<?php

declare(strict_types=1);

namespace Glacier\Core;

use PDO;

/**
 * PDO 数据访问封装（单库多表，架构约定见 docs/architecture.md §3.5）。
 * - 一律 prepared statement（防注入）
 * - utf8mb4 + 会话时区 UTC+8（三层统一约定）
 * - 异常模式（ERRMODE_EXCEPTION）
 */
final class Database
{
    private static ?PDO $pdo = null;

    public static function pdo(): PDO
    {
        if (self::$pdo === null) {
            $host = (string) Config::get('db.host', '127.0.0.1');
            $port = (int) Config::get('db.port', 3306);
            $name = (string) Config::get('db.name', 'glacier');
            $charset = (string) Config::get('db.charset', 'utf8mb4');
            $user = (string) Config::get('db.user', 'root');
            $pass = (string) Config::get('db.pass', '');

            $dsn = "mysql:host={$host};port={$port};dbname={$name};charset={$charset}";
            self::$pdo = new PDO($dsn, $user, $pass, [
                PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
                PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
                PDO::ATTR_EMULATE_PREPARES => false,
                PDO::ATTR_TIMEOUT => 5,
            ]);
            self::$pdo->exec("SET time_zone = '+08:00'");
        }
        return self::$pdo;
    }

    /** 执行 prepared statement（唯一写库/查询路径）。 */
    public static function run(string $sql, array $params = []): \PDOStatement
    {
        $stmt = self::pdo()->prepare($sql);
        $stmt->execute($params);
        return $stmt;
    }

    public static function fetchAll(string $sql, array $params = []): array
    {
        return self::run($sql, $params)->fetchAll();
    }

    public static function fetchOne(string $sql, array $params = []): ?array
    {
        $row = self::run($sql, $params)->fetch();
        return $row === false ? null : $row;
    }

    public static function fetchValue(string $sql, array $params = []): mixed
    {
        $value = self::run($sql, $params)->fetchColumn();
        return $value === false ? null : $value;
    }

    /** 插入一行（表名白名单校验），返回自增 ID。 */
    public static function insert(string $table, array $data): int
    {
        if (!preg_match('/^[a-z][a-z0-9_]*$/', $table)) {
            throw new \InvalidArgumentException("非法表名: {$table}");
        }
        $q = chr(96); // 反引号字符，MySQL 标识符引用
        $columns = array_keys($data);
        $quoted = array_map(static fn(string $c) => $q . $c . $q, $columns);
        $sql = sprintf(
            'INSERT INTO %s (%s) VALUES (%s)',
            $table,
            implode(', ', $quoted),
            implode(', ', array_map(static fn(string $c) => ':' . $c, $columns))
        );
        self::run($sql, $data);
        return (int) self::pdo()->lastInsertId();
    }
}