require('require-yaml');
let Docker = require('dockerode');
let handlebars = require('handlebars');
let ssh = require('node-ssh');
let fs = require('fs');
let shajs = require('sha.js');
let conf = require('./config.yml');
let package = require('./package.json');

let docker;
let template;
let lastInfoHash;
let appName = package.name;
let isProduction = process.env.NODE_ENV === 'production';
let tmpDir = isProduction ? `/tmp/${appName}` : `${__dirname}/tmp`;
let hashFile = `${tmpDir}/config.hash`;

async function updateProxy() {
    console.log('Updating reverse proxy configuration.');

    // Obtaining Docker settings

    let info;

    if (!isProduction) {
        info = require('./test.json');
    } else {
        info = {
            services: await docker.listServices(),
            nodes: await docker.listNodes()
        };
    }

    let services = [];
    for (let serviceInfo of info.services) {
        let ports = serviceInfo.Endpoint.Ports;
        if (!Array.isArray(ports) || !ports.length) continue;

        let name = serviceInfo.Spec.Name;
        let match = name.match(/^(.+)_main$/);
        if (match) name = match[1];

        let service = {
            name,
            port: ports[0].PublishedPort,
            nodes: []
        };
        services.push(service);

        for (let node of info.nodes) {
            let address = node.ManagerStatus
                ? node.ManagerStatus.Addr.split(':')[0]
                : node.Status.Addr;

            service.nodes.push({
                name: node.Description.Hostname,
                endpoint: `${address}:${service.port}`
            });
        }
    }

    // Cheking settings hash

    let infoHash = shajs('sha256')
        .update(JSON.stringify(services))
        .digest('hex');
    console.log('Settings hash:', infoHash);

    if (lastInfoHash == infoHash) {
        console.log(`Settings haven't changed, aborting.`);
        return;
    }

    lastInfoHash = infoHash;
    fs.writeFileSync(hashFile, infoHash);

    // Creating configuration file

    let tmpConf = `${tmpDir}/config.cfg`;
    let configString = template({info, services});
    fs.writeFileSync(tmpConf, configString);

    if (conf.debug) {
        let delimiter = '#'.repeat(80);
        console.log(delimiter);
        console.log(configString);
        console.log(delimiter);
    }

    // Updating reverse proxies

    let files = {
        local: tmpConf,
        remote: conf.rproxy.confPath
    };

    for (let host of conf.rproxy.hosts) {
        console.log(`Updating host: ${host}`);
        if (!isProduction) continue;

        let sshClient = new ssh();
        await sshClient.connect(Object.assign({host}, conf.rproxy.auth));
        await sshClient.putFiles([files]);
        if (conf.rproxy.reloadCmd)
            await sshClient.exec(conf.rproxy.reloadCmd);
        await sshClient.dispose();
    }

    console.log('Configuration updated.');
}

(async() => {
    console.log('Initializing.');
    let timeoutId;
    docker = new Docker(conf.docker);
    template = handlebars.compile(fs.readFileSync('rproxy.handlebars', 'utf8'));

    try {
        fs.mkdirSync(tmpDir);
    } catch (err) {
        if (err.code != 'EEXIST') throw err;
    }

    if (fs.existsSync(hashFile)) {
        lastInfoHash = fs.readFileSync(hashFile, 'utf8');
        console.log('Saved settings hash:', lastInfoHash);
    }

    await updateProxy();

    console.log('Listenig for events.')
    docker.getEvents({}, (err, stream) => {
        if (err || !stream) {
            console.error('Failed to monitor docker host', err);
            return;
        }

        stream.on('data', event => {
            event = JSON.parse(event);
            if (conf.events && conf.events.indexOf(event.Type) == -1) return;
            console.log(`Event: ${event.Type}: ${event.Action}`);

            if (timeoutId) return;
            timeoutId = setTimeout(async () => {
                timeoutId = null;
                await updateProxy();
            }, conf.delay * 1000);
        })
    });
})();