<?php
/**
 * advanced-cache.php drop-in installer.
 *
 * @package NBHPerformance
 */

namespace NBH\Performance\Modules\CacheEngine;

/**
 * Advanced-cache.php drop-in installer.
 */
final class DropInInstaller {
	const MARKER = 'NBH_PERFORMANCE_DROPIN';

	/**
	 * Install or refresh the NBH Performance page-cache drop-in.
	 *
	 * @return bool
	 */
	public function install() {
		$source = NBH_PERFORMANCE_PATH . 'advanced-cache.php';
		$target = WP_CONTENT_DIR . '/advanced-cache.php';

		if ( ! is_readable( $source ) ) {
			update_option( 'nbh_performance_dropin_error', 'source_unreadable', false );
			return false;
		}

		$status = $this->inspect( $target );
		if ( 'foreign' === $status || 'unreadable' === $status ) {
			update_option( 'nbh_performance_dropin_conflict', 1, false );
			return false;
		}

		// A previously reported conflict may have been removed manually.
		delete_option( 'nbh_performance_dropin_conflict' );

		if ( 'owned' === $status ) {
			$source_hash = hash_file( 'sha256', $source );
			$target_hash = hash_file( 'sha256', $target );
			if ( is_string( $source_hash ) && is_string( $target_hash ) && hash_equals( $source_hash, $target_hash ) ) {
				delete_option( 'nbh_performance_dropin_error' );
				update_option( 'nbh_performance_dropin_installed', 1, false );
				return true;
			}
		}

		$temp = tempnam( WP_CONTENT_DIR, '.nbh-performance-dropin-' );
		if ( false === $temp ) {
			update_option( 'nbh_performance_dropin_error', 'temp_unavailable', false );
			return false;
		}

		// The temporary file must be removed after every unsuccessful install.
		if ( ! \NBH\Performance\Modules\Core\Filesystem::copy( $source, $temp ) ) {
			\NBH\Performance\Modules\Core\Filesystem::unlink( $temp );
			update_option( 'nbh_performance_dropin_error', 'copy_failed', false );
			return false;
		}

		$source_hash = hash_file( 'sha256', $source );
		$temp_hash   = hash_file( 'sha256', $temp );
		if ( ! is_string( $source_hash ) || ! is_string( $temp_hash ) || ! hash_equals( $source_hash, $temp_hash ) ) {
			\NBH\Performance\Modules\Core\Filesystem::unlink( $temp );
			update_option( 'nbh_performance_dropin_error', 'integrity_failed', false );
			return false;
		}

		// Reject a newly created foreign drop-in before the final move.
		if ( $status !== $this->inspect( $target ) ) {
			\NBH\Performance\Modules\Core\Filesystem::unlink( $temp );
			update_option( 'nbh_performance_dropin_conflict', 1, false );
			update_option( 'nbh_performance_dropin_error', 'target_changed', false );
			return false;
		}

		\NBH\Performance\Modules\Core\Filesystem::chmod( $temp, 0644 );
		// Use an atomic same-directory replacement for the verified wp-content
		// drop-in; WP_Filesystem_Direct::move() deletes before renaming.
		$installed = \NBH\Performance\Modules\Core\Filesystem::atomic_replace( $temp, $target );
		if ( ! $installed ) {
			\NBH\Performance\Modules\Core\Filesystem::unlink( $temp );
			update_option( 'nbh_performance_dropin_error', 'rename_failed', false );
		} else {
			delete_option( 'nbh_performance_dropin_error' );
			delete_option( 'nbh_performance_dropin_conflict' );
		}

		update_option( 'nbh_performance_dropin_installed', (int) $installed, false );
		return $installed;
	}

	/**
	 * Reconcile the stored conflict flag with the actual filesystem state.
	 *
	 * @return string missing|owned|foreign|unreadable
	 */
	public function reconcile() {
		$target = WP_CONTENT_DIR . '/advanced-cache.php';
		$status = $this->inspect( $target );

		if ( 'foreign' === $status || 'unreadable' === $status ) {
			update_option( 'nbh_performance_dropin_conflict', 1, false );
		} else {
			delete_option( 'nbh_performance_dropin_conflict' );
		}

		return $status;
	}

	/**
	 * Inspect a drop-in without generating filesystem warnings.
	 *
	 * @param string $file Drop-in path.
	 * @return string
	 */
	public function inspect( $file ) {
		// A dangling symlink does not satisfy file_exists(), but is not a safe target.
		if ( is_link( $file ) ) {
			return 'unreadable';
		}
		if ( ! file_exists( $file ) ) {
			return 'missing';
		}
		if ( ! is_readable( $file ) || ! is_file( $file ) ) {
			return 'unreadable';
		}
		return $this->is_ours( $file ) ? 'owned' : 'foreign';
	}

	/**
	 * Determine whether a readable drop-in belongs to NBH Performance.
	 *
	 * @param string $file Drop-in path.
	 * @return bool
	 */
	public function is_ours( $file ) {
		if ( is_link( $file ) || ! is_readable( $file ) || ! is_file( $file ) ) {
			return false;
		}
		$header = \NBH\Performance\Modules\Core\Filesystem::get_contents( $file );
		if ( ! is_string( $header ) ) {
			return false;
		}
		return false !== strpos( substr( $header, 0, 1024 ), self::MARKER );
	}
}