Introduce new models to encapsulate encryption attributes

lib/models/decryption_params.dart

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+import 'dart:convert';
+
+class DecryptionParams {
+  final String encryptedKey;
+  final String keyDecryptionNonce;
+  String header;
+  String nonce;
+
+  DecryptionParams({
+    this.encryptedKey,
+    this.keyDecryptionNonce,
+    this.header,
+    this.nonce,
+  });
+
+  DecryptionParams copyWith({
+    String encryptedKey,
+    String keyDecryptionNonce,
+    String header,
+    String nonce,
+  }) {
+    return DecryptionParams(
+      encryptedKey: encryptedKey ?? this.encryptedKey,
+      keyDecryptionNonce: keyDecryptionNonce ?? this.keyDecryptionNonce,
+      header: header ?? this.header,
+      nonce: nonce ?? this.nonce,
+    );
+  }
+
+  Map<String, dynamic> toMap() {
+    return {
+      'encryptedKey': encryptedKey,
+      'keyDecryptionNonce': keyDecryptionNonce,
+      'header': header,
+      'nonce': nonce,
+    };
+  }
+
+  factory DecryptionParams.fromMap(Map<String, dynamic> map) {
+    if (map == null) return null;
+
+    return DecryptionParams(
+      encryptedKey: map['encryptedKey'],
+      keyDecryptionNonce: map['keyDecryptionNonce'],
+      header: map['header'],
+      nonce: map['nonce'],
+    );
+  }
+
+  String toJson() => json.encode(toMap());
+
+  factory DecryptionParams.fromJson(String source) {
+    if (source == null) {
+      return null;
+    }
+    return DecryptionParams.fromMap(json.decode(source));
+  }
+
+  @override
+  String toString() {
+    return 'DecryptionParams(encryptedKey: $encryptedKey, keyDecryptionNonce: $keyDecryptionNonce, header: $header, nonce: $nonce)';
+  }
+
+  @override
+  bool operator ==(Object o) {
+    if (identical(this, o)) return true;
+
+    return o is DecryptionParams &&
+        o.encryptedKey == encryptedKey &&
+        o.keyDecryptionNonce == keyDecryptionNonce &&
+        o.header == header &&
+        o.nonce == nonce;
+  }
+
+  @override
+  int get hashCode {
+    return encryptedKey.hashCode ^
+        keyDecryptionNonce.hashCode ^
+        header.hashCode ^
+        nonce.hashCode;
+  }
+}

lib/models/encrypted_data_attributes.dart

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+import 'package:photos/models/encryption_attribute.dart';
+
+class EncryptedData {
+  final EncryptionAttribute key;
+  final EncryptionAttribute nonce;
+  final EncryptionAttribute encryptedData;
+
+  EncryptedData(this.key, this.nonce, this.encryptedData);
+}

lib/models/encryption_attribute.dart

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+import 'dart:typed_data';
+
+import 'package:flutter_sodium/flutter_sodium.dart';
+
+class EncryptionAttribute {
+  String base64;
+  Uint8List bytes;
+
+  EncryptionAttribute({this.base64, this.bytes}) {
+    if (base64 != null) {
+      this.bytes = Sodium.base642bin(base64);
+    } else {
+      this.base64 = Sodium.bin2base64(bytes);
+    }
+  }
+}