zustand

# LobeHub Zustand State Management

## Action Type Hierarchy

### 1. Public Actions

Main interfaces for UI components:

- Naming: Verb form (`createTopic`, `sendMessage`)
- Responsibilities: Parameter validation, flow orchestration

### 2. Internal Actions (`internal_*`)

Core business logic implementation:

- Naming: `internal_` prefix (`internal_createTopic`)
- Responsibilities: Optimistic updates, service calls, error handling
- Should not be called directly by UI

### 3. Dispatch Methods (`internal_dispatch*`)

State update handlers:

- Naming: `internal_dispatch` + entity (`internal_dispatchTopic`)
- Responsibilities: Calling reducers, updating store

## When to Use Reducer vs Simple `set`

**Use Reducer Pattern:**

- Managing object lists/maps (`messagesMap`, `topicMaps`)
- Optimistic updates
- Complex state transitions

**Use Simple `set`:**

- Toggling booleans
- Updating simple values
- Setting single state fields

## Optimistic Update Pattern

```typescript
internal_createTopic: async (params) => {
  const tmpId = Date.now().toString();

  // 1. Immediately update frontend (optimistic)
  get().internal_dispatchTopic(
    { type: 'addTopic', value: { ...params, id: tmpId } },
    'internal_createTopic'
  );

  // 2. Call backend service
  const topicId = await topicService.createTopic(params);

  // 3. Refresh for consistency
  await get().refreshTopic();
  return topicId;
},
```

**Delete operations**: Don't use optimistic updates (destructive, complex recovery)

## Naming Conventions

**Actions:**

- Public: `createTopic`, `sendMessage`
- Internal: `internal_createTopic`, `internal_updateMessageContent`
- Dispatch: `internal_dispatchTopic`
- Toggle: `internal_toggleMessageLoading`

**State:**

- ID arrays: `messageLoadingIds`, `topicEditingIds`
- Maps: `topicMaps`, `messagesMap`
- Active: `activeTopicId`
- Init flags: `topicsInit`

## Detailed Guides

- Action patterns: `references/action-patterns.md`
- Slice organization: `references/slice-organization.md`

## Class-Based Action Implementation

We are migrating slices from plain `StateCreator` objects to **class-based actions**.

### Pattern

- Define a class that encapsulates actions and receives `(set, get, api)` in the constructor.
- Use `#private` fields (e.g., `#set`, `#get`) to avoid leaking internals.
- Prefer shared typing helpers:
  - `StoreSetter<T>` from `@/store/types` for `set`.
  - `Pick<ActionImpl, keyof ActionImpl>` to expose only public methods.
- Export a `create*Slice` helper that returns a class instance.

```ts
type Setter = StoreSetter<HomeStore>;
export const createRecentSlice = (set: Setter, get: () => HomeStore, _api?: unknown) =>
  new RecentActionImpl(set, get, _api);

export class RecentActionImpl {
  readonly #get: () => HomeStore;
  readonly #set: Setter;

  constructor(set: Setter, get: () => HomeStore, _api?: unknown) {
    void _api;
    this.#set = set;
    this.#get = get;
  }

  useFetchRecentTopics = () => {
    // ...
  };
}

export type RecentAction = Pick<RecentActionImpl, keyof RecentActionImpl>;
```

### Composition

- In store files, merge class instances with `flattenActions` (do not spread class instances).
- `flattenActions` binds methods to the original class instance and supports prototype methods and class fields.

```ts
const createStore: StateCreator<HomeStore, [['zustand/devtools', never]]> = (...params) => ({
  ...initialState,
  ...flattenActions<HomeStoreAction>([
    createRecentSlice(...params),
    createHomeInputSlice(...params),
  ]),
});
```

### Multi-Class Slices

- For large slices that need multiple action classes, compose them in the slice entry using `flattenActions`.
- Use a local `PublicActions<T>` helper if you need to combine multiple classes and hide private fields.

```ts
type PublicActions<T> = { [K in keyof T]: T[K] };

export type ChatGroupAction = PublicActions<
  ChatGroupInternalAction & ChatGroupLifecycleAction & ChatGroupMemberAction & ChatGroupCurdAction
>;

export const chatGroupAction: StateCreator<
  ChatGroupStore,
  [['zustand/devtools', never]],
  [],
  ChatGroupAction
> = (...params) =>
  flattenActions<ChatGroupAction>([
    new ChatGroupInternalAction(...params),
    new ChatGroupLifecycleAction(...params),
    new ChatGroupMemberAction(...params),
    new ChatGroupCurdAction(...params),
  ]);
```

### Store-Access Types

- For class methods that depend on actions in other classes, define explicit store augmentations:
  - `ChatGroupStoreWithSwitchTopic` for lifecycle `switchTopic`
  - `ChatGroupStoreWithRefresh` for member refresh
  - `ChatGroupStoreWithInternal` for curd `internal_dispatchChatGroup`

### Do / Don't

- **Do**: keep constructor signature aligned with `StateCreator` params `(set, get, api)`.
- **Do**: use `#private` to avoid `set/get` being exposed.
- **Do**: use `flattenActions` instead of spreading class instances.
- **Don't**: keep both old slice objects and class actions active at the same time.