> ## Documentation Index
> Fetch the complete documentation index at: https://docs.westyx.cloud/llms.txt
> Use this file to discover all available pages before exploring further.

# OpenFeature Web Provider - Usage

> Register the Nexus provider and evaluate flags and configs using the OpenFeature browser SDK.

## Register the provider

Call `setProviderAndWait` once at application startup. This performs the initial `/v1/sync` call and opens the SSE stream before the promise resolves, so all subsequent evaluations are backed by a warm cache.

```ts theme={null}
import { OpenFeature } from '@openfeature/web-sdk';
import { NexusProvider } from '@westyx-nexus/openfeature-web-provider';

await OpenFeature.setProviderAndWait(
  new NexusProvider({
    endpoint: 'https://api.westyx.dev', // Nexus API base URL
    apiKey: 'wxp_...',              // public (browser) key
  })
);
```

## Evaluating flags

```ts theme={null}
const client = OpenFeature.getClient();

// Boolean feature flag
const showBanner = client.getBooleanValue('banner.enabled', false);

// String config
const welcomeText = client.getStringValue('welcome.text', 'Welcome!');

// Number config
const maxItems = client.getNumberValue('list.max_items', 10);

// Object config
const theme = client.getObjectValue('ui.theme', { color: 'blue' });
```

## Reacting to live updates (SSE)

The provider maintains an SSE connection to Nexus. When a flag or config changes, it re-syncs and emits `PROVIDER_CONFIGURATION_CHANGED`.

```ts theme={null}
import { ProviderEvents } from '@openfeature/web-sdk';

client.addHandler(ProviderEvents.ConfigurationChanged, () => {
  const updatedValue = client.getBooleanValue('banner.enabled', false);
  console.log('banner.enabled is now', updatedValue);
});
```

## Type resolution rules

| OpenFeature method | Nexus source                  | Notes                                                                 |
| ------------------ | ----------------------------- | --------------------------------------------------------------------- |
| `getBooleanValue`  | Feature flag cache            | Returns `defaultValue` if the flag is absent                          |
| `getStringValue`   | Config cache                  | `TYPE_MISMATCH` if value is not a string; `FLAG_NOT_FOUND` if absent  |
| `getNumberValue`   | Config cache (via `Number()`) | `TYPE_MISMATCH` if result is `NaN`; `FLAG_NOT_FOUND` if absent        |
| `getObjectValue`   | Config cache                  | `TYPE_MISMATCH` if value is not an object; `FLAG_NOT_FOUND` if absent |

All evaluations return `reason: STATIC` - Nexus does not perform per-user targeting. `EvaluationContext` is accepted by the API but silently ignored.

## Framework examples

### Angular

```ts theme={null}
// app.config.ts
import { APP_INITIALIZER, ApplicationConfig } from '@angular/core';
import { OpenFeature } from '@openfeature/web-sdk';
import { NexusProvider } from '@westyx-nexus/openfeature-web-provider';

export const appConfig: ApplicationConfig = {
  providers: [
    {
      provide: APP_INITIALIZER,
      useFactory: () => () =>
        OpenFeature.setProviderAndWait(
          new NexusProvider({ endpoint: 'https://api.westyx.dev', apiKey: 'wxp_...' })
        ),
      multi: true,
    },
  ],
};
```

### React (with `@openfeature/react-sdk`)

```tsx theme={null}
import { OpenFeatureProvider, useBooleanFlagValue } from '@openfeature/react-sdk';
import { OpenFeature } from '@openfeature/web-sdk';
import { NexusProvider } from '@westyx-nexus/openfeature-web-provider';

OpenFeature.setProvider(new NexusProvider({ endpoint: 'https://api.westyx.dev', apiKey: 'wxp_...' }));

function MyComponent() {
  const showBeta = useBooleanFlagValue('beta.enabled', false);
  return showBeta ? <BetaUI /> : <StableUI />;
}

export function App() {
  return (
    <OpenFeatureProvider>
      <MyComponent />
    </OpenFeatureProvider>
  );
}
```

## Stopping the provider

```ts theme={null}
await OpenFeature.clearProviders();
```

This calls `onClose()` on the provider, which aborts the SSE connection and cleans up resources.

## Limitations

* **`EvaluationContext` is ignored.** Nexus does not perform per-user flag targeting server-side. All evaluations return `reason: STATIC`.
* **Public key only.** Use a `wxp_...` browser key. Secret backend keys (`wxs_...`) are not accepted.
* **No secrets.** Secret values are never exposed via browser SDK endpoints. Only feature flags and configs are available.