/*
 * Copyright (C) 2022 Yubico.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

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

import 'package:base32/base32.dart';
import 'package:flutter_gen/gen_l10n/app_localizations.dart';
import 'package:freezed_annotation/freezed_annotation.dart';

import '../core/models.dart';

part 'models.freezed.dart';
part 'models.g.dart';

const defaultPeriod = 30;
const defaultDigits = 6;
const defaultCounter = 0;
const defaultOathType = OathType.totp;
const defaultHashAlgorithm = HashAlgorithm.sha1;

enum HashAlgorithm {
  @JsonValue(0x01)
  sha1('SHA-1'),
  @JsonValue(0x02)
  sha256('SHA-256'),
  @JsonValue(0x03)
  sha512('SHA-512');

  final String displayName;
  const HashAlgorithm(this.displayName);
}

enum OathType {
  @JsonValue(0x10)
  hotp,
  @JsonValue(0x20)
  totp;

  const OathType();

  String getDisplayName(AppLocalizations l10n) => switch (this) {
        OathType.hotp => l10n.s_counter_based,
        OathType.totp => l10n.s_time_based
      };
}

enum KeystoreState { unknown, allowed, failed }

@freezed
class OathCredential with _$OathCredential {
  factory OathCredential(
      String deviceId,
      String id,
      String? issuer,
      String name,
      OathType oathType,
      int period,
      bool touchRequired) = _OathCredential;

  factory OathCredential.fromJson(Map<String, dynamic> json) {
    final value = _$OathCredentialFromJson(json);
    // Replace empty issuer string with null
    return switch (value.issuer) {
      (String issuer) when issuer.isEmpty => value.copyWith(issuer: null),
      _ => value,
    };
  }
}

@freezed
class OathCode with _$OathCode {
  factory OathCode(String value, int validFrom, int validTo) = _OathCode;

  factory OathCode.fromJson(Map<String, dynamic> json) =>
      _$OathCodeFromJson(json);
}

@freezed
class OathPair with _$OathPair {
  factory OathPair(OathCredential credential, OathCode? code) = _OathPair;

  factory OathPair.fromJson(Map<String, dynamic> json) =>
      _$OathPairFromJson(json);
}

@freezed
class OathState with _$OathState {
  factory OathState(
    String deviceId,
    Version version, {
    required bool hasKey,
    required bool remembered,
    required bool locked,
    required KeystoreState keystore,
  }) = _OathState;

  factory OathState.fromJson(Map<String, dynamic> json) =>
      _$OathStateFromJson(json);
}

@freezed
class CredentialData with _$CredentialData {
  const CredentialData._();

  factory CredentialData({
    String? issuer,
    required String name,
    required String secret,
    @Default(defaultOathType) OathType oathType,
    @Default(defaultHashAlgorithm) HashAlgorithm hashAlgorithm,
    @Default(defaultDigits) int digits,
    @Default(defaultPeriod) int period,
    @Default(defaultCounter) int counter,
  }) = _CredentialData;

  factory CredentialData.fromJson(Map<String, dynamic> json) =>
      _$CredentialDataFromJson(json);

  static List<CredentialData> fromUri(Uri uri) {
    if (uri.scheme.toLowerCase() == 'otpauth-migration') {
      return CredentialData.fromMigration(uri);
    } else if (uri.scheme.toLowerCase() == 'otpauth') {
      return [CredentialData.fromOtpauth(uri)];
    } else {
      throw ArgumentError('Invalid scheme');
    }
  }

  static List<CredentialData> fromMigration(Uri uri) {
    // Parse single protobuf encoded integer
    (int value, Uint8List rem) protoInt(Uint8List data) {
      final extras = data.takeWhile((b) => b & 0x80 != 0).length;
      int value = 0;
      for (int i = extras; i >= 0; i--) {
        value = (value << 7) | (data[i] & 0x7F);
      }
      return (value, data.sublist(1 + extras));
    }

    // Parse a single protobuf value from a buffer
    (int tag, dynamic value, Uint8List rem) protoValue(Uint8List data) {
      final first = data[0];
      final int len;
      (len, data) = protoInt(data.sublist(1));
      final index = first >> 3;
      switch (first & 0x07) {
        case 0:
          return (index, len, data);
        case 2:
          return (index, data.sublist(0, len), data.sublist(len));
      }
      throw ArgumentError('Unsupported value type!');
    }

    // Parse a protobuf message into map of tags and values
    Map<int, dynamic> protoMap(Uint8List data) {
      Map<int, dynamic> values = {};
      while (data.isNotEmpty) {
        final (tag, value, rem) = protoValue(data);
        values[tag] = value;
        data = rem;
      }
      return values;
    }

    // Parse encoded credentials from data (tag 1) ignoring trailing extra data
    Iterable<Map<int, dynamic>> splitCreds(Uint8List rem) sync* {
      Uint8List credrem;
      while (rem[0] == 0x0a) {
        (_, credrem, rem) = protoValue(rem);
        yield protoMap(credrem);
      }
    }

    // Convert parsed credential values into CredentialData objects
    return splitCreds(base64.decode(uri.queryParameters['data']!))
        .map((values) {
      String? issuer;
      String name = utf8.decode(values[2], allowMalformed: true);
      final nameIndex = name.indexOf(':');
      if (nameIndex >= 0) {
        issuer = name.substring(0, nameIndex);
        name = name.substring(nameIndex + 1);
      }
      return CredentialData(
        secret: base32.encode(values[1]),
        name: name,
        issuer: values[3] != null
            ? utf8.decode(values[3], allowMalformed: true)
            : issuer,
        hashAlgorithm: switch (values[4]) {
          2 => HashAlgorithm.sha256,
          3 => HashAlgorithm.sha512,
          _ => HashAlgorithm.sha1,
        },
        digits: values[5] == 2 ? 8 : defaultDigits,
        oathType: values[6] == 1 ? OathType.hotp : OathType.totp,
        counter: values[7] ?? defaultCounter,
      );
    }).toList();
  }

  factory CredentialData.fromOtpauth(Uri uri) {
    final oathType = OathType.values.byName(uri.host.toLowerCase());
    final params = uri.queryParameters;
    String? issuer;
    String name = uri.pathSegments.join('/');
    final nameIndex = name.indexOf(':');
    if (nameIndex >= 0) {
      issuer = name.substring(0, nameIndex);
      name = name.substring(nameIndex + 1);
    }
    return CredentialData(
      issuer: params['issuer'] ?? issuer,
      name: name,
      oathType: oathType,
      hashAlgorithm: HashAlgorithm.values
          .byName(params['algorithm']?.toLowerCase() ?? 'sha1'),
      secret: params['secret']!,
      digits: int.tryParse(params['digits'] ?? '') ?? defaultDigits,
      period: int.tryParse(params['period'] ?? '') ?? defaultPeriod,
      counter: int.tryParse(params['counter'] ?? '') ?? defaultCounter,
    );
  }

  Uri toUri() => Uri(
        scheme: 'otpauth',
        host: oathType.name,
        path: issuer != null ? '$issuer:$name' : name,
        queryParameters: {
          'secret': secret,
          if (oathType == OathType.totp) 'period': period.toString(),
          if (oathType == OathType.hotp) 'counter': counter.toString(),
          if (issuer != null) 'issuer': issuer!,
          if (digits != 6) 'digits': digits.toString(),
          if (hashAlgorithm != HashAlgorithm.sha1)
            'algorithm': hashAlgorithm.name,
        },
      );
}