Function processSessionFiles

src/utils/stats.ts:117–368

* Process session files and extract stats. * Can filter by date range.

(
  sessionFiles: string[],
  options: ProcessOptions = {},
)

 * Can filter by date range.
 */
async function processSessionFiles(
  sessionFiles: string[],
  options: ProcessOptions = {},
): Promise<ProcessedStats> {
  const { fromDate, toDate } = options
  const fs = getFsImplementation()

  const dailyActivityMap = new Map<string, DailyActivity>()
  const dailyModelTokensMap = new Map<string, { [modelName: string]: number }>()
  const sessions: SessionStats[] = []
  const hourCounts = new Map<number, number>()
  let totalMessages = 0
  let totalSpeculationTimeSavedMs = 0
  const modelUsageAgg: { [modelName: string]: ModelUsage } = {}
  const shotDistributionMap = feature('SHOT_STATS')
    ? new Map<number, number>()
    : undefined
  // Track parent sessions that already recorded a shot count (dedup across subagents)
  const sessionsWithShotCount = new Set<string>()

  // Process session files in parallel batches for better performance
  const BATCH_SIZE = 20
  for (let i = 0; i < sessionFiles.length; i += BATCH_SIZE) {
    const batch = sessionFiles.slice(i, i + BATCH_SIZE)
    const results = await Promise.all(
      batch.map(async sessionFile => {
        try {
          // If we have a fromDate filter, skip files that haven't been modified since then
          if (fromDate) {
            let fileSize = 0
            try {
              const fileStat = await fs.stat(sessionFile)
              const fileModifiedDate = toDateString(fileStat.mtime)
              if (isDateBefore(fileModifiedDate, fromDate)) {
                return {
                  sessionFile,
                  entries: null,
                  error: null,
                  skipped: true,
                }
              }
              fileSize = fileStat.size
            } catch {
              // If we can't stat the file, try to read it anyway
            }
            // For large files, peek at the session start date before reading everything.
            // Sessions that pass the mtime filter but started before fromDate are skipped
            // (e.g. a month-old session resumed today gets a new mtime write but old start date).
            if (fileSize > 65536) {
              const startDate = await readSessionStartDate(sessionFile)
              if (startDate && isDateBefore(startDate, fromDate)) {
                return {
                  sessionFile,
                  entries: null,
                  error: null,
                  skipped: true,
                }
              }