/* jslint node: true */
'use strict';

//  ENiGMA½
const Log                   = require('../../logger.js').log;
const { ServerModule }      = require('../../server_module.js');
const Config                = require('../../config.js').get;
const {
    getTransactionDatabase,
    getModDatabasePath
}                           = require('../../database.js');
const {
    getMessageAreaByTag,
    getMessageConferenceByTag,
}                           = require('../../message_area.js');
const User                  = require('../../user.js');
const Errors                = require('../../enig_error.js').Errors;
const Message               = require('../../message.js');
const FTNAddress            = require('../../ftn_address.js');
const {
    isAnsi,
    stripAnsiControlCodes,
    splitTextAtTerms,
}                           = require('../../string_util.js');
const AnsiPrep              = require('../../ansi_prep.js');
const {
    stripMciColorCodes
}                           = require('../../color_codes.js');

//  deps
const NNTPServerBase        = require('nntp-server');
const _                     = require('lodash');
const fs                    = require('fs-extra');
const forEachSeries         = require('async/forEachSeries');
const asyncReduce           = require('async/reduce');
const asyncMap              = require('async/map');
const asyncSeries           = require('async/series');
const asyncWaterfall        = require('async/waterfall');
const LRU                   = require('lru-cache');
const sqlite3               = require('sqlite3');
const paths                 = require('path');

//
//  Network News Transfer Protocol (NNTP)
//
//  RFCS
//  - https://www.w3.org/Protocols/rfc977/rfc977
//  - https://tools.ietf.org/html/rfc3977
//  - https://tools.ietf.org/html/rfc2980
//  - https://tools.ietf.org/html/rfc5536

//
exports.moduleInfo = {
    name        : 'NNTP',
    desc        : 'Network News Transfer Protocol (NNTP) Server',
    author      : 'NuSkooler',
    packageName : 'codes.l33t.enigma.nntp.server',
};

exports.performMaintenanceTask  = performMaintenanceTask;

/*
    General TODO
    - ACS checks need worked out. Currently ACS relies on |client|. We need a client
      spec that can be created even without a login server. Some checks and simply
      return false/fail.
*/

//  simple DB maps NNTP Message-ID's which are
//  sequential per group -> ENiG messages
//  A single instance is shared across NNTP and/or NNTPS
class NNTPDatabase
{
    constructor() {
    }

    init(cb) {
        asyncSeries(
            [
                (callback) => {
                    this.db = getTransactionDatabase(new sqlite3.Database(
                        getModDatabasePath(exports.moduleInfo),
                        err => {
                            return callback(err);
                        }
                    ));
                },
                (callback) => {
                    this.db.serialize( () => {
                        this.db.run(
                            `CREATE TABLE IF NOT EXISTS nntp_area_message (
                                nntp_message_id     INTEGER NOT NULL,
                                message_id          INTEGER NOT NULL,
                                message_area_tag    VARCHAR NOT NULL,
                                message_uuid        VARCHAR NOT NULL,

                                UNIQUE(nntp_message_id, message_area_tag)
                            );`
                        );

                        this.db.run(
                            `CREATE INDEX IF NOT EXISTS nntp_area_message_by_uuid_index
                            ON nntp_area_message (message_uuid);`
                        );

                        return callback(null);
                    });
                }
            ],
            err => {
                return cb(err);
            }
        );
    }
}

let nntpDatabase;

class NNTPServer extends NNTPServerBase {
    constructor(options, serverName) {
        super(options);

        this.log = Log.child( { server : serverName } );

        const config = Config();
        this.groupCache = new LRU({
            max     : _.get(config, 'contentServers.nntp.cache.maxItems', 200),
            maxAge  : _.get(config, 'contentServers.nntp.cache.maxAge', 1000 * 30), //  default=30s
        });
    }

    _needAuth(session, command) {
        return super._needAuth(session, command);
    }

