<?php
/**
 * Persistent maintenance owned by the explicit schema migration workflow.
 *
 * @package ABeCeBooking
 */
namespace ABeCe\Booking\Infrastructure\Database;

use RuntimeException;

/** The gate survives a plugin binary swap and never expires while migration is incomplete. */
final class OfflineGate {
	/** @param \wpdb $wpdb The guarded site's connection. */
	public function __construct( private readonly \wpdb $wpdb ) {}

	/** @return array<string, string> Fixed owned paths and their exact expected contents. */
	private function files(): array {
		$identity = hash( 'sha256', DB_NAME . ':' . $this->wpdb->prefix );
		$notice   = '<?php' . "\n// ABeCe Booking schema13 maintenance: " . $identity . "\n";
		$mu       = $notice . "defined('ABSPATH') || exit;\nif (PHP_SAPI !== 'cli') { http_response_code(503); header('Retry-After: 600'); exit('Temporarily unavailable for scheduled maintenance.'); }\n";
		$core     = $notice . "\$upgrading = PHP_SAPI === 'cli' ? 0 : time();\n";
		return array(
			WPMU_PLUGIN_DIR . '/abece-booking-schema13-maintenance.php' => $mu,
			ABSPATH . '.maintenance' => $core,
		);
	}

	/** @return void */
	public function install(): void {
		if ( PHP_SAPI !== 'cli' ) {
			throw new RuntimeException( 'ABECE_BOOKING_OFFLINE_CLI_REQUIRED' );
		}
		if ( ! is_dir( WPMU_PLUGIN_DIR ) && ! wp_mkdir_p( WPMU_PLUGIN_DIR ) ) {
			throw new RuntimeException( 'ABECE_BOOKING_GATE_DIRECTORY_UNWRITABLE' );
		}
		foreach ( $this->files() as $path => $content ) {
			if ( file_exists( $path ) ) {
				if ( file_get_contents( $path ) !== $content ) {
					throw new RuntimeException( 'ABECE_BOOKING_FOREIGN_MAINTENANCE_FILE' );
				}
				continue;
			}
			$temp = $path . '.' . bin2hex( random_bytes( 10 ) ) . '.tmp';
			if ( file_put_contents( $temp, $content, LOCK_EX ) !== strlen( $content ) || ! chmod( $temp, 0644 ) ) {
				throw new RuntimeException( 'ABECE_BOOKING_GATE_WRITE_FAILED' );
			}
			// Atomic no-clobber publication; never overwrite another maintenance owner.
			$published = link( $temp, $path );
			unlink( $temp );
			if ( ! $published ) {
				throw new RuntimeException( 'ABECE_BOOKING_GATE_PUBLISH_FAILED' );
			}
		}
		if ( ! $this->active() ) {
			throw new RuntimeException( 'ABECE_BOOKING_GATE_NOT_ACTIVE' );
		}
	}

	/** @return bool */
	public function active(): bool {
		foreach ( $this->files() as $path => $content ) {
			if ( ! is_file( $path ) || file_get_contents( $path ) !== $content ) {
				return false;
			}
		}
		return true;
	}

	/** @return void */
	public function release(): void {
		if ( PHP_SAPI !== 'cli' || ! DatabaseState::ready( $this->wpdb ) || ! $this->active() ) {
			throw new RuntimeException( 'ABECE_BOOKING_GATE_RELEASE_REFUSED' );
		}
		// Remove the core marker last, after the full current namespace is confirmed.
		foreach ( $this->files() as $path => $content ) {
			if ( file_get_contents( $path ) !== $content || ! unlink( $path ) ) {
				throw new RuntimeException( 'ABECE_BOOKING_GATE_RELEASE_FAILED' );
			}
		}
	}

	/**
	 * Wait for other site database sessions; never kill workers or unrelated sites.
	 *
	 * @param int $seconds Maximum time to wait.
	 * @return void
	 */
	public function drain( int $seconds = 15 ): void {
		if ( ! $this->active() ) {
			throw new RuntimeException( 'ABECE_BOOKING_GATE_NOT_ACTIVE' );
		}
		$id               = (int) $this->wpdb->get_var( 'SELECT CONNECTION_ID()' );
		$waiting_migrator = $this->wpdb->prepare( 'SELECT GET_LOCK(%s,15)', Tables::lock( $this->wpdb, 'schema' ) );
		$deadline         = microtime( true ) + $seconds;
		do {
			$processes = $this->wpdb->get_results( 'SHOW FULL PROCESSLIST', ARRAY_A );
			if ( $this->wpdb->last_error ) {
				throw new RuntimeException( 'ABECE_BOOKING_DRAIN_CHECK_FAILED' );
			}
			$others = array_filter( $processes, static fn( array $row ): bool => ( $row['db'] ?? '' ) === DB_NAME && (int) $row['Id'] !== $id && ( $row['Info'] ?? '' ) !== $waiting_migrator );
			if ( ! $others ) {
				return;
			}
			usleep( 100000 );
		} while ( microtime( true ) < $deadline );
		throw new RuntimeException( 'ABECE_BOOKING_ACTIVE_DATABASE_WORKERS' );
	}
}