refactor: separate discovered totals from flush deltas in LocalProgress

LocalProgress no longer carries bytesTotal/filesTotal — those are
passed separately from ctx.discovered. Pending state reset uses
emptyLocalProgress() instead of manual field-by-field assignment.

Author: rezk2ll

src/migration.ts

@@ -1,11 +1,12 @@
 import type { Logger } from 'pino'
 import type { StackClient } from './stack-client.js'
-import type { MigrationCommand, TrackingError, TrackingSkipped } from './types.js'
+import type { MigrationCommand } from './types.js'
 import {
   setRunning,
   setCompleted,
   setFailed,
   flushProgress,
+  emptyLocalProgress,
   isConflictError,
   type LocalProgress,
 } from './tracking.js'
@@ -43,15 +44,8 @@ async function flush(ctx: MigrationContext): Promise<void> {
   if (ctx.filesSinceFlush === 0 && ctx.pending.errors.length === 0 && ctx.pending.skipped.length === 0) {
     return
   }
-  await flushProgress(ctx.stackClient, ctx.command.migrationId, {
-    ...ctx.pending,
-    bytesTotal: ctx.discovered.bytesTotal,
-    filesTotal: ctx.discovered.filesTotal,
-  })
-  ctx.pending.bytesImported = 0
-  ctx.pending.filesImported = 0
-  ctx.pending.errors = []
-  ctx.pending.skipped = []
+  await flushProgress(ctx.stackClient, ctx.command.migrationId, ctx.pending, ctx.discovered)
+  ctx.pending = emptyLocalProgress()
   ctx.filesSinceFlush = 0
 }
 
@@ -167,7 +161,7 @@ export async function runMigration(
     logger: migrationLogger,
     discovered: { bytesTotal: 0, filesTotal: 0 },
     transferred: { bytes: 0, files: 0 },
-    pending: { bytesImported: 0, filesImported: 0, bytesTotal: 0, filesTotal: 0, errors: [], skipped: [] },
+    pending: emptyLocalProgress(),
     totalErrors: 0,
     totalSkipped: 0,
     filesSinceFlush: 0,

src/tracking.ts

@@ -97,36 +97,39 @@ export async function setFailed(
   }))
 }
 
-/** Local progress state accumulated between flushes. */
+/** Local progress deltas accumulated between flushes. */
 export interface LocalProgress {
   bytesImported: number
   filesImported: number
-  bytesTotal: number
-  filesTotal: number
   errors: TrackingError[]
   skipped: TrackingSkipped[]
 }
 
+export function emptyLocalProgress(): LocalProgress {
+  return { bytesImported: 0, filesImported: 0, errors: [], skipped: [] }
+}
+
 /**
  * Flushes locally accumulated progress to CouchDB in a single write.
- * Merges local deltas into the remote doc. On 409, re-reads _rev and
- * reapplies the patch (external conflict, not self-conflict).
+ * On 409, re-reads _rev and reapplies the patch.
  * @param stackClient - Stack API client
  * @param docId - Tracking document ID
- * @param local - Accumulated local progress to merge
+ * @param local - Accumulated deltas since last flush
+ * @param discovered - Latest discovered totals (bytes_total, files_total)
  */
 export async function flushProgress(
   stackClient: StackClient,
   docId: string,
-  local: LocalProgress
+  local: LocalProgress,
+  discovered: { bytesTotal: number; filesTotal: number }
 ): Promise<void> {
   await updateTracking(stackClient, docId, (doc) => ({
     ...doc,
     progress: {
       bytes_imported: doc.progress.bytes_imported + local.bytesImported,
       files_imported: doc.progress.files_imported + local.filesImported,
-      bytes_total: local.bytesTotal,
-      files_total: local.filesTotal,
+      bytes_total: discovered.bytesTotal,
+      files_total: discovered.filesTotal,
     },
     errors: [...doc.errors, ...local.errors],
     skipped: [...doc.skipped, ...local.skipped],

test/tracking.test.ts

@@ -132,11 +132,9 @@ describe('flushProgress', () => {
     await flushProgress(stack, 'mig-1', {
       bytesImported: 500,
       filesImported: 3,
-      bytesTotal: 9000,
-      filesTotal: 20,
       errors: [{ path: '/new.txt', message: 'new error', at: '2024-01-02T00:00:00Z' }],
       skipped: [{ path: '/dup.txt', reason: 'already exists', size: 42 }],
-    })
+    }, { bytesTotal: 9000, filesTotal: 20 })
 
     const calledDoc = vi.mocked(stack.updateTrackingDoc).mock.calls[0][0]
     // Deltas are added to existing values
@@ -158,9 +156,8 @@ describe('flushProgress', () => {
 
     await flushProgress(stack, 'mig-1', {
       bytesImported: 100, filesImported: 1,
-      bytesTotal: 100, filesTotal: 1,
       errors: [], skipped: [],
-    })
+    }, { bytesTotal: 100, filesTotal: 1 })
 
     // Re-reads doc and reapplies patch
     expect(stack.getTrackingDoc).toHaveBeenCalledTimes(2)