// @flow
import { promisify } from 'util';
import http from 'http';
import IO from 'socket.io';
import SocketAuth from 'socketio-auth';
import socketRedisAdapter from 'socket.io-redis';
import { getUserForJWT } from './utils/jwt';
import { Document, Collection, View } from './models';
import { client } from './redis';
import app from './app';
import policy from './policies';

const redisHget = promisify(client.hget).bind(client);
const redisHset = promisify(client.hset).bind(client);
const server = http.createServer(app.callback());
let io;

if (process.env.WEBSOCKETS_ENABLED === 'true') {
  const { can } = policy;

  io = IO(server, {
    path: '/realtime',
    serveClient: false,
    cookie: false,
  });

  io.adapter(socketRedisAdapter(process.env.REDIS_URL));

  SocketAuth(io, {
    authenticate: async (socket, data, callback) => {
      const { token } = data;

      try {
        const user = await getUserForJWT(token);
        socket.client.user = user;

        // store the mapping between socket id and user id in redis
        // so that it is accessible across multiple server nodes
        await redisHset(socket.id, 'userId', user.id);

        return callback(null, true);
      } catch (err) {
        return callback(err);
      }
    },
    postAuthenticate: async (socket, data) => {
      const { user } = socket.client;

      // the rooms associated with the current team
      // and user so we can send authenticated events
      let rooms = [`team-${user.teamId}`, `user-${user.id}`];

      // the rooms associated with collections this user
      // has access to on connection. New collection subscriptions
      // are managed from the client as needed through the 'join' event
      const collectionIds = await user.collectionIds();
      collectionIds.forEach(collectionId =>
        rooms.push(`collection-${collectionId}`)
      );

      // join all of the rooms at once
      socket.join(rooms);

      // allow the client to request to join rooms
      socket.on('join', async event => {
        // user is joining a collection channel, because their permissions have
        // changed, granting them access.
        if (event.collectionId) {
          const collection = await Collection.scope({
            method: ['withMembership', user.id],
          }).findByPk(event.collectionId);

          if (can(user, 'read', collection)) {
            socket.join(`collection-${event.collectionId}`);
          }
        }

        // user is joining a document channel, because they have navigated to
        // view a document.
        if (event.documentId) {
          const document = await Document.findByPk(event.documentId, {
            userId: user.id,
          });

          if (can(user, 'read', document)) {
            const room = `document-${event.documentId}`;

            await View.touch(event.documentId, user.id, event.isEditing);
            const editing = await View.findRecentlyEditingByDocument(
              event.documentId
            );

            socket.join(room, () => {
              // let everyone else in the room know that a new user joined
              io.to(room).emit('user.join', {
                userId: user.id,
                documentId: event.documentId,
                isEditing: event.isEditing,
              });

              // let this user know who else is already present in the room
              io.in(room).clients(async (err, sockets) => {
                if (err) throw err;

                // because a single user can have multiple socket connections we
                // need to make sure that only unique userIds are returned. A Map
                // makes this easy.
                let userIds = new Map();
                for (const socketId of sockets) {
                  const userId = await redisHget(socketId, 'userId');
                  userIds.set(userId, userId);
                }
                socket.emit('document.presence', {
                  documentId: event.documentId,
                  userIds: Array.from(userIds.keys()),
                  editingIds: editing.map(view => view.userId),
                });
              });
            });
          }
        }
      });

      // allow the client to request to leave rooms
      socket.on('leave', event => {
        if (event.collectionId) {
          socket.leave(`collection-${event.collectionId}`);
        }
        if (event.documentId) {
          const room = `document-${event.documentId}`;
          socket.leave(room, () => {
            io.to(room).emit('user.leave', {
              userId: user.id,
              documentId: event.documentId,
            });
          });
        }
      });

      socket.on('disconnecting', () => {
        const rooms = Object.keys(socket.rooms);

        rooms.forEach(room => {
          if (room.startsWith('document-')) {
            const documentId = room.replace('document-', '');
            io.to(room).emit('user.leave', {
              userId: user.id,
              documentId,
            });
          }
        });
      });

      socket.on('presence', async event => {
        const room = `document-${event.documentId}`;

        if (event.documentId && socket.rooms[room]) {
          const view = await View.touch(
            event.documentId,
            user.id,
            event.isEditing
          );
          view.user = user;

          io.to(room).emit('user.presence', {
            userId: user.id,
            documentId: event.documentId,
            isEditing: event.isEditing,
          });
        }
      });
    },
  });
}

server.on('error', err => {
  throw err;
});

server.on('listening', () => {
  const address = server.address();
  console.log(`\n> Listening on http://localhost:${address.port}\n`);
});

server.listen(process.env.PORT || '3000');

export const socketio = io;

export default server;