const gen = require('gen-thread');
const MailParser = require('mailparser').MailParser;
const htmlawed = require('htmlawed');

const http = require('http');
const socket_io = require('socket.io');
const express = require('express');
const express_session = require('express-session');
const bodyparser = require('body-parser');
const multer = require('multer');

const css = require('css');

const MAX_FETCH = 100;

module.exports = SyncerWeb;

function SyncerWeb(syncer, pg, cfg)
{
    this.syncer = syncer;
    this.pg = pg;
    this.cfg = cfg;
    this.app = express();
    this.http = http.Server(this.app);
    this.io = socket_io(this.http);
    this.app.use(bodyparser.urlencoded({ extended: false }));
    this.app.use(express_session({
        secret: this.cfg.sessionSecret || '1083581xm1l3s1l39k',
        resave: false,
        saveUninitialized: false
    }));
    this.app.get('/auth', this.get_auth);
    this.app.post('/auth', this.post_auth);
    this.app.get('/folders', genRequest(this.get_folders.bind(this)));
    this.app.get('/groups', genRequest(this.get_groups.bind(this)));
    this.app.get('/messages', genRequest(this.get_messages.bind(this)));
    this.app.get('/message', genRequest(this.get_message.bind(this)));
    this.app.post('/sync', genRequest(this.post_sync.bind(this)));
    this.syncer.events.on('sync', this.syncer_sync.bind(this));
}

SyncerWeb.prototype.listen = function(port)
{
    this.http.listen(port);
}

SyncerWeb.prototype.get_auth = function(req, res)
{
    return res.type('html').send(
        '<form action="/auth" method="post"><input name="login" />'+
        ' <input name="password" type="password" /> <input type="submit" /></form>'
    );
}

SyncerWeb.prototype.post_auth = function(req, res)
{
    if (!req.body)
        return res.sendStatus(400);
    if (req.body.login == this.cfg.login && req.body.password == this.cfg.password)
    {
        req.session.auth = true;
        return res.send({ ok: true });
    }
    return res.send({ ok: false });
}

SyncerWeb.prototype.get_folders = function*(req, res)
{
    if (this.cfg.login && (!req.session || !req.session.auth))
    {
        return res.sendStatus(401);
    }
    var [ accounts ] = yield this.pg.select(
        'id, name, email, settings->\'folders\' folderMap,'+
        ' (select count(*) from messages m, folders f where m.folder_id=f.id and f.account_id=a.id and (flags @> array[\'pinned\',\'unread\']::varchar(255)[])) pinned_unread_count'
    ).from('accounts a').rows(gen.ef());
    var [ folders ] = yield this.pg.select(
        'id, account_id, name,'+
        ' (select count(*) from messages m where m.folder_id=f.id) total_count,'+
        ' (select count(*) from messages m where m.folder_id=f.id and (flags @> array[\'unread\']::varchar(255)[])) unread_count'
    ).from('folders f').orderBy('account_id, name').rows(gen.ef());
    var fh = {};
    for (let i = 0; i < folders.length; i++)
    {
        fh[folders[i].account_id] = fh[folders[i].account_id] || [];
        fh[folders[i].account_id].push(folders[i]);
    }
    for (let i = 0; i < accounts.length; i++)
    {
        accounts[i].folders = fh[accounts[i].id] || [];
    }
    return res.send({ accounts: accounts });
}

function ymd(dt)
{
    var m = dt.getMonth()+1;
    var d = dt.getDate();
    return dt.getFullYear()+'-'+(m < 10 ? '0'+m : m)+'-'+(d < 10 ? '0'+d : d);
}

SyncerWeb.prototype.get_groups = function*(req, res)
{
    if (this.cfg.login && (!req.session || !req.session.auth))
        return res.sendStatus(401);
    var folderId = req.query.folderId;
    if (!folderId)
        return res.status(500).send('Need `folderId` query parameter');
    var intervals = [];
    var today, today_ts;
    today = new Date(ymd(new Date()));
    today_ts = today.getTime();
    var week_start = today_ts - ((today.getDay()+6)%7)*86400000;
    var prev_week = ymd(new Date(week_start - 86400000*7));
    for (var i = 1; i <= 12; i++)
    {
        var d = today.getFullYear()+'-'+(i < 10 ? '0' : '')+i+'-01';
        if (d >= prev_week)
            break;
        intervals.push({ date: d, name: 'm'+i });
    }
    intervals.push({ date: prev_week, name: 'pw' });
    for (var i = week_start, d = 1; i < today_ts; i += 86400000, d++)
    {
        intervals.push({ date: ymd(new Date(i)), name: 'd'+d });
    }
    intervals.push({ date: ymd(today), name: 't' });
    for (var i = 0; i < intervals.length-1; i++)
    {
        intervals[i].date_end = intervals[i+1].date;
    }
    intervals[i].date_end = '100000-12-31'; // it's faster than (is null or <)
    var [ groups ] = yield this.pg
        .select('d.name, d.date, count(*) count')
        .from('messages m')
        .innerJoin(this.pg.sql.values(intervals).as('d').columns(),
            this.pg.sql('m.time >= d.date::date and m.time < d.date_end::date'))
        .where({ folder_id: folderId })
        .groupBy('1, 2')
        .union(
            this.pg.select('date_part(\'year\', m.time)::text as name, date_part(\'year\', m.time)::text||\'-01-01\' date, count(*) count')
            .from('messages m').where({ folder_id: folderId })
            .where(this.pg.sql.lt('m.time', intervals[0].date))
            .groupBy('1, 2')
        )
        .orderBy('date desc').rows(gen.ef());
    return res.send({ groups: groups });
}

