Separate the cronet callbacks from the send method

pkgs/cronet_http/lib/src/cronet_client.dart

@@ -135,6 +135,103 @@ Map<String, String> _cronetToClientHeaders(
         key.toDartString(releaseOriginal: true).toLowerCase(),
         value.join(',')));
 
+jb.UrlRequestCallbackProxy_UrlRequestCallbackInterface _urlRequestCallbacks(
+    BaseRequest request, Completer<StreamedResponse> responseCompleter) {
+  StreamController<List<int>>? responseStream;
+  jb.ByteBuffer? byteBuffer;
+  var numRedirects = 0;
+
+  // The order of callbacks generated by Cronet is documented here:
+  // https://developer.android.com/guide/topics/connectivity/cronet/lifecycle
+  return jb.UrlRequestCallbackProxy_UrlRequestCallbackInterface.implement(
+      jb.$UrlRequestCallbackProxy_UrlRequestCallbackInterfaceImpl(
+    onResponseStarted: (urlRequest, responseInfo) {
+      responseStream = StreamController();
+      final responseHeaders =
+          _cronetToClientHeaders(responseInfo.getAllHeaders());
+      int? contentLength;
+
+      switch (responseHeaders['content-length']) {
+        case final contentLengthHeader?
+            when !_digitRegex.hasMatch(contentLengthHeader):
+          responseCompleter.completeError(ClientException(
+            'Invalid content-length header [$contentLengthHeader].',
+            request.url,
+          ));
+          urlRequest.cancel();
+          return;
+        case final contentLengthHeader?:
+          contentLength = int.parse(contentLengthHeader);
+      }
+      responseCompleter.complete(StreamedResponse(
+        responseStream!.stream,
+        responseInfo.getHttpStatusCode(),
+        contentLength: contentLength,
+        reasonPhrase: responseInfo
+            .getHttpStatusText()
+            .toDartString(releaseOriginal: true),
+        request: request,
+        isRedirect: false,
+        headers: responseHeaders,
+      ));
+
+      byteBuffer = jb.ByteBuffer.allocateDirect(1024 * 1024);
+      urlRequest.read(byteBuffer!);
+    },
+    onRedirectReceived: (urlRequest, responseInfo, newLocationUrl) {
+      if (!request.followRedirects) {
+        urlRequest.cancel();
+        responseCompleter.complete(StreamedResponse(
+            const Stream.empty(), // Cronet provides no body for redirects.
+            responseInfo.getHttpStatusCode(),
+            contentLength: 0,
+            reasonPhrase: responseInfo
+                .getHttpStatusText()
+                .toDartString(releaseOriginal: true),
+            request: request,
+            isRedirect: true,
+            headers: _cronetToClientHeaders(responseInfo.getAllHeaders())));
+        return;
+      }
+      ++numRedirects;
+      if (numRedirects <= request.maxRedirects) {
+        urlRequest.followRedirect();
+      } else {
+        urlRequest.cancel();
+        responseCompleter.completeError(
+            ClientException('Redirect limit exceeded', request.url));
+      }
+    },
+    onReadCompleted: (urlRequest, responseInfo, byteBuffer) {
+      byteBuffer.flip();
+
+      final remaining = byteBuffer.remaining();
+      final data = Uint8List(remaining);
+      // TODO: Use a more efficient approach when
+      // https://github.com/dart-lang/jnigen/issues/387 is fixed.
+      for (var i = 0; i < remaining; ++i) {
+        data[i] = byteBuffer.get1(i);
+      }
+      responseStream!.add(data);
+      byteBuffer.clear();
+      urlRequest.read(byteBuffer);
+    },
+    onSucceeded: (urlRequest, responseInfo) {
+      responseStream!.sink.close();
+    },
+    onFailed: (urlRequest, responseInfo, cronetException) {
+      final error = ClientException(
+          'Cronet exception: ${cronetException.toString()}', request.url);
+      if (responseStream == null) {
+        responseCompleter.completeError(error);
+      } else {
+        responseStream!.addError(error);
+        responseStream!.close();
+      }
+    },
+  ));
+}
+
 /// A HTTP [Client] based on the
 /// [Cronet](https://developer.android.com/guide/topics/connectivity/cronet)
 /// network stack.
@@ -219,106 +316,10 @@ class CronetClient extends BaseClient {
     final responseCompleter = Completer<StreamedResponse>();
     final engine = _engine!._engine;
 