    _authenticate(session) {
        const username  = session.authinfo_user;
        const password  = session.authinfo_pass;

        this.log.trace( { username }, 'Authentication request');

        return new Promise( resolve => {
            const user = new User();
            user.authenticate(username, password, err => {
                if(err) {
                    //  :TODO: Log IP address
                    this.log.debug( { username, reason : err.message }, 'Authentication failure');
                    return resolve(false);
                }

                session.authUser = user;

                this.log.debug( { username }, 'User authenticated successfully');
                return resolve(true);
            });
        });
    }

    isGroupSelected(session) {
        return Array.isArray(_.get(session, 'groupInfo.messageList'));
    }

    getJAMStyleFrom(message, fromName) {
        //
        //  Try to to create a (JamNTTPd) JAM style "From" field:
        //
        //  -   If we're dealing with a FTN address, create an email-like format
        //      but do not include ':' or '/' characters as it may cause clients
        //      to puke. FTN addresses are formatted how JamNTTPd does it for
        //      some sort of compliance. We also extend up to 5D addressing.
        //  -   If we have an email address, then it's ready to go.
        //
        const remoteFrom = _.get(message.meta, [ 'System', Message.SystemMetaNames.RemoteFromUser ]);
        let jamStyleFrom;
        if(remoteFrom) {
            const flavor = _.get(message.meta, [ 'System', Message.SystemMetaNames.ExternalFlavor ]);
            switch(flavor) {
                case [ Message.AddressFlavor.FTN ] :
                    {
                        let ftnAddr = FTNAddress.fromString(remoteFrom);
                        if(ftnAddr && ftnAddr.isValid()) {
                            //  In general, addresses are in point, node, net, zone, domain order
                            if(ftnAddr.domain) { //  5D
                                // point.node.net.zone@domain or node.net.zone@domain
                                jamStyleFrom = `${ftnAddr.node}.${ftnAddr.net}.${ftnAddr.zone}@${ftnAddr.domain}`;
                                if(ftnAddr.point) {
                                    jamStyleFrom = `${ftnAddr.point}.` + jamStyleFrom;
                                }
                            } else {
                                if(ftnAddr.point) {
                                    jamStyleFrom = `${ftnAddr.point}@${ftnAddr.node}.${ftnAddr.net}.${ftnAddr.zone}`;
                                } else {
                                    jamStyleFrom = `0@${ftnAddr.node}.${ftnAddr.net}.${ftnAddr.zone}`;
                                }
                            }
                        }
                    }
                    break;

                case [ Message.AddressFlavor.Email ] :
                    jamStyleFrom = `${fromName} <${remoteFrom}>`;
                    break;
            }
        }

        if(!jamStyleFrom) {
            jamStyleFrom = fromName;
        }

        return jamStyleFrom;
    }

    populateNNTPHeaders(session, message, cb) {
        //
        //  Build compliant headers
        //
        //  Resources:
        //  - https://tools.ietf.org/html/rfc5536#section-3.1
        //  - https://github.com/ftnapps/jamnntpd/blob/master/src/nntpserv.c#L962
        //
        const toName    = this.getMessageTo(message);
        const fromName  = this.getMessageFrom(message);

        message.nntpHeaders = {
            From            : this.getJAMStyleFrom(message, fromName),
            'X-Comment-To'  : toName,
            Newsgroups      : session.group.name,
            Subject         : message.subject,
            Date            : this.getMessageDate(message),
            'Message-ID'    : this.getMessageIdentifier(message),
            Path            : 'ENiGMA1/2!not-for-mail',
            'Content-Type'  : 'text/plain; charset=utf-8',
        };

        const externalFlavor = _.get(message.meta.System, [ Message.SystemMetaNames.ExternalFlavor ]);
        if(externalFlavor) {
            message.nntpHeaders['X-ENiG-MessageFlavor'] = externalFlavor;
        }

        //  Any FTN properties -> X-FTN-*
        _.each(message.meta.FtnProperty, (v, k) => {
            const suffix = {
                [ Message.FtnPropertyNames.FtnTearLine ]    : 'Tearline',
                [ Message.FtnPropertyNames.FtnOrigin ]      : 'Origin',
                [ Message.FtnPropertyNames.FtnArea ]        : 'AREA',
                [ Message.FtnPropertyNames.FtnSeenBy ]      : 'SEEN-BY',
            }[k];

            if(suffix) {
                //  some special treatment.
                if('Tearline' === suffix) {
                    v = v.replace(/^--- /, '');
                } else if('Origin' === suffix) {
                    v = v.replace(/^[ ]{1,2}\* Origin: /, '');
                }
                if(Array.isArray(v)) {  //  ie: SEEN-BY[] -> one big list
                    v = v.join(' ');
                }
                message.nntpHeaders[`X-FTN-${suffix}`] = v.trim();
            }
        });