SyncerWeb.prototype.get_messages = function*(req, res)
{
    if (this.cfg.login && (!req.session || !req.session.auth))
        return res.sendStatus(401);
    var folderId = req.query.folderId;
    if (!folderId)
        return res.status(500).send('Need `folderId` query parameter');
    var limit = req.query.limit || 50;
    if (limit > MAX_FETCH)
        limit = MAX_FETCH;
    var offset = req.query.offset || 0;
    var [ msgs ] = yield this.pg.select('*').from('messages').where({ folder_id: folderId })
        .orderBy('time desc').limit(limit).offset(offset).rows(gen.ef());
    for (var i = 0; i < msgs.length; i++)
    {
        delete msgs[i].text_index;
    }
    return res.send({ messages: msgs });
}

SyncerWeb.prototype.get_message = function*(req, res)
{
    if (this.cfg.login && (!req.session || !req.session.auth))
        return res.sendStatus(401);
    var msgId = req.query.msgId;
    var [ msg ] = yield this.pg.select('m.*, f.name folder_name, f.account_id')
        .from('messages m').join('folders f', this.pg.sql('f.id=m.folder_id'))
        .where({ 'm.id': msgId }).rows(gen.ef());
    if (!msg.length)
        return res.send({ error: 'not-found' });
    msg = msg[0];
    delete msg.text_index;
    if (!msg.body_html && !msg.body_text)
    {
        var srv = yield* this.syncer.imap.getConnection(msg.account_id, msg.folder_name);
        var [ upd ] = yield* this.syncer.imap.runFetch(
            srv, msg.uid, { bodies: '' },
            (messages, state) => this.getBody(messages, msg.folder_id)
        );
        this.syncer.imap.releaseConnection(msg.account_id);
        return res.send({ msg: { ...msg, ...upd } });
    }
    return res.send({ msg: msg });
}

SyncerWeb.prototype.syncer_sync = function(params)
{
    this.io.emit('sync', params);
}

SyncerWeb.prototype.post_sync = function*(req, res)
{
    if (this.cfg.login && (!req.session || !req.session.auth))
        return res.sendStatus(401);
    if (this.syncer.syncInProgress)
        return res.send({ error: 'already-running' });
    gen.run(this.syncer.syncAll());
    return res.send({ status: 'started' });
}

function rewriteCss(ast)
{
    var rules = ast.rules || ast.stylesheet && ast.stylesheet.rules;
    if (rules)
    {
        for (var i = 0; i < rules.length; i++)
        {
            if (rules[i].type == 'document')
            {
                // prune @document instructions (may spy on current URL)
                rules.splice(i--, 1);
            }
            else
                rewriteCss(rules[i]);
        }
    }
    else if (ast.type == 'rule')
    {
        for (var i = 0; i < ast.selectors.length; i++)
        {
            // FIXME: Do not hardcode css selector for frontend here
            // This will require generating unique substitution string,
            // so we may also generate 'blocked images' stubs when we do it.
            ast.selectors[i] = '.message-view .text '+ast.selectors[i];
        }
    }
}

function sanitizeHtml(html)
{
    let styles = '';
    html = (html||'').replace(/<style[^<>]*>([\s\S]*?)<\/style\s*>/ig, function(m, m1)
    {
        styles += m1+'\n';
        return '';
    });
    html = html.replace(/^[\s\S]*?<body[^<>]*>([\s\S]*)<\/body>[\s\S]*$/i, '$1');
    html = html.replace(/^[\s\S]*?<html[^<>]*>([\s\S]*)<\/html>[\s\S]*$/i, '$1');
    if (styles)
    {
        html = '<style>\n'+styles+'</style>\n'+html;
        styles = '';
    }
    html = htmlawed.sanitize(html||'', { safe: 1, elements: '* +style', keep_bad: 0, comment: 1 });
    html = html.replace(/<style[^>]*>([\s\S]*)<\/style\s*>/ig, function(m, m1)
    {
        var ast = css.parse(m1, { silent: true });
        rewriteCss(ast);
        return '<style>'+css.stringify(ast)+'</style>';
    });
    return html;
}

SyncerWeb.prototype.getBody = function*(messages, boxId)
{
    for (var i = 0; i < messages.length; i++)
    {
        let msg = messages[i];
        let obj = yield* this.syncer.parseMsg(msg[0].headers);
        obj.html = sanitizeHtml(obj.html);
        let upd = { body_text: obj.text||'', body_html: obj.html };
        upd.body_html_text = obj.html.replace(/<style[^>]*>.*<\/style\s*>|<\/?[^>]*>/g, '');
        yield this.pg.update('messages m', upd).where({ folder_id: boxId, uid: msg[0].uid }).run(gen.ef());
        if (messages.length == 1)
            return [ upd ];
    }
}

function genRequest(fn)
{
    return (req, res) => gen.run(fn(req, res), null, e => res.status(500).send('Internal Error: '+e.stack));
}