<?php
/**
 * Table preparation service.
 *
 * MultilingualPress 5 refuses to network-activate when it detects tables
 * with the original MLP2 prefix ({base_prefix}mlp_*). This class renames
 * those tables to a backup prefix ({base_prefix}mlp2bak_*) so that MLP5
 * can activate cleanly. The migration wizard then reads from the renamed
 * backup tables.
 *
 * Original name pattern : {base_prefix}mlp_{suffix}
 * Backup name  pattern  : {base_prefix}mlp2bak_{suffix}
 *
 * @package Robotstxt_Mlp2_Mlp5
 */

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

/**
 * Class Robotstxt_Mlp2_Mlp5_Table_Preparer
 *
 * All methods are static. No instantiation required.
 */
class Robotstxt_Mlp2_Mlp5_Table_Preparer {

	/**
	 * Table name fragment (after base_prefix) that identifies original MLP2 tables.
	 *
	 * @var string
	 */
	const ORIGINAL_FRAGMENT = 'mlp_';

	/**
	 * Table name fragment (after base_prefix) used for renamed backup copies.
	 *
	 * @var string
	 */
	const BACKUP_FRAGMENT = 'mlp2bak_';

	/**
	 * Table suffixes (after base_prefix + ORIGINAL_FRAGMENT) that belong to
	 * this plugin and must never be renamed to backup.
	 *
	 * @var string[]
	 */
	const PLUGIN_TABLE_SUFFIXES = array( 'migrator_log' );

	/**
	 * Return the backup table name for a given original MLP2 table.
	 *
	 * @param string $original_table Full original table name (including base_prefix).
	 * @return string Backup table name, or empty string if not a valid MLP2 table.
	 */
	public static function backup_name( string $original_table ): string {
		global $wpdb;

		$orig_prefix = $wpdb->base_prefix . self::ORIGINAL_FRAGMENT;

		if ( ! str_starts_with( $original_table, $orig_prefix ) ) {
			return '';
		}

		return $wpdb->base_prefix . self::BACKUP_FRAGMENT . substr( $original_table, strlen( $orig_prefix ) );
	}

	/**
	 * Return the original table name for a given backup table.
	 *
	 * @param string $backup_table Full backup table name (including base_prefix).
	 * @return string Original table name, or empty string if not a backup table.
	 */
	public static function original_name( string $backup_table ): string {
		global $wpdb;

		$bak_prefix = $wpdb->base_prefix . self::BACKUP_FRAGMENT;

		if ( ! str_starts_with( $backup_table, $bak_prefix ) ) {
			return '';
		}

		return $wpdb->base_prefix . self::ORIGINAL_FRAGMENT . substr( $backup_table, strlen( $bak_prefix ) );
	}

	/**
	 * Return all tables in the database with the original MLP2 prefix.
	 *
	 * @return string[] Array of full table names.
	 */
	public static function get_original_tables(): array {
		global $wpdb;

		$like = $wpdb->esc_like( $wpdb->base_prefix . self::ORIGINAL_FRAGMENT ) . '%';

		// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching
		$tables = $wpdb->get_col( $wpdb->prepare( 'SHOW TABLES LIKE %s', $like ) );

		return is_array( $tables ) ? $tables : array();
	}

	/**
	 * Return all tables in the database with the backup prefix.
	 *
	 * @return string[] Array of full table names.
	 */
	public static function get_backup_tables(): array {
		global $wpdb;

		$like = $wpdb->esc_like( $wpdb->base_prefix . self::BACKUP_FRAGMENT ) . '%';

		// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching
		$tables = $wpdb->get_col( $wpdb->prepare( 'SHOW TABLES LIKE %s', $like ) );

		return is_array( $tables ) ? $tables : array();
	}

	/**
	 * Whether any original MLP2 tables exist in the database.
	 *
	 * @return bool
	 */
	public static function has_original_tables(): bool {
		return count( self::get_original_tables() ) > 0;
	}

	/**
	 * Whether any backup (renamed) MLP2 tables exist in the database.
	 *
	 * @return bool
	 */
	public static function has_backup_tables(): bool {
		return count( self::get_backup_tables() ) > 0;
	}

	/**
	 * Rename all original MLP2 tables to their backup equivalents.
	 *
	 * Tables that already have a backup copy are skipped. Tables that cannot
	 * be converted to a valid backup name are recorded as errors.
	 *
	 * @return array {
	 *     @type string[] $renamed Tables successfully renamed.
	 *     @type string[] $skipped Tables skipped (backup name already exists).
	 *     @type string[] $errors  Tables that could not be renamed.
	 * }
	 */
	public static function rename_to_backup(): array {
		global $wpdb;

		$result = array(
			'renamed' => array(),
			'skipped' => array(),
			'errors'  => array(),
		);

		foreach ( self::get_original_tables() as $table ) {
			$backup = self::backup_name( $table );

			if ( '' === $backup ) {
				$result['errors'][] = $table;
				continue;
			}

			// Skip tables that belong to this plugin.
			$suffix = substr( $table, strlen( $wpdb->base_prefix . self::ORIGINAL_FRAGMENT ) );
			if ( in_array( $suffix, self::PLUGIN_TABLE_SUFFIXES, true ) ) {
				$result['skipped'][] = $table;
				continue;
			}

			if ( self::table_exists( $backup ) ) {
				$result['skipped'][] = $table;
				continue;
			}

			// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.DirectDatabaseQuery.SchemaChange, WordPress.DB.PreparedSQL.InterpolatedNotPrepared
			$renamed = $wpdb->query( "RENAME TABLE `{$table}` TO `{$backup}`" );

			if ( false === $renamed ) {
				$result['errors'][] = $table;
			} else {
				$result['renamed'][] = $table;
			}
		}

		return $result;
	}

	/**
	 * Restore backup tables to their original names.
	 *
	 * Intended as a recovery mechanism if the rename needs to be undone before
	 * MLP5 has been activated. Tables whose original name already exists in the
	 * database are skipped.
	 *
	 * @return array {
	 *     @type string[] $restored Tables successfully restored.
	 *     @type string[] $skipped  Tables skipped (original name already exists).
	 *     @type string[] $errors   Tables that could not be restored.
	 * }
	 */
	public static function restore_from_backup(): array {
		global $wpdb;

		$result = array(
			'restored' => array(),
			'skipped'  => array(),
			'errors'   => array(),
		);

		foreach ( self::get_backup_tables() as $table ) {
			$original = self::original_name( $table );

			if ( '' === $original ) {
				$result['errors'][] = $table;
				continue;
			}

			if ( self::table_exists( $original ) ) {
				$result['skipped'][] = $table;
				continue;
			}

			// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching, WordPress.DB.DirectDatabaseQuery.SchemaChange, WordPress.DB.PreparedSQL.InterpolatedNotPrepared
			$restored = $wpdb->query( "RENAME TABLE `{$table}` TO `{$original}`" );

			if ( false === $restored ) {
				$result['errors'][] = $table;
			} else {
				$result['restored'][] = $table;
			}
		}

		return $result;
	}

	/**
	 * Check whether a table exists in the database.
	 *
	 * @param string $table Full table name.
	 * @return bool
	 */
	private static function table_exists( string $table ): bool {
		global $wpdb;

		// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.NoCaching
		return (string) $wpdb->get_var( $wpdb->prepare( 'SHOW TABLES LIKE %s', $table ) ) === $table;
	}
}