From 1aae510e9db22a1cb0ee898f1f15b58089209cff Mon Sep 17 00:00:00 2001
From: Francisco Paisana <paisanaf@tcd.ie>
Date: Thu, 2 Apr 2020 18:29:16 +0100
Subject: [PATCH] enter/exit are now being called in order

---
 lib/include/srslte/common/choice_type.h |  4 +-
 lib/include/srslte/common/fsm.h         | 49 +++++++++++++++++++++----
 lib/test/common/fsm_test.cc             | 10 ++---
 3 files changed, 49 insertions(+), 14 deletions(-)

diff --git a/lib/include/srslte/common/choice_type.h b/lib/include/srslte/common/choice_type.h
index 8be6b0b95..5d951c623 100644
--- a/lib/include/srslte/common/choice_type.h
+++ b/lib/include/srslte/common/choice_type.h
@@ -401,8 +401,8 @@ bool holds_alternative(const Choice& u)
   return u.template is<T>();
 }
 
-template <typename T, typename Choice>
-T* get_if(Choice& c)
+template <typename T, typename... Args>
+T* get_if(choice_t<Args...>& c)
 {
   return c.template get_if<T>();
 }
diff --git a/lib/include/srslte/common/fsm.h b/lib/include/srslte/common/fsm.h
index fbaf7a2a5..0100b87e7 100644
--- a/lib/include/srslte/common/fsm.h
+++ b/lib/include/srslte/common/fsm.h
@@ -35,8 +35,6 @@ namespace srslte {
 // using same_state = mpark::monostate;
 struct same_state {
 };
-template <typename... Args>
-using state_list = choice_t<Args...>;
 
 namespace fsm_details {
 
@@ -60,7 +58,7 @@ struct variant_convert {
     if (p != nullptr) {
       srslte::get<PrevState>(*v).exit();
     }
-    *v = std::move(s);
+    v->transit(std::move(s));
     srslte::get<State>(*v).enter();
   }
   TargetVariant* v;
@@ -76,6 +74,14 @@ struct fsm_helper {
   template <typename FSM, typename State>
   using disable_if_fsm_state = typename get_fsm_state_list<FSM>::template disable_if_can_hold<State>;
 
+  struct enter_visitor {
+    template <typename State>
+    void operator()(State&& s)
+    {
+      s.do_enter();
+    }
+  };
+
   //! Stayed in same state
   template <typename FSM, typename PrevState>
   static void handle_state_change(FSM* f, same_state* s, PrevState* p)
@@ -97,8 +103,8 @@ struct fsm_helper {
     if (p != nullptr) {
       srslte::get<PrevState>(f->states).exit();
     }
-    f->states = std::move(*s);
-    srslte::get<State>(f->states).enter();
+    f->states.transit(std::move(*s));
+    srslte::get<State>(f->states).do_enter();
   }
   //! State not present in current FSM. Attempt state transition in parent FSM in the case of NestedFSM
   template <typename FSM, typename State, typename PrevState>
@@ -164,8 +170,12 @@ class state_t
 public:
   state_t()                        = default;
   virtual const char* name() const = 0;
-  virtual void        enter() {}
-  virtual void        exit() {}
+  void                do_enter() { enter(); }
+  void                do_exit() { exit(); }
+
+protected:
+  virtual void enter() {}
+  virtual void exit() {}
 };
 
 //! CRTP Class for all non-nested FSMs
@@ -185,6 +195,24 @@ protected:
 public:
   static const bool is_nested = false;
 
+  template <typename... States>
+  struct state_list : public choice_t<States...> {
+    using base_t = choice_t<States...>;
+    template <typename... Args>
+    state_list(Args&&... args) : base_t(std::forward<Args>(args)...)
+    {
+      if (not Derived::is_nested) {
+        fsm_details::fsm_helper::enter_visitor visitor{};
+        this->visit(visitor);
+      }
+    }
+    template <typename State>
+    void transit(State&& s)
+    {
+      this->template emplace<State>(std::forward<State>(s));
+    }
+  };
+
   // Push Events to FSM
   template <typename Ev>
   void trigger(Ev&& e)
@@ -225,6 +253,13 @@ protected:
   // Access to CRTP derived class
   derived_view*       derived() { return static_cast<derived_view*>(this); }
   const derived_view* derived() const { return static_cast<const derived_view*>(this); }
+
+  void do_enter()
+  {
+    enter();
+    fsm_details::fsm_helper::enter_visitor visitor{};
+    derived()->states.visit(visitor);
+  }
 };
 
 template <typename Derived, typename ParentFSM>
diff --git a/lib/test/common/fsm_test.cc b/lib/test/common/fsm_test.cc
index ee96b6979..f2f7f9735 100644
--- a/lib/test/common/fsm_test.cc
+++ b/lib/test/common/fsm_test.cc
@@ -79,19 +79,19 @@ public:
     auto react(state_inner& s, ev2 e) -> state1;
 
     // list of states
-    srslte::state_list<state_inner> states;
+    state_list<state_inner> states;
   };
 
 protected:
   // transitions
   auto react(idle_st& s, ev1 e) -> state1;
   auto react(state1& s, ev1 e) -> fsm2;
-  auto react(state1& s, ev2 e) -> srslte::state_list<idle_st, fsm2>;
+  auto react(state1& s, ev2 e) -> srslte::choice_t<idle_st, fsm2>;
 
   void foo(ev1 e) { foo_counter++; }
 
   // list of states
-  srslte::state_list<idle_st, state1, fsm2> states{idle_st{this}};
+  state_list<idle_st, state1, fsm2> states{idle_st{this}};
 };
 
 // FSM event handlers
@@ -118,7 +118,7 @@ auto fsm1::react(state1& s, ev1 e) -> fsm2
   test_log->info("fsm1::%s::react called\n", s.name());
   return fsm2{this};
 }
-auto fsm1::react(state1& s, ev2 e) -> srslte::state_list<idle_st, fsm2>
+auto fsm1::react(state1& s, ev2 e) -> srslte::choice_t<idle_st, fsm2>
 {
   test_log->info("fsm1::%s::react called\n", s.name());
   return idle_st{this};
@@ -130,7 +130,7 @@ namespace srslte {
 namespace fsm_details {
 
 static_assert(std::is_same<fsm_helper::get_fsm_state_list<fsm1>,
-                           srslte::state_list<fsm1::idle_st, fsm1::state1, fsm1::fsm2> >::value,
+                           fsm1::state_list<fsm1::idle_st, fsm1::state1, fsm1::fsm2> >::value,
               "get state list failed\n");
 static_assert(std::is_same<fsm_helper::enable_if_fsm_state<fsm1, fsm1::idle_st>, void>::value,
               "get state list failed\n");