'use strict';

module.exports = exports = {
    fqdn,
    getName,

    getDnsRecords,
    upsertDnsRecords,
    removeDnsRecords,

    waitForDnsRecord,

    validateHostname,

    makeWildcard,

    registerLocations,
    unregisterLocations,

    checkDnsRecords,
    syncDnsRecords,

    resolve,

    promises: {
        resolve: require('util').promisify(resolve)
    }
};

const apps = require('./apps.js'),
    assert = require('assert'),
    BoxError = require('./boxerror.js'),
    constants = require('./constants.js'),
    debug = require('debug')('box:dns'),
    dns = require('dns'),
    domains = require('./domains.js'),
    mail = require('./mail.js'),
    promiseRetry = require('./promise-retry.js'),
    safe = require('safetydance'),
    settings = require('./settings.js'),
    sysinfo = require('./sysinfo.js'),
    tld = require('tldjs'),
    util = require('util'),
    _ = require('underscore');

// choose which subdomain backend we use for test purpose we use route53
function api(provider) {
    assert.strictEqual(typeof provider, 'string');

    switch (provider) {
    case 'cloudflare': return require('./dns/cloudflare.js');
    case 'route53': return require('./dns/route53.js');
    case 'gcdns': return require('./dns/gcdns.js');
    case 'digitalocean': return require('./dns/digitalocean.js');
    case 'gandi': return require('./dns/gandi.js');
    case 'godaddy': return require('./dns/godaddy.js');
    case 'linode': return require('./dns/linode.js');
    case 'vultr': return require('./dns/vultr.js');
    case 'namecom': return require('./dns/namecom.js');
    case 'namecheap': return require('./dns/namecheap.js');
    case 'netcup': return require('./dns/netcup.js');
    case 'noop': return require('./dns/noop.js');
    case 'manual': return require('./dns/manual.js');
    case 'wildcard': return require('./dns/wildcard.js');
    default: return null;
    }
}

function fqdn(location, domainObject) {
    assert.strictEqual(typeof location, 'string');
    assert.strictEqual(typeof domainObject, 'object');

    return location + (location ? '.' : '') + domainObject.domain;
}

// Hostname validation comes from RFC 1123 (section 2.1)
// Domain name validation comes from RFC 2181 (Name syntax)
// https://en.wikipedia.org/wiki/Hostname#Restrictions_on_valid_host_names
// We are validating the validity of the location-fqdn as host name (and not dns name)
function validateHostname(location, domainObject) {
    assert.strictEqual(typeof location, 'string');
    assert.strictEqual(typeof domainObject, 'object');

    const hostname = fqdn(location, domainObject);

    const RESERVED_LOCATIONS = [
        constants.SMTP_LOCATION,
        constants.IMAP_LOCATION
    ];
    if (RESERVED_LOCATIONS.indexOf(location) !== -1) return new BoxError(BoxError.BAD_FIELD, location + ' is reserved', { field: 'location' });

    if (hostname === settings.dashboardFqdn()) return new BoxError(BoxError.BAD_FIELD, location + ' is reserved', { field: 'location' });

    // workaround https://github.com/oncletom/tld.js/issues/73
    var tmp = hostname.replace('_', '-');
    if (!tld.isValid(tmp)) return new BoxError(BoxError.BAD_FIELD, 'Hostname is not a valid domain name', { field: 'location' });

    if (hostname.length > 253) return new BoxError(BoxError.BAD_FIELD, 'Hostname length exceeds 253 characters', { field: 'location' });

    if (location) {
        // label validation
        if (location.split('.').some(function (p) { return p.length > 63 || p.length < 1; })) return new BoxError(BoxError.BAD_FIELD, 'Invalid subdomain length', { field: 'location' });
        if (location.match(/^[A-Za-z0-9-.]+$/) === null) return new BoxError(BoxError.BAD_FIELD, 'Subdomain can only contain alphanumeric, hyphen and dot', { field: 'location' });
        if (/^[-.]/.test(location)) return new BoxError(BoxError.BAD_FIELD, 'Subdomain cannot start or end with hyphen or dot', { field: 'location' });
    }

    return null;
}

// returns the 'name' that needs to be inserted into zone
// eslint-disable-next-line no-unused-vars
function getName(domain, location, type) {
    const part = domain.domain.slice(0, -domain.zoneName.length - 1);

    if (location === '') return part;

    return part ? `${location}.${part}` : location;
}

function maybePromisify(func) {
    if (util.types.isAsyncFunction(func)) return func;
    return util.promisify(func);
}

