'use strict';

const db = require('../db/knex');
const {
  broadcastPhotoEvent,
  broadcastActivityEvent,
} = require('../ws-server');

const {
  ensureServerEventOutbox,
  getNextPendingServerEvent,
  completeServerEvent,
  failServerEvent,
} = require('../db/serverEventOutbox');

function sleep(ms) {
  return new Promise(resolve => setTimeout(resolve, ms));
}

async function dispatchEvent(event) {
  let payload;

  try {
    payload = JSON.parse(event.payload);
  } catch (err) {
    throw new Error(
      `Payload JSON non valido per evento ${event.id}: ${err.message}`
    );
  }

  switch (event.channel) {
    case 'photo':
      await broadcastPhotoEvent(event.user, payload);
      return;

    case 'activity':
      await broadcastActivityEvent(event.user, payload);
      return;

    default:
      throw new Error(
        `Canale outbox sconosciuto: ${event.channel}`
      );
  }
}

function startWsOutboxConsumer(options = {}) {
  const pollMs = Math.max(
    100,
    Number(options.pollMs) || 250
  );

  let stopping = false;

  async function loop() {
    await ensureServerEventOutbox(db);

    console.log(
      `[WsOutboxConsumer] avviato; polling ${pollMs} ms`
    );

    while (!stopping) {
      try {
        const event = await getNextPendingServerEvent(db);

        if (!event) {
          await sleep(pollMs);
          continue;
        }

        try {
          await dispatchEvent(event);
          await completeServerEvent(db, event.id);

          console.log(
            `[WsOutboxConsumer] evento ${event.id} inviato ` +
            `channel=${event.channel} user=${event.user}`
          );
        } catch (err) {
          await failServerEvent(
            db,
            event.id,
            err.message
          );

          console.error(
            `[WsOutboxConsumer] evento ${event.id} fallito:`,
            err.message
          );

          // Evita un busy-loop continuo su un evento non valido.
          await sleep(pollMs);
        }
      } catch (err) {
        console.error(
          '[WsOutboxConsumer] errore ciclo:',
          err
        );

        await sleep(pollMs);
      }
    }
  }

  loop().catch((err) => {
    console.error(
      '[WsOutboxConsumer] errore fatale:',
      err
    );
  });

  return () => {
    stopping = true;
  };
}

module.exports = {
  startWsOutboxConsumer,
};