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# @json-render/vue

Vue 3 components, providers, and composables.

## Providers

### StateProvider

```vue
<StateProvider :initial-state="object" :on-state-change="fn">
  <!-- children -->
</StateProvider>
```

| Prop | Type | Description |
|------|------|-------------|
| `store` | `StateStore` | External store (controlled mode). When provided, `initialState` and `onStateChange` are ignored. |
| `initialState` | `Record<string, unknown>` | Initial state model (uncontrolled mode). |
| `onStateChange` | `(changes: Array<{ path: string; value: unknown }>) => void` | Callback when state changes (uncontrolled mode). Called once per `set` or `update` with all changed entries. |

#### External Store (Controlled Mode)

Pass a `StateStore` to bypass the internal state and wire json-render to any state management library:

```typescript
import { createStateStore, type StateStore } from "@json-render/vue";

const store = createStateStore({ count: 0 });
```

```vue
<StateProvider :store="store">
  <!-- children -->
</StateProvider>
```

```typescript
// Mutate from anywhere — Vue re-renders automatically:
store.set("/count", 1);
```

### ActionProvider

```vue
<ActionProvider :handlers="Record<string, ActionHandler>" :navigate="fn">
  <!-- children -->
</ActionProvider>

// type ActionHandler = (params: Record<string, unknown>) => void | Promise<void>;
```

### VisibilityProvider

```vue
<VisibilityProvider>
  <!-- children -->
</VisibilityProvider>
```

`VisibilityProvider` reads state from the parent `StateProvider` automatically. Conditions in specs use the `VisibilityCondition` format with `$state` paths (e.g. `{ "$state": "/path" }`, `{ "$state": "/path", "eq": value }`). See [visibility](/docs/visibility) for the full syntax.

### ValidationProvider

```vue
<ValidationProvider :custom-functions="Record<string, ValidationFunction>">
  <!-- children -->
</ValidationProvider>

// type ValidationFunction = (value: unknown, args?: object) => boolean | Promise<boolean>;
```

## defineRegistry

Create a type-safe component registry from a catalog. Components receive `props`, `children`, `emit`, `on`, and `loading` with catalog-inferred types.

When the catalog declares actions, the `actions` field is required. When the catalog has no actions (e.g. `actions: {}`), the field is optional. When passing stubs, any `async () => {}` is sufficient.

```typescript
import { h } from "vue";
import { defineRegistry } from "@json-render/vue";

const { registry } = defineRegistry(catalog, {
  components: {
    Card: ({ props, children }) =>
      h("div", { class: "card" }, [h("h3", null, props.title), children]),
    Button: ({ props, emit }) =>
      h("button", { onClick: () => emit("press") }, props.label),
  },
  // Required when catalog declares actions:
  actions: {
    submit: async (params) => { /* ... */ },
  },
});

// Pass to <Renderer>
// <Renderer :spec="spec" :registry="registry" />
```

## Components

### Renderer

```vue
<Renderer
  :spec="Spec"           // The UI spec to render
  :registry="Registry"   // Component registry (from defineRegistry)
  :loading="boolean"     // Optional loading state
  :fallback="Component"  // Optional fallback for unknown types
/>
```

### Component Props (via defineRegistry)

```typescript
import type { VNode } from "vue";

interface ComponentContext<P> {
  props: P;                          // Typed props from catalog
  children?: VNode | VNode[];        // Rendered children (for container components)
  emit: (event: string) => void;     // Emit a named event (always defined)
  on: (event: string) => EventHandle; // Get event handle with metadata
  loading?: boolean;
  bindings?: Record<string, string>; // State paths from $bindState/$bindItem expressions
}

interface EventHandle {
  emit: () => void;              // Fire the event
  shouldPreventDefault: boolean; // Whether any binding requested preventDefault
  bound: boolean;                // Whether any handler is bound
}
```

