<?php
/**
 * Durable restore-point pin ledger.
 *
 * @package Shiftora\Backup
 */

declare(strict_types=1);

namespace Shiftora\Backup;

use RuntimeException;

// phpcs:disable WordPress.Security.EscapeOutput.ExceptionNotEscaped -- Exception messages are not output.

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

/**
 * Tracks which backups retention cleanup must not sweep because a live or
 * failed migration could still restore from them.
 *
 * A lock's transient is only a cache and is lost on an object cache flush.
 * This table is the durable counterpart, written and cleared with the lock.
 */
final class BackupPinStore {

	private string $table;

	public function __construct( private readonly \wpdb $wpdb ) {
		$this->table = $wpdb->prefix . 'shiftora_backup_pins';
	}

	/**
	 * The CREATE TABLE statement for dbDelta, without IF NOT EXISTS because
	 * dbDelta cannot diff a declaration that has it.
	 */
	public static function table_ddl( string $table, string $charset_collate ): string {
		return "CREATE TABLE `{$table}` (
			backup_id BIGINT UNSIGNED NOT NULL,
			migration_id BIGINT UNSIGNED NOT NULL,
			pin_kind VARCHAR(16) NOT NULL DEFAULT 'recovery',
			created_at DATETIME NOT NULL,
			PRIMARY KEY (backup_id),
			KEY migration_id (migration_id)
		) {$charset_collate}";
	}

	/** Records or refreshes the pin a lock places on its restore point. */
	public function pin( int $backup_id, int $migration_id ): void {
		$wpdb   = $this->wpdb;
		$now    = current_time( 'mysql', true );
		// phpcs:ignore WordPress.DB.DirectDatabaseQuery -- custom table, fresh read required
		$result = $wpdb->query(
			$wpdb->prepare(
				"INSERT INTO %i
				(backup_id, migration_id, pin_kind, created_at)
				VALUES (%d, %d, 'recovery', %s)
				ON DUPLICATE KEY UPDATE migration_id = VALUES(migration_id), pin_kind = VALUES(pin_kind), created_at = VALUES(created_at)",
				$this->table,
				$backup_id,
				$migration_id,
				$now
			)
		);

		if ( false === $result ) {
			throw new RuntimeException( "Failed to pin backup {$backup_id}: {$this->wpdb->last_error}" );
		}
	}

	/** Releases every pin a migration placed, when its lock is cleared. */
	public function unpin_for_migration( int $migration_id ): void {
		$wpdb   = $this->wpdb;
		// phpcs:ignore WordPress.DB.DirectDatabaseQuery -- custom table, fresh read required
		$result = $wpdb->query(
			$wpdb->prepare( 'DELETE FROM %i WHERE migration_id = %d', $this->table, $migration_id )
		);

		if ( false === $result ) {
			throw new RuntimeException( "Failed to unpin migration {$migration_id}: {$this->wpdb->last_error}" );
		}
	}

	/**
	 * Backup ids retention may not delete.
	 *
	 * @return int[]
	 */
	public function pinned_backup_ids(): array {
		$wpdb = $this->wpdb;
		// phpcs:ignore WordPress.DB.DirectDatabaseQuery -- custom table, fresh read required
		$rows = $wpdb->get_results( $wpdb->prepare( 'SELECT backup_id FROM %i', $this->table ) );
		if ( ! is_array( $rows ) ) {
			return [];
		}

		$ids = array_map( static fn( object $r ): int => (int) $r->backup_id, $rows );
		sort( $ids, SORT_NUMERIC );

		return $ids;
	}

	/**
	 * Migration ids that still hold a pin, for the unfinished-scan filter.
	 *
	 * @return int[]
	 */
	public function pinned_migration_ids(): array {
		$wpdb = $this->wpdb;
		// phpcs:ignore WordPress.DB.DirectDatabaseQuery -- custom table, fresh read required
		$rows = $wpdb->get_results( $wpdb->prepare( 'SELECT DISTINCT migration_id FROM %i', $this->table ) );
		if ( ! is_array( $rows ) ) {
			return [];
		}

		$ids = array_map( static fn( object $r ): int => (int) $r->migration_id, $rows );
		sort( $ids, SORT_NUMERIC );

		return $ids;
	}

	/**
	 * Every current pin, grouped by migration. The durable half of a lock, so a
	 * failed run is still reported after the authorizing transient is gone. Read
	 * once per recovery pass, not per migration.
	 *
	 * @return array<int, int[]> Migration id => backup ids, ascending.
	 */
	public function pins_by_migration(): array {
		$wpdb = $this->wpdb;
		// phpcs:ignore WordPress.DB.DirectDatabaseQuery -- custom table, fresh read required
		$rows = $wpdb->get_results( $wpdb->prepare( 'SELECT migration_id, backup_id FROM %i', $this->table ) );
		if ( ! is_array( $rows ) ) {
			return [];
		}

		$grouped = [];
		foreach ( $rows as $row ) {
			$grouped[ (int) $row->migration_id ][] = (int) $row->backup_id;
		}

		foreach ( $grouped as $migration_id => $backup_ids ) {
			sort( $backup_ids, SORT_NUMERIC );
			$grouped[ $migration_id ] = $backup_ids;
		}
		ksort( $grouped, SORT_NUMERIC );

		return $grouped;
	}

// phpcs:enable WordPress.Security.EscapeOutput.ExceptionNotEscaped
}