Refactor context reducer to TypeScript (#34506)

app/javascript/mastodon/selectors/contexts.ts

@@ -0,0 +1,94 @@
+import { createAppSelector } from 'mastodon/store';
+
+export const getAncestorsIds = createAppSelector(
+  [(_, id: string) => id, (state) => state.contexts.inReplyTos],
+  (statusId, inReplyTos) => {
+    const ancestorsIds: string[] = [];
+
+    let currentId: string | undefined = statusId;
+
+    while (currentId && !ancestorsIds.includes(currentId)) {
+      ancestorsIds.unshift(currentId);
+      currentId = inReplyTos[currentId];
+    }
+
+    return ancestorsIds;
+  },
+);
+
+export const getDescendantsIds = createAppSelector(
+  [
+    (_, id: string) => id,
+    (state) => state.contexts.replies,
+    (state) => state.statuses,
+  ],
+  (statusId, contextReplies, statuses) => {
+    const descendantsIds: string[] = [];
+
+    const visitIds = [statusId];
+
+    while (visitIds.length > 0) {
+      const id = visitIds.pop();
+
+      if (!id) {
+        break;
+      }
+
+      const replies = contextReplies[id];
+
+      if (statusId !== id) {
+        descendantsIds.push(id);
+      }
+
+      if (replies) {
+        replies.reverse().forEach((replyId) => {
+          if (
+            !visitIds.includes(replyId) &&
+            !descendantsIds.includes(replyId) &&
+            statusId !== replyId
+          ) {
+            visitIds.push(replyId);
+          }
+        });
+      }
+    }
+
+    let insertAt = descendantsIds.findIndex((id) => {
+      const status = statuses.get(id);
+
+      if (!status) {
+        return false;
+      }
+
+      const inReplyToAccountId = status.get('in_reply_to_account_id') as
+        | string
+        | null;
+      const accountId = status.get('account') as string;
+
+      return inReplyToAccountId !== accountId;
+    });
+
+    if (insertAt !== -1) {
+      descendantsIds.forEach((id, idx) => {
+        const status = statuses.get(id);
+
+        if (!status) {
+          return;
+        }
+
+        const inReplyToAccountId = status.get('in_reply_to_account_id') as
+          | string
+          | null;
+        const accountId = status.get('account') as string;
+
+        if (idx > insertAt && inReplyToAccountId === accountId) {
+          descendantsIds.splice(idx, 1);
+          descendantsIds.splice(insertAt, 0, id);
+          insertAt += 1;
+        }
+      });
+    }
+
+    return descendantsIds;
+  },
+);