Refactor photo embed analytics to post:photoEmbed:* namespace

Replaces the legacy post:gallery:* events, which only instrumented the
carousel layout (and so were biased by the PostGalleryEmbedEnable rollout)
with a coherent, layout-agnostic family that fires identically across the
single image, 2-4 image grid, and carousel renderers.

The new events all carry uri, authorDid, and an optional feedDescriptor,
and a layout discriminator ('single' | 'grid' | 'carousel') so opens and
impressions are directly comparable across layouts.

- post:photoEmbed:impression: fires once per mount of a post photo embed
- post:photoEmbed:open: fires from the shared onPress in ImageEmbed, so
  all three layouts emit it without per-layout duplication
- post:photoEmbed:carouselSwipe: in-feed carousel swipe (debounced)
- post:photoEmbed:lightboxSwipe: fires from the lightbox pager regardless
  of which layout opened it

The dead post:gallery:impression definition is removed, and
post:gallery:openLightbox / post:gallery:swipe are hard-removed with no
dual-emit period.

Quoted-post photos are attributed to the quoted post (quote.uri /
quote.author.did), not the surrounding post.

src/analytics/metrics/types.ts

@@ -1175,18 +1175,37 @@ export type Events = {
   'profile:associated:germ:self-disconnect': {}
   'profile:associated:germ:self-reconnect': {}
 
-  // Gallery carousel events
+  // Post photo embed events
-  'post:gallery:swipe': {
+  'post:photoEmbed:impression': {
+    layout: 'single' | 'grid' | 'carousel'
+    totalImages: number
+    uri: string
+    authorDid: string
+    feedDescriptor?: string
+  }
+  'post:photoEmbed:open': {
+    layout: 'single' | 'grid' | 'carousel'
+    fromImage: number
+    totalImages: number
+    uri: string
+    authorDid: string
+    feedDescriptor?: string
+  }
+  'post:photoEmbed:carouselSwipe': {
     fromImage: number
     toImage: number
     totalImages: number
+    uri: string
+    authorDid: string
+    feedDescriptor?: string
   }
-  'post:gallery:openLightbox': {
+  'post:photoEmbed:lightboxSwipe': {
+    layout: 'single' | 'grid' | 'carousel'
     fromImage: number
+    toImage: number
     totalImages: number
-  }
+    uri: string
-  'post:gallery:impression': {
+    authorDid: string
-    totalImages: number
+    feedDescriptor?: string
-    postUri: string
   }
 }

src/components/Lightbox/pager/ImagePager.tsx

@@ -39,6 +39,7 @@ import {type Dimensions} from '#/lib/media/types'
 import {useTheme} from '#/alf'
 import {setSystemUITheme} from '#/alf/util/systemUI'
 import {type Lightbox} from '#/components/Lightbox/state'
+import {useAnalytics} from '#/analytics'
 import {IS_IOS} from '#/env'
 import {PlatformInfo} from '../../../../modules/expo-bluesky-swiss-army'
 import {Footer} from '../chrome/Footer'
@@ -228,7 +229,8 @@ function ImageView({
   openProgress: SharedValue<number>
   thumbRects: SharedValue<Record<number, MeasuredDimensions | null>>
 }) {
-  const {images, index: initialImageIndex} = lightbox
+  const {images, index: initialImageIndex, metricsContext} = lightbox
+  const ax = useAnalytics()
   const isAnimated = useMemo(() => canAnimate(lightbox), [lightbox])
   const [isScaled, setIsScaled] = useState(false)
   const [isDragging, setIsDragging] = useState(false)
@@ -377,7 +379,21 @@ function ImageView({
         scrollEnabled={!isScaled}
         initialPage={initialImageIndex}
         onPageSelected={e => {
-          setImageIndex(e.nativeEvent.position)
+          const next = e.nativeEvent.position
+          setImageIndex(prev => {
+            if (metricsContext && prev !== next) {
+              ax.metric('post:photoEmbed:lightboxSwipe', {
+                layout: metricsContext.layout,
+                fromImage: prev + 1,
+                toImage: next + 1,
+                totalImages: images.length,
+                uri: metricsContext.uri,
+                authorDid: metricsContext.authorDid,
+                feedDescriptor: metricsContext.feedDescriptor,
+              })
+            }
+            return next
+          })
           setIsScaled(false)
         }}
         onPageScrollStateChanged={e => {

src/components/Lightbox/state.tsx

@@ -11,10 +11,20 @@ import {useNonReactiveCallback} from '#/lib/hooks/useNonReactiveCallback'
 import {useHotkeysContext} from '#/lib/hotkeys'
 import {type ImageSource} from '#/components/Lightbox/types'
 
