Key Authentication

/**
 * Represents a credential defined by a static API key.
 */
interface KeyCredential {
  /** The value of the API key represented as a string */
  readonly key: string;
}

/**
 * A static-key-based credential that supports updating the underlying key value.
 */
class AzureKeyCredential implements KeyCredential {
  /**
   * Create an instance of an AzureKeyCredential for use with a service client.
   * @param key - The initial value of the key to use in authentication
   * @throws Error if key is empty or undefined
   */
  constructor(key: string);
  
  /** The value of the key to be used in authentication */
  get key(): string;
  
  /**
   * Change the value of the key.
   * Updates will take effect upon the next request after updating the key value.
   * @param newKey - The new key value to be used
   */
  update(newKey: string): void;
}

import { AzureKeyCredential } from "@azure/core-auth";

// Create credential with initial API key
const keyCredential = new AzureKeyCredential("your-api-key-here");

// Use with Azure service client
const serviceClient = new SomeAzureServiceClient(endpoint, keyCredential);

// Access the current key
console.log(keyCredential.key); // "your-api-key-here"

// Update the key (useful for key rotation)
keyCredential.update("new-rotated-api-key");

// Future requests will use the new key
const result = await serviceClient.someOperation();

// Common pattern for key rotation
async function rotateApiKey(credential: AzureKeyCredential) {
  const newKey = await getNewKeyFromKeyVault();
  credential.update(newKey);
  console.log("API key rotated successfully");
}

/**
 * Tests an object to determine whether it implements KeyCredential.
 * @param credential - The assumed KeyCredential to be tested
 * @returns true if the object implements KeyCredential, false otherwise
 */
function isKeyCredential(credential: unknown): credential is KeyCredential;

import { isKeyCredential, AzureKeyCredential } from "@azure/core-auth";

function processCredential(credential: unknown) {
  if (isKeyCredential(credential)) {
    // TypeScript now knows credential has a 'key' property
    console.log(`Using API key: ${credential.key.substring(0, 4)}...`);
    return true;
  }
  return false;
}

// Usage in credential validation
function validateCredentials(credentials: unknown[]) {
  const keyCredentials = credentials.filter(isKeyCredential);
  
  keyCredentials.forEach(cred => {
    if (cred.key.length < 10) {
      console.warn("Key appears to be too short");
    }
  });
}

// Usage with multiple credential types
function getCredentialInfo(credential: unknown): string {
  if (isKeyCredential(credential)) {
    return `Key credential with key length: ${credential.key.length}`;
  }
  return "Unknown credential type";
}

import { AzureKeyCredential } from "@azure/core-auth";

try {
  const credential = new AzureKeyCredential(""); // Throws Error
} catch (error) {
  console.error(error.message); // "key must be a non-empty string"
}

try {
  const credential = new AzureKeyCredential(null as any); // Throws Error  
} catch (error) {
  console.error(error.message); // "key must be a non-empty string"
}