const {SubscriptionManager} = require('graphql-subscriptions');
const {SubscriptionServer} = require('subscriptions-transport-ws');
const debug = require('debug')('talk:graph:subscriptions');

const pubsub = require('../services/pubsub');
const schema = require('./schema');
const Context = require('./context');
const plugins = require('../services/plugins');

const {deserializeUser} = require('../services/subscriptions');
const setupFunctions = require('./setupFunctions');

const ms = require('ms');
const {
  KEEP_ALIVE
} = require('../config');

const {BASE_PATH} = require('../url');

// Collect all the plugin hooks that should be executed onConnect and
// onDisconnect.
const hooks = plugins.get('server', 'websockets')
  .map(({plugin, websockets}) => {
    debug(`added websocket hooks ${Object.keys(websockets)} from plugin '${plugin.name}'`);

    return websockets;
  })
  .reduce((hooks, {onConnect = null, onDisconnect = null}) => {
    if (onConnect) {
      hooks.onConnect.push(onConnect);
    }

    if (onDisconnect) {
      hooks.onDisconnect.push(onDisconnect);
    }

    return hooks;
  }, {
    onConnect: [],
    onDisconnect: [],
  });

const onConnect = async (connectionParams, connection) => {

  // Attach the token from the connection options if it was provided.
  if (connectionParams.token) {

    debug('token sent via onConnect, attaching to the headers of the upgrade request');

    // Attach it to the upgrade request.
    connection.upgradeReq.headers['authorization'] = `Bearer ${connectionParams.token}`;
  }

  // Call all the hooks.
  await Promise.all(hooks.onConnect.map((hook) => hook(connectionParams, connection)));
};

const onOperation = (parsedMessage, baseParams, connection) => {

  // Cache the upgrade request.
  let upgradeReq = connection.upgradeReq;

  // Attach the context per request.
  baseParams.context = async () => {
    let req;

    try {
      req = await deserializeUser(upgradeReq);
      debug(`user ${req.user ? 'was' : 'was not'} on websocket request`);
    } catch (e) {
      console.error(e);

      return new Context({});
    }

    return new Context(req);
  };

  return baseParams;
};

const onDisconnect = (connection) =>
  Promise.all(hooks.onDisconnect.map((hook) => hook(connection)));

/**
 * This creates a new subscription manager.
 */
const createSubscriptionManager = (server) => new SubscriptionServer({
  subscriptionManager: new SubscriptionManager({
    schema,
    pubsub: pubsub.getClient(),
    setupFunctions,
  }),
  onConnect,
  onDisconnect,
  onOperation,
  keepAlive: ms(KEEP_ALIVE)
}, {
  server,
  path: `${BASE_PATH}api/v1/live`
});

module.exports = {
  createSubscriptionManager
};