buildPlaintextCredential function

String buildPlaintextCredential(dynamic credential, String? holderDid, { bool addHashAlg = true, })

Builds a json-Object where every Attribute gets a value and salt from json-Object credential.

E.g.

{
  "type" : "NameAgeCredential",
  "name" : "Max",
  "age" : 20
}

becomes to

{
"id": "did:ethr:0x82734",
"type": ["HashedPlaintextCredential2021","NameAgeCredential"],
"hashAlg" : "keccak-256",
"name":
{
  "value":"Max",
  "salt":"dc0931a0-60c6-4bc8-a27d-b3fd13e62c63"
 },
 "age":
  {
  "value":20,
  "salt":"3e9bacd3-aa74-42c1-9895-e490e3931a73"
 }
}

where salt is a Version 4 UUID. credential could be a string or Map<String, dynamic> representing a valid json-Object.

Implementation

String buildPlaintextCredential(dynamic credential, String? holderDid,
    {bool addHashAlg = true}) {
  Map<String, dynamic> credMap = credentialToMap(credential);
  Map<String, dynamic> finalCred = {};

  if (credMap.containsKey('credentialSubject')) {
    credMap = credMap['credentialSubject'];
  }
  if (credMap.containsKey('@context')) {
    finalCred['@context'] = credMap['@context'];
    credMap.remove('@context');
  }

  if (addHashAlg) {
    List<String> types = [];
    types.add('HashedPlaintextCredential2021');
    if (credMap.containsKey('type') || credMap.containsKey('@type')) {
      var value = credMap['type'];
      credMap.remove('type');
      if (value == null) {
        value = credMap['@type'];
        credMap.remove('@type');
      }
      if (value is String) {
        if (!types.contains(value)) types.add(value);
      } else if (value is List) {
        for (var element in value) {
          if (!types.contains(element)) types.add(element);
        }
      } else {
        throw Exception('Unsupported datatype for type key');
      }
      finalCred['type'] = types;
    }
  }

  if (holderDid != '') {
    finalCred['id'] = holderDid;
  }
  if (addHashAlg) finalCred['hashAlg'] = 'keccak-256';

  credMap.forEach((key, value) {
    if (key == 'type' || key == '@type') {
      finalCred[key] = value;
    } else if (value is String || value is num || value is bool) {
      finalCred[key] = _hashStringOrNum(value);
    } else if (value is List) {
      List<Map<String, dynamic>?> newValue = [];
      for (var element in value) {
        if (element is String || element is num || element is bool) {
          newValue.add(_hashStringOrNum(element));
        } else if (element is Map<String, dynamic>) {
          newValue.add(jsonDecode(
              buildPlaintextCredential(element, '', addHashAlg: false)));
        } else {
          throw Exception('unknown type with key $key');
        }
      }
      finalCred[key] = newValue;
    } else if (value is Map<String, dynamic>) {
      finalCred[key] =
          jsonDecode(buildPlaintextCredential(value, '', addHashAlg: false));
    } else {
      throw Exception('unknown datatype  with key $key');
    }
  });

  return jsonEncode(finalCred);
}