        //  Other FTN kludges
        _.each(message.meta.FtnKludge, (v, k) => {
            if(Array.isArray(v)) {
                v = v.join(' ');    //  same as above
            }
            message.nntpHeaders[`X-FTN-${k.toUpperCase()}`] = v.toString().trim();
        });

        //
        //  Set X-FTN-To and X-FTN-From:
        //  - If remote to/from : joeuser <remoteAddr>
        //  - Without remote    : joeuser
        //
        const remoteFrom = _.get(message.meta, [ 'System', Message.SystemMetaNames.RemoteFromUser ]);
        message.nntpHeaders['X-FTN-From'] = remoteFrom ? `${fromName} <${remoteFrom}>` : fromName;
        const  remoteTo = _.get(message.meta [ 'System', Message.SystemMetaNames.RemoteToUser ]);
        message.nntpHeaders['X-FTN-To'] = remoteTo ? `${toName} <${remoteTo}>` : toName;

        if(!message.replyToMsgId) {
            return cb(null);
        }

        //  replyToMessageId -> Message-ID formatted ID
        const filter = {
            resultType          : 'uuid',
            ids                 : [ parseInt(message.replyToMsgId) ],
            limit               : 1,
        };
        Message.findMessages(filter, (err, uuids) => {
            if(!err && Array.isArray(uuids)) {
                message.nntpHeaders.References = this.makeMessageIdentifier(message.replyToMsgId, uuids[0]);
            }
            return cb(null);
        });
    }

    getMessageUUIDFromMessageID(session, messageId) {
        let messageUuid;

        //  Direct ID request
        if((_.isString(messageId) && '<' !== messageId.charAt(0)) || _.isNumber(messageId)) {
            //  group must be in session
            if(!this.isGroupSelected(session)) {
                return null;
            }

            messageId = parseInt(messageId);
            if(isNaN(messageId)) {
                return null;
            }

            const msg = session.groupInfo.messageList.find(m => {
                return m.index === messageId;
            });

            messageUuid = msg && msg.messageUuid;
        } else {
            //  <Message-ID> request
            [ , messageUuid ] = this.getMessageIdentifierParts(messageId);
        }

        if(!_.isString(messageUuid)) {
            return null;
        }

        return messageUuid;
    }

    _getArticle(session, messageId) {
        return new Promise( resolve => {
            this.log.trace( { messageId }, 'Get article');

            const messageUuid = this.getMessageUUIDFromMessageID(session, messageId);
            if(!messageUuid) {
                this.log.debug( { messageId }, 'Unable to retrieve message UUID for article request');
                return resolve(null);
            }

            const message = new Message();
            asyncSeries(
                [
                    (callback) => {
                        return message.load( { uuid : messageUuid }, callback);
                    },
                    (callback) => {
                        if(!_.has(session, 'groupInfo.areaTag')) {
                            //  :TODO: if this is needed, how to validate properly?
                            this.log.warn( { messageUuid, messageId }, 'Get article request without group selection');
                            return resolve(null);
                        }

                        if(session.groupInfo.areaTag !== message.areaTag) {
                            return resolve(null);
                        }

                        if(!this.hasConfAndAreaReadAccess(session, session.groupInfo.confTag, session.groupInfo.areaTag)) {
                            this.log.info( { messageUuid, messageId}, 'Access denied for message');
                            return resolve(null);
                        }

                        return callback(null);
                    },
                    (callback) => {
                        return this.populateNNTPHeaders(session, message, callback);
                    },
                    (callback) => {
                        return this.prepareMessageBody(message, callback);
                    }
                ],
                err => {
                    if(err) {
                        this.log.error( { error : err.message, messageUuid }, 'Failed to load article');
                        return resolve(null);
                    }

                    this.log.info( { messageUuid, messageId, areaTag : message.areaTag }, 'Serving article');
                    return resolve(message);
                }
            );
        });
    }

