feat: paginate tweet conversations

src/features/posts/page.test.ts

@@ -1,6 +1,10 @@
 import { describe, expect, it } from 'vitest'
-import { flattenPostPages } from './page'
-import type { Post, PostPage } from './types'
+import {
+  flattenConversationPages,
+  flattenPostPages,
+  focalPostFromPages,
+} from './page'
+import type { Post, PostPage, ThreadPage } from './types'
 
 const post = (id: string): Post => ({
   id,
@@ -18,3 +22,29 @@ describe('flattenPostPages', () => {
     expect(flattenPostPages(pages).map(({ id }) => id)).toEqual(['1', '2', '3'])
   })
 })
+
+describe('thread page helpers', () => {
+  const focal = post('2')
+  const pages: ThreadPage[] = [
+    {
+      focalPost: focal,
+      conversationId: '1',
+      nextCursor: 'next',
+      tweets: [post('1'), focal],
+    },
+    {
+      conversationId: '1',
+      tweets: [focal, post('3')],
+    },
+  ]
+
+  it('takes the focal post from the first page', () => {
+    expect(focalPostFromPages(pages)).toEqual(focal)
+  })
+
+  it('deduplicates the conversation and removes the focal post', () => {
+    expect(
+      flattenConversationPages(pages, focal.id).map(({ id }) => id),
+    ).toEqual(['1', '3'])
+  })
+})