'use strict';

const config = require('wild-config');
const log = require('npmlog');
const POP3Server = require('./lib/pop3/server');
const UserHandler = require('./lib/user-handler');
const MessageHandler = require('./lib/message-handler');
const packageData = require('./package.json');
const ObjectID = require('mongodb').ObjectID;
const db = require('./lib/db');
const certs = require('./lib/certs');
const LimitedFetch = require('./lib/limited-fetch');

const MAX_MESSAGES = 250;

let messageHandler;
let userHandler;

const serverOptions = {
    port: config.pop3.port,
    host: config.pop3.host,

    secure: config.pop3.secure,
    secured: config.pop3.secured,

    disableSTARTTLS: config.pop3.disableSTARTTLS,
    ignoreSTARTTLS: config.pop3.ignoreSTARTTLS,

    disableVersionString: !!config.pop3.disableVersionString,

    useProxy: !!config.imap.useProxy,
    ignoredHosts: config.pop3.ignoredHosts,

    id: {
        name: config.pop3.name || 'WildDuck POP3 Server',
        version: config.pop3.version || packageData.version
    },

    // log to console
    logger: {
        info(...args) {
            args.shift();
            log.info('POP3', ...args);
        },
        debug(...args) {
            args.shift();
            log.silly('POP3', ...args);
        },
        error(...args) {
            args.shift();
            log.error('POP3', ...args);
        }
    },

    onAuth(auth, session, callback) {
        userHandler.authenticate(
            auth.username,
            auth.password,
            'pop3',
            {
                protocol: 'POP3',
                sess: session.id,
                ip: session.remoteAddress
            },
            (err, result) => {
                if (err) {
                    return callback(err);
                }

                if (!result) {
                    return callback();
                }

                if (result.scope === 'master' && result.require2fa) {
                    // master password not allowed if 2fa is enabled!
                    return callback();
                }

                callback(null, {
                    user: {
                        id: result.user,
                        username: result.username
                    }
                });
            }
        );
    },

    onListMessages(session, callback) {
        // only list messages in INBOX
        db.database.collection('mailboxes').findOne(
            {
                user: session.user.id,
                path: 'INBOX'
            },
            (err, mailbox) => {
                if (err) {
                    return callback(err);
                }

                if (!mailbox) {
                    return callback(new Error('Mailbox not found for user'));
                }

                session.user.mailbox = mailbox._id;

                db.database
                    .collection('messages')
                    .find({
                        mailbox: mailbox._id
                    })
                    .project({
                        uid: true,
                        size: true,
                        mailbox: true,
                        // required to decide if we need to update flags after RETR
                        flags: true,
                        unseen: true
                    })
                    .sort([['uid', -1]])
                    .limit(config.pop3.maxMessages || MAX_MESSAGES)
                    .toArray((err, messages) => {
                        if (err) {
                            return callback(err);
                        }

                        return callback(null, {
                            messages: messages
                                // showolder first
                                .reverse()
                                // compose message objects
                                .map(message => ({
                                    id: message._id.toString(),
                                    uid: message.uid,
                                    mailbox: message.mailbox,
                                    size: message.size,
                                    flags: message.flags,
                                    seen: !message.unseen
                                })),
                            count: messages.length,
                            size: messages.reduce((acc, message) => acc + message.size, 0)
                        });
                    });
            }
        );
    },

    onFetchMessage(message, session, callback) {
        userHandler.userCache.get(session.user.id, 'pop3MaxDownload', (config.pop3.maxDownloadMB || 10) * 1024 * 1024, (err, limit) => {
            if (err) {
                return callback(err);
            }

            messageHandler.counters.ttlcounter('pdw:' + session.user.id, 0, limit, false, (err, res) => {
                if (err) {
                    return callback(err);
                }
                if (!res.success) {
                    let err = new Error('Download was rate limited. Check again in ' + res.ttl + ' seconds');
                    return callback(err);
                }
                db.database.collection('messages').findOne(
                    {
                        _id: new ObjectID(message.id),
                        // shard key
                        mailbox: message.mailbox,
                        uid: message.uid
                    },
                    {
                        mimeTree: true,
                        size: true
                    },
                    (err, message) => {
                        if (err) {
                            return callback(err);
                        }
                        if (!message) {
                            return callback(new Error('Message does not exist or is already deleted'));
                        }

                        let response = messageHandler.indexer.rebuild(message.mimeTree);
                        if (!response || response.type !== 'stream' || !response.value) {
                            return callback(new Error('Can not fetch message'));
                        }