async function getDnsRecords(location, domain, type) {
    assert.strictEqual(typeof location, 'string');
    assert.strictEqual(typeof domain, 'string');
    assert.strictEqual(typeof type, 'string');

    const domainObject = await domains.get(domain);
    return await maybePromisify(api(domainObject.provider).get)(domainObject, location, type);
}

async function checkDnsRecords(location, domain) {
    assert.strictEqual(typeof location, 'string');
    assert.strictEqual(typeof domain, 'string');

    const values = await getDnsRecords(location, domain, 'A');

    const ip = await sysinfo.getServerIp();

    if (values.length === 0) return { needsOverwrite: false }; // does not exist
    if (values[0] === ip) return { needsOverwrite: false }; // exists but in sync

    return { needsOverwrite: true };
}

// note: for TXT records the values must be quoted
async function upsertDnsRecords(location, domain, type, values) {
    assert.strictEqual(typeof location, 'string');
    assert.strictEqual(typeof domain, 'string');
    assert.strictEqual(typeof type, 'string');
    assert(Array.isArray(values));

    debug(`upsertDNSRecord: location ${location} on domain ${domain} of type ${type} with values ${JSON.stringify(values)}`);

    const domainObject = await domains.get(domain);
    await maybePromisify(api(domainObject.provider).upsert)(domainObject, location, type, values);
}

async function removeDnsRecords(location, domain, type, values) {
    assert.strictEqual(typeof location, 'string');
    assert.strictEqual(typeof domain, 'string');
    assert.strictEqual(typeof type, 'string');
    assert(Array.isArray(values));

    debug('removeDNSRecord: %s on %s type %s values', location, domain, type, values);

    const domainObject = await domains.get(domain);
    const [error] = await safe(maybePromisify(api(domainObject.provider).del)(domainObject, location, type, values));
    if (error && error.reason !== BoxError.NOT_FOUND) throw error;
}

async function waitForDnsRecord(location, domain, type, value, options) {
    assert.strictEqual(typeof location, 'string');
    assert.strictEqual(typeof domain, 'string');
    assert(type === 'A' || type === 'TXT');
    assert.strictEqual(typeof value, 'string');
    assert(options && typeof options === 'object'); // { interval: 5000, times: 50000 }

    const domainObject = await domains.get(domain);

    // linode DNS takes ~15mins
    if (!options.interval) options.interval = domainObject.provider === 'linode' ? 20000 : 5000;

    await maybePromisify(api(domainObject.provider).wait)(domainObject, location, type, value, options);
}

function makeWildcard(vhost) {
    assert.strictEqual(typeof vhost, 'string');

    // if the vhost is like *.example.com, this function will do nothing
    let parts = vhost.split('.');
    parts[0] = '*';
    return parts.join('.');
}

async function registerLocations(locations, options, progressCallback) {
    assert(Array.isArray(locations));
    assert.strictEqual(typeof options, 'object');
    assert.strictEqual(typeof progressCallback, 'function');

    debug(`registerLocations: Will register ${JSON.stringify(locations)} with options ${JSON.stringify(options)}`);

    const overwriteDns = options.overwriteDns || false;

    const ip = await sysinfo.getServerIp();

    for (const location of locations) {
        const error = await promiseRetry({ times: 200, interval: 5000 }, async function () {
            progressCallback({ message: `Registering location: ${location.subdomain ? (location.subdomain + '.') : ''}${location.domain}` });

            // get the current record before updating it
            const [error, values] = await safe(getDnsRecords(location.subdomain, location.domain, 'A'));
            if (error && error.reason === BoxError.EXTERNAL_ERROR) throw new BoxError(BoxError.EXTERNAL_ERROR, error.message, { domain: location }); // try again
            // give up for other errors
            if (error && error.reason === BoxError.ACCESS_DENIED) return new BoxError(BoxError.ACCESS_DENIED, error.message, { domain: location });
            if (error && error.reason === BoxError.NOT_FOUND) return new BoxError(BoxError.NOT_FOUND, error.message, { domain: location });
            if (error) return new BoxError(BoxError.EXTERNAL_ERROR, error.message, location);

            if (values.length !== 0 && values[0] === ip) return null; // up-to-date

            // refuse to update any existing DNS record for custom domains that we did not create
            if (values.length !== 0 && !overwriteDns) return new BoxError(BoxError.ALREADY_EXISTS, 'DNS Record already exists', { domain: location });

            const [upsertError] = await safe(upsertDnsRecords(location.subdomain, location.domain, 'A', [ ip ]));
            if (upsertError && (upsertError.reason === BoxError.BUSY || upsertError.reason === BoxError.EXTERNAL_ERROR)) {
                progressCallback({ message: `registerSubdomains: Upsert error. Will retry. ${upsertError.message}` });
                throw new BoxError(BoxError.EXTERNAL_ERROR, upsertError.message, { domain: location }); // try again
            }

