unt( $entry )
			&& array_key_exists( 'service', $entry )
			&& array_key_exists( 'since', $entry )
			&& is_string( $entry['service'] )
			&& is_int( $entry['since'] );
	}

	private static function invalidate_option_cache( $option_name ) {
		if ( ! function_exists( 'wp_cache_delete' ) ) {
			return;
		}

		wp_cache_delete( $option_name, 'options' );
		wp_cache_delete( 'alloptions', 'options' );
		wp_cache_delete( 'notoptions', 'options' );
	}

	private static function known_project_id( array $history, $key ) {
		if ( ! isset( $history[ $key ]['project_id'] ) ) {
			return '?';
		}

		$project_id = self::normalize_project_id( $history[ $key ]['project_id'] );

		return $project_id ? $project_id : '?';
	}

	private static function normalize_project_id( $project_id ) {
		if ( ! is_int( $project_id ) && ! is_string( $project_id ) ) {
			return '';
		}

		$project_id = trim( (string) $project_id );

		return '' !== $project_id && '0' !== $project_id ? $project_id : '';
	}

	private static function has_access_key( $access_key ) {
		return is_string( $access_key ) && '' !== trim( $access_key );
	}

	private static function is_malformed_access_key( $access_key ) {
		return null !== $access_key && ! is_string( $access_key );
	}

	private static function get_stored_project( $service ) {
		global $sitepress;
		if (
			! is_object( $service )
			|| ! is_object( $sitepress )
			|| ! method_exists( $sitepress, 'get_setting' )
			|| ! class_exists( 'TranslationProxy_Project' )
		) {
			return null;
		}

		$projects = $sitepress->get_setting( 'icl_translation_projects' );
		if ( ! is_array( $projects ) ) {
			return null;
		}

		$service_for_index = clone $service;
		$project_index     = TranslationProxy_Project::generate_service_index( $service_for_index );
		if ( ! is_string( $project_index ) || '' === $project_index || ! array_key_exists( $project_index, $projects ) ) {
			return null;
		}

		return $projects[ $project_index ];
	}

	private static function has_partial_project_credentials( $project ) {
		if ( null === $project ) {
			return false;
		}
		if ( ! is_array( $project ) ) {
			return true;
		}
		if ( array() === $project ) {
			return false;
		}

		if ( ! array_key_exists( 'id', $project ) ) {
			return true;
		}

		return array( 'id' ) !== array_keys( $project )
			|| ! is_string( $project['id'] )
			|| '' !== $project['id'];
	}

	private static function stored_project_has_credentials( $project, $expected_project_id ) {
		return is_array( $project )
			&& isset( $project['id'], $project['access_key'] )
			&& self::normalize_project_id( $project['id'] ) === self::normalize_project_id( $expected_project_id )
			&& self::has_access_key( $project['access_key'] );
	}

	private static function block( $service, $known_project_id, $reason ) {
		$service_id = self::service_key( $service );
		$project_id = self::normalize_project_id( $known_project_id );
		$state      = array(
			'project_id' => $project_id ? $project_id : '?',
			'service_id' => $service_id,
			'reason'     => $reason,
			'time'       => time(),
		);
		$status     = self::persist_blocked_state( $state );
		if ( 'unreadable' === $status ) {
			self::surface_unreadable_blocked_state();
			return;
		}

		if ( 'changed' === $status ) {
			error_log(
				'automatic_project_creation' === $reason
					? sprintf(
						'WPML: BLOCKED automatic Translation Proxy project creation. This site previously used TP project "%s" for service "%s"; reconnect the service explicitly before creating another project.',
						$known_project_id,
						$service_id ? $service_id : '?'
					)
					: ( 'backfill' === $reason
						? sprintf(
							'WPML: Current Translation Proxy credentials do not match the independently recorded project identity for service "%s" (previous project "%s"). No send or project creation was attempted; reconnect the service explicitly before continuing.',
							$service_id ? $service_id : '?',
							$known_project_id
						)
						: sprintf(
							'WPML: BLOCKED a Translation Proxy send with missing or mismatched project credentials. This site previously used TP project "%s"; sending now could silently create a new, empty project or target the wrong project. Restore the translation service configuration (or reconnect the service) before sending.',
							$known_project_id
						)
					)
			);

