docs(pq-key-fingerprint/ts): phase 3 - add package documentation (ENG-1762)

Author: eacet

packages/pq-key-fingerprint/ts/README.md

@@ -11,11 +11,99 @@ npm install pq-key-fingerprint
 ## Usage
 
 ```typescript
-import { } from 'pq-key-fingerprint';
+import {
+  FingerprintError,
+  fingerprintJWK,
+  fingerprintPEM,
+  fingerprintPublicKey,
+  fingerprintPublicKeyBytes,
+  fingerprintSPKI,
+} from 'pq-key-fingerprint';
 
-// Coming soon
+const mlKem512PublicKey = new Uint8Array(800);
+
+// 1) Raw bytes + algorithm
+const fromBytes = await fingerprintPublicKeyBytes(mlKem512PublicKey, 'ML-KEM-512');
+console.log(fromBytes); // hex string (default)
+
+// 2) KeyData-like input
+const fromPublicKeyObject = await fingerprintPublicKey({
+  alg: 'ML-KEM-512',
+  type: 'public',
+  bytes: mlKem512PublicKey,
+});
+
+// 3) SPKI DER bytes
+const spkiDer = new Uint8Array(/* SPKI DER bytes */);
+const fromSpki = await fingerprintSPKI(spkiDer);
+
+// 4) PEM
+const pem = `-----BEGIN PUBLIC KEY-----
+...
+-----END PUBLIC KEY-----`;
+const fromPem = await fingerprintPEM(pem);
+
+// 5) JWK
+const jwk = {
+  kty: 'PQC' as const,
+  alg: 'ML-KEM-512' as const,
+  x: 'base64url-encoded-public-key-bytes',
+};
+const fromJwk = await fingerprintJWK(jwk);
+
+// Digest and encoding options
+const sha512Base64Url = await fingerprintPublicKeyBytes(mlKem512PublicKey, 'ML-KEM-512', {
+  digest: 'SHA-512',
+  encoding: 'base64url',
+});
+
+const rawDigestBytes = await fingerprintPublicKeyBytes(mlKem512PublicKey, 'ML-KEM-512', {
+  digest: 'SHA-384',
+  encoding: 'bytes',
+});
+
+console.log(sha512Base64Url, rawDigestBytes.length);
+
+// Error handling
+try {
+  await fingerprintPEM('not-a-valid-pem');
+} catch (error) {
+  if (error instanceof FingerprintError) {
+    console.error('Fingerprint failed:', error.message);
+  } else {
+    throw error;
+  }
+}
 ```
 
+## API
+
+```typescript
+type FingerprintDigest = 'SHA-256' | 'SHA-384' | 'SHA-512';
+type FingerprintEncoding = 'hex' | 'base64' | 'base64url' | 'bytes';
+
+interface FingerprintOptions {
+  digest?: FingerprintDigest;
+  encoding?: FingerprintEncoding;
+}
+
+type FingerprintResult = string | Uint8Array;
+
+function fingerprintPublicKey(input: PublicKeyInput, options?: FingerprintOptions): Promise<FingerprintResult>;
+function fingerprintPublicKeyBytes(
+  bytes: Uint8Array,
+  alg: AlgorithmName,
+  options?: FingerprintOptions,
+): Promise<FingerprintResult>;
+function fingerprintSPKI(spki: Uint8Array, options?: FingerprintOptions): Promise<FingerprintResult>;
+function fingerprintPEM(pem: string, options?: FingerprintOptions): Promise<FingerprintResult>;
+function fingerprintJWK(jwk: PQJwk, options?: FingerprintOptions): Promise<FingerprintResult>;
+```
+
+## Compatibility Note
+
+All exported fingerprint entrypoints enforce a strict local error boundary by design. Upstream parser/validation failures from `pq-key-encoder` are translated into `pq-key-fingerprint` error classes (subclasses of `FingerprintError`) before they leave this package. This behavior is intentional and part of the package contract.
+
 ## License
 
 MIT