parse(data);
      console.log(message);
      if (
        message.filter &&
        message.filter._id &&
        typeof message.filter._id === "string"
      ) {
        try {
          message.filter._id = new ObjectId(message.filter._id);
          console.log(message.filter._id);
        } catch (e) {
          console.error("Invalid ObjectId in filter:", e);
        }
      }
      console.log("message action is " + message.action);

      switch (message.action) {
        case "set":
          executeSet(message, ws).catch(console.error);
          break;
        case "subscribe":
          let subject = collections[message.subject];
          if (!subject) {
            subject = collections[message.subject] = db.collection(
              message.subject
            );
          }
          subject
            .find(message.filter, {})
            .toArray()
            .then((r) => {
              ws.send(
                JSON.stringify({
                  subject: message.subject,
                  field: message.field,
                  filter: message.filter,
                  value: r.map((v) => v[message.field]),
                })
              );
            });

          break;
      }
    } catch (e) {
      console.error("error while processing message", e);
      ws.send(JSON.stringify(e));
    }
  });
});