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# Factory and Configuration
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The adapter factory provides fine-grained control over which browser shims are applied, allowing developers to create customized adapter instances for specific use cases or performance optimization.
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## Capabilities
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### Adapter Factory Function
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Creates adapter instances with configurable shim options.
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```javascript { .api }
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/**
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 * Creates an adapter instance with configurable shim options
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 * @param window - Object containing window reference (optional)
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 * @param options - Configuration options for enabling/disabling shims
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 * @returns Configured adapter instance
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 */
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function adapterFactory(
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  {window}?: {window?: Window}, 
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  options?: {
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    shimChrome?: boolean;
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    shimFirefox?: boolean; 
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    shimSafari?: boolean;
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  }
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): IAdapter;
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```
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**Default Options:**
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```javascript
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{
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  shimChrome: true,
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  shimFirefox: true,
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  shimSafari: true
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}
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```
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**Usage Examples:**
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```javascript
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import { adapterFactory } from 'webrtc-adapter/src/js/adapter_factory.js';
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// Default configuration (all shims enabled)
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const adapter = adapterFactory({window});
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// Disable Safari shims for performance
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const chromeFirefoxAdapter = adapterFactory({window}, {
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  shimChrome: true,
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  shimFirefox: true,
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  shimSafari: false
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});
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// Chrome-only adapter
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const chromeOnlyAdapter = adapterFactory({window}, {
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  shimChrome: true,
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  shimFirefox: false,
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  shimSafari: false
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});
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// Custom window object (useful for Node.js or testing environments)
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const serverAdapter = adapterFactory({window: undefined}, {
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  shimChrome: false,
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  shimFirefox: false,
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  shimSafari: false
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});
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// Testing with mock window
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const mockWindow = { RTCPeerConnection: MockRTCPeerConnection };
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const testAdapter = adapterFactory({window: mockWindow});
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```
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### Adapter Interface
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The complete interface returned by the factory function.
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```javascript { .api }
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interface IAdapter {
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  /** Browser detection information */
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  browserDetails: IBrowserDetails;
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  /** Common shims applied to all browsers */
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  commonShim: ICommonShim;
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  /** Browser-specific shims (only populated for detected browser) */
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  browserShim: IChromeShim | IFirefoxShim | ISafariShim | undefined;
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  /** Version extraction utility function */
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  extractVersion: (uastring: string, expr: string, pos: number) => number;
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  /** Logging control function */
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  disableLog: (disable: boolean) => string | Error;
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  /** Deprecation warning control function */
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  disableWarnings: (disable: boolean) => string | Error;
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  /** SDP utilities from sdp package dependency */
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  sdp: typeof SDPUtils;
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}
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```
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### Configuration Behavior
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The factory applies shims based on browser detection and configuration:
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**When `shimChrome: true` and Chrome detected:**
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- Applies all Chrome-specific shims
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- Sets `adapter.browserShim` to Chrome shim interface
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- Logs "adapter.js shimming chrome."
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**When `shimFirefox: true` and Firefox detected:**
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- Applies all Firefox-specific shims
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- Sets `adapter.browserShim` to Firefox shim interface  
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- Logs "adapter.js shimming firefox."
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**When `shimSafari: true` and Safari detected:**
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- Applies all Safari-specific shims
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- Sets `adapter.browserShim` to Safari shim interface
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- Logs "adapter.js shimming safari."
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**When shims are disabled:**
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- Logs appropriate warning message
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- Returns minimal adapter with only browser detection
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- `adapter.browserShim` remains `undefined`
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## Advanced Configuration Patterns
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### Conditional Shim Loading
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```javascript
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import { adapterFactory } from 'webrtc-adapter/src/js/adapter_factory.js';
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// Load shims based on environment
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const isInstrumented = process.env.NODE_ENV === 'development';
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const adapter = adapterFactory({window}, {
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  shimChrome: !isInstrumented, // Disable for debugging
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  shimFirefox: true,
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  shimSafari: true
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});
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```
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### Library Integration
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```javascript
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// Create adapter for specific library requirements
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function createWebRTCAdapter(targetBrowser) {
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  const options = {
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    shimChrome: targetBrowser === 'chrome' || targetBrowser === 'all',
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    shimFirefox: targetBrowser === 'firefox' || targetBrowser === 'all',
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    shimSafari: targetBrowser === 'safari' || targetBrowser === 'all'
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  };
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  return adapterFactory({window}, options);
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}
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const adapter = createWebRTCAdapter('chrome'); // Chrome-only shims
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```
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### Server-Side Usage
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```javascript
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// Node.js environment without window object
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const serverAdapter = adapterFactory({window: undefined}, {
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  shimChrome: false,
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  shimFirefox: false,
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  shimSafari: false
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});
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// Access utilities without browser shims
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const version = serverAdapter.extractVersion(userAgentString, pattern, position);
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```
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## Performance Considerations
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- **Selective Shimming**: Disabling unused browser shims reduces bundle size and initialization time
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- **Memory Usage**: Each adapter instance maintains separate shim state
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- **Browser Detection**: Performed once during adapter creation
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- **Lazy Loading**: Shims are only applied when the corresponding browser is detected