[main] add `Application` class (#1146)

This commit adds the `Application` class for better managing different
program components.

4 files changed, 259 insertions, 92 deletions

diff --git a/src/agent/CMakeLists.txt b/src/agent/CMakeLists.txt
index d204a1e4..45c0aceb 100644
--- a/src/agent/CMakeLists.txt
+++ b/src/agent/CMakeLists.txt
@@ -27,6 +27,7 @@
 #
 
 add_executable(otbr-agent
+    application.cpp
     main.cpp
     uris.hpp
     instance_params.cpp
diff --git a/src/agent/application.cpp b/src/agent/application.cpp
new file mode 100644
index 00000000..a25002b7
--- /dev/null
+++ b/src/agent/application.cpp
@@ -0,0 +1,125 @@
+/*
+ *    Copyright (c) 2021, The OpenThread Authors.
+ *    All rights reserved.
+ *
+ *    Redistribution and use in source and binary forms, with or without
+ *    modification, are permitted provided that the following conditions are met:
+ *    1. Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *    2. Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *    3. Neither the name of the copyright holder nor the
+ *       names of its contributors may be used to endorse or promote products
+ *       derived from this software without specific prior written permission.
+ *
+ *    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ *    AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ *    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ *    ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ *    LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ *    CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ *    SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ *    INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ *    CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ *    ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ *    POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/**
+ * @file
+ *   The file implements the OTBR Agent.
+ */
+
+#define OTBR_LOG_TAG "APP"
+
+#include "agent/application.hpp"
+#include "common/code_utils.hpp"
+#include "common/mainloop_manager.hpp"
+
+namespace otbr {
+
+bool                 Application::sShouldTerminate = false;
+const struct timeval Application::kPollTimeout     = {10, 0};
+
+Application::Application(Ncp::ControllerOpenThread &aOpenThread)
+    : mBorderAgent(aOpenThread)
+#if OTBR_ENABLE_OPENWRT
+    , mUbusAgent(aOpenThread)
+#endif
+#if OTBR_ENABLE_REST_SERVER
+    , mRestWebServer(aOpenThread)
+#endif
+#if OTBR_ENABLE_DBUS_SERVER
+    , mDBusAgent(aOpenThread)
+#endif
+#if OTBR_ENABLE_VENDOR_SERVER
+    , mVendorServer(aOpenThread)
+#endif
+{
+}
+
+void Application::Init(void)
+{
+    mBorderAgent.Init();
+#if OTBR_ENABLE_OPENWRT
+    mUbusAgent.Init();
+#endif
+#if OTBR_ENABLE_REST_SERVER
+    mRestWebServer.Init();
+#endif
+#if OTBR_ENABLE_DBUS_SERVER
+    mDBusAgent.Init();
+#endif
+#if OTBR_ENABLE_VENDOR_SERVER
+    mVendorServer.Init();
+#endif
+}
+
+otbrError Application::Run(void)
+{
+    otbrError error = OTBR_ERROR_NONE;
+
+    otbrLogInfo("Border router agent started.");
+    // allow quitting elegantly
+    signal(SIGTERM, HandleSignal);
+
+    while (!sShouldTerminate)
+    {
+        otbr::MainloopContext mainloop;
+        int                   rval;
+
+        mainloop.mMaxFd   = -1;
+        mainloop.mTimeout = kPollTimeout;
+
+        FD_ZERO(&mainloop.mReadFdSet);
+        FD_ZERO(&mainloop.mWriteFdSet);
+        FD_ZERO(&mainloop.mErrorFdSet);
+
+        MainloopManager::GetInstance().Update(mainloop);
+
+        rval = select(mainloop.mMaxFd + 1, &mainloop.mReadFdSet, &mainloop.mWriteFdSet, &mainloop.mErrorFdSet,
+                      &mainloop.mTimeout);
+
+        if (rval >= 0)
+        {
+            MainloopManager::GetInstance().Process(mainloop);
+        }
+        else if (errno != EINTR)
+        {
+            error = OTBR_ERROR_ERRNO;
+            otbrLogErr("select() failed: %s", strerror(errno));
+            break;
+        }
+    }
+
+    return error;
+}
