simplified code across the app and consolidated duplicated helpers

lib/api/marianumcloud/talk/chat/fetch_chat_page.dart

@@ -0,0 +1,46 @@
+import 'package:flutter/foundation.dart';
+import 'package:http/http.dart' as http;
+
+import '../../../errors/server_exception.dart';
+import '../../../http_errors.dart';
+import '../../nextcloud_ocs.dart';
+import 'get_chat_params.dart';
+import 'get_chat_response.dart';
+
+/// GETs a chat page outside [TalkApi], which treats non-2xx as errors: here
+/// HTTP 304 (nothing new / no older messages) is a normal outcome and yields
+/// `null`.
+Future<GetChatResponse?> fetchChatPage({
+  required String label,
+  required String chatToken,
+  required GetChatParams params,
+  Duration? timeout,
+  bool parseOffIsolate = false,
+}) async {
+  final uri = NextcloudOcs.uri(
+    'apps/spreed/api/v1/chat/$chatToken',
+    queryParameters: params.toJson(),
+  );
+  final headers = NextcloudOcs.headers();
+
+  final response = (await sendGuarded('$label $uri', () {
+    final request = http.get(uri, headers: headers);
+    return timeout == null ? request : request.timeout(timeout);
+  }))!;
+
+  final status = response.statusCode;
+  if (status == 304) return null;
+  if (status >= 200 && status < 300) {
+    final parsed = parseOffIsolate
+        ? await compute(_parseChatResponse, response.body)
+        : _parseChatResponse(response.body);
+    return parsed..headers = response.headers;
+  }
+  throw ServerException(
+    statusCode: status,
+    technicalDetails: '$label $uri: HTTP $status',
+  );
+}
+
+GetChatResponse _parseChatResponse(String body) =>
+    GetChatResponse.fromJson(NextcloudOcs.decode(body));

lib/api/marianumcloud/talk/chat/get_chat.dart

@@ -1,6 +1,3 @@
-import 'package:http/http.dart' as http;
-import 'package:http/http.dart';
-
 import '../../nextcloud_ocs.dart';
 import '../talk_api.dart';
 import 'get_chat_params.dart';
@@ -16,11 +13,4 @@ class GetChat extends TalkApi<GetChatResponse> {
   @override
   GetChatResponse assemble(String raw) =>
       GetChatResponse.fromJson(NextcloudOcs.decode(raw));
-
-  @override
-  Future<Response> request(
-    Uri uri,
-    Object? body,
-    Map<String, String>? headers,
-  ) => http.get(uri, headers: headers);
 }

lib/api/marianumcloud/talk/chat/get_chat_history.dart

@@ -1,17 +1,12 @@
-import 'package:flutter/foundation.dart';
-import 'package:http/http.dart' as http;
-
-import '../../../errors/server_exception.dart';
-import '../../../http_errors.dart';
-import '../../nextcloud_ocs.dart';
+import 'fetch_chat_page.dart';
 import 'get_chat_params.dart';
 import 'get_chat_response.dart';
 
 /// Backwards-paging variant of GetChat (`lookIntoFuture=0` + `lastKnownMessageId`)
-/// that fetches the page of messages *older* than a given id. Bypasses [TalkApi]
-/// because that layer treats non-2xx as errors, and the server answers HTTP 304
-/// when there are no older messages left — a normal "start of chat" outcome here.
-/// `setReadMarker=off` so paging into history never moves the read cursor.
+/// that fetches the page of messages *older* than a given id. The server
+/// answers HTTP 304 when there are no older messages left — a normal "start of
+/// chat" outcome (see [fetchChatPage]). `setReadMarker=off` so paging into
+/// history never moves the read cursor.
 class GetChatHistory {
   final String chatToken;
   final int lastKnownMessageId;
@@ -24,39 +19,18 @@ class GetChatHistory {
   });
 
