import http from "http";
import path from "path";
import express from "express";
import {Server, Socket} from "socket.io";
import type mongodb from "mongodb";
import {MongoClient} from "mongodb";
import axios from "axios";
import log, {LogLevelDesc} from "loglevel";

import {AppUser, Comment, CommentThread, CurrentEditorsEvent, MousePointerEvent, Policy} from "./models";
import {VERSION as buildVersion} from "./version"; // release version of the api

const RTS_BASE_PATH = "/rts";

const APP_ROOM_PREFIX = "app:";
const PAGE_ROOM_PREFIX = "page:";
const ROOT_NAMESPACE = "/";
const PAGE_EDIT_NAMESPACE = "/page/edit";

const EDITORS_EVENT_NAME = "collab:online_editors";
const START_EDIT_EVENT_NAME = "collab:start_edit";
const LEAVE_EDIT_EVENT_NAME = "collab:leave_edit";
const MOUSE_POINTER_EVENT_NAME = "collab:mouse_pointer";
const RELEASE_VERSION_EVENT_NAME = "info:release_version";

// Setting the logLevel for all log messages
const logLevel: LogLevelDesc = (process.env.APPSMITH_LOG_LEVEL || "debug") as LogLevelDesc;
log.setLevel(logLevel);

const MONGODB_URI = process.env.APPSMITH_MONGODB_URI;
if (MONGODB_URI == null || MONGODB_URI === "" || !MONGODB_URI.startsWith("mongodb")) {
    log.error("Please provide a valid value for `APPSMITH_MONGODB_URI`.");
    process.exit(1);
}

const API_BASE_URL = process.env.APPSMITH_API_BASE_URL;
if (API_BASE_URL == null || API_BASE_URL === "") {
    log.error("Please provide a valid value for `APPSMITH_API_BASE_URL`.");
    process.exit(1);
}

main();

function main() {
    const app = express();
    //Disable x-powered-by header to prevent information disclosure
    app.disable("x-powered-by");
    const server = new http.Server(app);
    const io = new Server(server, {
        path: RTS_BASE_PATH,
    });

    const port = 8091;

    app.get("/", (req, res) => {
        res.redirect("/index.html");
    });

    io.on("connection", (socket: Socket) => {
        socket.emit(RELEASE_VERSION_EVENT_NAME, buildVersion);
        subscribeToEditEvents(socket, APP_ROOM_PREFIX);
        onAppSocketConnected(socket)
            .catch((error) => log.error("Error in socket connected handler", error));
    });

    io.of(PAGE_EDIT_NAMESPACE).on("connection", (socket: Socket) => {
        subscribeToEditEvents(socket, PAGE_ROOM_PREFIX);
        onPageSocketConnected(socket, io)
            .catch((error) => log.error("Error in socket connected handler", error));
    });

    io.of(ROOT_NAMESPACE).adapter.on("leave-room", (room, id) => {
        if (room.startsWith(APP_ROOM_PREFIX)) {
            log.debug(`ns:${ROOT_NAMESPACE}# socket ${id} left the room ${room}`);
        }
        sendCurrentUsers(io, room, APP_ROOM_PREFIX);
    });

    io.of(ROOT_NAMESPACE).adapter.on("join-room", (room, id) => {
        if (room.startsWith(APP_ROOM_PREFIX)) {
            log.debug(`ns:${ROOT_NAMESPACE}# socket ${id} joined the room ${room}`);
        }
        sendCurrentUsers(io, room, APP_ROOM_PREFIX);
    });

    io.of(PAGE_EDIT_NAMESPACE).adapter.on("leave-room", (room, id) => {
        if (room.startsWith(PAGE_ROOM_PREFIX)) { // someone left the page edit, notify others
            log.debug(`ns:${PAGE_EDIT_NAMESPACE} # socket ${id} left the room ${room}`);
            io.of(PAGE_EDIT_NAMESPACE).to(room).emit(LEAVE_EDIT_EVENT_NAME, id);
        }
        sendCurrentUsers(io.of(PAGE_EDIT_NAMESPACE), room, PAGE_ROOM_PREFIX);
    });

    io.of(PAGE_EDIT_NAMESPACE).adapter.on("join-room", (room, id) => {
        if (room.startsWith(PAGE_ROOM_PREFIX)) {
            log.debug(`ns:${PAGE_EDIT_NAMESPACE}# socket ${id} joined the room ${room}`);
        }
        sendCurrentUsers(io.of(PAGE_EDIT_NAMESPACE), room, PAGE_ROOM_PREFIX);
    });

    app.use(express.static(path.join(__dirname, "static")));

    watchMongoDB(io).catch((error) => log.error("Error watching MongoDB", error));

