'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 ObjectID = require('mongodb').ObjectID;
const db = require('./lib/db');
const certs = require('./lib/certs');

const MAX_MESSAGES = 250;

let messageHandler;
let userHandler;

const serverOptions = {
    port: config.pop3.port,
    host: config.pop3.host,
    secure: config.pop3.secure,
    disableVersionString: !!config.pop3.disableVersionString,

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

    // 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) {
        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'));
            }

            callback(null, response.value);
        });
    },

    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,
                false,
                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, mailboxData.path);
                    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);
    });
};