perf(mobile): summarize diff review counts in one pass (#17460)

mobile/src/session/mobile-diff-review-queue.test.ts

@@ -5,7 +5,9 @@ import type { MobileGitStatusEntry } from '../source-control/mobile-git-status'
 import {
   buildMobileDiffReviewQueue,
   createMobileDiffReviewFileKey,
-  filterMobileDiffReviewQueue
+  filterMobileDiffReviewQueue,
+  summarizeMobileDiffReviewQueue,
+  type MobileDiffReviewQueueItem
 } from './mobile-diff-review-queue'
 
 const emptyReviewState: MobileDiffReviewState = { version: 1, files: {} }
@@ -117,4 +119,61 @@ describe('mobile diff review queue', () => {
       'b.ts'
     ])
   })
+
+  it('summarizes review counts in one pass without rereading item fields', () => {
+    const entryCount = 1_000
+    const reads = { isReviewed: 0, scope: 0, canStage: 0 }
+    let expectedReviewedCount = 0
+    let expectedReviewedUnstagedItems = 0
+    let expectedReviewedUnstagedCount = 0
+    const queue = Array.from({ length: entryCount }, (_, index) => {
+      const isReviewed = index % 2 === 0
+      const scope = index % 3 === 0 ? 'unstaged' : 'staged'
+      const canStage = index % 5 === 0
+      if (isReviewed) {
+        expectedReviewedCount += 1
+        if (scope === 'unstaged') {
+          expectedReviewedUnstagedItems += 1
+          if (canStage) {
+            expectedReviewedUnstagedCount += 1
+          }
+        }
+      }
+      const item = {} as MobileDiffReviewQueueItem
+      Object.defineProperties(item, {
+        isReviewed: {
+          enumerable: true,
+          get: () => {
+            reads.isReviewed += 1
+            return isReviewed
+          }
+        },
+        scope: {
+          enumerable: true,
+          get: () => {
+            reads.scope += 1
+            return scope
+          }
+        },
+        canStage: {
+          enumerable: true,
+          get: () => {
+            reads.canStage += 1
+            return canStage
+          }
+        }
+      })
+      return item
+    })
+
+    expect(summarizeMobileDiffReviewQueue(queue)).toEqual({
+      reviewedCount: expectedReviewedCount,
+      reviewedUnstagedCount: expectedReviewedUnstagedCount
+    })
+    expect(reads).toEqual({
+      isReviewed: entryCount,
+      scope: expectedReviewedCount,
+      canStage: expectedReviewedUnstagedItems
+    })
+  })
 })

mobile/src/session/mobile-diff-review-queue.ts

@@ -272,3 +272,25 @@ export function filterMobileDiffReviewQueue(
       return [...queue]
   }
 }
+
+export type MobileDiffReviewQueueSummary = {
+  reviewedCount: number
+  reviewedUnstagedCount: number
+}
+
+export function summarizeMobileDiffReviewQueue(
+  queue: readonly MobileDiffReviewQueueItem[]
+): MobileDiffReviewQueueSummary {
+  let reviewedCount = 0
+  let reviewedUnstagedCount = 0
+  for (const item of queue) {
+    if (!item.isReviewed) {
+      continue
+    }
+    reviewedCount += 1
+    if (item.scope === 'unstaged' && item.canStage) {
+      reviewedUnstagedCount += 1
+    }
+  }
+  return { reviewedCount, reviewedUnstagedCount }
+}

mobile/src/session/use-mobile-diff-review-controller.ts

@@ -9,6 +9,7 @@ import {
   buildMobileDiffReviewQueue,
   filterMobileDiffReviewQueue,
   mobileDiffReviewCommentMatchesItem,
+  summarizeMobileDiffReviewQueue,
   type MobileDiffReviewQueueFilter,
   type MobileDiffReviewQueueItem
 } from './mobile-diff-review-queue'
@@ -133,12 +134,12 @@ export function useMobileDiffReviewController(input: ControllerInput) {
 
   const filteredQueue = useMemo(() => filterMobileDiffReviewQueue(queue, filter), [filter, queue])
   const currentItem = filteredQueue[currentIndex] ?? null
-  const reviewedCount = queue.filter((item) => item.isReviewed).length
+  const { reviewedCount, reviewedUnstagedCount } = useMemo(
+    () => summarizeMobileDiffReviewQueue(queue),
+    [queue]
+  )
   const unsentComments =
     screenState.kind === 'ready' ? getUnsentMobileDiffComments(screenState.comments) : []
-  const reviewedUnstagedCount = queue.filter(
-    (item) => item.scope === 'unstaged' && item.isReviewed && item.canStage
-  ).length
 
   useEffect(() => {
     seededInitialTargetRef.current = false