extract method to create a PostgreSQL Epoch Base DateTime using the correct local timezone, restore original _messageTypeMap

Author: Isaque Neves

example/example.dart

@@ -83,4 +83,4 @@ void main() async {
   print(await subscription.schema);
 
   await conn.close();
-}
+}

lib/src/message_window.dart

@@ -15,74 +15,35 @@ const int _headerByteSize = 5;
 typedef _ServerMessageFn = ServerMessage Function(
     PgByteDataReader reader, int length);
 
-// Map<int, _ServerMessageFn> _messageTypeMap = {
-//   49: (_, __) => ParseCompleteMessage(),
-//   50: (_, __) => BindCompleteMessage(),
-//   65: (r, _) => NotificationResponseMessage.parse(r),
-//   67: (r, _) => CommandCompleteMessage.parse(r),
-//   68: (r, _) => DataRowMessage.parse(r),
-//   69: ErrorResponseMessage.parse,
-//   75: (r, _) => BackendKeyMessage.parse(r),
-//   82: AuthenticationMessage.parse,
-//   83: (r, l) => ParameterStatusMessage.parse(r),
-//   84: (r, _) => RowDescriptionMessage.parse(r),
-//   87: (r, _) => CopyBothResponseMessage.parse(r),
-//   90: ReadyForQueryMessage.parse,
-//   100: _parseCopyDataMessage,
-//   110: (_, __) => NoDataMessage(),
-//   116: (r, _) => ParameterDescriptionMessage.parse(r),
-//   $3: (_, __) => CloseCompleteMessage(),
-//   $N: NoticeMessage.parse,
-// };
+Map<int, _ServerMessageFn> _messageTypeMap = {
+  49: (_, __) => ParseCompleteMessage(),
+  50: (_, __) => BindCompleteMessage(),
+  65: (r, _) => NotificationResponseMessage.parse(r),
+  67: (r, _) => CommandCompleteMessage.parse(r),
+  68: (r, _) => DataRowMessage.parse(r),
+  69: ErrorResponseMessage.parse,
+  75: (r, _) => BackendKeyMessage.parse(r),
+  82: AuthenticationMessage.parse,
+  83: (r, l) => ParameterStatusMessage.parse(r),
+  84: (r, _) => RowDescriptionMessage.parse(r),
+  87: (r, _) => CopyBothResponseMessage.parse(r),
+  90: ReadyForQueryMessage.parse,
+  100: _parseCopyDataMessage,
+  110: (_, __) => NoDataMessage(),
+  116: (r, _) => ParameterDescriptionMessage.parse(r),
+  $3: (_, __) => CloseCompleteMessage(),
+  $N: NoticeMessage.parse,
+};
 
 class MessageFramer {
   final Encoding _encoding;
   TimeZoneSettings timeZone;
-  late final _reader = PgByteDataReader(encoding: _encoding, timeZone: timeZone);
+  late final _reader =
+      PgByteDataReader(encoding: _encoding, timeZone: timeZone);
   final messageQueue = Queue<ServerMessage>();
 
   MessageFramer(this._encoding, this.timeZone);
 
-  _ServerMessageFn? _messageTypeMap(int? messageType) {
-    switch (messageType) {
-      case 49:
-        return (_, __) => ParseCompleteMessage();
-      case 50:
-        return (_, __) => BindCompleteMessage();
-      case 65:
-        return (r, _) => NotificationResponseMessage.parse(r);
-      case 67:
-        return (r, _) => CommandCompleteMessage.parse(r);
-      case 68:
-        return (r, _) => DataRowMessage.parse(r);
-      case 69:
-        return ErrorResponseMessage.parse;
-      case 75:
-        return (r, _) => BackendKeyMessage.parse(r);
-      case 82:
-        return AuthenticationMessage.parse;
-      case 83:
-        return (r, l) => ParameterStatusMessage.parse(r);
-      case 84:
-        return (r, _) => RowDescriptionMessage.parse(r);
-      case 87:
-        return (r, _) => CopyBothResponseMessage.parse(r);
-      case 90:
-        return ReadyForQueryMessage.parse;
-      case 100:
-        return _parseCopyDataMessage;
-      case 110:
-        return (_, __) => NoDataMessage();
-      case 116:
-        return (r, _) => ParameterDescriptionMessage.parse(r);
-      case $3:
-        return (_, __) => CloseCompleteMessage();
-      case $N:
-        return NoticeMessage.parse;
-    }
-    return null;
-  }
-
   int? _type;
   int _expectedLength = 0;
 
