<?php
/**
 * Clase Database - Manejo de conexión a base de datos
 * Fecha: 13 de noviembre de 2025
 */

class Database {
    private static $instance = null;
    private $pdo;
    
    private function __construct() {
        try {
            $dsn = "mysql:host=" . DB_HOST . ";port=" . DB_PORT . ";dbname=" . DB_NAME . ";charset=" . DB_CHARSET;
            $options = [
                PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
                PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
                PDO::ATTR_EMULATE_PREPARES => false,
                PDO::ATTR_PERSISTENT => true,
                PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES " . DB_CHARSET . " COLLATE utf8mb4_unicode_ci"
            ];
            
            $this->pdo = new PDO($dsn, DB_USER, DB_PASS, $options);
        } catch (PDOException $e) {
            error_log("Database connection failed: " . $e->getMessage());
            throw new Exception("Error de conexión a la base de datos");
        }
    }
    
    public static function getInstance() {
        if (self::$instance === null) {
            self::$instance = new self();
        }
        return self::$instance;
    }
    
    public function getConnection() {
        return $this->pdo;
    }
    
    public function query($sql, $params = []) {
        try {
            $stmt = $this->pdo->prepare($sql);
            $stmt->execute($params);
            return $stmt;
        } catch (PDOException $e) {
            error_log("Query failed: " . $e->getMessage() . " SQL: " . $sql);
            throw new Exception("Error en la consulta a la base de datos");
        }
    }
    
    public function fetch($sql, $params = []) {
        $stmt = $this->query($sql, $params);
        return $stmt->fetch();
    }
    
    public function fetchAll($sql, $params = []) {
        $stmt = $this->query($sql, $params);
        return $stmt->fetchAll();
    }
    
    public function insert($table, $data) {
        $keys = array_keys($data);
        $fields = implode(',', $keys);
        $placeholders = ':' . implode(', :', $keys);
        
        $sql = "INSERT INTO {$table} ({$fields}) VALUES ({$placeholders})";
        $stmt = $this->query($sql, $data);
        
        return $this->pdo->lastInsertId();
    }
    
    public function update($table, $data, $where, $whereParams = []) {
        $fields = [];
        foreach (array_keys($data) as $key) {
            $fields[] = "{$key} = :{$key}";
        }
        $fieldsStr = implode(', ', $fields);
        
        $sql = "UPDATE {$table} SET {$fieldsStr} WHERE {$where}";
        $params = array_merge($data, $whereParams);
        
        return $this->query($sql, $params);
    }
    
    public function delete($table, $where, $params = []) {
        $sql = "DELETE FROM {$table} WHERE {$where}";
        return $this->query($sql, $params);
    }
    
    public function beginTransaction() {
        return $this->pdo->beginTransaction();
    }
    
    public function commit() {
        return $this->pdo->commit();
    }
    
    public function rollback() {
        return $this->pdo->rollback();
    }
    
    public function lastInsertId() {
        return $this->pdo->lastInsertId();
    }
    
    // Prevenir clonación
    private function __clone() {}
    
    // Prevenir deserialización
    public function __wakeup() {
        throw new Exception("Cannot unserialize singleton");
    }
}
?>