   /// Returns the older page, or `null` on HTTP 304 (no older messages).
-  Future<GetChatResponse?> run() async {
-    final params = GetChatParams(
+  Future<GetChatResponse?> run() => fetchChatPage(
+    label: 'GetChatHistory',
+    chatToken: chatToken,
+    params: GetChatParams(
       lookIntoFuture: GetChatParamsSwitch.off,
       lastKnownMessageId: lastKnownMessageId,
       includeLastKnown: GetChatParamsSwitch.off,
       setReadMarker: GetChatParamsSwitch.off,
       limit: limit,
-    );
-    final uri = NextcloudOcs.uri(
-      'apps/spreed/api/v1/chat/$chatToken',
-      queryParameters: params.toJson(),
-    );
-    final headers = NextcloudOcs.headers();
-
-    final response = (await sendGuarded(
-      'GetChatHistory $uri',
-      () => http.get(uri, headers: headers),
-    ))!;
-
-    final status = response.statusCode;
-    if (status == 304) return null;
-    if (status >= 200 && status < 300) {
-      // A page holds up to 200 messages and lands while the user is scrolling;
-      // decoding it on the UI isolate stalls the fling.
-      final parsed = await compute(_parseChatResponse, response.body);
-      return parsed..headers = response.headers;
-    }
-    throw ServerException(
-      statusCode: status,
-      technicalDetails: 'GetChatHistory $uri: HTTP $status',
-    );
-  }
+    ),
+    // A page holds up to 200 messages and lands while the user is scrolling;
+    // decoding it on the UI isolate stalls the fling.
+    parseOffIsolate: true,
+  );
 }
-
-GetChatResponse _parseChatResponse(String body) =>
-    GetChatResponse.fromJson(NextcloudOcs.decode(body));

lib/api/marianumcloud/talk/chat/long_poll_chat.dart

@@ -1,15 +1,10 @@
-import 'package:http/http.dart' as http;
-
-import '../../../errors/server_exception.dart';
-import '../../../http_errors.dart';
-import '../../nextcloud_ocs.dart';
+import 'fetch_chat_page.dart';
 import 'get_chat_params.dart';
 import 'get_chat_response.dart';
 
-/// Long-poll variant of GetChat (`lookIntoFuture=1`). Bypasses [TalkApi]
-/// because that layer treats non-2xx as errors, and we need 304 to be a
-/// normal "no new messages" outcome. `setReadMarker=on` lets the server
-/// move the read cursor whenever the call returns messages.
+/// Long-poll variant of GetChat (`lookIntoFuture=1`); HTTP 304 is the normal
+/// "no new messages" outcome (see [fetchChatPage]). `setReadMarker=on` lets
+/// the server move the read cursor whenever the call returns messages.
 class LongPollChat {
   final String chatToken;
   final int lastKnownMessageId;
@@ -22,37 +17,17 @@ class LongPollChat {
   });
 
   /// Returns the response, or `null` on HTTP 304 (server timeout, nothing new).
-  Future<GetChatResponse?> run() async {
-    final params = GetChatParams(
+  Future<GetChatResponse?> run() => fetchChatPage(
+    label: 'LongPollChat',
+    chatToken: chatToken,
+    params: GetChatParams(
       lookIntoFuture: GetChatParamsSwitch.on,
       timeout: timeoutSeconds,
       lastKnownMessageId: lastKnownMessageId,
       includeLastKnown: GetChatParamsSwitch.off,
       setReadMarker: GetChatParamsSwitch.on,
       limit: 100,
-    );
-    final uri = NextcloudOcs.uri(
-      'apps/spreed/api/v1/chat/$chatToken',
-      queryParameters: params.toJson(),
-    );
-    final headers = NextcloudOcs.headers();
-
-    final response = (await sendGuarded(
-      'LongPollChat $uri',
-      () => http
-          .get(uri, headers: headers)
-          .timeout(Duration(seconds: timeoutSeconds + 15)),
-    ))!;
-
-    final status = response.statusCode;
-    if (status == 304) return null;
-    if (status >= 200 && status < 300) {
-      return GetChatResponse.fromJson(NextcloudOcs.decode(response.body))
-        ..headers = response.headers;
-    }
-    throw ServerException(
-      statusCode: status,
-      technicalDetails: 'LongPollChat $uri: HTTP $status',
-    );
-  }
+    ),
+    timeout: Duration(seconds: timeoutSeconds + 15),
+  );
 }