		}

		add_action( 'admin_notices', [ self::class, 'render_blocked_notice' ] );
	}

	private static function persist_blocked_state( array $state ) {
		global $wpdb;

		if ( ! self::can_compare_and_swap( $wpdb ) ) {
			$missing = new stdClass();
			try {
				$existing = get_option( self::BLOCKED_OPTION, $missing );
			} catch ( Throwable $e ) {
				return 'unreadable';
			}
			if ( $missing !== $existing ) {
				$states = self::decode_blocked_states( $existing );
				if ( null === $states ) {
					return 'unreadable';
				}
				if ( self::blocked_states_contain_identity( $states, $state ) ) {
					return 'same';
				}
				$states[] = $state;

				return update_option( self::BLOCKED_OPTION, self::encode_blocked_states( $states ), false )
					? 'changed'
					: 'unreadable';
			}

			return update_option( self::BLOCKED_OPTION, $state, false ) ? 'changed' : 'unreadable';
		}

		for ( $attempt = 0; $attempt < self::CAS_ATTEMPTS; $attempt++ ) {
			$wpdb->last_error = '';
			$raw              = $wpdb->get_var(
				$wpdb->prepare(
					"SELECT option_value FROM {$wpdb->options} WHERE option_name = %s LIMIT 1",
					self::BLOCKED_OPTION
				)
			);
			if ( $wpdb->last_error ) {
				return 'unreadable';
			}

			$exists = null !== $raw;
			if ( $exists ) {
				try {
					$value = self::unserialize_safety_state( $raw );
				} catch ( Throwable $e ) {
					return 'unreadable';
				}
				$states = self::decode_blocked_states( $value );
				if ( null === $states ) {
					return 'unreadable';
				}
				if ( self::blocked_states_contain_identity( $states, $state ) ) {
					return 'same';
				}
				$states[] = $state;
			} else {
				$states = array( $state );
			}

			$serialized = serialize( self::encode_blocked_states( $states ) );
			if ( $exists ) {
				$written = $wpdb->query(
					$wpdb->prepare(
						"UPDATE {$wpdb->options} SET option_value = %s, autoload = 'no' WHERE option_name = %s AND BINARY option_value = BINARY %s",
						$serialized,
						self::BLOCKED_OPTION,
						$raw
					)
				);
			} else {
				$written = $wpdb->query(
					$wpdb->prepare(
						"INSERT IGNORE INTO {$wpdb->options} (option_name, option_value, autoload) VALUES (%s, %s, 'no')",
						self::BLOCKED_OPTION,
						$serialized
					)
				);
			}

			if ( false === $written ) {
				return 'unreadable';
			}
			self::invalidate_option_cache( self::BLOCKED_OPTION );
			if ( 1 === (int) $written ) {
				return 'changed';
			}
		}

		$record = self::read_blocked_state_record();

		return 'valid' === $record['status'] && self::blocked_states_contain_identity( $record['states'], $state )
			? 'same'
			: 'unreadable';
	}

	private static function blocked_states_contain_identity( array $states, array $needle ) {
		$identity = self::blocked_state_identity( $needle );
		foreach ( $states as $state ) {
			if ( self::blocked_state_identity( $state ) === $identity ) {
				return true;
			}
		}

		return false;
	}

	private static function blocked_state_identity( array $state ) {
		return serialize( array( $state['service_id'], $state['project_id'] ) );
	}

	private static function surface_unreadable_blocked_state() {
		error_log( 'WPML: Translation Proxy operations remain blocked because the independent safety record is unreadable. The original value was preserved; reconnect the service or contact WPML support.' );
		add_action( 'admin_notices', [ self::class, 'render_unreadable_blocked_notice' ] );
	}
}