Add useEntityLookup hook

app/soapbox/entity-store/hooks/useEntity.ts

@@ -59,4 +59,5 @@ function useEntity<TEntity extends Entity>(
 
 export {
   useEntity,
+  type UseEntityOpts,
 };

app/soapbox/entity-store/hooks/useEntityLookup.ts

@@ -0,0 +1,66 @@
+import { useEffect } from 'react';
+import { z } from 'zod';
+
+import { useAppDispatch, useAppSelector, useLoading } from 'soapbox/hooks';
+import { type RootState } from 'soapbox/store';
+
+import { importEntities } from '../actions';
+import { Entity } from '../types';
+
+import { EntityFn } from './types';
+import { type UseEntityOpts } from './useEntity';
+
+/** Entities will be filtered through this function until it returns true. */
+type LookupFn<TEntity extends Entity> = (entity: TEntity) => boolean
+
+function useEntityLookup<TEntity extends Entity>(
+  entityType: string,
+  lookupFn: LookupFn<TEntity>,
+  entityFn: EntityFn<void>,
+  opts: UseEntityOpts<TEntity> = {},
+) {
+  const { schema = z.custom<TEntity>() } = opts;
+
+  const dispatch = useAppDispatch();
+  const [isFetching, setPromise] = useLoading(true);
+
+  const entity = useAppSelector(state => findEntity(state, entityType, lookupFn));
+  const isLoading = isFetching && !entity;
+
+  const fetchEntity = async () => {
+    try {
+      const response = await setPromise(entityFn());
+      const entity = schema.parse(response.data);
+      dispatch(importEntities([entity], entityType));
+    } catch (e) {
+      // do nothing
+    }
+  };
+
+  useEffect(() => {
+    if (!entity || opts.refetch) {
+      fetchEntity();
+    }
+  }, []);
+
+  return {
+    entity,
+    fetchEntity,
+    isFetching,
+    isLoading,
+  };
+}
+
+function findEntity<TEntity extends Entity>(
+  state: RootState,
+  entityType: string,
+  lookupFn: LookupFn<TEntity>,
+) {
+  const cache = state.entities[entityType];
+
+  if (cache) {
+    return (Object.values(cache.store) as TEntity[]).find(lookupFn);
+  }
+}
+
+export default useEntityLookup;