'use strict';

const config = require('wild-config');
const IMAPServerModule = require('../../imap-core');
const imapHandler = IMAPServerModule.imapHandler;
const db = require('../db');
const tools = require('../tools');
const consts = require('../consts');
const LimitedFetch = require('../limited-fetch');

module.exports = (server, messageHandler, userCache) => (mailbox, options, session, callback) => {
    server.logger.debug(
        {
            tnx: 'fetch',
            cid: session.id
        },
        '[%s] Requested FETCH for "%s"',
        session.id,
        mailbox
    );

    db.database.collection('mailboxes').findOne(
        {
            _id: mailbox
        },
        {
            maxTimeMS: consts.DB_MAX_TIME_MAILBOXES
        },
        (err, mailboxData) => {
            if (err) {
                return callback(err);
            }
            if (!mailboxData) {
                return callback(null, 'NONEXISTENT');
            }

            userCache.get(session.user.id, 'imapMaxDownload', (config.imap.maxDownloadMB || 10000) * 1024 * 1024, (err, limit) => {
                if (err) {
                    return callback(err);
                }

                messageHandler.counters.ttlcounter('idw:' + 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');
                        err.response = 'NO';
                        err.code = 'DownloadRateLimited';
                        return callback(err);
                    }

                    let projection = {
                        _id: true,
                        uid: true,
                        modseq: true
                    };

                    if (options.flagsExist) {
                        projection.flags = true;
                    }

                    if (options.idateExist) {
                        projection.idate = true;
                    }

                    if (options.bodystructureExist) {
                        projection.bodystructure = true;
                    }

                    if (options.rfc822sizeExist) {
                        projection.size = true;
                    }

                    if (options.envelopeExist) {
                        projection.envelope = true;
                    }

                    if (!options.metadataOnly) {
                        projection.mimeTree = true;
                    }

                    let query = {
                        mailbox: mailboxData._id
                    };

                    if (options.changedSince) {
                        query = {
                            mailbox: mailboxData._id,
                            modseq: {
                                $gt: options.changedSince
                            }
                        };
                    }

                    let queryAll = false;
                    if (options.messages.length !== session.selected.uidList.length) {
                        // do not use uid selector for 1:*
                        query.uid = tools.checkRangeQuery(options.messages);
                    } else {
                        // 1:*
                        queryAll = true;
                    }

                    let isUpdated = false;
                    let updateEntries = [];
                    let notifyEntries = [];

                    let done = (...args) => {
                        if (updateEntries.length) {
                            return db.database.collection('messages').bulkWrite(
                                updateEntries,
                                {
                                    ordered: false,
                                    w: 1
                                },
                                () => {
                                    updateEntries = [];
                                    server.notifier.addEntries(mailboxData, notifyEntries, () => {
                                        notifyEntries = [];
                                        server.notifier.fire(session.user.id);
                                        return callback(...args);
                                    });
                                }
                            );
                        }
                        if (isUpdated) {
                            server.notifier.fire(session.user.id);
                        }
                        return callback(...args);
                    };

                    let sort = { uid: 1 };
                    let cursor = db.database
                        .collection('messages')
                        .find(query)
                        .project(projection)
                        .sort(sort)
                        .setReadPreference('secondaryPreferred')
                        .maxTimeMS(consts.DB_MAX_TIME_MESSAGES);

                    let limitedKeys = ['_id', 'flags', 'modseq', 'uid'];
                    if (!Object.keys(projection).some(key => !limitedKeys.includes(key))) {
                        // limited query, use extra large batch size
                        cursor = cursor.batchSize(1000);
                    }

                    let startTime = Date.now();
                    let rowCount = 0;
                    let totalBytes = 0;
                    let processNext = () => {
                        cursor.next((err, messageData) => {
                            if (err) {
                                server.logger.error(
                                    {
                                        tnx: 'fetch',
                                        cid: session.id,
                                        err
                                    },
                                    '[%s] FETCHERR error=%s query=%s',
                                    session.id,
                                    err.message,
                                    JSON.stringify(query)
                                );
                                return done(err);
                            }
                            if (!messageData) {
                                return cursor.close(() => {
                                    server.logger.debug(
                                        {
                                            tnx: 'fetch',
                                            cid: session.id
                                        },
                                        '[%s] FETCHOK rows=%s user=%s mailbox=%s time=%s',
                                        session.id,
                                        rowCount,
                                        mailboxData.user,
                                        mailboxData._id,
                                        (Date.now() - startTime) / 1000
                                    );

