import 'dart:typed_data';

import 'package:pointycastle/asn1/asn1_encoding_rule.dart';
import 'package:pointycastle/asn1/asn1_object.dart';
import 'package:pointycastle/asn1/asn1_parser.dart';
import 'package:pointycastle/asn1/asn1_tags.dart';
import 'package:pointycastle/asn1/unsupported_asn1_encoding_rule_exception.dart';

class ASN1Sequence extends ASN1Object {
  ///
  /// The decoded string value
  ///
  List<ASN1Object>? elements = [];

  ///
  /// Create an [ASN1Sequence] entity with the given [elements].
  ///
  ASN1Sequence({this.elements, int tag = ASN1Tags.SEQUENCE}) : super(tag: tag);

  ///
  /// Creates an [ASN1Sequence] entity from the given [encodedBytes].
  ///
  ASN1Sequence.fromBytes(Uint8List super.encodedBytes) : super.fromBytes() {
    elements = [];
    var parser = ASN1Parser(valueBytes);
    while (parser.hasNext()) {
      elements!.add(parser.nextObject());
    }
  }

  ///
  /// Encodes this ASN1Object depending on the given [encodingRule]
  ///
  /// If no [ASN1EncodingRule] is given, ENCODING_DER will be used.
  ///
  /// Supported encoding rules are :
  /// * [ASN1EncodingRule.ENCODING_DER]
  ///
  /// Throws an [UnsupportedAsn1EncodingRuleException] if the given [encodingRule] is not supported.
  ///
  @override
  Uint8List encode(
      {ASN1EncodingRule encodingRule = ASN1EncodingRule.ENCODING_DER}) {
    if (encodingRule != ASN1EncodingRule.ENCODING_DER) {
      throw UnsupportedAsn1EncodingRuleException(encodingRule);
    }
    valueBytes = Uint8List(0);
    valueByteLength = 0;
    if (elements != null) {
      valueByteLength = _childLength();
      valueBytes = Uint8List(valueByteLength!);
      var i = 0;
      for (var obj in elements!) {
        var b = obj.encode();
        valueBytes!.setRange(i, i + b.length, b);
        i += b.length;
      }
    }
    return super.encode();
  }

  ///
  /// Calculate encoded length of all children
  ///
  int _childLength() {
    var l = 0;
    for (var obj in elements!) {
      l += obj.encode().length;
    }
    return l;
  }

  ///
  /// Adds the given [obj] to the [elements] list.
  ///
  void add(ASN1Object obj) {
    elements ??= [];
    elements!.add(obj);
  }

  @override
  String dump({int spaces = 0}) {
    var sb = StringBuffer();
    for (var i = 0; i < spaces; i++) {
      sb.write(' ');
    }
    sb.write('SEQUENCE (${elements!.length} elem)');
    for (var e in elements!) {
      var dump = e.dump(spaces: spaces + dumpIndent);
      sb.write('\n$dump');
    }
    return sb.toString();
  }
}