Use `emit("press")` for simple event firing. Use `on("click")` when you need metadata like `shouldPreventDefault`:

```typescript
Link: ({ props, on }) => {
  const click = on("click");
  return h("a", {
    href: props.href,
    onClick: (e: MouseEvent) => {
      if (click.shouldPreventDefault) e.preventDefault();
      click.emit();
    },
  }, props.label);
},
```

### BaseComponentProps

Catalog-agnostic base type for building reusable component libraries that are not tied to a specific catalog:

```typescript
import type { BaseComponentProps } from "@json-render/vue";

const Card = ({ props, children }: BaseComponentProps<{ title?: string }>) =>
  h("div", null, [props.title, children]);
```

## Composables

### useStateStore

```typescript
const {
  state,   // ShallowRef<StateModel> — access with state.value
  get,     // (path: string) => unknown
  set,     // (path: string, value: unknown) => void
  update,  // (updates: Record<string, unknown>) => void
} = useStateStore();
```

> **Note:** `state` is a `ShallowRef<StateModel>`, not a plain object. Use `state.value` to read the current state. This differs from the React renderer.

### useStateValue

```typescript
const value = useStateValue(path: string); // ComputedRef<T | undefined>
```

Returns a `ComputedRef` that automatically updates when the state at `path` changes. Use `.value` to access the current value.

### useStateBinding (deprecated)

> **Deprecated.** Use `$bindState` expressions with `bindings` prop instead.

```typescript
const [value, setValue] = useStateBinding(path: string);
// value: ComputedRef<T | undefined>
// setValue: (value: T) => void
```

### useActions

```typescript
const { execute } = useActions();
// execute(binding: ActionBinding) => Promise<void>
```

### useAction

```typescript
const { execute, isLoading } = useAction(binding: ActionBinding);
// execute: () => Promise<void>
// isLoading: ComputedRef<boolean>
```

### useIsVisible

```typescript
const isVisible = useIsVisible(condition?: VisibilityCondition);
```

### useFieldValidation

```typescript
const {
  state,     // ComputedRef<FieldValidationState>
  validate,  // () => ValidationResult
  touch,     // () => void
  clear,     // () => void
  errors,    // ComputedRef<string[]>
  isValid,   // ComputedRef<boolean>
} = useFieldValidation(path: string, config?: ValidationConfig);
```

`ValidationConfig` is `{ checks?: ValidationCheck[], validateOn?: 'change' | 'blur' | 'submit' }`.

## Differences from `@json-render/react`

| API | React | Vue | Note |
|-----|-------|-----|------|
| `useStateStore().state` | `StateModel` (plain object) | `ShallowRef<StateModel>` | Vue reactivity; use `state.value` |
| `useStateValue()` | `T \| undefined` | `ComputedRef<T \| undefined>` | Vue reactivity; use `.value` |
| `useStateBinding()` | `[T \| undefined, setter]` | `[ComputedRef<T \| undefined>, setter]` | Vue reactivity; use `value.value` |
| `useAction().isLoading` | `boolean` | `ComputedRef<boolean>` | Vue reactivity; use `.value` |
| `useFieldValidation().state` | `FieldValidationState` | `ComputedRef<FieldValidationState>` | Vue reactivity; use `.value` |
| `useFieldValidation().errors` | `string[]` | `ComputedRef<string[]>` | Vue reactivity; use `.value` |
| `useFieldValidation().isValid` | `boolean` | `ComputedRef<boolean>` | Vue reactivity; use `.value` |
| `VisibilityContextValue.ctx` | `CoreVisibilityContext` | `ComputedRef<CoreVisibilityContext>` | Vue reactivity; use `ctx.value` |
| `children` type | `React.ReactNode` | `VNode \| VNode[]` | Platform-specific |
| `useBoundProp` | exported | exported | Same API; returns `[value, setValue]` |
| `VisibilityProviderProps` | exported | not exported (no props) | Vue uses slot, no prop needed |
| Streaming hooks | `useUIStream`, `useChatUI` | `useUIStream`, `useChatUI` | Same API; returns Vue `Ref` values |