import 'dart:convert';
import 'dart:typed_data';

import 'package:dart_spectre/src/scope.dart';
import 'package:dart_spectre/src/template.dart';
import "package:pointycastle/export.dart";

final scrypt = Scrypt();
final hmac = HMac(SHA256Digest(), 64);

class Spectre {
  final String _name;
  final String _secret;
  late Scoper _scoper;

  late Uint8List _key;

  Spectre(this._name, this._secret, [Scoper? scoper]) {
    _scoper = scoper ?? defaultScoper;
    _key = _userKey();
  }

  Uint8List _userKey() {
    var nameBytes = utf8.encode(_name);
    var secretBytes = utf8.encode(_secret);
    var keyScope = utf8.encode(_scoper.scope(Scope.authentication));

    var nameBytesLen = nameBytes.length;
    var keySalt = keyScope +
        List.from([
          nameBytesLen >> 24,
          nameBytesLen >> 16,
          nameBytesLen >> 8,
          nameBytesLen,
        ]) +
        nameBytes;

    scrypt.init(ScryptParameters(32768, 8, 2, 64, Uint8List.fromList(keySalt)));
    return scrypt.process(Uint8List.fromList(secretBytes));
  }

  Uint8List _siteKey(String name, int counter, Scope scope) {
    var nameBytes = utf8.encode(name);
    var scopeBytes = utf8.encode(_scoper.scope(scope));

    var nameBytesLen = nameBytes.length;
    var keySalt = scopeBytes +
        List.from([
          nameBytesLen >> 24,
          nameBytesLen >> 16,
          nameBytesLen >> 8,
          nameBytesLen,
        ]) +
        nameBytes +
        List.from([
          counter >> 24,
          counter >> 16,
          counter >> 8,
          counter,
        ]);

    hmac.init(KeyParameter(_key));
    return hmac.process(Uint8List.fromList(keySalt));
  }

  String site(String siteName,
      {Template? templateType,
      int counter = 1,
      Scope scope = Scope.authentication}) {
    templateType = templateType ?? scopeDefaultTemplate(scope);

    var siteKey = _siteKey(siteName, counter, scope);

    var templateSet = templates[templateType]!;
    var template = templateSet[siteKey[0] % templateSet.length];

    var out = StringBuffer();
    var idx = 0;
    for (var rune in template.runes) {
      var chars = characters[String.fromCharCode(rune)]!;
      var char = chars[siteKey[++idx] % chars.length];
      out.write(char);
    }
    return out.toString();
  }
}