+
+void Application::HandleSignal(int aSignal)
+{
+    sShouldTerminate = true;
+    signal(aSignal, SIG_DFL);
+}
+
+} // namespace otbr
diff --git a/src/agent/application.hpp b/src/agent/application.hpp
new file mode 100644
index 00000000..80f10327
--- /dev/null
+++ b/src/agent/application.hpp
@@ -0,0 +1,127 @@
+/*
+ *    Copyright (c) 2021, The OpenThread Authors.
+ *    All rights reserved.
+ *
+ *    Redistribution and use in source and binary forms, with or without
+ *    modification, are permitted provided that the following conditions are met:
+ *    1. Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *    2. Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *    3. Neither the name of the copyright holder nor the
+ *       names of its contributors may be used to endorse or promote products
+ *       derived from this software without specific prior written permission.
+ *
+ *    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ *    AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ *    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ *    ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ *    LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ *    CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ *    SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ *    INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ *    CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ *    ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ *    POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/**
+ * @file
+ *   This file includes definition for OTBR Agent.
+ */
+
+#ifndef OTBR_AGENT_APPLICATION_HPP_
+#define OTBR_AGENT_APPLICATION_HPP_
+
+#include <signal.h>
+#include <stdint.h>
+#include <vector>
+
+#include "border_agent/border_agent.hpp"
+#include "ncp/ncp_openthread.hpp"
+
+#if OTBR_ENABLE_REST_SERVER
+#include "rest/rest_web_server.hpp"
+#endif
+#if OTBR_ENABLE_DBUS_SERVER
+#include "dbus/server/dbus_agent.hpp"
+#endif
+#if OTBR_ENABLE_OPENWRT
+#include "openwrt/ubus/otubus.hpp"
+#endif
+#if OTBR_ENABLE_VENDOR_SERVER
+#include "agent/vendor.hpp"
+#endif
+
+namespace otbr {
+
+/**
+ * @addtogroup border-router-agent
+ *
+ * @brief
+ *   This module includes definition for OTBR application.
+ *
+ * @{
+ */
+
+/**
+ * This class implements OTBR application management.
+ *
+ */
+class Application
+{
+public:
+    /**
+     * This constructor initializes the Application instance.
+     *
+     * @param[in] aOpenThread  A reference to the OpenThread instance.
+     *
+     */
+    explicit Application(Ncp::ControllerOpenThread &aOpenThread);
+
+    /**
+     * This method initializes the Application instance.
+     *
+     */
+    void Init(void);
+
+    /**
+     * This method runs the application until exit.
+     *
+     * @retval OTBR_ERROR_NONE  The application exited without any error.
+     * @retval OTBR_ERROR_ERRNO The application exited with some system error.
+     *
+     */
+    otbrError Run(void);
+
+private:
+    // Default poll timeout.
+    static const struct timeval kPollTimeout;
+
+    static void HandleSignal(int aSignal);
+
+    BorderAgent mBorderAgent;
+#if OTBR_ENABLE_OPENWRT
+    ubus::UBusAgent mUbusAgent;
+#endif
+#if OTBR_ENABLE_REST_SERVER
+    rest::RestWebServer mRestWebServer;
+#endif
+#if OTBR_ENABLE_DBUS_SERVER
+    DBus::DBusAgent mDBusAgent;
+#endif
+#if OTBR_ENABLE_VENDOR_SERVER
+    vendor::VendorServer mVendorServer;
+#endif
+
+    static bool sShouldTerminate;
+};
+
+/**
+ * @}
+ */
+
+} // namespace otbr
+
+#endif // OTBR_AGENT_APPLICATION_HPP_
diff --git a/src/agent/main.cpp b/src/agent/main.cpp
index 5ec22df9..0d055080 100644
--- a/src/agent/main.cpp
+++ b/src/agent/main.cpp
@@ -31,11 +31,8 @@
 #include <fstream>
 #include <mutex>
 #include <sstream>
-#include <thread>
 
-#include <errno.h>
 #include <getopt.h>
-#include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -49,29 +46,13 @@
 #include <cutils/properties.h>
 #endif
 
