export type MobileWebViewHistoryStateMessage = {
  canGoBack: boolean;
};

export function parseMobileWebViewHistoryStateMessage(
  rawMessage: string,
): MobileWebViewHistoryStateMessage | null {
  try {
    const value = JSON.parse(rawMessage) as unknown;
    if (!value || typeof value !== 'object') {
      return null;
    }

    const candidate = value as {
      type?: unknown;
      canGoBack?: unknown;
    };
    if (
      candidate.type !== 'genarrative.mobile.historyState' ||
      typeof candidate.canGoBack !== 'boolean'
    ) {
      return null;
    }

    return {
      canGoBack: candidate.canGoBack,
    };
  } catch {
    return null;
  }
}