// @flow
import http from "http";
import * as Sentry from "@sentry/node";
import IO from "socket.io";
import socketRedisAdapter from "socket.io-redis";
import SocketAuth from "socketio-auth";
import app from "./app";
import { Document, Collection, View } from "./models";
import policy from "./policies";
import { client, subscriber } from "./redis";
import { getUserForJWT } from "./utils/jwt";
import * as metrics from "./utils/metrics";
import { checkMigrations } from "./utils/startup";

const server = http.createServer(app.callback());
let io;

const { can } = policy;

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

io.adapter(
  socketRedisAdapter({
    pubClient: client,
    subClient: subscriber,
  })
);

io.origins((_, callback) => {
  callback(null, true);
});

io.of("/").adapter.on("error", (err) => {
  if (err.name === "MaxRetriesPerRequestError") {
    console.error(`Redis error: ${err.message}. Shutting down now.`);
    throw err;
  } else {
    console.error(`Redis error: ${err.message}`);
  }
});

io.on("connection", (socket) => {
  metrics.increment("websockets.connected");
  metrics.gaugePerInstance(
    "websockets.count",
    socket.client.conn.server.clientsCount
  );

  socket.on("disconnect", () => {
    metrics.increment("websockets.disconnected");
    metrics.gaugePerInstance(
      "websockets.count",
      socket.client.conn.server.clientsCount
    );
  });
});

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 client.hset(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}`, () => {
            metrics.increment("websockets.collections.join");
          });
        }
      }

      // 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, () => {
            metrics.increment("websockets.documents.join");

            // 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) {
                if (process.env.SENTRY_DSN) {
                  Sentry.withScope(function (scope) {
                    scope.setExtra("clients", sockets);
                    Sentry.captureException(err);
                  });
                } else {
                  console.error(err);
                }
                return;
              }

              // 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 client.hget(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-${event.collectionId}`, () => {
          metrics.increment("websockets.collections.leave");
        });
      }
      if (event.documentId) {
        const room = `document-${event.documentId}`;
        socket.leave(room, () => {
          metrics.increment("websockets.documents.leave");

          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) => {
      metrics.increment("websockets.presence");

      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`);
});

(async () => {
  await checkMigrations();
  server.listen(process.env.PORT || "3000");
})();

export const socketio = io;

export default server;