@@ -111,7 +72,7 @@ class MessageFramer {
       }
 
       if (_hasReadHeader && _isComplete) {
-        final msgMaker = _messageTypeMap(_type);
+        final msgMaker = _messageTypeMap[_type];
         if (msgMaker == null) {
           _addMsg(UnknownMessage(_type!, _reader.read(_expectedLength)));
           continue;
@@ -158,7 +119,8 @@ ServerMessage _parseCopyDataMessage(PgByteDataReader reader, int length) {
   if (code == ReplicationMessageId.primaryKeepAlive) {
     return PrimaryKeepAliveMessage.parse(reader);
   } else if (code == ReplicationMessageId.xLogData) {
-    return XLogDataMessage.parse(reader.read(length - 1), reader.encoding, reader.timeZone);
+    return XLogDataMessage.parse(
+        reader.read(length - 1), reader.encoding, reader.timeZone);
   } else {
     final bb = BytesBuffer();
     bb.addByte(code);

lib/src/types/binary_codec.dart

@@ -796,14 +796,8 @@ class PostgresBinaryDecoder {
         if (dinput.timeZone.forceDecodeDateAsUTC) {
           return DateTime.utc(2000).add(Duration(days: value));
         }
-        // https://github.com/dart-lang/sdk/issues/56312
-        // ignore past timestamp transitions and use only current timestamp in local datetime
-        final nowDt = DateTime.now();
-        var baseDt = DateTime(2000);
-        if (baseDt.timeZoneOffset != nowDt.timeZoneOffset) {
-          final difference = baseDt.timeZoneOffset - nowDt.timeZoneOffset;
-          baseDt = baseDt.add(difference);
-        }
+
+        final baseDt = _getPostgreSQLEpochBaseDate();
         return baseDt.add(Duration(days: value));
       case TypeOid.timestampWithoutTimezone:
         final value = buffer.getInt64(0);
@@ -815,14 +809,8 @@ class PostgresBinaryDecoder {
         if (dinput.timeZone.forceDecodeTimestampAsUTC) {
           return DateTime.utc(2000).add(Duration(microseconds: value));
         }
-        // https://github.com/dart-lang/sdk/issues/56312
-        // ignore previous timestamp transitions and use only the current system timestamp in local date and time so that the behavior is correct on Windows and Linux
-        final nowDt = DateTime.now();
-        var baseDt = DateTime(2000);
-        if (baseDt.timeZoneOffset != nowDt.timeZoneOffset) {
-          final difference = baseDt.timeZoneOffset - nowDt.timeZoneOffset;
-          baseDt = baseDt.add(difference);
-        }
+
+        final baseDt = _getPostgreSQLEpochBaseDate();
         return baseDt.add(Duration(microseconds: value));
 
       case TypeOid.timestampWithTimezone:
@@ -1054,6 +1042,29 @@ class PostgresBinaryDecoder {
     );
   }
 
+  /// Returns a base DateTime object representing the PostgreSQL epoch
+  /// (January 1, 2000), adjusted to the current system's timezone offset.
+  ///
+  /// This method ensures that the base DateTime object is consistent across
+  /// different system environments (e.g., Windows, Linux) by adjusting the
+  /// base DateTime's timezone offset to match the current system's timezone
+  /// offset. This adjustment is necessary due to potential differences in
+  /// how different operating systems handle timezone transitions.
+  /// Returns:
+  /// - A `DateTime` object representing January 1, 2000, adjusted to the
+  ///   current system's timezone offset.
+  DateTime _getPostgreSQLEpochBaseDate() {
+    // https://github.com/dart-lang/sdk/issues/56312
+    // ignore past timestamp transitions and use only current timestamp in local datetime
+    final nowDt = DateTime.now();
+    var baseDt = DateTime(2000);
+    if (baseDt.timeZoneOffset != nowDt.timeZoneOffset) {
+      final difference = baseDt.timeZoneOffset - nowDt.timeZoneOffset;
+      baseDt = baseDt.add(difference);
+    }
+    return baseDt;
+  }
+
   List<V> readListBytes<V>(Uint8List data,
       V Function(ByteDataReader reader, int length) valueDecoder) {
     if (data.length < 16) {