import mysql, { Connection } from "mysql";
import { exec } from "child_process";
import { promisify } from "util";

// Configuration interface
interface DatabaseConfig {
    host: string;
    user: string;
    password: string;
    database?: string; // Optional for global connection
}

// Master status interface
interface MasterStatus {
    File: string;
    Position: number;
    Binlog_Do_DB?: string;
    Binlog_Ignore_DB?: string;
}

function getConnection(config: DatabaseConfig): Connection {
    return mysql.createConnection(config);
}

function getMasterStatus(config: DatabaseConfig): Promise<MasterStatus> {
    return new Promise((resolve, reject) => {
        const connection = getConnection(config);
        connection.query("SHOW MASTER STATUS", (error, results) => {
            connection.end();
            if (error) reject(error);
            else resolve(results[0] as MasterStatus);
        });
    });
}

async function syncDatabases() {
    const config: DatabaseConfig = {
        host: "localhost",
        user: "root",
        password: "your_password",
    };

    let lastPosition: number | null = null; // Track last synced position

    while (true) {
        try {
            // Get current master status
            const { File, Position } = await getMasterStatus(config);

            // Determine start position (use lastPosition or 4 if first run)
            const startPosition = lastPosition !== null ? lastPosition + 1 : 4;
            if (startPosition >= Position) {
                await new Promise((resolve) => setTimeout(resolve, 5000)); // Wait 5 seconds if no new changes
                continue;
            }

            // Execute mysqlbinlog to get changes
            const execPromise = promisify(exec);
            const { stdout } = await execPromise(
                `mysqlbinlog --database=db_master ${File} --start-position=${startPosition} --stop-position=${Position}`
            );

            if (stdout) {
                const connection = getConnection({
                    ...config,
                    database: "db_slave",
                });
                return new Promise((resolve, reject) => {
                    connection.query(stdout, (error) => {
                        connection.end();
                        if (error) reject(error);
                        else {
                            lastPosition = Position;
                            console.log(
                                `Synced up to position ${Position} at ${new Date().toISOString()}`
                            );
                            resolve(null);
                        }
                    });
                });
            }
        } catch (error) {
            console.error("Sync error:", error);
        }

        await new Promise((resolve) => setTimeout(resolve, 5000)); // Check every 5 seconds
    }
}

// Initialize db_slave with db_master data
async function initializeSlave() {
    const config: DatabaseConfig = {
        host: "localhost",
        user: "root",
        password: "your_password",
    };

    try {
        await promisify(exec)(
            `mysqldump -u ${config.user} -p${config.password} db_master > db_master_backup.sql`
        );
        await promisify(exec)(
            `mysql -u ${config.user} -p${config.password} db_slave < db_master_backup.sql`
        );
        console.log("Slave initialized with master data");
    } catch (error) {
        console.error("Initialization error:", error);
    }
}

// Run the sync process
async function main() {
    await initializeSlave();
    await syncDatabases();
}

main().catch(console.error);