package utils;

import java.lang.reflect.Proxy;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;

public final class ConnectionManager {
    private static final String DB_URL_KEY = "db.url";
    private static final String DB_USER_KEY = "db.user";
    private static final String DB_PASSWORD_KEY = "db.password";
    private static final String DB_POOL_SIZE_KEY = "db.pool.size";
    private static final int DEFAULT_POOL_SIZE = 10;
    private static BlockingQueue<Connection> pool;

    static {
        loadDriver();
        initConnectionPool();
    }

    private static void loadDriver() {
        try {
            Class.forName("org.postgresql.Driver");
            Class.forName("utils.UrlPath");
        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        }
    }

    private static void initConnectionPool() {
        String poolSize = PropertiesUtil.get(DB_POOL_SIZE_KEY);
        int size = poolSize == null ? DEFAULT_POOL_SIZE : Integer.parseInt(poolSize);

        pool = new ArrayBlockingQueue<>(size);

        for (int i = 0; i < size; i++) {
            Connection connection = open();
            var proxyConnection = (Connection) Proxy.newProxyInstance(ConnectionManager.class.getClassLoader(),
                    new Class[]{Connection.class},
                    (proxy, method, args) -> method.getName().equals("close") ?
                            pool.add((Connection) proxy) :
                            method.invoke(connection, args)
            );
            pool.add(proxyConnection);
        }
    }

    public static Connection get() {
        try {
            return pool.take();
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
    }

    private static Connection open() {
        try {
            return DriverManager.getConnection(PropertiesUtil.get(DB_URL_KEY),
                    PropertiesUtil.get(DB_USER_KEY),
                    PropertiesUtil.get(DB_PASSWORD_KEY));

        } catch (SQLException e) {
            throw new RuntimeException(e);
        }
    }

    private ConnectionManager() {
    }
}