    _getRange(session, first, last /*options*/) {
        return new Promise(resolve => {
            //
            //  Build an array of message objects that can later
            //  be used with the various _build* methods.
            //
            //  :TODO: Handle |options|
            if(!this.isGroupSelected(session)) {
                return resolve(null);
            }

            const uuids = session.groupInfo.messageList.filter(m => {
                if(m.areaTag !== session.groupInfo.areaTag) {
                    return false;
                }
                if(m.index < first || m.index > last) {
                    return false;
                }
                return true;
            }).map(m => {
                return { uuid : m.messageUuid, index : m.index };
            });

            asyncMap(uuids, (msgInfo, nextMessageUuid) => {
                const message = new Message();
                message.load( { uuid : msgInfo.uuid }, err => {
                    if(err) {
                        return nextMessageUuid(err);
                    }

                    message.index = msgInfo.index;

                    this.populateNNTPHeaders(session, message, () => {
                        this.prepareMessageBody(message, () => {
                            return nextMessageUuid(null, message);
                        });
                    });
                });
            },
            (err, messages) => {
                return resolve(err ? null : messages);
            });
        });
    }

    _selectGroup (session, groupName) {
        this.log.trace( { groupName }, 'Select group request');

        return new Promise( resolve => {
            this.getGroup(session, groupName, (err, group) => {
                if(err) {
                    return resolve(false);
                }

                session.group = Object.assign(
                    {}, //  start clean
                    {
                        description     : group.friendlyDesc || group.friendlyName,
                        current_article : group.nntp.total ? group.nntp.min_index : 0,
                    },
                    group.nntp
                );

                session.groupInfo = group;  //  full set of info

                return resolve(true);
            });
        });
    }

    _getGroups(session, time, wildmat) {
        this.log.trace( { time, wildmat }, 'Get groups request');

        //  :TODO: handle time - probably use as caching mechanism - must consider user/auth/rights
        //  :TODO: handle |time| if possible.
        return new Promise( (resolve, reject) => {
            const config = Config();

            //  :TODO: merge confs avail to authenticated user
            const publicConfs = _.get(config, 'contentServers.nntp.publicMessageConferences', {});

            asyncReduce(Object.keys(publicConfs), [], (groups, confTag, nextConfTag) => {
                const areaTags = publicConfs[confTag];
                //  :TODO: merge area tags available to authenticated user
                asyncMap(areaTags, (areaTag, nextAreaTag) => {
                    const groupName = this.getGroupName(confTag, areaTag);

                    //  filter on |wildmat| if supplied. We will remove
                    //  empty areas below in the final results.
                    if(wildmat && !wildmat.test(groupName)) {
                        return nextAreaTag(null, null);
                    }

                    this.getGroup(session, groupName, (err, group) => {
                        if(err) {
                            return nextAreaTag(null, null); //  try others
                        }
                        return nextAreaTag(null, group.nntp);
                    });
                },
                (err, areas) => {
                    if(err) {
                        return nextConfTag(err);
                    }

                    areas = areas.filter(a => a && Object.keys(a).length > 0);  //  remove empty
                    groups.push(...areas);

                    return nextConfTag(null, groups);
                });
            },
            (err, groups) => {
                if(err) {
                    return reject(err);
                }
                return resolve(groups);
            });
        });
    }

    isConfAndAreaPubliclyExposed(confTag, areaTag) {
        const publicAreaTags = _.get(Config(), [ 'contentServers', 'nntp', 'publicMessageConferences', confTag ] );
        return Array.isArray(publicAreaTags) && publicAreaTags.includes(areaTag);
    }

    hasConfAndAreaReadAccess(session, confTag, areaTag) {
        if(Message.isPrivateAreaTag(areaTag)) {
            return false;
        }

        if(this.isConfAndAreaPubliclyExposed(confTag, areaTag)) {
            return true;
        }

