TF-2667 Validate email in recipient form before send email

core/lib/utils/mail/domain.dart

@@ -0,0 +1,107 @@
+import 'package:equatable/equatable.dart';
+
+class Domain with EquatableMixin {
+  static final RegExp _dashMatcher = RegExp(r"[-_]");
+  static final RegExp _digitMatcher = RegExp(r"[0-9]");
+  static final RegExp _partCharMatcher = RegExp(r"[a-zA-Z0-9\-._]");
+
+  static final Domain localhost = Domain.of('localhost');
+  static const int maximumDomainLength = 253;
+
+  static String _removeBrackets(String domainName) {
+    if (!(domainName.startsWith("[") && domainName.endsWith("]"))) {
+      return domainName;
+    }
+    return domainName.substring(1, domainName.length - 1);
+  }
+
+  static Domain of(String domain) {
+    assert(
+      domain.length <= maximumDomainLength,
+      'Domain name length should not exceed $maximumDomainLength characters'
+    );
+
+    String domainWithoutBrackets = _removeBrackets(domain);
+    assert(
+      _partCharMatcher
+        .allMatches(domainWithoutBrackets)
+        .every((match) => match.group(0) != null),
+      'Domain parts ASCII chars must be a-z A-Z 0-9 - or _'
+    );
+
+    int pos = 0;
+    int nextDot = domainWithoutBrackets.indexOf('.');
+
+    while (nextDot > -1) {
+      if (pos + 1 > domainWithoutBrackets.length) {
+        throw ArgumentError('Last domain part should not be empty');
+      }
+      _assertValidPart(domainWithoutBrackets, pos, nextDot);
+      pos = nextDot + 1;
+      nextDot = domainWithoutBrackets.indexOf('.', pos);
+    }
+    _assertValidPart(domainWithoutBrackets, pos, domainWithoutBrackets.length);
+    _assertValidLastPart(domainWithoutBrackets, pos);
+    return Domain._(domainWithoutBrackets);
+  }
+
+  static void _assertValidPart(String domainPart, int begin, int end) {
+    assert(begin != end, "Domain part should not be empty");
+    assert(!_dashMatcher.hasMatch(domainPart[begin]),
+        "Domain part should not start with '-' or '_'");
+    assert(!_dashMatcher.hasMatch(domainPart[end - 1]),
+        "Domain part should not end with '-' or '_'");
+    assert(
+        end - begin <= 63, "Domain part should not not exceed 63 characters");
+  }
+
+  static void _assertValidLastPart(String domainPart, int pos) {
+    bool onlyDigits = _digitMatcher.hasMatch(domainPart[pos]);
+    bool invalid = onlyDigits && !_validIPAddress(domainPart);
+    assert(!invalid, "The last domain part must not start with 0-9");
+  }
+
+  static bool _validIPAddress(String value) {
+    try {
+      Uri.parseIPv6Address(value);
+      return true;
+    } catch (e) {
+      return false;
+    }
+  }
+
+  final String domainName;
+  final String normalizedDomainName;
+
+  Domain._(this.domainName)
+      : normalizedDomainName = _removeBrackets(domainName.toLowerCase());
+
+  String name() {
+    return domainName;
+  }
+
+  String asString() {
+    return normalizedDomainName;
+  }
+
+  @override
+  bool operator ==(Object other) {
+    if (other is Domain) {
+      return normalizedDomainName == other.normalizedDomainName;
+    }
+    return false;
+  }
+
+  @override
+  int get hashCode {
+    return normalizedDomainName.hashCode;
+  }
+
+  @override
+  String toString() {
+    return "Domain : $domainName";
+  }
+
+  @override
+  List<Object?> get props => [domainName];
+}