<?php
/**
 * Makes a source server's CREATE TABLE runnable on this server.
 *
 * @package Shiftora\Support\Db
 */

declare(strict_types=1);

namespace Shiftora\Support\Db;

use Shiftora\Support\ServerCapabilities;

// Prevent direct file access.
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * MySQL 8 prints a versioned comment around DEFAULT ENCRYPTION='N' and utf8mb4_0900_*
 * collations in SHOW CREATE TABLE. MariaDB runs the comment's content as live SQL because
 * its own version number is higher, then rejects the clause and the collation.
 * On MySQL nothing is touched here; CollationMap still remaps what that server lacks.
 */
final class ServerDdl {

	/** What MariaDB has closest to each MySQL 8 collation. */
	private const MARIADB_STAND_INS = [
		'utf8mb4_0900_bin' => 'utf8mb4_bin',
	];

	private const MARIADB_DEFAULT_STAND_IN = 'utf8mb4_unicode_520_ci';

	/** Prepares a CREATE TABLE for this server. */
	public static function adapt( \wpdb $wpdb, string $sql ): string {
		// phpcs:ignore WordPress.DB.DirectDatabaseQuery -- server metadata, nothing to cache
		$raw = (string) $wpdb->get_var( 'SELECT VERSION()' );

		if ( ServerCapabilities::is_mariadb_version( $raw ) ) {
			$sql = self::for_mariadb( $sql, CollationMap::known( $wpdb ) );
		}

		return CollationMap::adapt( $wpdb, $sql );
	}

	/**
	 * Removes MySQL 8 only versioned comments and maps its 0900 collations.
	 *
	 * @param array<string, true> $known Collations the server reports, lowercase; empty when unreadable.
	 */
	public static function for_mariadb( string $sql, array $known ): string {
		// Versions 8NNNN are MySQL 8 only. Older ones, such as 40101, are portable and stay.
		$sql = (string) preg_replace( '/[ \t]*\/\*!8\d{4}\b.*?\*\//s', '', $sql );

		return (string) preg_replace_callback(
			'/\butf8mb4_0900_[a-z0-9_]+/i',
			static function ( array $m ) use ( $known ): string {
				$name = strtolower( $m[0] );
				if ( isset( $known[ $name ] ) ) {
					return $m[0];
				}

				return self::MARIADB_STAND_INS[ $name ] ?? self::MARIADB_DEFAULT_STAND_IN;
			},
			$sql
		);
	}
}