Add CastPlatformClient for handling sender requests

This change adds a new class for handling request/response sequences
initiated by a Cast sender.  It will initially be used for app
availability requests and is modelled after Chrome's CastMessageHandler.

Bug: openscreen:60
Change-Id: Iba5ae0ee343e23a2c0214b5b17a2b59dca2cbe99
Reviewed-on: https://chromium-review.googlesource.com/c/openscreen/+/2044149
Commit-Queue: Brandon Tolsch <btolsch@chromium.org>
Reviewed-by: mark a. foltz <mfoltz@chromium.org>
Reviewed-by: Takumi Fujimoto <takumif@chromium.org>

1 files changed, 97 insertions, 0 deletions

diff --git a/cast/sender/cast_platform_client.h b/cast/sender/cast_platform_client.h
new file mode 100644
index 00000000..41ad7fc7
--- /dev/null
+++ b/cast/sender/cast_platform_client.h
@@ -0,0 +1,97 @@
+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_SENDER_CAST_PLATFORM_CLIENT_H_
+#define CAST_SENDER_CAST_PLATFORM_CLIENT_H_
+
+#include <functional>
+#include <map>
+#include <string>
+
+#include "absl/types/optional.h"
+#include "cast/common/channel/cast_message_handler.h"
+#include "cast/sender/channel/message_util.h"
+#include "util/alarm.h"
+#include "util/json/json_value.h"
+
+namespace openscreen {
+namespace cast {
+
+struct ServiceInfo;
+class VirtualConnectionManager;
+class VirtualConnectionRouter;
+
+// This class handles Cast messages that generally relate to the "platform", in
+// other words not a specific app currently running (e.g. app availability,
+// receiver status).  These messages follow a request/response format, so each
+// request requires a corresponding response callback.  These requests will also
+// timeout if there is no response after a certain amount of time (currently 5
+// seconds).  The timeout callbacks will be called on the thread managed by
+// |task_runner|.
+class CastPlatformClient final : public CastMessageHandler {
+ public:
+  using AppAvailabilityCallback =
+      std::function<void(const std::string& app_id, AppAvailabilityResult)>;
+
+  CastPlatformClient(VirtualConnectionRouter* router,
+                     VirtualConnectionManager* manager,
+                     ClockNowFunctionPtr clock,
+                     TaskRunner* task_runner);
+  ~CastPlatformClient() override;
+
+  // Requests availability information for |app_id| from the receiver identified
+  // by |device_id|.  |callback| will be called exactly once with a result.
+  absl::optional<int> RequestAppAvailability(const std::string& device_id,
+                                             const std::string& app_id,
+                                             AppAvailabilityCallback callback);
+
+  // Notifies this object about general receiver connectivity or property
+  // changes.
+  void AddOrUpdateReceiver(const ServiceInfo& device, int socket_id);
+  void RemoveReceiver(const ServiceInfo& device);
+
+  void CancelRequest(int request_id);
+
+ private:
+  struct AvailabilityRequest {
+    int request_id;
+    std::string app_id;
+    std::unique_ptr<Alarm> timeout;
+    AppAvailabilityCallback callback;
+  };
+
+  struct PendingRequests {
+    std::vector<AvailabilityRequest> availability;
+  };
+
+  // CastMessageHandler overrides.
+  void OnMessage(VirtualConnectionRouter* router,
+                 CastSocket* socket,
+                 ::cast::channel::CastMessage message) override;
+
+  void HandleResponse(const std::string& device_id,
+                      int request_id,
+                      const Json::Value& message);
+
+  void CancelAppAvailabilityRequest(int request_id);
+
+  static int GetNextRequestId();
+
+  static int next_request_id_;
+
+  const std::string sender_id_;
+  VirtualConnectionRouter* const virtual_conn_router_;
+  VirtualConnectionManager* const virtual_conn_manager_;
+  std::map<std::string /* device_id */, int> socket_id_by_device_id_;
+  std::map<std::string /* device_id */, PendingRequests>
+      pending_requests_by_device_id_;
+
+  const ClockNowFunctionPtr clock_;
+  TaskRunner* const task_runner_;
+};
+
+}  // namespace cast
+}  // namespace openscreen
+
+#endif  // CAST_SENDER_CAST_PLATFORM_CLIENT_H_