text/event-stream handle (#555)

lib/network/http/content_type.dart

@@ -30,7 +30,10 @@ enum ContentType {
   font,
   image,
   video,
-  http;
+  http,
+  sse
+
+  ;
 
   static ContentType valueOf(String name) {
     return ContentType.values.firstWhere((element) => element.name == name.toLowerCase(), orElse: () => http);

lib/network/http/http.dart

@@ -43,7 +43,8 @@ abstract class HttpMessage {
     "form-data": ContentType.formData,
     "image": ContentType.image,
     "video": ContentType.video,
-    "application/json": ContentType.json
+    "application/json": ContentType.json,
+    "text/event-stream": ContentType.sse,
   };
 
   String protocolVersion;

lib/network/http/sse.dart

@@ -0,0 +1,117 @@
+/*
+ * Server-Sent Events (text/event-stream) incremental decoder
+ */
+
+import 'dart:convert';
+import 'dart:typed_data';
+
+import 'package:proxypin/network/http/websocket.dart';
+
+/// Parse SSE stream chunks into message frames.
+/// We reuse WebSocketFrame as a generic message container so UI and listeners work.
+class SseDecoder {
+  final StringBuffer _lineBuf = StringBuffer();
+
+  // current event fields
+  final StringBuffer _data = StringBuffer();
+  String? _event;
+  String? _id;
+  int? _retry;
+
+  /// Feed a chunk of bytes and return zero or more frames assembled.
+  List<WebSocketFrame> feed(Uint8List bytes) {
+    final List<WebSocketFrame> frames = [];
+
+    // Append decoded text to buffer; allowMalformed to survive split UTF-8 sequences.
+    _lineBuf.write(utf8.decode(bytes, allowMalformed: true));
+
+    while (true) {
+      final String current = _lineBuf.toString();
+      final int nl = current.indexOf('\n');
+      if (nl == -1) break;
+
+      String line = current.substring(0, nl);
+      _lineBuf.clear();
+      if (nl + 1 < current.length) _lineBuf.write(current.substring(nl + 1));
+
+      if (line.endsWith('\r')) line = line.substring(0, line.length - 1);
+
+      if (line.isEmpty) {
+        // End of event: emit if any data collected
+        if (_data.isNotEmpty) {
+          String dataValue = _data.toString();
+          if (dataValue.endsWith('\n')) dataValue = dataValue.substring(0, dataValue.length - 1);
+
+          // Build a text frame from the SSE event. Include event/id headers if present as a prefix comment.
+          final String payloadText = _event == null && _id == null
+              ? dataValue
+              : _buildLabeledPayload(dataValue, event: _event, id: _id, retry: _retry);
+
+          frames.add(_textFrame(payloadText));
+        }
+        _resetEventState();
+        continue;
+      }
+
+      if (line.startsWith(':')) {
+        // comment line – ignore
+        continue;
+      }
+
+      final int colon = line.indexOf(':');
+      final String field = (colon == -1) ? line : line.substring(0, colon);
+      String value = (colon == -1) ? '' : line.substring(colon + 1);
+      if (value.startsWith(' ')) value = value.substring(1);
+
+      switch (field) {
+        case 'data':
+          _data.write(value);
+          _data.write('\n');
+          break;
+        case 'event':
+          _event = value;
+          break;
+        case 'id':
+          _id = value;
+          break;
+        case 'retry':
+          _retry = int.tryParse(value);
+          break;
+        default:
+          // ignore unknown fields
+          break;
+      }
+    }
+
+    return frames;
+  }
+
+  void _resetEventState() {
+    _data.clear();
+    _event = null;
+    _id = null;
+    _retry = null;
+  }
+
+  String _buildLabeledPayload(String data, {String? event, String? id, int? retry}) {
+    final StringBuffer b = StringBuffer();
+    if (event != null && event.isNotEmpty) b.writeln('event: $event');
+    if (id != null && id.isNotEmpty) b.writeln('id: $id');
+    if (retry != null) b.writeln('retry: $retry');
+    b.write(data);
+    return b.toString();
+  }
+
+  WebSocketFrame _textFrame(String text) {
+    final bytes = utf8.encode(text);
+    return WebSocketFrame(
+      fin: true,
+      opcode: 0x01, // text
+      mask: false,
+      payloadLength: bytes.length,
+      maskingKey: 0,
+      payloadData: Uint8List.fromList(bytes),
+    );
+  }
+}
+