import 'dart:typed_data';
import 'package:pointycastle/asn1.dart';

///
///```
/// PrivateKeyInfo ::= OneAsymmetricKey
///
/// OneAsymmetricKey ::= SEQUENCE {
///        version                   Version,
///        privateKeyAlgorithm       PrivateKeyAlgorithmIdentifier,
///        privateKey                PrivateKey,
///        attributes            [0] Attributes OPTIONAL,
///        ...,
///        [[2: publicKey        [1] PublicKey OPTIONAL ]],
///        ...
/// }
///```
///
class ASN1PrivateKeyInfo extends ASN1Object {
  late ASN1Integer version;
  late ASN1AlgorithmIdentifier privateKeyAlgorithm;
  late ASN1OctetString privateKey;
  ASN1Set? attributes;
  ASN1BitString? publicKey;

  ASN1PrivateKeyInfo(this.version, this.privateKeyAlgorithm, this.privateKey);

  ///
  /// Creates an instance of PrivateKeyInfo for the given [pem].
  /// The [pem] should represent a RSA private key in PKCS1.
  ///
  ASN1PrivateKeyInfo.fromPkcs1RsaPem(String pem) {
    var bytes = ASN1Utils.getBytesFromPEMString(pem);
    var asn1Parser = ASN1Parser(bytes);
    var privateKeySeq = asn1Parser.nextObject();
    privateKey = ASN1OctetString(octets: privateKeySeq.encode());
    version = ASN1Integer.fromtInt(0);
    privateKeyAlgorithm =
        ASN1AlgorithmIdentifier.fromIdentifier('1.2.840.113549.1.1.1');
  }

  ///
  /// Creates an instance of PrivateKeyInfo for the given [pem].
  /// The [pem] should represent a RSA private key in PKCS1.
  ///
  ASN1PrivateKeyInfo.fromEccPem(String pem) {
    var bytes = ASN1Utils.getBytesFromPEMString(pem);
    var private = ASN1Utils.ecPrivateKeyFromDerBytes(bytes);
    var asn1Parser = ASN1Parser(bytes);
    var privateKeySeq = asn1Parser.nextObject() as ASN1Sequence;
    var seq = ASN1Sequence(elements: [
      privateKeySeq.elements!.elementAt(0),
      privateKeySeq.elements!.elementAt(1),
      privateKeySeq.elements!.elementAt(3),
    ]);

    privateKey = ASN1OctetString(octets: seq.encode());

    version = ASN1Integer.fromtInt(0);
    var param = ASN1ObjectIdentifier.fromName(private.parameters!.domainName);
    privateKeyAlgorithm = ASN1AlgorithmIdentifier.fromName(
      'ecPublicKey',
      parameters: param,
    );
  }

  ///
  /// Creates an instance of PrivateKeyInfo for the given [pem].
  /// The [pem] should represent a RSA private key in PKCS8.
  ///
  ASN1PrivateKeyInfo.fromPkcs8RsaPem(String pem) {
    var bytes = ASN1Utils.getBytesFromPEMString(pem);
    var asn1Parser = ASN1Parser(bytes);
    var privateKeySeq = asn1Parser.nextObject() as ASN1Sequence;
    version = privateKeySeq.elements!.elementAt(0) as ASN1Integer;
    privateKeyAlgorithm = ASN1AlgorithmIdentifier.fromSequence(
        privateKeySeq.elements!.elementAt(1) as ASN1Sequence);
    privateKey = privateKeySeq.elements!.elementAt(2) as ASN1OctetString;
  }

  ///
  /// Creates an instance of PrivateKeyInfo for the given [key].
  /// The [key] should represent a RSA private key in PKCS1 format as an [ASN1Sequence].
  ///
  ASN1PrivateKeyInfo.fromPkcs1Rsa(ASN1Object key) {
    privateKey = ASN1OctetString(octets: key.encode());
    version = ASN1Integer.fromtInt(0);
    privateKeyAlgorithm =
        ASN1AlgorithmIdentifier.fromIdentifier('1.2.840.113549.1.1.1');
  }

  @override
  Uint8List encode(
      {ASN1EncodingRule encodingRule = ASN1EncodingRule.ENCODING_DER}) {
    var tmp = ASN1Sequence(elements: [
      version,
      privateKeyAlgorithm,
      privateKey,
    ]);
    if (attributes != null) {
      tmp.add(attributes!);
    }
    if (publicKey != null) {
      tmp.add(publicKey!);
    }
    return tmp.encode(encodingRule: encodingRule);
  }
}