<?php
/**
 * Files the Media Library does not know (1.9.0, D-500 gap 10): a report, in bounded steps, of the files in the uploads
 * folder's own files and its year/month folders that belong to no attachment (its file, sizes, original and the backups of
 * WordPress's image editor). Nothing is deleted or moved. Other folders (those of other plugins) are named, not checked.
 *
 * @package AffStackDevImageManager
 */

namespace AffStackDev\ImageManager;

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/** The uploads folder against the Media Library. */
final class Unknown_Files {
	public const OPTION       = 'afsd_im_unknown_files';
	private const SLICE       = 3000;
	private const MAX_LISTED  = 2000;
	private const MAX_FOLDERS = 2400;
	/** Placeholders hosts and security plugins put into folders; they are no media. */
	private const IGNORED = array( 'index.php', 'index.html', 'index.htm', 'web.config' );

	/**
	 * The saved check, or an empty array.
	 *
	 * @return array
	 */
	public static function state(): array {
		$s = get_option( self::OPTION, array() );
		return is_array( $s ) ? $s : array();
	}

	/**
	 * The uploads folder, or ''.
	 *
	 * @return string
	 */
	private static function base(): string {
		$u = wp_get_upload_dir();
		return empty( $u['error'] ) && is_dir( $u['basedir'] ) ? untrailingslashit( $u['basedir'] ) : '';
	}

	/**
	 * The folders checked (the uploads folder itself and its year/month folders) and the other top-level folders.
	 *
	 * @param string $base The uploads folder.
	 * @return array [checked, other]
	 */
	private static function folders( string $base ): array {
		$checked = array( '' );
		$other   = array();
		foreach ( (array) scandir( $base ) as $year ) {
			if ( '.' === $year[0] || ! is_dir( $base . '/' . $year ) ) {
				continue;
			}
			if ( ! preg_match( '/^\d{4}$/D', $year ) ) {
				$other[] = $year;
				continue;
			}
			foreach ( (array) scandir( $base . '/' . $year ) as $month ) {
				if ( preg_match( '/^\d{2}$/D', $month ) && is_dir( $base . '/' . $year . '/' . $month ) && count( $checked ) < self::MAX_FOLDERS ) {
					$checked[] = $year . '/' . $month;
				}
			}
		}
		sort( $other );
		return array( $checked, array_slice( $other, 0, 50 ) );
	}

	/**
	 * The file names in one folder that belong to attachments: each attachment's file, its sizes, its original and the
	 * files WordPress's image editor kept.
	 *
	 * @param string $folder Relative to the uploads folder ('' for the uploads folder itself).
	 * @return array Lower-case file names as keys.
	 */
	private static function known( string $folder ): array {
		global $wpdb;
		if ( '' === $folder ) {
			// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching -- one folder of a bounded check the administrator starts; it must read the current rows.
			$rows = $wpdb->get_results( $wpdb->prepare( "SELECT post_id, meta_value FROM %i WHERE meta_key = '_wp_attached_file' AND meta_value NOT LIKE %s", $wpdb->postmeta, '%/%' ), ARRAY_A );
		} else {
			// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching -- one folder of a bounded check the administrator starts; it must read the current rows.
			$rows = $wpdb->get_results( $wpdb->prepare( "SELECT post_id, meta_value FROM %i WHERE meta_key = '_wp_attached_file' AND meta_value LIKE %s", $wpdb->postmeta, $wpdb->esc_like( $folder . '/' ) . '%' ), ARRAY_A );
		}
		$names = array();
		foreach ( (array) $rows as $row ) {
			$file = (string) $row['meta_value'];
			if ( ( '' === $folder ? '' : $folder ) !== ( str_contains( $file, '/' ) ? dirname( $file ) : '' ) ) {
				continue;
			}
			$names[ strtolower( wp_basename( $file ) ) ] = true;
			$meta                                        = wp_get_attachment_metadata( (int) $row['post_id'] );
			if ( is_array( $meta ) ) {
				foreach ( (array) ( $meta['sizes'] ?? array() ) as $size ) {
					if ( is_array( $size ) && is_string( $size['file'] ?? null ) ) {
						$names[ strtolower( wp_basename( $size['file'] ) ) ] = true;
					}
				}
				if ( is_string( $meta['original_image'] ?? null ) && '' !== $meta['original_image'] ) {
					$names[ strtolower( wp_basename( $meta['original_image'] ) ) ] = true;
				}
			}
			foreach ( (array) get_post_meta( (int) $row['post_id'], '_wp_attachment_backup_sizes', true ) as $backup ) {
				if ( is_array( $backup ) && is_string( $backup['file'] ?? null ) ) {
					$names[ strtolower( wp_basename( $backup['file'] ) ) ] = true;
				}
			}
		}
		return $names;
	}

