/*
    ! /database/commands.js
    ? The command library for mariadb
*/

// % imports
import pools from './pools.js'; // functions "add(this)", "remove(this.name)", "status(name)"

// = command manager class
export default class Commands {
    constructor(name, db, protocol = 'read', address = process.env.DB_CONN_IP) {
        this.name = name; // persistent identifier
        this.address = address; // database adress (host)
        this.database = db; // database name
        this.protocol = protocol; // user protocol
        this.pool = null; // pool reference
        this.connStat = false; // connection status
    }

    // $ add a connection to the pool manager
    async connect() {
        console.log(`[Database] Connecting command instance "${this.name}" to database "${this.database}"...`);
        const result = await pools.add(this);
        this.connStat = result.connStat;
        this.pool = result.pool;
        console.log(`[Database] Connection status for "${this.name}": ${this.connStat ? 'SUCCESS' : 'FAILED'}`);
    }

    // $ remove a connection from the pool manager
    async disconnect() {
        if (this.connStat) {
            console.log(`[Database] Disconnecting instance "${this.name}"...`);
            const result = await pools.remove(this.name);
            this.connStat = result?.connStat ?? false;
            this.pool = null;
            console.log(`[Database] Instance "${this.name}" successfully disconnected.`);
        }
    }

    // $ get the status of a connection from the pool manager
    async status() {
        if (this.connStat) {
            console.log(`[Database] Checking status for instance "${this.name}"...`);
            const result = await pools.status(this.name);
            this.connStat = result?.connStat ?? false;
            this.pool = result?.pool ?? null;
            console.log(`[Database] Status for "${this.name}": Active = ${this.connStat}`);
            return result;
        } else {
            console.log(`[Database] Status check skipped for "${this.name}" (currently not connected).`);
        }
    }

    // $ execute an sql query
    async query(query, params = []) {
        // ~ check if connection is established
        if (!this.connStat || !this.pool) {
            console.error(`[Database Error] Tried to execute query on disconnected instance "${this.name}".`);
            throw new Error(`Database connection '${this.name}' is not established.`);
        }

        // ~ connection reference
        let conn;
        
        // ~ try executing the query
        try {
            conn = await this.pool.getConnection();
            const rows = await conn.query(query, params);
            console.log(`[Database Query] [${this.name}] Executed successfully (${duration}ms):`, { query, params });
            return rows;

        // ~ throw error if failed
        } catch(e) {
            console.error(`[Database Error] Query failed in "${this.name}":`, e.message);
            console.error(`[Failed Query]:`, query, params);
            throw e;

        // ~ release the connection back to the pool
        } finally {
            if (conn) conn.release();
        }
    }

    // $ insert a record into a table
    async insert(table, data) {
        if (Object.keys(data).length === 0) return null;
        const keys = Object.keys(data);
        const values = Object.values(data);
        const placeholders = keys.map(() => '?').join(', ');
        const columns = keys.join(', ');

        const query = `INSERT INTO ${table} (${columns}) VALUES (${placeholders})`;
        return await this.query(query, values);
    }

    // $ update a record in a table
    async update(table, data, where, whereParams = []) {
        if (Object.keys(data).length === 0) return null;
        const keys = Object.keys(data);
        const values = Object.values(data);
        const setClause = keys.map(key => `${key} = ?`).join(', ');

        const query = `UPDATE ${table} SET ${setClause} WHERE ${where}`;
        return await this.query(query, [...values, ...whereParams]);
    }

    // $ select records from a table
    async select(table, columns = '*', where = '', params = []) {
        let query = `SELECT ${Array.isArray(columns) ? columns.join(', ') : columns} FROM ${table}`;
        if (where) {
            query += ` WHERE ${where}`;
        }
        return await this.query(query, params);
    }

    // $ delete records from a table
    async delete(table, where, params = []) {
        const query = `DELETE FROM ${table} WHERE ${where}`;
        return await this.query(query, params);
    }

    // $ create a new table
    async createTable(table, columns = 'id INT AUTO_INCREMENT PRIMARY KEY') {
        const query = `CREATE TABLE IF NOT EXISTS ${table} (${columns}) ENGINE=InnoDB DEFAULT CHARSET=utf8mb3 COLLATE=utf8mb3_general_ci`;
        return await this.query(query);
    }

    // $ alter an existing table
    async alterTable(table, modificationClause) {
        const query = `ALTER TABLE ${table} ${modificationClause}`;
        return await this.query(query);
    }
};