        //  further checks require an authenticated user & ACS
        if(!session || !session.authUser) {
            return false;
        }

        const conf = getMessageConferenceByTag(confTag);
        if(!conf) {
            return false;
        }
        //  :TODO: validate ACS

        const area = getMessageAreaByTag(areaTag, confTag);
        if(!area) {
            return false;
        }
        //  :TODO: validate ACS

        return false;
    }

    getGroup(session, groupName, cb) {
        let group = this.groupCache.get(groupName);
        if(group) {
            return cb(null, group);
        }

        const [ confTag, areaTag ] = groupName.split('.');
        if(!confTag || !areaTag) {
            return cb(Errors.UnexpectedState(`Invalid NNTP group name: ${groupName}`));
        }

        if(!this.hasConfAndAreaReadAccess(session, confTag, areaTag)) {
            return cb(Errors.AccessDenied(`No access to conference ${confTag} and/or area ${areaTag}`));
        }

        const area = getMessageAreaByTag(areaTag, confTag);
        if(!area) {
            return cb(Errors.DoesNotExist(`No area for areaTag "${areaTag}" / confTag "${confTag}"`));
        }

        this.getMappedMessageListForArea(areaTag, (err, messageList) => {
            if(err) {
                return cb(err);
            }

            if(0 === messageList.length) {
                //
                //  Handle empty group
                //  See https://tools.ietf.org/html/rfc3977#section-6.1.1.2
                //
                return cb(null, {
                    messageList : [],
                    confTag,
                    areaTag,
                    friendlyName    : area.name,
                    friendlyDesc    : area.desc,
                    nntp : {
                        name        : groupName,
                        description : area.desc,
                        min_index   : 0,
                        max_index   : 0,
                        total       : 0,
                    }
                });
            }

            group = {
                messageList,
                confTag,
                areaTag,
                friendlyName    : area.name,
                friendlyDesc    : area.desc,
                nntp : {
                    name        : groupName,
                    min_index   : messageList[0].index,
                    max_index   : messageList[messageList.length - 1].index,
                    total       : messageList.length,
                },
            };

            this.groupCache.set(groupName, group);

            return cb(null, group);
        });
    }

    getMappedMessageListForArea(areaTag, cb) {
        //
        //  Get all messages in mapped database. Then, find any messages that are not
        //  yet mapped with ID's > the highest ID we have. Any new messages will have
        //  new mappings created.
        //
        //  :TODO: introduce caching
        asyncWaterfall(
            [
                (callback) => {
                    nntpDatabase.db.all(
                        `SELECT nntp_message_id, message_id, message_uuid
                        FROM nntp_area_message
                        WHERE message_area_tag = ?
                        ORDER BY nntp_message_id;`,
                        [ areaTag ],
                        (err, rows) => {
                            if(err) {
                                return callback(err);
                            }

                            let messageList;
                            const lastMessageId = rows.length > 0 ? rows[rows.length - 1].message_id : 0;
                            if(!lastMessageId) {
                                messageList = [];
                            } else {
                                messageList = rows.map(r => {
                                    return {
                                        areaTag,
                                        index       : r.nntp_message_id,    //  node-nntp wants this name
                                        messageUuid : r.message_uuid,
                                    };
                                });
                            }

                            return callback(null, messageList, lastMessageId);
                        }
                    );
                },
                (messageList, lastMessageId, callback) => {
                    //  Find any new entries
                    const filter = {
                        areaTag,
                        newerThanMessageId  : lastMessageId,
                        sort                : 'messageId',
                        order               : 'ascending',
                        resultType          : 'messageList',
                    };
                    Message.findMessages(filter, (err, newMessageList) => {
                        if(err) {
                            return callback(err);
                        }

                        let index = messageList.length > 0 ?
                            messageList[messageList.length - 1].index + 1
                            : 1;
                        newMessageList = newMessageList.map(m => {
                            return Object.assign(m, { index : index++ } );
                        });

                        if(0 === newMessageList.length) {
                            return callback(null, messageList);
                        }

                        //  populate mapping DB with any new entries
                        nntpDatabase.db.beginTransaction( (err, trans) => {
                            if(err) {
                                return callback(err);
                            }

                            forEachSeries(newMessageList, (newMessage, nextNewMessage) => {
                                trans.run(
                                    `INSERT INTO nntp_area_message (nntp_message_id, message_id, message_area_tag, message_uuid)
                                    VALUES (?, ?, ?, ?);`,
                                    [ newMessage.index, newMessage.messageId, areaTag, newMessage.messageUuid ],
                                    err => {
                                        return nextNewMessage(err);
                                    }
                                );
                            },
                            err => {
                                if(err) {
                                    return trans.rollback( () => {
                                        return callback(err);
                                    });
                                }

