Function fileHistoryGetDiffStats

src/utils/fileHistory.ts:416–486

(
  state: FileHistoryState,
  messageId: UUID,
)

 * if reverting to that snapshot.
 */
export async function fileHistoryGetDiffStats(
  state: FileHistoryState,
  messageId: UUID,
): Promise<DiffStats> {
  if (!fileHistoryEnabled()) {
    return undefined
  }

  const targetSnapshot = state.snapshots.findLast(
    snapshot => snapshot.messageId === messageId,
  )

  if (!targetSnapshot) {
    return undefined
  }

  const results = await Promise.all(
    Array.from(state.trackedFiles, async trackingPath => {
      try {
        const filePath = maybeExpandFilePath(trackingPath)
        const targetBackup = targetSnapshot.trackedFileBackups[trackingPath]

        const backupFileName: BackupFileName | undefined = targetBackup
          ? targetBackup.backupFileName
          : getBackupFileNameFirstVersion(trackingPath, state)

        if (backupFileName === undefined) {
          // Error resolving the backup, so don't touch the file
          logError(
            new Error('FileHistory: Error finding the backup file to apply'),
          )
          logEvent('tengu_file_history_rewind_restore_file_failed', {
            dryRun: true,
          })
          return null
        }

        const stats = await computeDiffStatsForFile(
          filePath,
          backupFileName === null ? undefined : backupFileName,
        )
        if (stats?.insertions || stats?.deletions) {
          return { filePath, stats }
        }
        if (backupFileName === null && (await pathExists(filePath))) {
          // Zero-byte file created after snapshot: counts as changed even
          // though diffLines reports 0/0.
          return { filePath, stats }
        }
        return null
      } catch (error) {
        logError(error)
        logEvent('tengu_file_history_rewind_restore_file_failed', {
          dryRun: true,
        })
        return null
      }
    }),