feat: add topic hierarchy APIs

src/queries/topics.ts

@@ -53,3 +53,31 @@ export async function findConnectedTopicRows(
     .orderBy('topics.normalized_name', 'asc')
     .execute() as Promise<ConnectedTopicRow[]>;
 }
+
+export async function findChildTopicRows(
+  executor: DatabaseExecutor,
+  parentTopicId: string,
+): Promise<TopicRecord[]> {
+  return executor
+    .selectFrom('topic_relations')
+    .innerJoin('topics', 'topics.id', 'topic_relations.child_topic_id')
+    .selectAll('topics')
+    .where('topic_relations.parent_topic_id', '=', parentTopicId)
+    .where('topic_relations.relation', '=', 'parent_of')
+    .orderBy('topics.normalized_name', 'asc')
+    .execute();
+}
+
+export async function findParentTopicRows(
+  executor: DatabaseExecutor,
+  childTopicId: string,
+): Promise<TopicRecord[]> {
+  return executor
+    .selectFrom('topic_relations')
+    .innerJoin('topics', 'topics.id', 'topic_relations.parent_topic_id')
+    .selectAll('topics')
+    .where('topic_relations.child_topic_id', '=', childTopicId)
+    .where('topic_relations.relation', '=', 'parent_of')
+    .orderBy('topics.normalized_name', 'asc')
+    .execute();
+}