                        let limiter = new LimitedFetch({
                            key: 'pdw:' + session.user.id,
                            ttlcounter: messageHandler.counters.ttlcounter,
                            maxBytes: limit
                        });

                        response.value.pipe(limiter);
                        response.value.once('error', err => limiter.emit('error', err));

                        callback(null, limiter);
                    }
                );
            });
        });
    },

    onUpdate(update, session, callback) {
        let handleSeen = next => {
            if (update.seen && update.seen.length) {
                return markAsSeen(session, update.seen, next);
            }
            next(null, 0);
        };

        let handleDeleted = next => {
            if (update.deleted && update.deleted.length) {
                return trashMessages(session, update.deleted, next);
            }
            next(null, 0);
        };

        handleSeen((err, seenCount) => {
            if (err) {
                return log.error('POP3', err);
            }
            handleDeleted((err, deleteCount) => {
                if (err) {
                    return log.error('POP3', err);
                }
                log.info('POP3', '[%s] Deleted %s messages, marked %s messages as seen', session.user.username, deleteCount, seenCount);
            });
        });

        // return callback without waiting for the update result
        setImmediate(callback);
    }
};

certs.loadTLSOptions(serverOptions, 'pop3');

const server = new POP3Server(serverOptions);

certs.registerReload(server, 'pop3');

// move messages to trash
function trashMessages(session, messages, callback) {
    // find Trash folder
    db.database.collection('mailboxes').findOne(
        {
            user: session.user.id,
            specialUse: '\\Trash'
        },
        (err, trashMailbox) => {
            if (err) {
                return callback(err);
            }

            if (!trashMailbox) {
                return callback(new Error('Trash mailbox not found for user'));
            }

            messageHandler.move(
                {
                    user: session.user.id,
                    // folder to move messages from
                    source: {
                        mailbox: session.user.mailbox
                    },
                    // folder to move messages to
                    destination: trashMailbox,
                    // list of UIDs to move
                    messages: messages.map(message => message.uid),

                    // add \Seen flags to deleted messages
                    markAsSeen: true
                },
                (err, success, meta) => {
                    if (err) {
                        return callback(err);
                    }
                    callback(null, (success && meta && meta.destinationUid && meta.destinationUid.length) || 0);
                }
            );
        }
    );
}

function markAsSeen(session, messages, callback) {
    let ids = messages.map(message => new ObjectID(message.id));

    return db.database.collection('mailboxes').findOneAndUpdate(
        {
            _id: session.user.mailbox
        },
        {
            $inc: {
                modifyIndex: 1
            }
        },
        {
            returnOriginal: false
        },
        (err, item) => {
            if (err) {
                return callback(err);
            }

            let mailboxData = item && item.value;
            if (!item) {
                return callback(new Error('Mailbox does not exist'));
            }

            db.database.collection('messages').updateMany(
                {
                    _id: {
                        $in: ids
                    },
                    user: session.user.id,
                    mailbox: mailboxData._id,
                    modseq: {
                        $lt: mailboxData.modifyIndex
                    }
                },
                {
                    $set: {
                        modseq: mailboxData.modifyIndex,
                        unseen: false
                    },
                    $addToSet: {
                        flags: '\\Seen'
                    }
                },
                {
                    multi: true,
                    w: 1
                },
                err => {
                    if (err) {
                        return callback(err);
                    }
                    messageHandler.notifier.addEntries(
                        mailboxData,
                        messages.map(message => {
                            let result = {
                                command: 'FETCH',
                                uid: message.uid,
                                flags: message.flags.concat('\\Seen'),
                                message: new ObjectID(message.id),
                                modseq: mailboxData.modifyIndex,
                                // Indicate that unseen values are changed. Not sure how much though
                                unseenChange: true
                            };
                            return result;
                        }),
                        () => {
                            messageHandler.notifier.fire(mailboxData.user);
                            callback(null, messages.length);
                        }
                    );
                }
            );
        }
    );
}

module.exports = done => {
    if (!config.pop3.enabled) {
        return setImmediate(() => done(null, false));
    }

    let started = false;

    messageHandler = new MessageHandler({
        database: db.database,
        redis: db.redis,
        gridfs: db.gridfs,
        attachments: config.attachments
    });

    userHandler = new UserHandler({
        database: db.database,
        users: db.users,
        redis: db.redis,
        authlogExpireDays: config.log.authlogExpireDays
    });

    server.on('error', err => {
        if (!started) {
            started = true;
            return done(err);
        }
        log.error('POP3', err.message);
    });

    server.listen(config.pop3.port, config.pop3.host, () => {
        if (started) {
            return server.close();
        }
        started = true;
        done(null, server);
    });
};