            return upsertError ? new BoxError(BoxError.EXTERNAL_ERROR, upsertError.message, location) : null;
        });

        if (error) throw error;
    }
}

async function unregisterLocations(locations, progressCallback) {
    assert(Array.isArray(locations));
    assert.strictEqual(typeof progressCallback, 'function');

    const ip = await sysinfo.getServerIp();

    for (const location of locations) {
        const error = await promiseRetry({ times: 30, interval: 5000 }, async function () {
            progressCallback({ message: `Unregistering location: ${location.subdomain ? (location.subdomain + '.') : ''}${location.domain}` });

            const [error] = await safe(removeDnsRecords(location.subdomain, location.domain, 'A', [ ip ]));
            if (error && error.reason === BoxError.NOT_FOUND) return;
            if (error && (error.reason === BoxError.BUSY || error.reason === BoxError.EXTERNAL_ERROR)) {
                progressCallback({ message: `Error unregistering location. Will retry. ${error.message}`});
                throw new BoxError(BoxError.EXTERNAL_ERROR, error.message, { domain: location }); // try again
            }

            return error ? new BoxError(BoxError.EXTERNAL_ERROR, error.message, { domain: location }) : null; // give up for other errors
        });

        if (error) throw error;
    }
}

async function syncDnsRecords(options, progressCallback) {
    assert.strictEqual(typeof options, 'object');
    assert.strictEqual(typeof progressCallback, 'function');

    if (options.domain && options.type === 'mail') return await mail.setDnsRecords(options.domain);

    let allDomains = await domains.list();

    if (options.domain) allDomains = allDomains.filter(d => d.domain === options.domain);

    const mailSubdomain = settings.mailFqdn().substr(0, settings.mailFqdn().length - settings.mailDomain().length - 1);

    const allApps = await apps.list();

    let progress = 1, errors = [];

    // we sync by domain only to get some nice progress
    for (const domain of allDomains) {
        progressCallback({ percent: progress, message: `Updating DNS of ${domain.domain}`});
        progress += Math.round(100/(1+allDomains.length));

        let locations = [];
        if (domain.domain === settings.dashboardDomain()) locations.push({ subdomain: constants.DASHBOARD_LOCATION, domain: settings.dashboardDomain() });
        if (domain.domain === settings.mailDomain() && settings.mailFqdn() !== settings.dashboardFqdn()) locations.push({ subdomain: mailSubdomain, domain: settings.mailDomain() });

        allApps.forEach(function (app) {
            const appLocations = [{ subdomain: app.location, domain: app.domain }].concat(app.alternateDomains).concat(app.aliasDomains);
            locations = locations.concat(appLocations.filter(al => al.domain === domain.domain));
        });

        try {
            await registerLocations(locations, { overwriteDns: true }, progressCallback);
            progressCallback({ message: `Updating mail DNS of ${domain.domain}`});
            await mail.setDnsRecords(domain.domain);
        } catch (error) {
            errors.push({ domain: domain.domain, message: error.message });
        }
    }

    return { errors };
}

// a note on TXT records. It doesn't have quotes ("") at the DNS level. Those quotes
// are added for DNS server software to enclose spaces. Such quotes may also be returned
// by the DNS REST API of some providers
function resolve(hostname, rrtype, options, callback) {
    assert.strictEqual(typeof hostname, 'string');
    assert.strictEqual(typeof rrtype, 'string');
    assert(options && typeof options === 'object');
    assert.strictEqual(typeof callback, 'function');

    const defaultOptions = { server: '127.0.0.1', timeout: 5000 }; // unbound runs on 127.0.0.1
    const resolver = new dns.Resolver();
    options = _.extend({ }, defaultOptions, options);

    // Only use unbound on a Cloudron
    if (constants.CLOUDRON) resolver.setServers([ options.server ]);

    // should callback with ECANCELLED but looks like we might hit https://github.com/nodejs/node/issues/14814
    const timerId = setTimeout(resolver.cancel.bind(resolver), options.timeout || 5000);

    resolver.resolve(hostname, rrtype, function (error, result) {
        clearTimeout(timerId);

        if (error && error.code === 'ECANCELLED') error.code = 'TIMEOUT';

        // result is an empty array if there was no error but there is no record. when you query a random
        // domain, it errors with ENOTFOUND. But if you query an existing domain (A record) but with different
        // type (CNAME) it is not an error and empty array
        // for TXT records, result is 2d array of strings
        callback(error, result);
    });
}