1 files changed, 170 insertions, 0 deletions
diff --git a/src/state/queries/usePostThread/utils.ts b/src/state/queries/usePostThread/utils.ts
new file mode 100644
index 000000000..b8ab340d8
--- /dev/null
+++ b/src/state/queries/usePostThread/utils.ts
@@ -0,0 +1,170 @@
+import {
+  type AppBskyFeedDefs,
+  AppBskyFeedPost,
+  AppBskyFeedThreadgate,
+  AppBskyUnspeccedDefs,
+  type AppBskyUnspeccedGetPostThreadV2,
+  AtUri,
+} from '@atproto/api'
+
+import {
+  type ApiThreadItem,
+  type ThreadItem,
+  type TraversalMetadata,
+} from '#/state/queries/usePostThread/types'
+import {isDevMode} from '#/storage/hooks/dev-mode'
+import * as bsky from '#/types/bsky'
+
+export function getThreadgateRecord(
+  view: AppBskyUnspeccedGetPostThreadV2.OutputSchema['threadgate'],
+) {
+  return bsky.dangerousIsType<AppBskyFeedThreadgate.Record>(
+    view?.record,
+    AppBskyFeedThreadgate.isRecord,
+  )
+    ? view?.record
+    : undefined
+}
+
+export function getRootPostAtUri(post: AppBskyFeedDefs.PostView) {
+  if (
+    bsky.dangerousIsType<AppBskyFeedPost.Record>(
+      post.record,
+      AppBskyFeedPost.isRecord,
+    )
+  ) {
+    if (post.record.reply?.root?.uri) {
+      return new AtUri(post.record.reply.root.uri)
+    }
+  }
+}
+
+export function getPostRecord(post: AppBskyFeedDefs.PostView) {
+  return post.record as AppBskyFeedPost.Record
+}
+
+export function getTraversalMetadata({
+  item,
+  prevItem,
+  nextItem,
+  parentMetadata,
+}: {
+  item: ApiThreadItem
+  prevItem?: ApiThreadItem
+  nextItem?: ApiThreadItem
+  parentMetadata?: TraversalMetadata
+}): TraversalMetadata {
+  if (!AppBskyUnspeccedDefs.isThreadItemPost(item.value)) {
+    throw new Error(`Expected thread item to be a post`)
+  }
+  const repliesCount = item.value.post.replyCount || 0
+  const repliesUnhydrated = item.value.moreReplies || 0
+  const metadata = {
+    depth: item.depth,
+    /*
+     * Unknown until after traversal
+     */
+    isLastChild: false,
+    /*
+     * Unknown until after traversal
+     */
+    isLastSibling: false,
+    /*
+     * If it's a top level reply, bc we render each top-level branch as a
+     * separate tree, it's implicitly part of the last branch. For subsequent
+     * replies, we'll override this after traversal.
+     */
+    isPartOfLastBranchFromDepth: item.depth === 1 ? 1 : undefined,
+    nextItemDepth: nextItem?.depth,
+    parentMetadata,
+    prevItemDepth: prevItem?.depth,
+    /*
+     * Unknown until after traversal
+     */
+    precedesChildReadMore: false,
+    /*
+     * Unknown until after traversal
+     */
+    followsReadMoreUp: false,
+    postData: {
+      uri: item.uri,
+      authorHandle: item.value.post.author.handle,
+    },
+    repliesCount,
+    repliesUnhydrated,
+    repliesSeenCounter: 0,
+    repliesIndexCounter: 0,
+    replyIndex: 0,
+    skippedIndentIndices: new Set<number>(),
+  }
+
+  if (isDevMode()) {
+    // @ts-ignore dev only for debugging
+    metadata.postData.text = getPostRecord(item.value.post).text
+  }
+
+  return metadata
+}
+
+export function storeTraversalMetadata(
+  metadatas: Map<string, TraversalMetadata>,
+  metadata: TraversalMetadata,
+) {
+  metadatas.set(metadata.postData.uri, metadata)
+
+  if (isDevMode()) {
+    // @ts-ignore dev only for debugging
+    metadatas.set(metadata.postData.text, metadata)
+    // @ts-ignore
+    window.__thread = metadatas
+  }
+}
+
+export function getThreadPostUI({
+  depth,
+  repliesCount,
+  prevItemDepth,
+  isLastChild,
+  skippedIndentIndices,
+  repliesSeenCounter,
+  repliesUnhydrated,
+  precedesChildReadMore,
+  followsReadMoreUp,
+}: TraversalMetadata): Extract<ThreadItem, {type: 'threadPost'}>['ui'] {
+  const isReplyAndHasReplies =
+    depth > 0 &&
+    repliesCount > 0 &&
+    (repliesCount - repliesUnhydrated === repliesSeenCounter ||
+      repliesSeenCounter > 0)
+  return {
+    isAnchor: depth === 0,
+    showParentReplyLine:
+      followsReadMoreUp ||
+      (!!prevItemDepth && prevItemDepth !== 0 && prevItemDepth < depth),
+    showChildReplyLine: depth < 0 || isReplyAndHasReplies,
+    indent: depth,
+    /*
+     * If there are no slices below this one, or the next slice has a depth <=
+     * than the depth of this post, it's the last child of the reply tree. It
+     * is not necessarily the last leaf in the parent branch, since it could
+     * have another sibling.
+     */
+    isLastChild,
+    skippedIndentIndices,
+    precedesChildReadMore: precedesChildReadMore ?? false,
+  }
+}
+
+export function getThreadPostNoUnauthenticatedUI({
+  depth,
+  prevItemDepth,
+}: {
+  depth: number
+  prevItemDepth?: number
+  nextItemDepth?: number
+}): Extract<ThreadItem, {type: 'threadPostNoUnauthenticated'}>['ui'] {
+  return {
+    showChildReplyLine: depth < 0,
+    showParentReplyLine: Boolean(prevItemDepth && prevItemDepth < depth),
+  }
+}