import jsigs from 'jsonld-signatures';
const {purposes: {AssertionProofPurpose}} = jsigs;
import {Ed25519VerificationKey2020} from
  '@digitalbazaar/ed25519-verification-key-2020';
import {Ed25519Signature2020, suiteContext} from
  '@digitalbazaar/ed25519-signature-2020';

// create the unsigned credential
const unsignedCredential = {
  '@context': [
    'https://www.w3.org/2018/credentials/v1',
    {
      AlumniCredential: 'https://schema.org#AlumniCredential',
      alumniOf: 'https://schema.org#alumniOf'
    }
  ],
  id: 'http://example.edu/credentials/1872',
  type: [ 'VerifiableCredential', 'AlumniCredential' ],
  issuer: 'https://example.edu/issuers/565049',
  issuanceDate: '2010-01-01T19:23:24Z',
  credentialSubject: {
    id: 'https://example.edu/students/alice',
    alumniOf: 'Example University'
  }
};

// create the keypair to use when signing
const controller = 'https://example.edu/issuers/565049';
const keyPair = await Ed25519VerificationKey2020.from({
  type: 'Ed25519VerificationKey2020',
  controller,
  id: controller + '#z6MknCCLeeHBUaHu4aHSVLDCYQW9gjVJ7a63FpMvtuVMy53T',
  publicKeyMultibase: 'z6MknCCLeeHBUaHu4aHSVLDCYQW9gjVJ7a63FpMvtuVMy53T',
  privateKeyMultibase: 'zrv2EET2WWZ8T1Jbg4fEH5cQxhbUS22XxdweypUbjWVzv1YD6VqYu' +
    'W6LH7heQCNYQCuoKaDwvv2qCWz3uBzG2xesqmf'
});

const suite = new Ed25519Signature2020({key: keyPair});
suite.date = '2010-01-01T19:23:24Z';

signedCredential = await jsigs.sign(unsignedCredential, {
  suite,
  purpose: new AssertionProofPurpose(),
  documentLoader
});

// results in the following signed VC
{
  "@context": [
    "https://www.w3.org/2018/credentials/v1",
    {
      "AlumniCredential": "https://schema.org#AlumniCredential",
      "alumniOf": "https://schema.org#alumniOf"
    },
    "https://w3id.org/security/suites/ed25519-2020/v1"
  ],
  "id": "http://example.edu/credentials/1872",
  "type": ["VerifiableCredential", "AlumniCredential"],
  "issuer": "https://example.edu/issuers/565049",
  "issuanceDate": "2010-01-01T19:23:24Z",
  "credentialSubject": {
    "id": "https://example.edu/students/alice",
    "alumniOf": "Example University"
  },
  "proof": {
    "type": "Ed25519Signature2020",
    "created": "2010-01-01T19:23:24Z",
    "verificationMethod": "https://example.edu/issuers/565049#z6MknCCLeeHBUaHu4aHSVLDCYQW9gjVJ7a63FpMvtuVMy53T",
    "proofPurpose": "assertionMethod",
    "proofValue": "z3MvGcVxzRzzpKF1HA11EjvfPZsN8NAb7kXBRfeTm3CBg2gcJLQM5hZNmj6Ccd9Lk4C1YueiFZvkSx4FuHVYVouQk"
  }
}