                                trans.commit( () => {
                                    messageList.push(...newMessageList.map(m => {
                                        return {
                                            areaTag,
                                            index       : m.nntpMessageId,
                                            messageUuid : m.messageUuid,
                                        };
                                    }));

                                    return callback(null, messageList);
                                });
                            });
                        });
                    });
                }
            ],
            (err, messageList) => {
                return cb(err, messageList);
            }
        );
    }

    _buildHead(session, message) {
        return _.map(message.nntpHeaders, (v, k) => `${k}: ${v}`).join('\r\n');
    }

    _buildBody(session, message) {
        return message.preparedBody;
    }

    _buildHeaderField(session, message, field) {
        const body = message.preparedBody || message.message;
        const value = {
            ':bytes'    : Buffer.byteLength(body).toString(),
            ':lines'    : splitTextAtTerms(body).length.toString(),
        }[field]
            || _.find(message.nntpHeaders, (v, k) => {
                return k.toLowerCase() === field;
            });

        if(!value) {
            //
            //  Clients will check some headers just to see if they exist.
            //  Don't spam logs with these. For others, it's good to know.
            //
            if(!['references', 'xref'].includes(field)) {
                this.log.trace(`No value for requested header field "${field}"`);
            }
        }

        return value;
    }

    _getOverviewFmt(session) {
        return super._getOverviewFmt(session);
    }

    _getNewNews(session, time, wildmat) {
        //  Currently seems pointless to implement. No semi-modern clients seem to use it anyway.
        this.log.debug( { time, wildmat }, 'Request made using unsupported NEWNEWS command');
        throw new Errors.Invalid('NEWNEWS is not enabled on this server');
    }

    getMessageDate(message) {
        //  https://tools.ietf.org/html/rfc5536#section-3.1.1 -> https://tools.ietf.org/html/rfc5322#section-3.3
        return message.modTimestamp.format('ddd, D MMM YYYY HH:mm:ss ZZ');
    }

    makeMessageIdentifier(messageId, messageUuid) {
        //
        //  Spec        : RFC-5536 Section 3.1.3 @ https://tools.ietf.org/html/rfc5536#section-3.1.3
        //  Example     : <2456.0f6587f7-5512-4d03-8740-4d592190145a@enigma-bbs>
        //
        return `<${messageId}.${messageUuid}@enigma-bbs>`;
    }

    getMessageIdentifier(message) {
        //  note that we use the *real* message ID here, not the NNTP-specific index.
        return this.makeMessageIdentifier(message.messageId, message.messageUuid);
    }

    getMessageIdentifierParts(messageId) {
        const m = messageId.match(/<([0-9]+)\.([0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12})@enigma-bbs>/);
        if(m) {
            return [ m[1], m[2] ];
        }
        return [];
    }

    getMessageTo(message) {
        //  :TODO: same as From -- check config
        return message.toUserName;
    }

    getMessageFrom(message) {
        //  :TODO: NNTP config > conf > area config for real names
        return message.fromUserName;
    }

    prepareMessageBody(message, cb) {
        if(isAnsi(message.message)) {
            AnsiPrep(
                message.message,
                {
                    rows            : 'auto',
                    cols            : 79,
                    forceLineTerm   : true,
                    asciiMode       : true,
                    fillLines       : false,
                },
                (err, prepped) => {
                    message.preparedBody = prepped || message.message;
                    return cb(null);
                }
            );
        } else {
            message.preparedBody = stripMciColorCodes(stripAnsiControlCodes(message.message, { all : true }));
            return cb(null);
        }
    }

    getGroupName(confTag, areaTag) {
        //
        //  Example:
        //  input : fsxNet (confTag) fsx_bbs (areaTag)
        //  output: fsx_net.fsx_bbs
        //
        //  Note also that periods are replaced in conf and area
        //  tags such that we *only* have a period separator
        //  between the two for a group name!
        //
        return `${_.snakeCase(confTag).replace(/\./g, '_')}.${_.snakeCase(areaTag).replace(/\./g, '_')}`;
    }
}

exports.getModule = class NNTPServerModule extends ServerModule {
    constructor() {
        super();
    }

    isEnabled() {
        return this.enableNntp || this.enableNttps;
    }

    get enableNntp() {
        return _.get(Config(), 'contentServers.nntp.nntp.enabled', false);
    }

    get enableNttps() {
        return _.get(Config(), 'contentServers.nntp.nntps.enabled', false);
    }

    isConfigured() {
        const config = Config();