+export type LightboxMetricsContext = {
+  layout: 'single' | 'grid' | 'carousel'
+  uri: string
+  authorDid: string
+  feedDescriptor?: string
+}
+
 export type Lightbox = {
   id: string
   images: ImageSource[]
   index: number
+  // Set for post photo embeds so the lightbox can emit post:photoEmbed:lightboxSwipe.
+  // Left unset for non-post contexts (e.g. profile avatar/banner lightbox).
+  metricsContext?: LightboxMetricsContext
 }
 
 const LightboxContext = createContext<{

src/components/Post/Embed/ImageEmbed.tsx

@@ -1,4 +1,4 @@
-import {useRef} from 'react'
+import {useEffect, useRef} from 'react'
 import {InteractionManager, View} from 'react-native'
 import {type AnimatedRef} from 'react-native-reanimated'
 import {Image} from 'expo-image'
@@ -8,7 +8,10 @@ import {atoms as a, tokens} from '#/alf'
 import {AutoSizedImage} from '#/components/images/AutoSizedImage'
 import {Gallery} from '#/components/images/Gallery'
 import {ImageLayoutGrid} from '#/components/images/ImageLayoutGrid'
-import {useLightboxControls} from '#/components/Lightbox/state'
+import {
+  type LightboxMetricsContext,
+  useLightboxControls,
+} from '#/components/Lightbox/state'
 import {type Dimensions} from '#/components/Lightbox/types'
 import {ImageContextMenu} from '#/components/Post/Embed/ImageContextMenu'
 import {PostEmbedViewContext} from '#/components/Post/Embed/types'
@@ -40,6 +43,35 @@ export function ImageEmbed({
       ? images.length > MAX_GRID_IMAGES
       : ax.features.enabled(ax.features.PostGalleryEmbedEnable)
 
+  const layout: 'single' | 'grid' | 'carousel' =
+    images.length === 1 ? 'single' : useExpandedLayout ? 'carousel' : 'grid'
+
+  const postContext =
+    rest.uri && rest.authorDid
+      ? {
+          uri: rest.uri,
+          authorDid: rest.authorDid,
+          feedDescriptor: rest.feedDescriptor,
+        }
+      : undefined
+  const metricsContext: LightboxMetricsContext | undefined = postContext
+    ? {layout, ...postContext}
+    : undefined
+
+  // Impression: one per mount of a post photo embed. Covers all three layouts
+  // identically so the opens/impressions CTR is unbiased by layout.
+  useEffect(() => {
+    if (images.length > 0 && postContext) {
+      ax.metric('post:photoEmbed:impression', {
+        layout,
+        totalImages: images.length,
+        ...postContext,
+      })
+    }
+    // Fire once per mount; intentionally not reactive to post context changes.
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [])
+
   // Captured from AutoSizedImage so the peek-commit handler can reuse the same
   // ref + dims that a tap would — keeps the lightbox's return animation intact.
   const singleContainerRef = useRef<AnimatedRef<any> | null>(null)
@@ -57,6 +89,14 @@ export function ImageEmbed({
       refs: AnimatedRef<any>[],
       fetchedDims: (Dimensions | null)[],
     ) => {
+      if (postContext) {
+        ax.metric('post:photoEmbed:open', {
+          layout,
+          fromImage: index + 1,
+          totalImages: images.length,
+          ...postContext,
+        })
+      }
       openLightbox({
         images: items.map((item, i) => ({
           ...item,
@@ -67,6 +107,7 @@ export function ImageEmbed({
           type: 'image',
         })),
         index,
+        metricsContext,
       })
     }
     const onPressIn = (_: number) => {
@@ -132,6 +173,7 @@ export function ImageEmbed({
             onPressIn={onPressIn}
             viewContext={rest.viewContext}
             isWithinQuote={rest.isWithinQuote}
+            metricsPostContext={postContext}
           />
         </View>
       )

src/components/Post/Embed/index.tsx

@@ -345,6 +345,10 @@ export function QuoteEmbed({
           allowNestedQuotes={
             parentIsWithinQuote ? false : parentAllowNestedQuotes
           }
+          // The photo embed belongs to the quoted post, so attribute its
+          // analytics to the quoted post rather than the parent.
+          uri={quote.uri}
+          authorDid={quote.author.did}
         />
       )}
     </>

src/components/Post/Embed/types.ts

@@ -15,6 +15,12 @@ export type CommonProps = {
   viewContext?: PostEmbedViewContext
   isWithinQuote?: boolean
   allowNestedQuotes?: boolean
+  // Post context for analytics on photo embed events (post:photoEmbed:*).
+  // When the embed has no owning post (e.g. previews), leave these undefined
+  // and no events will be emitted.
+  uri?: string
+  authorDid?: string
+  feedDescriptor?: string
 }
 