                                    done(null, true, {
                                        rowCount,
                                        totalBytes
                                    });
                                });
                            }

                            if (queryAll && !session.selected.uidList.includes(messageData.uid)) {
                                // skip processing messages that we do not know about yet
                                return processNext();
                            }

                            let markAsSeen = options.markAsSeen && !messageData.flags.includes('\\Seen');
                            if (markAsSeen) {
                                messageData.flags.unshift('\\Seen');
                            }

                            if (options.metadataOnly && !markAsSeen) {
                                // quick response
                                const data = session.formatResponse('FETCH', messageData.uid, {
                                    query: options.query,
                                    values: session.getQueryResponse(options.query, messageData, {
                                        logger: server.logger,
                                        fetchOptions: {},
                                        database: db.database,
                                        attachmentStorage: messageHandler.attachmentStorage,
                                        acceptUTF8Enabled: session.isUTF8Enabled()
                                    })
                                });

                                const compiled = imapHandler.compiler(data);

                                // `compiled` is a 'binary' string
                                totalBytes += compiled.length;
                                session.writeStream.write({ compiled });

                                rowCount++;
                                return setImmediate(processNext);
                            }

                            let stream = imapHandler.compileStream(
                                session.formatResponse('FETCH', messageData.uid, {
                                    query: options.query,
                                    values: session.getQueryResponse(options.query, messageData, {
                                        logger: server.logger,
                                        fetchOptions: {},
                                        database: db.database,
                                        attachmentStorage: messageHandler.attachmentStorage,
                                        acceptUTF8Enabled: session.isUTF8Enabled()
                                    })
                                })
                            );

                            rowCount++;

                            stream.once('error', err => {
                                err.processed = true;
                                server.logger.error(
                                    {
                                        err,
                                        tnx: 'fetch',
                                        cid: session.id,
                                        mid: messageData._id
                                    },
                                    '[%s] FETCHFAIL message=%s rows=%s user=%s mailbox=%s time=%s error=%s',
                                    session.id,
                                    messageData._id,
                                    rowCount,
                                    mailboxData.user,
                                    mailboxData._id,
                                    (Date.now() - startTime) / 1000,
                                    err.message
                                );

                                session.socket.end('\n* BYE Internal Server Error\n');
                                return cursor.close(() =>
                                    done(err, false, {
                                        rowCount,
                                        totalBytes
                                    })
                                );
                            });

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

                            limiter._uid = messageData.uid;
                            limiter._message = messageData._id;
                            limiter._mailbox = mailbox;

                            // send formatted response to socket
                            session.writeStream.write(limiter, () => {
                                totalBytes += limiter.bytes;

                                if (!markAsSeen) {
                                    return processNext();
                                }

                                server.logger.debug(
                                    {
                                        tnx: 'flags',
                                        cid: session.id
                                    },
                                    '[%s] UPDATE FLAGS message=%s',
                                    session.id,
                                    messageData.uid
                                );

                                isUpdated = true;

                                updateEntries.push({
                                    updateOne: {
                                        filter: {
                                            _id: messageData._id,
                                            // include sharding key in query
                                            mailbox: mailboxData._id,
                                            uid: messageData.uid
                                        },
                                        update: {
                                            $addToSet: {
                                                flags: '\\Seen'
                                            },
                                            $set: {
                                                unseen: false
                                            }
                                        }
                                    }
                                });

                                notifyEntries.push({
                                    command: 'FETCH',
                                    ignore: session.id,
                                    uid: messageData.uid,
                                    flags: messageData.flags,
                                    message: messageData._id,
                                    unseenChange: true
                                });

                                if (updateEntries.length >= consts.BULK_BATCH_SIZE) {
                                    return db.database.collection('messages').bulkWrite(
                                        updateEntries,
                                        {
                                            ordered: false,
                                            w: 1
                                        },
                                        err => {
                                            updateEntries = [];
                                            if (err) {
                                                return cursor.close(() =>
                                                    done(err, false, {
                                                        rowCount,
                                                        totalBytes
                                                    })
                                                );
                                            }

                                            server.notifier.addEntries(mailboxData, notifyEntries, () => {
                                                notifyEntries = [];
                                                server.notifier.fire(session.user.id);
                                                processNext();
                                            });
                                        }
                                    );
                                } else {
                                    processNext();
                                }
                            });
                        });
                    };

                    processNext();
                });
            });
        }
    );
};