#!/usr/bin/env node
/**
 * Capture and react to alerts generated by Q-See cameras over SMTP
 *
 * Author: Dave Eddy <dave@daveeddy.com>
 * Date: March 11, 2017
 * License: MIT
 */

var f = require('util').format;
var fs = require('fs');
var path = require('path');

var assert = require('assert-plus');
var mkdirp = require('mkdirp');

var MailParser = require('mailparser').MailParser;
var SMTPServer = require('smtp-server').SMTPServer;

var ATTACHMENT_RE = /^[a-zA-Z0-9_-]+\.(jpg|png)$/;
var ATTACHMENT_DIR = path.join(__dirname, 'data');
var USERNAME = 'foo@example.com';
var PASSWORD = 'bar';
var HOST = '0.0.0.0';
var PORT = 10465;

var connections = {};

var server = new SMTPServer({
    secure: false,
    disabledCommands: ['STARTTLS'],
    authOptional: true,
    onAuth: onAuth,
    onConnect: onConnect,
    onData: onData,
    onClose: onClose
});
server.listen(PORT, HOST, onconnected);

function log() {
    var s = f.apply(null, arguments);
    console.log('[%s] %s', new Date().toISOString(), s);
}

function onconnected() {
    log('Listening on smtp://%s:%d', HOST, PORT);
}

function onConnect(session, cb) {
    log('[%s] Connection from %s', session.id, session.remoteAddress);
    connections[session.id] = session;
    cb();
}

function onAuth(auth, session, cb) {
    var msg;

    // find the session
    if (!connections[session.id]) {
        msg = f('[%s] Unexpected auth from user "%s" (%s)',
            session.id, auth.username, session.remoteAddress);
        log(msg);
        cb(new Error(msg));
        return;
    }

    // check username and password
    if (auth.username !== USERNAME || auth.password !== PASSWORD) {
        msg = f('[%s] Auth failure for user "%s" (%s)',
            session.id, auth.username, session.remoteAddress);
        log(msg);
        cb(new Error(msg));
        return;
    }

    log('[%s] Successfully authed user "%s" (%s)',
        session.id, auth.username, session.remoteAddress);
    cb(null, {user: auth.username});
}

function onData(stream, session, cb) {
    // find the session
    if (!connections[session.id]) {
        msg = f('[%s] Unexpected auth from user "%s" (%s)',
            session.id, auth.username, session.remoteAddress);
        log(msg);
        cb(new Error(msg));
        return;
    }

    var parser = new MailParser();
    var dname = path.join(ATTACHMENT_DIR, Date.now().toString());

    // callback object
    var ret = {
        attachments: {
            dir: dname,
            files: []
        }
    };

    parser.on('headers', function (headers) {
        ret.subject = headers.get('subject');
        ret.date = headers.get('date');
        ret.from = headers.get('from').text;
        ret.to = headers.get('to').text;
    });

    parser.on('data', function (data) {
        switch (data.type) {
        case 'attachment':
            if (!ATTACHMENT_RE.test(data.filename)) {
                log('filename failed regex match: "%s"',
                    data.filename);
                data.release();
                return;
            }

            mkdirp.sync(dname);
            var fname = path.join(dname, data.filename);

            var ws = fs.createWriteStream(fname);
            data.content.pipe(ws);
            ws.on('close', function () {
                ret.attachments.files.push(fname);
                data.release();
            });
            break;
        case 'text':
            ret.rawBody = data.text;

            /*
             * attempt to parse the email body, exmaple output:
             *
             * Device ID: 0, Device Name: EDVR
             *
             *
             * Channel ID: 1, Camera Name:CAMERA01
             * Alarm Type:Motion Alarm, Time:2017-3-11 12:59:33
             */
            ret.data = {};
            data.text.split('\n').forEach(function (line) {
                if (line.trim() === '') {
                    return;
                }
                line.split(', ').forEach(function (s) {
                    var match = s.match(/([^:]+):(.*)$/);
                    if (!match) {
                        return;
                    }

                    var key = match[1];
                    var value = match[2].trim();
                    ret.data[key] = value;
                });
            });
            break;
        default:
            log('unexpected data.type "%s"', data.type);
            break;
        }
    });

    parser.on('end', function () {
        if (ret.attachments.files.length === 0) {
            delete ret.attachments;
        }
        console.log(JSON.stringify(ret, null, 2));
        cb();
    });

    stream.pipe(parser);
}

function onClose(session) {
    // find the session
    if (!connections[session.id]) {
        msg = f('[%s] Unexpected close (%s)',
            session.id, session.remoteAddress);
        log(msg);
        cb(new Error(msg));
        return;
    }

    log('[%s] Connection closed', session.id);
    delete connections[session];
}