Model store hooked up

packages/model-store/src/index.ts

@@ -0,0 +1,71 @@
+import { atom } from "jotai";
+import { selectAtom } from "jotai/utils";
+
+/** Any model must at least have an id. */
+type BaseModel = { id: string };
+
+/** The raw store shape: model type string → id → model instance. */
+type StoreData<M extends BaseModel> = Record<string, Record<string, M>>;
+
+export type ModelChange = { type: "upsert" } | { type: "delete" };
+
+export function createModelStore<M extends BaseModel>() {
+  const dataAtom = atom<StoreData<M>>({});
+
+  /** Apply a single upsert or delete to the store. */
+  function applyChange(
+    prev: StoreData<M>,
+    modelType: string,
+    model: M,
+    change: ModelChange,
+  ): StoreData<M> {
+    if (change.type === "upsert") {
+      return {
+        ...prev,
+        [modelType]: { ...prev[modelType], [model.id]: model },
+      };
+    } else {
+      const bucket = { ...prev[modelType] };
+      delete bucket[model.id];
+      return { ...prev, [modelType]: bucket };
+    }
+  }
+
+  /** Atom that selects all models of a given type as an array. */
+  function listAtom(modelType: string) {
+    return selectAtom(
+      dataAtom,
+      (data) => Object.values(data[modelType] ?? {}),
+      shallowEqual,
+    );
+  }
+
+  /** Atom that selects all models of a given type, sorted by a field. */
+  function orderedListAtom<K extends keyof M>(
+    modelType: string,
+    field: K,
+    order: "asc" | "desc",
+  ) {
+    return selectAtom(
+      dataAtom,
+      (data) => {
+        const vals = Object.values(data[modelType] ?? {});
+        return vals.sort((a, b) => {
+          const n = a[field] > b[field] ? 1 : -1;
+          return order === "desc" ? -n : n;
+        });
+      },
+      shallowEqual,
+    );
+  }
+
+  return { dataAtom, applyChange, listAtom, orderedListAtom };
+}
+
+function shallowEqual<T>(a: T[], b: T[]): boolean {
+  if (a.length !== b.length) return false;
+  for (let i = 0; i < a.length; i++) {
+    if (a[i] !== b[i]) return false;
+  }
+  return true;
+}