    // run the server
    server.listen(port, () => {
        log.info(`RTS version ${buildVersion} running at http://localhost:${port}`);
    });
}

function joinEditRoom(socket: Socket, roomId: string, roomPrefix: string) {
    // remove this socket from any other rooms with roomPrefix
    if (socket.rooms) {
        socket.rooms.forEach(roomName => {
            if (roomName.startsWith(roomPrefix)) {
                socket.leave(roomName);
            }
        });
    }

    // add this socket to room with application id
    let roomName = roomPrefix + roomId;
    socket.join(roomName);
}

function subscribeToEditEvents(socket: Socket, appRoomPrefix: string) {
    socket.on(START_EDIT_EVENT_NAME, (resourceId) => {
        if (socket.data.email) {  // user is authenticated, join the room now
            joinEditRoom(socket, resourceId, appRoomPrefix);
        } else { // user not authenticated yet, save the resource id and room prefix to join later after auth
            socket.data.pendingRoomId = resourceId;
            socket.data.pendingRoomPrefix = appRoomPrefix;
        }
    });

    socket.on(LEAVE_EDIT_EVENT_NAME, (resourceId) => {
        let roomName = appRoomPrefix + resourceId;
        socket.leave(roomName);  // remove this socket from room
    });
}

async function onAppSocketConnected(socket: Socket) {
    let isAuthenticated = await tryAuth(socket);
    if (isAuthenticated) {
        socket.join("email:" + socket.data.email);
    }
}

async function onPageSocketConnected(socket: Socket, socketIo: Server) {
    let isAuthenticated = await tryAuth(socket);
    if (isAuthenticated) {
        socket.on(MOUSE_POINTER_EVENT_NAME, (event: MousePointerEvent) => {
            event.user = new AppUser(socket.data.name, socket.data.email);
            event.socketId = socket.id;
            socketIo.of(PAGE_EDIT_NAMESPACE).to(PAGE_ROOM_PREFIX + event.pageId).emit(MOUSE_POINTER_EVENT_NAME, event);
        });
    }
}

async function tryAuth(socket: Socket) {

    /* ********************************************************* */
    // TODO: This change is not being used at the moment. Instead of using the environment variable API_BASE_URL
    // we should be able to derive the API_BASE_URL from the host header. This will make configuration simpler
    // for the user. The problem with this implementation is that Axios doesn't work for https endpoints currently.
    // This needs to be debugged.
    /* ********************************************************* */

    // const host = socket.handshake.headers.host;
    const connectionCookie = socket?.handshake?.headers?.cookie;
    if (connectionCookie === undefined || connectionCookie === null || connectionCookie === "") {
        return false;
    }

    const matchedCookie = connectionCookie.match(/\bSESSION=\S+/);
    if (!matchedCookie) {
        return false;
    }

    const sessionCookie = matchedCookie[0];
    let response;
    try {
        response = await axios.request({
            method: "GET",
            url: API_BASE_URL + "/users/me",
            headers: {
                Cookie: sessionCookie,
            },
        });
    } catch (error) {
        if (error.response?.status === 401) {
            console.info("401 received when authenticating user with cookie: " + sessionCookie);
        } else if (error.response) {
            log.error("Error response received while authentication: ", error.response);
        } else {
            log.error("Error authenticating", error);
        }
        return false;
    }

    const email = response?.data?.data?.email;
    const name = response?.data?.data?.name ?? email;

    // If the session check API succeeds & the email/name is anonymousUser, then the user is not authenticated
    // and we should not allow them to join any rooms
    if (email == null || email === "anonymousUser" || name === "anonymousUser") {
        return false;
    }

    socket.data.email = email;
    socket.data.name = name;

    if (socket.data.pendingRoomId) {  // an appId or pageId is pending for this socket, join now
        joinEditRoom(socket, socket.data.pendingRoomId, socket.data.pendingRoomPrefix);
    }

    return true;
}

async function watchMongoDB(io) {
    const client = await MongoClient.connect(MONGODB_URI, {useUnifiedTopology: true});
    const db = client.db();

    const threadCollection: mongodb.Collection<CommentThread> = db.collection("commentThread");

    const commentChangeStream = db.collection("comment").watch(
        [
            // Prevent server-internal fields from being sent to the client.
            {
                $unset: [
                    "deletedAt",
                    "_class",
                ].map(f => "fullDocument." + f)
            },
        ],
        {fullDocument: "updateLookup"}
    );

