<?php
// ============================================================
// SURVAM - Database Connection (PDO Singleton)
// ============================================================
require_once __DIR__ . '/config.php';

class DB {
    private static ?PDO $instance = null;

    public static function get(): PDO {
        if (self::$instance === null) {
            $dsn = "mysql:host=" . DB_HOST . ";dbname=" . DB_NAME . ";charset=" . DB_CHARSET;
            $options = [
                PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
                PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
                PDO::ATTR_EMULATE_PREPARES   => false,
                PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8mb4 COLLATE utf8mb4_unicode_ci",
            ];
            try {
                self::$instance = new PDO($dsn, DB_USER, DB_PASS, $options);
            } catch (PDOException $e) {
                // Never expose DB details in production
                error_log("DB Connection failed: " . $e->getMessage());
                die(json_encode(['error' => 'Database connection failed. Please try again later.']));
            }
        }
        return self::$instance;
    }

    // Quick helper: run a query with params, return PDOStatement
    public static function query(string $sql, array $params = []): PDOStatement {
        $stmt = self::get()->prepare($sql);
        $stmt->execute($params);
        return $stmt;
    }

    // Fetch single row
    public static function row(string $sql, array $params = []): ?array {
        $row = self::query($sql, $params)->fetch();
        return $row ?: null;
    }

    // Fetch all rows
    public static function all(string $sql, array $params = []): array {
        return self::query($sql, $params)->fetchAll();
    }

    // Insert and return last insert id
    public static function insert(string $sql, array $params = []): int {
        self::query($sql, $params);
        return (int) self::get()->lastInsertId();
    }

    // Get app setting from DB
    public static function getSetting(string $key, string $default = ''): string {
        $row = self::row("SELECT `value` FROM settings WHERE `key` = ?", [$key]);
        return $row ? (string)($row['value'] ?? $default) : $default;
    }
}