	/**
	 * Start a check, or continue the saved one, for about eight seconds.
	 *
	 * @param bool $start Start a new check.
	 * @return array The saved check.
	 * @throws \RuntimeException When the check may not run now.
	 */
	public static function step( bool $start ): array {
		$lock = Reviewed_Store::enter();
		try {
			if ( ! current_user_can( 'manage_options' ) || ! current_user_can( 'upload_files' ) ) {
				throw new \RuntimeException( 'unknown_files_access' );
			}
			$token = Repository::acquire( 'unknown_files', 300 );
			if ( ! $token ) {
				throw new \RuntimeException( 'unknown_files_busy' );
			}
			try {
				$base = self::base();
				if ( '' === $base ) {
					throw new \RuntimeException( 'unknown_files_storage' );
				}
				$s = self::state();
				if ( $start ) {
					list( $checked, $other ) = self::folders( $base );
					$s                       = array(
						'v'       => 1,
						'started' => time(),
						'updated' => time(),
						'folders' => $checked,
						'other'   => $other,
						'cursor'  => 0,
						'offset'  => 0,
						'files'   => 0,
						'listed'  => array(),
						'more'    => 0,
						'bytes'   => 0,
						'status'  => 'more',
					);
				} elseif ( ! $s || 'more' !== ( $s['status'] ?? '' ) ) {
					throw new \RuntimeException( 'unknown_files_stale' );
				}
				$until = microtime( true ) + 8;
				while ( 'more' === $s['status'] && microtime( true ) < $until ) {
					if ( $s['cursor'] >= count( $s['folders'] ) ) {
						$s['status'] = 'done';
						break;
					}
					$folder = (string) $s['folders'][ $s['cursor'] ];
					$dir    = '' === $folder ? $base : $base . '/' . $folder;
					$names  = is_dir( $dir ) ? array_values( array_filter( (array) scandir( $dir ), static fn( $n ) => '.' !== $n[0] && is_file( $dir . '/' . $n ) ) ) : array();
					$known  = self::known( $folder );
					foreach ( array_slice( $names, (int) $s['offset'], self::SLICE ) as $name ) {
						++$s['files'];
						if ( isset( $known[ strtolower( $name ) ] ) || in_array( strtolower( $name ), self::IGNORED, true ) ) {
							continue;
						}
						$bytes       = (int) filesize( $dir . '/' . $name );
						$s['bytes'] += $bytes;
						if ( count( $s['listed'] ) < self::MAX_LISTED ) {
							$s['listed'][] = array( ( '' === $folder ? '' : $folder . '/' ) . $name, $bytes, (int) filemtime( $dir . '/' . $name ) );
						} else {
							++$s['more'];
						}
					}
					if ( (int) $s['offset'] + self::SLICE < count( $names ) ) {
						$s['offset'] += self::SLICE;
					} else {
						++$s['cursor'];
						$s['offset'] = 0;
					}
					if ( ! Repository::owns( $token, 'unknown_files' ) ) {
						throw new \RuntimeException( 'unknown_files_busy' );
					}
				}
				$s['updated'] = time();
				if ( ! Reviewed_Store::update_option( self::OPTION, $s, false ) && self::state() !== $s ) {
					throw new \RuntimeException( 'unknown_files_storage' );
				}
				return $s;
			} finally {
				Repository::release( $token, 'unknown_files' );
			}
		} finally {
			Reviewed_Store::leave( $lock );
		}
	}

	/**
	 * Words for the check's error codes.
	 *
	 * @param string $code The code.
	 * @return string
	 */
	public static function human_error( string $code ): string {
		$messages = array(
			'unknown_files_access'  => __( 'Only an administrator who may upload files can check the uploads folder.', 'affstackdev-image-manager' ),
			'unknown_files_busy'    => __( 'Another check of the uploads folder is running. Try again in a few minutes.', 'affstackdev-image-manager' ),
			'unknown_files_storage' => __( 'The uploads folder could not be read, or the check could not be saved.', 'affstackdev-image-manager' ),
			'unknown_files_stale'   => __( 'There is no check to continue. Start a new one.', 'affstackdev-image-manager' ),
		);
		return $messages[ $code ] ?? '';
	}
}