    commentChangeStream.on("change", async (event: mongodb.ChangeEventCR<Comment>) => {
        let eventName = event.operationType + ":" + event.ns.coll;

        const comment: Comment = event.fullDocument;
        if (comment.deleted) {
            eventName = 'delete' + ":" + event.ns.coll;  // emit delete event if deleted=true
        }

        comment.creationTime = comment.createdAt;
        comment.updationTime = comment.updatedAt;

        delete comment.createdAt;
        delete comment.updatedAt;
        delete comment.deleted;

        let target = io;
        let shouldEmit = false;

        for (const email of findPolicyEmails(comment.policies, "read:comments")) {
            shouldEmit = true;
            target = target.to("email:" + email);
        }

        if (shouldEmit) {
            target.emit(eventName, {comment});
        }
    });

    const threadChangeStream = threadCollection.watch(
        [
            // Prevent server-internal fields from being sent to the client.
            {
                $unset: [
                    "deletedAt",
                    "_class",
                ].map(f => "fullDocument." + f)
            },
        ],
        {fullDocument: "updateLookup"}
    );

    threadChangeStream.on("change", async (event: mongodb.ChangeEventCR) => {
        let eventName = event.operationType + ":" + event.ns.coll;

        const thread = event.fullDocument;
        if (thread.deleted) {
            eventName = 'delete' + ":" + event.ns.coll;  // emit delete event if deleted=true
        }

        if (thread === null) {
            // This happens when `event.operationType === "drop"`, when a comment is deleted.
            log.error("Null document recieved for comment change event", event);
            return;
        }

        thread.creationTime = thread.createdAt;
        thread.updationTime = thread.updatedAt;

        delete thread.createdAt;
        delete thread.updatedAt;
        delete thread.deleted;

        thread.isViewed = false;

        let target = io;
        let shouldEmit = false;

        for (const email of findPolicyEmails(thread.policies, "read:commentThreads")) {
            shouldEmit = true;
            target = target.to("email:" + email);
        }

        if (shouldEmit) {
            target.emit(eventName, {thread});
        }
    });

    const notificationsStream = db.collection("notification").watch(
        [
            // Prevent server-internal fields from being sent to the client.
            {
                $unset: [
                    "deletedAt",
                    "deleted",
                ].map(f => "fullDocument." + f)
            },
        ],
        {fullDocument: "updateLookup"}
    );

    notificationsStream.on("change", async (event: mongodb.ChangeEventCR) => {
        const notification = event.fullDocument;

        if (notification === null) {
            // This happens when `event.operationType === "drop"`, when a notification is deleted.
            log.error("Null document recieved for notification change event", event);
            return;
        }

        // set the type from _class attribute
        notification.type = notification._class.slice(notification._class.lastIndexOf(".") + 1);
        delete notification._class;

        const eventName = event.operationType + ":" + event.ns.coll;
        io.to("email:" + notification.forUsername).emit(eventName, {notification});
    });

    process.on('uncaughtExceptionMonitor', (err, origin) => {
        log.error(`Caught exception: ${err}\n` + `Exception origin: ${origin}`);
    });

    process.on('unhandledRejection', (reason, promise) => {
        log.debug('Unhandled Rejection at:', promise, 'reason:', reason);
    });

    process.on("exit", () => {
        (commentChangeStream != null ? commentChangeStream.close() : Promise.bind(client).resolve())
            .then(client.close.bind(client))
            .finally("Fin");
    });

    log.debug("Watching MongoDB");
}

function findPolicyEmails(policies: Policy[], permission: string): string[] {
    const emails: string[] = [];
    for (const policy of policies) {
        if (policy.permission === permission) {
            for (const email of policy.users) {
                emails.push(email);
            }
            break;
        }
    }
    return emails;
}

function sendCurrentUsers(socketIo, roomName: string, roomPrefix: string) {
    if (roomName.startsWith(roomPrefix)) {
        socketIo.in(roomName).fetchSockets().then(sockets => {
            let onlineUsernames = new Set<string>();
            let onlineUsers = new Array<AppUser>();
            if (sockets) {
                sockets.forEach(s => {
                    if (!onlineUsernames.has(s.data.email)) {
                        onlineUsers.push(new AppUser(s.data.name, s.data.email));
                    }
                    onlineUsernames.add(s.data.email);
                });
            }
            let resourceId = roomName.replace(roomPrefix, ""); // get resourceId from room name by removing the prefix
            let response = new CurrentEditorsEvent(resourceId, onlineUsers);
            socketIo.to(roomName).emit(EDITORS_EVENT_NAME, response);
        });
    }
}