From ebd39886344b4d43f5c4748910c5cd750a67f4ed Mon Sep 17 00:00:00 2001
From: mptyl <mp@tylconsulting.it>
Date: Sun, 28 Jun 2026 12:17:16 +0200
Subject: [PATCH] feat(frontend): Zustand session store + applyEvent

---
 frontend/src/store/sessionStore.test.ts | 26 +++++++++++++++
 frontend/src/store/sessionStore.ts      | 44 +++++++++++++++++++++++++
 2 files changed, 70 insertions(+)
 create mode 100644 frontend/src/store/sessionStore.test.ts
 create mode 100644 frontend/src/store/sessionStore.ts

diff --git a/frontend/src/store/sessionStore.test.ts b/frontend/src/store/sessionStore.test.ts
new file mode 100644
index 00000000..00d43a9c
--- /dev/null
+++ b/frontend/src/store/sessionStore.test.ts
@@ -0,0 +1,26 @@
+import { useSessionStore } from "./sessionStore";
+
+beforeEach(() => useSessionStore.getState().resetSession());
+
+test("ui_request sets pendingWidget", () => {
+  useSessionStore.getState().applyEvent({ type: "ui_request", ui_request: { id: "u1", widget: "select" } });
+  expect(useSessionStore.getState().pendingWidget?.id).toBe("u1");
+});
+
+test("text_delta accumulates into transcript", () => {
+  const s = useSessionStore.getState();
+  s.applyEvent({ type: "text_delta", text: "Ana" });
+  s.applyEvent({ type: "text_delta", text: "lisi" });
+  expect(useSessionStore.getState().transcript.at(-1)?.text).toBe("Analisi");
+});
+
+test("info pushes a toast", () => {
+  useSessionStore.getState().applyEvent({ type: "info", level: "warning", text: "attenzione" });
+  expect(useSessionStore.getState().toasts.at(-1)).toEqual({ level: "warning", text: "attenzione" });
+});
+
+test("clearPending removes the widget", () => {
+  useSessionStore.getState().applyEvent({ type: "ui_request", ui_request: { id: "u1", widget: "select" } });
+  useSessionStore.getState().clearPending();
+  expect(useSessionStore.getState().pendingWidget).toBeNull();
+});
diff --git a/frontend/src/store/sessionStore.ts b/frontend/src/store/sessionStore.ts
new file mode 100644
index 00000000..e80b330e
--- /dev/null
+++ b/frontend/src/store/sessionStore.ts
@@ -0,0 +1,44 @@
+import { create } from "zustand";
+import type { StreamEvent, WidgetDescriptor } from "../api/types";
+
+interface Entry {
+  role: "assistant";
+  text: string;
+}
+
+interface SessionState {
+  pendingWidget: WidgetDescriptor | null;
+  transcript: Entry[];
+  toasts: { level: string; text: string }[];
+  lastSystemEvent: StreamEvent | null;
+  applyEvent: (e: StreamEvent) => void;
+  clearPending: () => void;
+  resetSession: () => void;
+}
+
+const empty = {
+  pendingWidget: null,
+  transcript: [] as Entry[],
+  toasts: [] as { level: string; text: string }[],
+  lastSystemEvent: null,
+};
+
+export const useSessionStore = create<SessionState>((set) => ({
+  ...empty,
+  applyEvent: (e) =>
+    set((st) => {
+      if (e.type === "ui_request") return { pendingWidget: e.ui_request };
+      if (e.type === "text_delta") {
+        const t = [...st.transcript];
+        const last = t.at(-1);
+        if (last && !st.pendingWidget) t[t.length - 1] = { role: "assistant", text: last.text + e.text };
+        else t.push({ role: "assistant", text: e.text });
+        return { transcript: t };
+      }
+      if (e.type === "info") return { toasts: [...st.toasts, { level: e.level ?? "info", text: e.text }] };
+      if (e.type === "system_event") return { lastSystemEvent: e };
+      return {};
+    }),
+  clearPending: () => set({ pendingWidget: null }),
+  resetSession: () => set({ ...empty }),
+}));