From 8b4ace6fb8889b1ed7ec8f2493c59d2e3e3bd606 Mon Sep 17 00:00:00 2001
From: James Turner <zakalawe@mac.com>
Date: Wed, 25 Apr 2018 22:20:12 +0100
Subject: [PATCH] Subsystems: stub code for smart add+remove

Groups track their state, which will enable them to correctly transition
added and removed children in the future. Only stubbed for now, to avoid
breakage on the FG side.
---
 simgear/structure/subsystem_mgr.cxx  | 30 ++++++++++++++++++++++++++++
 simgear/structure/subsystem_mgr.hxx  |  6 +++++-
 simgear/structure/subsystem_test.cxx |  9 +++++++--
 3 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/simgear/structure/subsystem_mgr.cxx b/simgear/structure/subsystem_mgr.cxx
index 52ca6fda..033bb244 100644
--- a/simgear/structure/subsystem_mgr.cxx
+++ b/simgear/structure/subsystem_mgr.cxx
@@ -157,6 +157,7 @@ SGSubsystemMgr* SGSubsystem::get_manager() const
 std::string SGSubsystem::nameForState(State s)
 {
     switch (s) {
+    case State::INVALID: return "invalid";
     case State::INIT: return "init";
     case State::REINIT: return "reinit";
     case State::POSTINIT: return "post-init";
@@ -216,11 +217,13 @@ SGSubsystemGroup::~SGSubsystemGroup ()
 void
 SGSubsystemGroup::init ()
 {
+    assert(_state == State::BIND);
     forEach([this](SGSubsystem* s){
         this->notifyWillChange(s, State::INIT);
         s->init();
         this->notifyDidChange(s, State::INIT);
     });
+    _state = State::INIT;
 }
 
 SGSubsystem::InitStatus
@@ -233,11 +236,13 @@ SGSubsystemGroup::incrementalInit()
 
     // termination test
     if (_initPosition >= static_cast<int>(_members.size())) {
+        _state = State::INIT;
         return INIT_DONE;
     }
   
     if (_initPosition < 0) {
         // first call
+        assert(_state == State::BIND);
         _initPosition = 0;
         notifyWillChange(_members.front()->subsystem, State::INIT);
     }
@@ -279,11 +284,13 @@ void SGSubsystemGroup::reverseForEach(std::function<void(SGSubsystem*)> f)
 void
 SGSubsystemGroup::postinit ()
 {
+    assert(_state == State::INIT);
     forEach([this](SGSubsystem* s){
         this->notifyWillChange(s, State::POSTINIT);
         s->postinit();
         this->notifyDidChange(s, State::POSTINIT);
     });
+    _state = State::POSTINIT;
 }
 
 void
@@ -304,6 +311,7 @@ SGSubsystemGroup::shutdown ()
         s->shutdown();
         this->notifyDidChange(s, State::SHUTDOWN);
     });
+    _state = State::SHUTDOWN;
     _initPosition = -1;
 }
 
@@ -315,6 +323,7 @@ SGSubsystemGroup::bind ()
         s->bind();
         this->notifyDidChange(s, State::BIND);
     });
+    _state = State::BIND;
 }
 
 void
@@ -325,6 +334,7 @@ SGSubsystemGroup::unbind ()
         s->unbind();
         this->notifyDidChange(s, State::UNBIND);
     });
+    _state = State::UNBIND;
 }
 
 void
@@ -420,6 +430,16 @@ SGSubsystemGroup::set_subsystem (const string &name, SGSubsystem * subsystem,
     member->min_step_sec = min_step_sec;
     subsystem->set_group(this);
     notifyDidChange(subsystem, State::ADD);
+    
+    if (_state != State::INVALID) {
+        SG_LOG(SG_GENERAL, SG_DEV_WARN, "TODO: implement SGSubsystemGroup transition when adding after init");
+        // transition to the correct state
+        // bind
+        
+        // init
+        
+        // post-init
+    }
 }
 
 void
@@ -457,6 +477,16 @@ SGSubsystemGroup::remove_subsystem(const string &name)
     if (it != _members.end()) {
         // found it, great
         const auto sub = (*it)->subsystem;
+        
+        if (_state != State::INVALID) {
+            // transition out correctly
+            SG_LOG(SG_GENERAL, SG_DEV_WARN, "TODO: implement SGSubsystemGroup transition when removing before shutdown");
+
+            // shutdown
+            
+            // unbind
+        }
+        
         notifyWillChange(sub, State::REMOVE);
         delete *it;
         _members.erase(it);
diff --git a/simgear/structure/subsystem_mgr.hxx b/simgear/structure/subsystem_mgr.hxx
index 63257dc9..6ce18dfc 100644
--- a/simgear/structure/subsystem_mgr.hxx
+++ b/simgear/structure/subsystem_mgr.hxx
@@ -288,7 +288,8 @@ public:
     SGSubsystemGroup* get_group() const;
     
     enum class State {
-        ADD,
+        INVALID = -1,
+        ADD = 0,
         BIND,
         INIT,
         POSTINIT,
@@ -401,6 +402,9 @@ private:
     using MemberVec = std::vector<Member*>;
     MemberVec _members;
 
+    // track the state of this group, so we can transition added/removed
+    // members correctly
+    SGSubsystem::State _state = SGSubsystem::State::INVALID;
     double _fixedUpdateTime;
     double _updateTimeRemainder;
 
diff --git a/simgear/structure/subsystem_test.cxx b/simgear/structure/subsystem_test.cxx
index 90bcab5f..cd604272 100644
--- a/simgear/structure/subsystem_test.cxx
+++ b/simgear/structure/subsystem_test.cxx
@@ -30,7 +30,8 @@ public:
     void bind() override
     {
         auto node = get_manager()->root_node();
-        node->setIntValue("mysub/foo", 42);
+        if (node)
+            node->setIntValue("mysub/foo", 42);
     }
     
     void update(double dt) override
@@ -54,7 +55,8 @@ public:
     void bind() override
     {
         auto node = get_manager()->root_node();
-        node->setIntValue("anothersub/bar", 172);
+        if (node)
+            node->setIntValue("anothersub/bar", 172);
     }
     
     void update(double dt) override
@@ -246,6 +248,7 @@ void testSubGrouping()
     // lookup of the group should also work
     SG_CHECK_EQUAL(manager->get_subsystem<InstrumentGroup>(), instruments);
     
+    manager->bind();
     manager->init();
     
     SG_VERIFY(instruments->wasInited);
@@ -304,6 +307,7 @@ void testIncrementalInit()
     instruments->set_subsystem(radio1);
     instruments->set_subsystem(radio2);
     
+    manager->bind();
     for ( ; ; ) {
         auto status = manager->incrementalInit();
         if (status == SGSubsystemMgr::INIT_DONE)
@@ -347,6 +351,7 @@ void testSuspendResume()
     instruments->set_subsystem(radio1);
     instruments->set_subsystem(radio2);
     
+    manager->bind();
     manager->init();
     manager->update(1.0);