const exec = require('child_process').exec;
const log = require('fancy-log');
const dataSources = require('../loopback/server/datasources.json');

module.exports = class Docker {
    constructor(name) {
        Object.assign(this, {
            id: name,
            name,
            isRandom: name == null,
            dbConf: Object.assign({}, dataSources.vn)
        });
    }

    /**
     * Builds the database image and runs a container. It only rebuilds the
     * image when fixtures have been modified or when the day on which the
     * image was built is different to today. Some workarounds have been used
     * to avoid a bug with OverlayFS driver on MacOS.
     *
     * @param {Boolean} ci continuous integration environment argument
     */
    async run(ci) {
        let d = new Date();
        let pad = v => v < 10 ? '0' + v : v;
        let stamp = `${d.getFullYear()}-${pad(d.getMonth() + 1)}-${pad(d.getDate())}`;
        await this.execP(`docker build --build-arg STAMP=${stamp} -t salix-db ./db`);

        let dockerArgs;

        if (this.isRandom)
            dockerArgs = '-p 3306';
        else {
            try {
                await this.rm();
            } catch (e) {}
            dockerArgs = `--name ${this.name} -p 3306:${this.dbConf.port}`;
        }

        let runChown = process.platform != 'linux';

        const container = await this.execP(`docker run --env RUN_CHOWN=${runChown} -d ${dockerArgs} salix-db`);
        this.id = container.stdout;

        try {
            if (this.isRandom) {
                let inspect = await this.execP(`docker inspect -f "{{json .NetworkSettings}}" ${this.id}`);
                let netSettings = JSON.parse(inspect.stdout);

                if (ci)
                    this.dbConf.host = netSettings.Gateway;

                this.dbConf.port = netSettings.Ports['3306/tcp'][0]['HostPort'];
            }

            await this.waitForHealthy();
        } catch (err) {
            if (this.isRandom)
                await this.rm();
            throw err;
        }
    }

    /**
     * Does the minium effort to start the database container, if it doesn't exists
     * calls the 'docker' task, if it is started does nothing. Keep in mind that when
     * you do not rebuild the docker you may be using an outdated version of it.
     * See the 'docker' task for more info.
     */
    async start() {
        let state;
        try {
            let result = await this.execP(`docker inspect -f "{{json .State}}" ${this.id}`);
            state = JSON.parse(result.stdout);
        } catch (err) {
            return await this.run();
        }

        switch (state.Status) {
        case 'running':
            return;
        case 'exited':
            await this.execP(`docker start ${this.id}`);
            await this.wait();
            return;
        default:
            throw new Error(`Unknown docker status: ${state.Status}`);
        }
    }

    waitForHealthy() {
        return new Promise((resolve, reject) => {
            let interval = 100;
            let elapsedTime = 0;
            let maxInterval = 4 * 60 * 1000;

            log('Waiting for MySQL init process...');

            async function checker() {
                elapsedTime += interval;
                let status;

                try {
                    let result = await this.execP(`docker inspect -f "{{.State.Health.Status}}" ${this.id}`);
                    status = result.stdout.trimEnd();
                } catch (err) {
                    return reject(new Error(err.message));
                }

                if (status == 'unhealthy')
                    return reject(new Error('Docker exited, please see the docker logs for more info'));

                if (status == 'healthy') {
                    log('MySQL process ready.');
                    return resolve();
                }

                if (elapsedTime >= maxInterval)
                    reject(new Error(`MySQL not initialized whithin ${elapsedTime / 1000} secs`));
                else
                    setTimeout(bindedChecker, interval);
            }
            let bindedChecker = checker.bind(this);
            bindedChecker();
        });
    }

    wait() {
        return new Promise((resolve, reject) => {
            const mysql = require('mysql2');

            let interval = 100;
            let elapsedTime = 0;
            let maxInterval = 4 * 60 * 1000;

            let myConf = {
                user: this.dbConf.username,
                password: this.dbConf.password,
                host: this.dbConf.host,
                port: this.dbConf.port
            };

            log('Waiting for MySQL init process...');

            async function checker() {
                elapsedTime += interval;
                let state;

                try {
                    let result = await this.execP(`docker container inspect -f "{{json .State}}" ${this.id}`);
                    state = JSON.parse(result.stdout);
                } catch (err) {
                    return reject(new Error(err.message));
                }

                if (state.Status === 'exited')
                    return reject(new Error('Docker exited, please see the docker logs for more info'));

                let conn = mysql.createConnection(myConf);
                conn.on('error', () => {});
                conn.connect(err => {
                    conn.destroy();
                    if (!err) {
                        log('MySQL process ready.');
                        return resolve();
                    }

                    if (elapsedTime >= maxInterval)
                        reject(new Error(`MySQL not initialized whithin ${elapsedTime / 1000} secs`));
                    else
                        setTimeout(bindedChecker, interval);
                });
            }
            let bindedChecker = checker.bind(this);
            bindedChecker();
        });
    }

    rm() {
        return this.execP(`docker rm -fv ${this.id}`);
    }

    /**
     * Promisified version of exec().
     *
     * @param {String} command The exec command
     * @return {Promise} The promise
     */
    execP(command) {
        return new Promise((resolve, reject) => {
            exec(command, (err, stdout, stderr) => {
                if (err)
                    reject(err);
                else {
                    resolve({
                        stdout: stdout,
                        stderr: stderr
                    });
                }
            });
        });
    }
};