resolver.ts

import { AccountId, ChainIdParams } from 'caip'
import type {
  DIDResolutionResult,
  DIDResolutionOptions,
  ResolverRegistry,
  ParsedDID,
  Resolver,
  Resolvable
} from 'did-resolver'

const DID_LD_JSON = 'application/did+ld+json'
const DID_JSON = 'application/did+json'
const SECPK1_NAMESPACES = ['eip155', 'bip122']
const TZ_NAMESPACE = 'tezos'


function toDidDoc(did: string, accountId: string): any {
  const { namespace } = AccountId.parse(accountId).chainId as ChainIdParams
  const vmId = did + '#blockchainAccountId'
  const doc = {
    '@context': [
      'https://www.w3.org/ns/did/v1',
      {
        blockchainAccountId: 'https://w3id.org/security#blockchainAccountId',
        EcdsaSecp256k1RecoveryMethod2020:
          'https://identity.foundation/EcdsaSecp256k1RecoverySignature2020#EcdsaSecp256k1RecoveryMethod2020',
        Ed25519VerificationKey2018: 'https://w3id.org/security#Ed25519VerificationKey2018',
      },
    ],
    id: did,
    verificationMethod: [
      {
        id: vmId,
        type: 'EcdsaSecp256k1RecoveryMethod2020',
        controller: did,
        blockchainAccountId: accountId,
      },
    ],
    authentication: [vmId],
    assertionMethod: [vmId],
  }
  if (SECPK1_NAMESPACES.includes(namespace)) {
    // nothing to do here
  } else if (namespace === TZ_NAMESPACE) {
    (doc['@context'][1] as any).TezosMethod2021 = 'https://w3id.org/security#TezosMethod2021'
    const tzId = did + '#TezosMethod2021'
    doc.verificationMethod.push({
      id: tzId,
      type: 'TezosMethod2021',
      controller: did,
      blockchainAccountId: accountId,
    })
    doc.authentication.push(tzId)
    doc.assertionMethod.push(tzId)
  } else {
    throw new Error(`chain namespace not supported ${namespace}`)
  }
  return doc
}

export function getResolver(): ResolverRegistry {
  return {
    pkh: async (
      did: string,
      parsed: ParsedDID,
      r: Resolvable,
      options: DIDResolutionOptions
    ): Promise<DIDResolutionResult> => {
      const contentType = options.accept || DID_JSON
      const response: DIDResolutionResult = {
        didResolutionMetadata: { contentType },
        didDocument: null,
        didDocumentMetadata: {},
      }
      try {
        const doc = toDidDoc(did, parsed.id)
        if (contentType === DID_LD_JSON) {
          response.didDocument = doc
        } else if (contentType === DID_JSON) {
          delete doc['@context']
          response.didDocument = doc
        } else {
          delete response.didResolutionMetadata.contentType
          response.didResolutionMetadata.error = 'representationNotSupported'
        }
      } catch (e) {
        response.didResolutionMetadata.error = 'invalidDid'
        response.didResolutionMetadata.message = e.toString()
      }
      return response
    },
  }
}