const pg = require('pg');

class Database {
    constructor(connectionStr) {
        this.pool = new pg.Pool({connectionString: connectionStr});
    }

    async registerQRTeam(name, owner) {
        let client = await this.pool.connect();
        try {
            await client.query('BEGIN');
            await client.query('INSERT INTO qr_team (team_name, owner_id) values ($1,$2)', [name, owner]);
            await client.query('COMMIT');
        } finally {
            client.release();
        }
    }

    /**
     *
     * @param code
     * @returns {Promise<null|{id:number,task_text:number,code:string}>}
     */
    async getQRTask(code) {
        let client = await this.pool.connect();
        let task = null;
        try {
            await client.query('BEGIN');
            let res = await client.query('SELECT * FROM qr_tasks WHERE code = $1', [code]);
            await client.query('COMMIT');
            task = res.rows[0];
        } finally {
            client.release();
        }
        return task;
    }

    async getTask(id) {
        if(id === 0) return {short_name: "Начало"}
        let client = await this.pool.connect();
        let task = null;
        try {
            await client.query('BEGIN');
            let res = await client.query('SELECT * FROM qr_tasks WHERE id = $1', [id]);
            await client.query('COMMIT');
            task = res.rows[0];
        } finally {
            client.release();
        }
        return task;
    }

    async getTop() {
        let client = await this.pool.connect();
        let teams = [];
        try {
            await client.query('BEGIN');
            let res = await client.query('SELECT qr_team.*, COUNT(task) as count\n' +
                'FROM qr_team\n' +
                '         join qr_completion as com on qr_team.id = com.group_id\n' +
                'group by id, team_name, owner_id\n' +
                'ORDER BY count DESC', []);
            await client.query('COMMIT');
            teams = res.rows;
        } finally {
            client.release();
        }
        return teams;
    }

    /**
     *
     * @param team
     * @param task
     * @returns {Promise<boolean>}
     */
    async checkPreviousTasks(team, task) {
        if(task === 1) return true;
        let client = await this.pool.connect();
        let prevtasks = 0;
        try {
            await client.query('BEGIN');
            let res = await client.query('SELECT * FROM qr_view WHERE task < $1 AND group_id = $2', [task, team]);
            prevtasks = res.rowCount;
            await client.query('COMMIT');
        } finally {
            client.release();
        }
        return prevtasks === task - 1;
    }

    async getTeam(user) {
        let client = await this.pool.connect();
        let team = null;
        try {
            await client.query('BEGIN');
            let res = await client.query('SELECT * FROM qr_team WHERE owner_id = $1', [user]);
            await client.query('COMMIT');
            team = res.rows[0];
        } finally {
            client.release();
        }
        return team;
    }

    async addCompletion(team, task) {
        let client = await this.pool.connect();
        try {
            await client.query('BEGIN');
            await client.query('INSERT INTO qr_completion (group_id, task) values ($1,$2)', [team, task]);
            await client.query('COMMIT');
        } finally {
            client.release();
        }
    }

    async addView(team, task) {
        let client = await this.pool.connect();
        try {
            await client.query('BEGIN');
            await client.query('INSERT INTO qr_view (group_id, task) values ($1,$2)', [team, task]);
            await client.query('COMMIT');
        } finally {
            client.release();
        }
    }
}

module.exports = Database;