+#include "agent/application.hpp"
 #include "border_agent/border_agent.hpp"
 #include "common/code_utils.hpp"
 #include "common/logging.hpp"
 #include "common/mainloop.hpp"
-#include "common/mainloop_manager.hpp"
 #include "common/types.hpp"
 #include "ncp/ncp_openthread.hpp"
-#if OTBR_ENABLE_REST_SERVER
-#include "rest/rest_web_server.hpp"
-using otbr::rest::RestWebServer;
-#endif
-#if OTBR_ENABLE_DBUS_SERVER
-#include "dbus/server/dbus_agent.hpp"
-using otbr::DBus::DBusAgent;
-#endif
-#if OTBR_ENABLE_OPENWRT
-#include "openwrt/ubus/otubus.hpp"
-using otbr::ubus::UBusAgent;
-#endif
-#if OTBR_ENABLE_VENDOR_SERVER
-#include "agent/vendor.hpp"
-using otbr::vendor::VendorServer;
-#endif
 
 static const char kSyslogIdent[]          = "otbr-agent";
 static const char kDefaultInterfaceName[] = "wpan0";
@@ -88,16 +69,10 @@ enum
     OTBR_OPT_RADIO_VERSION,
 };
 
-using otbr::MainloopManager;
-
 static jmp_buf sResetJump;
-static bool    sShouldTerminate = false;
-
-void __gcov_flush();
 
-// Default poll timeout.
-static const struct timeval kPollTimeout = {10, 0};
-static const struct option  kOptions[]   = {
+void                       __gcov_flush();
+static const struct option kOptions[] = {
     {"backbone-ifname", required_argument, nullptr, OTBR_OPT_BACKBONE_INTERFACE_NAME},
     {"debug-level", required_argument, nullptr, OTBR_OPT_DEBUG_LEVEL},
     {"help", no_argument, nullptr, OTBR_OPT_HELP},
@@ -107,74 +82,13 @@ static const struct option  kOptions[]   = {
     {"radio-version", no_argument, nullptr, OTBR_OPT_RADIO_VERSION},
     {0, 0, 0, 0}};
 
-static void HandleSignal(int aSignal)
-{
-    sShouldTerminate = true;
-    signal(aSignal, SIG_DFL);
-}
-
 static int Mainloop(otbr::Ncp::ControllerOpenThread &aOpenThread)
 {
-    int error = EXIT_SUCCESS;
-
-    otbr::BorderAgent borderAgent{aOpenThread};
-
-    borderAgent.Init();
-
-#if OTBR_ENABLE_OPENWRT
-    UBusAgent ubusAgent{aOpenThread};
-    ubusAgent.Init();
-#endif
-
-#if OTBR_ENABLE_REST_SERVER
-    RestWebServer restWebServer{aOpenThread};
-    restWebServer.Init();
-#endif
-
-#if OTBR_ENABLE_DBUS_SERVER
-    DBusAgent dbusAgent{aOpenThread};
-    dbusAgent.Init();
-#endif
-
-#if OTBR_ENABLE_VENDOR_SERVER
-    VendorServer vendorServer{aOpenThread};
-    vendorServer.Init();
-#endif
-
-    otbrLogInfo("Border router agent started.");
-    // allow quitting elegantly
-    signal(SIGTERM, HandleSignal);
-
-    while (!sShouldTerminate)
-    {
-        otbr::MainloopContext mainloop;
-        int                   rval;
-
-        mainloop.mMaxFd   = -1;
-        mainloop.mTimeout = kPollTimeout;
-
-        FD_ZERO(&mainloop.mReadFdSet);
-        FD_ZERO(&mainloop.mWriteFdSet);
-        FD_ZERO(&mainloop.mErrorFdSet);
+    otbr::Application app(aOpenThread);
 
-        MainloopManager::GetInstance().Update(mainloop);
-
-        rval = select(mainloop.mMaxFd + 1, &mainloop.mReadFdSet, &mainloop.mWriteFdSet, &mainloop.mErrorFdSet,
-                      &mainloop.mTimeout);
-
-        if (rval >= 0)
-        {
-            MainloopManager::GetInstance().Process(mainloop);
-        }
-        else if (errno != EINTR)
-        {
-            error = OTBR_ERROR_ERRNO;
-            otbrLogErr("select() failed: %s", strerror(errno));
-            break;
-        }
-    }
+    app.Init();
 
-    return error;
+    return app.Run();
 }
 
 static void PrintHelp(const char *aProgramName)