privetd: Implement privet/v3/commands/status

Privetd just forwards IDs to the buffet and buffet returns JSON
representation of the command.

BUG=brillo:430
TEST=unittest

Change-Id: I5698f9fc915ae32dc2b9be3cc35f8efe919ee4e3
Reviewed-on: https://chromium-review.googlesource.com/261641
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Reviewed-by: Vitaly Buka <vitalybuka@chromium.org>
Commit-Queue: Vitaly Buka <vitalybuka@chromium.org>
Tested-by: Vitaly Buka <vitalybuka@chromium.org>

buffet/dbus_bindings/org.chromium.Buffet.Manager.xml

diff --git a/buffet/dbus_bindings/org.chromium.Buffet.Manager.xml b/buffet/dbus_bindings/org.chromium.Buffet.Manager.xml
index 8473fe2..8b59b42 100644
--- a/buffet/dbus_bindings/org.chromium.Buffet.Manager.xml
+++ b/buffet/dbus_bindings/org.chromium.Buffet.Manager.xml
@@ -33,6 +33,11 @@
       <arg name="json_command" type="s" direction="in"/>
       <annotation name="org.chromium.DBus.Method.Kind" value="async"/>
     </method>
+    <method name="GetCommand">
+      <arg name="id" type="s" direction="in"/>
+      <arg name="json_command" type="s" direction="out"/>
+      <annotation name="org.chromium.DBus.Method.Kind" value="async"/>
+    </method>
     <method name="TestMethod">
       <arg name="message" type="s" direction="in"/>
       <arg name="echoed_message" type="s" direction="out"/>

buffet/manager.cc

diff --git a/buffet/manager.cc b/buffet/manager.cc
index 6097b09..01f73b1 100644
--- a/buffet/manager.cc
+++ b/buffet/manager.cc
@@ -189,6 +189,19 @@
   response->Return();
 }
 
+void Manager::GetCommand(DBusMethodResponse<std::string> response,
+                         const std::string& id) {
+  const CommandInstance* command = command_manager_->FindCommand(id);
+  if (!command) {
+    response->ReplyWithError(FROM_HERE, kErrorDomainGCD, "unknown_command",
+                             "Can't find command with id: " + id);
+    return;
+  }
+  std::string command_str;
+  base::JSONWriter::Write(command->ToJson().get(), &command_str);
+  response->Return(command_str);
+}
+
 std::string Manager::TestMethod(const std::string& message) {
   LOG(INFO) << "Received call to test method: " << message;
   return message;

buffet/manager.h

diff --git a/buffet/manager.h b/buffet/manager.h
index d307ca2..d61c6fa 100644
--- a/buffet/manager.h
+++ b/buffet/manager.h
@@ -70,6 +70,9 @@
   // Handles calls to org.chromium.Buffet.Manager.AddCommand().
   void AddCommand(DBusMethodResponse<> response,
                   const std::string& json_command) override;
+  // Handles calls to org.chromium.Buffet.Manager.GetCommand().
+  void GetCommand(DBusMethodResponse<std::string> response,
+                  const std::string& id) override;
   // Handles calls to org.chromium.Buffet.Manager.Test()
   std::string TestMethod(const std::string& message) override;