-    late jb.UrlRequest cronetRequest;
-    var numRedirects = 0;
-    StreamController<List<int>>? responseStream;
-    jb.ByteBuffer? byteBuffer;
-
-    // The order of callbacks generated by Cronet is documented here:
-    // https://developer.android.com/guide/topics/connectivity/cronet/lifecycle
-
-    final cronetCallbacks =
-        jb.UrlRequestCallbackProxy_UrlRequestCallbackInterface.implement(
-            jb.$UrlRequestCallbackProxy_UrlRequestCallbackInterfaceImpl(
-      onResponseStarted: (urlRequest, responseInfo) {
-        responseStream = StreamController();
-        final responseHeaders =
-            _cronetToClientHeaders(responseInfo.getAllHeaders());
-        int? contentLength;
-
-        switch (responseHeaders['content-length']) {
-          case final contentLengthHeader?
-              when !_digitRegex.hasMatch(contentLengthHeader):
-            responseCompleter.completeError(ClientException(
-              'Invalid content-length header [$contentLengthHeader].',
-              request.url,
-            ));
-            urlRequest.cancel();
-            return;
-          case final contentLengthHeader?:
-            contentLength = int.parse(contentLengthHeader);
-        }
-        responseCompleter.complete(StreamedResponse(
-          responseStream!.stream,
-          responseInfo.getHttpStatusCode(),
-          contentLength: contentLength,
-          reasonPhrase: responseInfo
-              .getHttpStatusText()
-              .toDartString(releaseOriginal: true),
-          request: request,
-          isRedirect: false,
-          headers: responseHeaders,
-        ));
-
-        byteBuffer = jb.ByteBuffer.allocateDirect(1024 * 1024);
-        urlRequest.read(byteBuffer!);
-      },
-      onRedirectReceived: (urlRequest, responseInfo, newLocationUrl) {
-        if (!request.followRedirects) {
-          cronetRequest.cancel();
-          responseCompleter.complete(StreamedResponse(
-              const Stream.empty(), // Cronet provides no body for redirects.
-              responseInfo.getHttpStatusCode(),
-              contentLength: 0,
-              reasonPhrase: responseInfo
-                  .getHttpStatusText()
-                  .toDartString(releaseOriginal: true),
-              request: request,
-              isRedirect: true,
-              headers: _cronetToClientHeaders(responseInfo.getAllHeaders())));
-          return;
-        }
-        ++numRedirects;
-        if (numRedirects <= request.maxRedirects) {
-          cronetRequest.followRedirect();
-        } else {
-          cronetRequest.cancel();
-          responseCompleter.completeError(
-              ClientException('Redirect limit exceeded', request.url));
-        }
-      },
-      onReadCompleted: (urlRequest, responseInfo, byteBuffer) {
-        byteBuffer.flip();
-
-        final remaining = byteBuffer.remaining();
-        final data = Uint8List(remaining);
-        // TODO: Use a more efficient approach when
-        // https://github.com/dart-lang/jnigen/issues/387 is fixed.
-        for (var i = 0; i < remaining; ++i) {
-          data[i] = byteBuffer.get1(i);
-        }
-        responseStream!.add(data);
-        byteBuffer.clear();
-        cronetRequest.read(byteBuffer);
-      },
-      onSucceeded: (urlRequest, responseInfo) {
-        responseStream!.sink.close();
-      },
-      onFailed: (urlRequest, responseInfo, cronetException) {
-        final error = ClientException(
-            'Cronet exception: ${cronetException.toString()}', request.url);
-        if (responseStream == null) {
-          responseCompleter.completeError(error);
-        } else {
-          responseStream!.addError(error);
-          responseStream!.close();
-        }
-      },
-    ));
-
     final builder = engine.newUrlRequestBuilder(
       request.url.toString().toJString(),
-      jb.UrlRequestCallbackProxy.new1(cronetCallbacks),
+      jb.UrlRequestCallbackProxy.new1(
+          _urlRequestCallbacks(request, responseCompleter)),
       _executor,
     );
 
@@ -341,7 +342,7 @@ class CronetClient extends BaseClient {
       builder.setUploadDataProvider(
           jb.UploadDataProviders.create4(bodyBytes), _executor);
     }
-    cronetRequest = builder.build()..start();
-    return responseCompleter.future.whenComplete(() => byteBuffer?.release());
+    builder.build().start();
+    return responseCompleter.future;
   }
 }