        //
        //  Any conf/areas exposed?
        //
        const publicConfs = _.get(config, 'contentServers.nntp.publicMessageConferences', {});
        const areasExposed = _.some(publicConfs, areas => {
            return Array.isArray(areas) && areas.length > 0;
        });

        if(!areasExposed) {
            return false;
        }

        const nntp = _.get(config, 'contentServers.nntp.nntp');
        if(nntp && this.enableNntp) {
            if(isNaN(nntp.port)) {
                return false;
            }
        }

        const nntps = _.get(config, 'contentServers.nntp.nntps');
        if(nntps && this.enableNttps) {
            if(isNaN(nntps.port)) {
                return false;
            }

            if(!_.isString(nntps.certPem) || !_.isString(nntps.keyPem)) {
                return false;
            }
        }

        return true;
    }

    createServer(cb) {
        if(!this.isEnabled() || !this.isConfigured()) {
            return cb(null);
        }

        const config = Config();

        const commonOptions = {
            //requireAuth : true,   //  :TODO: re-enable!
            //  :TODO: override |session| - use our own debug to Bunyan, etc.
        };

        if(this.enableNntp) {
            this.nntpServer = new NNTPServer(
                //  :TODO: according to docs: if connection is non-tls, but behind proxy (assuming TLS termination?!!) then set this to true
                Object.assign( { secure : false }, commonOptions),
                'NNTP'
            );
        }

        if(this.enableNttps) {
            this.nntpsServer  = new NNTPServer(
                Object.assign(
                    {
                        secure  : true,
                        tls : {
                            cert    : fs.readFileSync(config.contentServers.nntp.nntps.certPem),
                            key     : fs.readFileSync(config.contentServers.nntp.nntps.keyPem),
                        }
                    },
                    commonOptions
                ),
                'NTTPS'
            );
        }

        nntpDatabase = new NNTPDatabase();
        nntpDatabase.init(err => {
            return cb(err);
        });
    }

    listen(cb) {
        const config = Config();
        forEachSeries([ 'nntp', 'nntps' ], (service, nextService) => {
            const server = this[`${service}Server`];
            if(server) {
                const port = config.contentServers.nntp[service].port;
                server.listen(this.listenURI(port, service))
                    .catch(e => {
                        Log.warn( { error : e.message, port }, `${service.toUpperCase()} failed to listen`);
                        return nextService(null);   //  try next anyway
                    }).then( () => {
                        return nextService(null);
                    });
            } else {
                return nextService(null);
            }
        },
        err => {
            return cb(err);
        });
    }

    listenURI(port, service = 'nntp') {
        return `${service}://0.0.0.0:${port}`;
    }
};

function performMaintenanceTask(args, cb) {
    //
    //  Delete any message mapping that no longer have
    //  an actual message associated with them.
    //
    if(!nntpDatabase) {
        Log.trace('Cannot perform NNTP maintenance without NNTP database initialized');
        return cb(null);
    }

    let attached = false;
    asyncSeries(
        [
            (callback) => {
                const messageDbPath = paths.join(Config().paths.db, 'message.sqlite3');
                nntpDatabase.db.run(
                    `ATTACH DATABASE "${messageDbPath}" AS msgdb;`,
                    err => {
                        attached = !err;
                        return callback(err);
                    }
                );
            },
            (callback) => {
                nntpDatabase.db.run(
                    `DELETE FROM nntp_area_message
                    WHERE message_uuid NOT IN (
                        SELECT message_uuid
                        FROM msgdb.message
                    );`,
                    function result(err) {  //  no arrow func; need |this.changes|
                        if(err) {
                            Log.warn( { error : err.message }, 'Failed to delete from NNTP database');
                        } else {
                            Log.debug( { count : this.changes }, 'Deleted mapped message IDs from NNTP database');
                        }
                        return callback(err);
                    }
                );
            }
        ],
        err => {
            if(attached) {
                nntpDatabase.db.run('DETACH DATABASE msgdb;');
            }
            return cb(err);
        }
    );
}