<?php
declare(strict_types=1);

namespace App;

final class Database
{
    public static function createPdo(Config $config): ?\PDO
    {
        if (!$config->dbEnabled) {
            return null;
        }

        try {
            $pdo = self::createFromArray($config->db);
            self::ensureKeaSchema($pdo, [
                'auto_init' => $config->dbAutoInit,
                'init_cmd' => $config->dbInitCmd,
                'init_script' => $config->dbInitScript,
                'kea_db_version' => $config->keaDbVersion,
            ]);

            return $pdo;
        } catch (\PDOException $e) {
            http_response_code(500);

            $dbDebug = defined('APP_DB_DEBUG') && APP_DB_DEBUG;
            $details = 'Database connection error.';

            if ($dbDebug) {
                $details .= ' ' . $e->getMessage();
            }

            error_log('[DB] ' . $e->getMessage());
            echo $details;
            exit;
        }
    }

    public static function createBasePdo(Config $config): ?\PDO
    {
        if (!$config->baseDbEnabled || empty($config->baseDb)) {
            return null;
        }

        try {
            return self::createFromArray($config->baseDb);
        } catch (\PDOException $e) {
            http_response_code(500);
            $details = 'Base database connection error.';
            error_log('[Base DB] ' . $e->getMessage());
            echo $details;
            exit;
        }
    }

    public static function createFromArray(array $db): \PDO
    {
        $driver = (string)($db['driver'] ?? '');
        if ($driver === '') {
            throw new \RuntimeException('DB config missing "driver"');
        }

        $dsn = match ($driver) {
            'mysql'  => self::buildMysqlDsn($db),
            'pgsql'  => self::buildPgsqlDsn($db),
            'sqlite' => self::buildSqliteDsn($db),
            default  => throw new \RuntimeException('Unsupported PDO driver: ' . $driver),
        };

        $pdo = new \PDO(
            $dsn,
            (string)($db['user'] ?? ''),
            (string)($db['password'] ?? ''),
            (array)($db['options'] ?? [])
        );

        if ($driver === 'pgsql' && !empty($db['schema'])) {
            $schema = preg_replace('/[^a-zA-Z0-9_]/', '', (string)$db['schema']);
            if ($schema !== '') {
                $pdo->exec('SET search_path TO ' . $schema);
            }
        }

        return $pdo;
    }

    public static function ensureKeaSchema(\PDO $pdo, array $options): void
    {
        $driver = (string)$pdo->getAttribute(\PDO::ATTR_DRIVER_NAME);
        if ($driver !== 'pgsql') {
            return;
        }

        if (!self::tableExists($pdo, 'hosts')) {
            if (!empty($options['auto_init'])) {
                self::initKeaSchema($pdo, $options);
            }
        }

    }

    private static function tableExists(\PDO $pdo, string $table): bool
    {
        $stmt = $pdo->prepare(
            "SELECT 1
             FROM information_schema.tables
             WHERE table_schema = current_schema()
               AND table_name = :table
             LIMIT 1"
        );
        $stmt->execute(['table' => $table]);
        return (bool)$stmt->fetchColumn();
    }

    private static function initKeaSchema(\PDO $pdo, array $options): void
    {
        if (!empty($options['init_cmd'])) {
            self::runInitCommand((string)$options['init_cmd']);
            return;
        }

        $script = $options['init_script'] ?? null;
        if (!$script && !empty($options['kea_db_version'])) {
            $script = __DIR__ . '/../../tools/sql/kea/' . $options['kea_db_version'] . '/dhcpdb_create.pgsql';
        }

        if ($script) {
            self::execSqlFile($pdo, (string)$script);
            return;
        }

        throw new \RuntimeException(
            'DB auto-init enabled but no APP_DB_INIT_CMD or APP_DB_INIT_SCRIPT configured.'
        );
    }

    private static function runInitCommand(string $cmd): void
    {
        $descriptor = [
            1 => ['pipe', 'w'],
            2 => ['pipe', 'w'],
        ];
        $process = proc_open($cmd, $descriptor, $pipes);
        if (!is_resource($process)) {
            throw new \RuntimeException('Failed to start DB init command.');
        }

        $stdout = stream_get_contents($pipes[1]);
        $stderr = stream_get_contents($pipes[2]);
        foreach ($pipes as $pipe) {
            fclose($pipe);
        }
        $code = proc_close($process);

        if ($code !== 0) {
            throw new \RuntimeException('DB init command failed: ' . trim($stderr ?: $stdout));
        }
    }

    private static function execSqlFile(\PDO $pdo, string $path): void
    {
        if (!is_readable($path)) {
            throw new \RuntimeException('DB init script not readable: ' . $path);
        }

        $sql = file_get_contents($path);
        if ($sql === false) {
            throw new \RuntimeException('Failed to read DB init script: ' . $path);
        }

        // Strip psql meta-commands (lines starting with backslash)
        $sql = preg_replace('/^\\\\.+$/m', '', $sql);

        $pdo->exec($sql);
    }

    private static function buildMysqlDsn(array $db): string
    {
        if (empty($db['dbname'])) {
            throw new \RuntimeException('MySQL config missing "dbname"');
        }

        $charset = (string)($db['charset'] ?? 'utf8mb4');

        // Unix socket takes precedence
        if (!empty($db['unix_socket'])) {
            return sprintf(
                'mysql:unix_socket=%s;dbname=%s;charset=%s',
                (string)$db['unix_socket'],
                (string)$db['dbname'],
                $charset
            );
        }

        $host = (string)($db['host'] ?? 'localhost');
        $port = (int)($db['port'] ?? 3306);

        return sprintf(
            'mysql:host=%s;port=%d;dbname=%s;charset=%s',
            $host,
            $port,
            (string)$db['dbname'],
            $charset
        );
    }

    private static function buildPgsqlDsn(array $db): string
    {
        if (empty($db['dbname'])) {
            throw new \RuntimeException('PostgreSQL config missing "dbname"');
        }

        $host = (string)($db['host'] ?? 'localhost');
        $port = (int)($db['port'] ?? 5432);

        // Hinweis: charset gehört bei pgsql nicht in den DSN
        return sprintf(
            'pgsql:host=%s;port=%d;dbname=%s',
            $host,
            $port,
            (string)$db['dbname']
        );
    }

    private static function buildSqliteDsn(array $db): string
    {
        // SQLite kann :memory: oder einen Pfad nutzen
        $path = (string)($db['path'] ?? '');

        if ($path === '') {
            // Default: Memory-DB
            $path = ':memory:';
        }

        // Wenn es ein Pfad ist, stelle sicher, dass das Verzeichnis existiert.
        if ($path !== ':memory:') {
            $dir = \dirname($path);
            if ($dir && !is_dir($dir)) {
                @mkdir($dir, 0775, true);
            }
        }

        return 'sqlite:' . $path;
    }
}