 export type EmbedProps = CommonProps & {

src/components/images/Gallery/index.tsx

@@ -55,6 +55,13 @@ interface GalleryProps {
   onPressIn?: (index: number) => void
   viewContext?: PostEmbedViewContext
   isWithinQuote?: boolean
+  // Post context for the in-feed carousel swipe metric. Omit for non-post
+  // contexts (no event will be emitted).
+  metricsPostContext?: {
+    uri: string
+    authorDid: string
+    feedDescriptor?: string
+  }
 }
 
 const Context = createContext<{
@@ -99,6 +106,7 @@ export function Gallery({
   onPressIn,
   viewContext,
   isWithinQuote,
+  metricsPostContext,
 }: GalleryProps) {
   const {t: l} = useLingui()
   const ax = useAnalytics()
@@ -169,13 +177,17 @@ export function Gallery({
   const emitSwipeMetric = useMemo(
     () =>
       debounce((fromIndex: number, toIndex: number) => {
-        ax.metric('post:gallery:swipe', {
+        if (!metricsPostContext) return
+        ax.metric('post:photoEmbed:carouselSwipe', {
           fromImage: fromIndex + 1, // convert to 1-based index for easier analysis
           toImage: toIndex + 1, // convert to 1-based index for easier analysis
           totalImages: images.length,
+          uri: metricsPostContext.uri,
+          authorDid: metricsPostContext.authorDid,
+          feedDescriptor: metricsPostContext.feedDescriptor,
         })
       }, 200),
-    [ax, images.length],
+    [ax, images.length, metricsPostContext],
   )
 
   const setCurrentIndex = (index: number) => {
@@ -277,10 +289,6 @@ export function Gallery({
           renderItem={({item, index}) => {
             const openLightboxAtIndex = onPress
               ? () => {
-                  ax.metric('post:gallery:openLightbox', {
-                    fromImage: index + 1, // convert to 1-based index for easier analysis
-                    totalImages: images.length,
-                  })
                   const refs: AnimatedRef<any>[] = []
                   const dims: (Dimensions | null)[] = []
                   for (let i = 0; i < images.length; i++) {

src/screens/PostThread/components/ThreadItemAnchor.tsx

@@ -414,6 +414,8 @@ const ThreadItemAnchorInner = memo(function ThreadItemAnchorInner({
                     moderation={moderation}
                     viewContext={PostEmbedViewContext.ThreadHighlighted}
                     onOpen={onOpenEmbed}
+                    uri={post.uri}
+                    authorDid={post.author.did}
                   />
                 </View>
               )}

src/screens/PostThread/components/ThreadItemPost.tsx

@@ -349,6 +349,8 @@ const ThreadItemPostInner = memo(function ThreadItemPostInner({
                     embed={post.embed}
                     moderation={moderation}
                     viewContext={PostEmbedViewContext.Feed}
+                    uri={post.uri}
+                    authorDid={post.author.did}
                   />
                 </View>
               )}

src/screens/PostThread/components/ThreadItemTreePost.tsx

@@ -371,6 +371,8 @@ const ThreadItemTreePostInner = memo(function ThreadItemTreePostInner({
                         embed={post.embed}
                         moderation={moderation}
                         viewContext={PostEmbedViewContext.Feed}
+                        uri={post.uri}
+                        authorDid={post.author.did}
                       />
                     </View>
                   )}

src/view/com/post/Post.tsx

@@ -255,6 +255,8 @@ function PostInner({
                     embed={post.embed}
                     moderation={moderation}
                     viewContext={PostEmbedViewContext.Feed}
+                    uri={post.uri}
+                    authorDid={post.author.did}
                   />
                 </View>
               ) : null}

src/view/com/posts/PostFeedItem.tsx

@@ -429,6 +429,7 @@ let FeedItemInner = ({
               onOpenEmbed={onOpenEmbed}
               post={post}
               additionalPostAlerts={additionalPostAlerts}
+              feedDescriptor={feedDescriptor}
             />
             <PostControls
               post={post}
@@ -460,6 +461,7 @@ let PostContent = ({
   postAuthor,
   onOpenEmbed,
   additionalPostAlerts,
+  feedDescriptor,
 }: {
   moderation: ModerationDecision
   richText: RichTextAPI
@@ -468,6 +470,7 @@ let PostContent = ({
   onOpenEmbed: () => void
   post: AppBskyFeedDefs.PostView
   additionalPostAlerts?: AppModerationCause[]
+  feedDescriptor?: string
 }): React.ReactNode => {
   const [limitLines, setLimitLines] = useState(
     () => countLines(richText.text) >= MAX_POST_LINES,
@@ -528,6 +531,9 @@ let PostContent = ({
             moderation={moderation}
             onOpen={onOpenEmbed}
             viewContext={PostEmbedViewContext.Feed}
+            uri={post.uri}
+            authorDid={post.author.did}
+            feedDescriptor={feedDescriptor}
           />
         </View>
       ) : null}