chore: import upstream snapshot with attribution

apps/webapp/app/hooks/useList.tsx

@@ -0,0 +1,73 @@
+import type { Reducer } from "react";
+import { useReducer } from "react";
+
+export type ListState<T> = {
+  items: T[];
+};
+
+type AppendAction<T> = {
+  type: "append";
+  items: T[];
+};
+
+type UpdateAction<T> = {
+  type: "update";
+  index: number;
+  item: T;
+};
+
+type DeleteAction<_T> = {
+  type: "delete";
+  index: number;
+};
+
+type InsertAfter<T> = {
+  type: "insertAfter";
+  index: number;
+  items: T[];
+};
+
+type Action<T> = AppendAction<T> | UpdateAction<T> | DeleteAction<T> | InsertAfter<T>;
+
+function reducer<T>(state: ListState<T>, action: Action<T>): ListState<T> {
+  switch (action.type) {
+    case "append":
+      return { items: [...state.items, ...action.items] };
+    case "update":
+      return {
+        items: state.items.map((v, i) => (i === action.index ? action.item : v)),
+      };
+    case "delete":
+      return { items: state.items.filter((_, i) => i !== action.index) };
+    case "insertAfter":
+      return {
+        items: [
+          ...state.items.slice(0, action.index + 1),
+          ...action.items,
+          ...state.items.slice(action.index + 1),
+        ],
+      };
+  }
+}
+
+type HookReturn<T> = {
+  items: T[];
+  append: (items: T[]) => void;
+  update: (index: number, item: T) => void;
+  delete: (index: number) => void;
+  insertAfter: (index: number, items: T[]) => void;
+};
+
+export function useList<T>(initialItems: T[]): HookReturn<T> {
+  const [state, dispatch] = useReducer<Reducer<ListState<T>, Action<T>>>(reducer, {
+    items: initialItems,
+  });
+
+  return {
+    items: state.items,
+    append: (items: T[]) => dispatch({ type: "append", items }),
+    update: (index: number, item: T) => dispatch({ type: "update", index, item }),
+    delete: (index: number) => dispatch({ type: "delete", index }),
+    insertAfter: (index: number, items: T[]) => dispatch({ type: "insertAfter", index, items }),
+  };
+}