From 12dda03bb817caa74096e379b574309f9a1263ea Mon Sep 17 00:00:00 2001
From: Francisco Paisana <francisco.paisana@softwareradiosystems.com>
Date: Wed, 10 Jun 2020 12:45:54 +0100
Subject: [PATCH] add ability for fsms to self-trigger

---
 lib/include/srslte/common/fsm.h | 30 +++++++++++++++++++----
 lib/test/common/fsm_test.cc     | 42 +++++++++++++++++++++++++++++++++
 2 files changed, 67 insertions(+), 5 deletions(-)

diff --git a/lib/include/srslte/common/fsm.h b/lib/include/srslte/common/fsm.h
index 6ccbe1133..8e4537b67 100644
--- a/lib/include/srslte/common/fsm.h
+++ b/lib/include/srslte/common/fsm.h
@@ -25,6 +25,7 @@
 #include "srslte/common/logmap.h"
 #include "type_utils.h"
 #include <cstdio>
+#include <functional>
 #include <limits>
 #include <memory>
 #include <tuple>
@@ -418,9 +419,18 @@ public:
   template <typename Ev>
   bool trigger(Ev&& e)
   {
-    fsm_details::trigger_visitor<derived_view, Ev> visitor{derived(), std::forward<Ev>(e)};
-    srslte::visit(visitor, derived()->states);
-    return visitor.result;
+    if (trigger_locked) {
+      pending_events.emplace_back([e](fsm_t<Derived>* d) { d->process_event(e); });
+      return false;
+    }
+    trigger_locked = true;
+    bool ret       = process_event(std::forward<Ev>(e));
+    while (not pending_events.empty()) {
+      pending_events.front()(this);
+      pending_events.pop_front();
+    }
+    trigger_locked = false;
+    return ret;
   }
 
   template <typename State>
@@ -493,8 +503,18 @@ protected:
 
   const derived_view* derived() const { return static_cast<const derived_view*>(this); }
 
-  srslte::log_ref        log_h;
-  srslte::LOG_LEVEL_ENUM fsm_event_log_level = LOG_LEVEL_INFO;
+  template <typename Ev>
+  bool process_event(Ev&& e)
+  {
+    fsm_details::trigger_visitor<derived_view, Ev> visitor{derived(), std::forward<Ev>(e)};
+    srslte::visit(visitor, derived()->states);
+    return visitor.result;
+  }
+
+  srslte::log_ref                                   log_h;
+  srslte::LOG_LEVEL_ENUM                            fsm_event_log_level = LOG_LEVEL_INFO;
+  bool                                              trigger_locked      = false;
+  std::deque<std::function<void(fsm_t<Derived>*)> > pending_events;
 };
 
 template <typename Derived, typename ParentFSM>
diff --git a/lib/test/common/fsm_test.cc b/lib/test/common/fsm_test.cc
index 785903a82..8d416dd22 100644
--- a/lib/test/common/fsm_test.cc
+++ b/lib/test/common/fsm_test.cc
@@ -451,6 +451,46 @@ int test_nas_fsm()
   return SRSLTE_SUCCESS;
 }
 
+struct fsm3 : public srslte::fsm_t<fsm3> {
+  struct st1 {};
+  struct st2 {
+    int  counter = 0;
+    void enter(fsm3* fsm) { counter++; }
+  };
+
+  fsm3() : base_t(srslte::log_ref{"TEST"}) {}
+
+protected:
+  void handle_ev1(st1& s, st2& d, const ev1& ev) { trigger(ev2{}); }
+  void handle_ev2(st2& s, st1& d, const ev2& ev)
+  {
+    if (s.counter < 2) {
+      trigger(ev1{});
+    }
+  }
+
+  state_list<st1, st2> states{this};
+  // clang-format off
+  using transitions = transition_table<
+  //     Start                    Target                   Event               Action
+  //  +------------------------+-------------------------+-------------------+--------------------+
+  row<  st1,                      st2,                     ev1,                &fsm3::handle_ev1>,
+  row<  st2,                      st1,                     ev2,                &fsm3::handle_ev2>
+  >;
+  // clang-format on
+};
+
+int test_fsm_self_trigger()
+{
+  fsm3 fsm;
+
+  TESTASSERT(fsm.is_in_state<fsm3::st1>());
+  fsm.trigger(ev1{});
+  TESTASSERT(fsm.is_in_state<fsm3::st1>());
+
+  return SRSLTE_SUCCESS;
+}
+
 int main()
 {
   srslte::log_ref testlog{"TEST"};
@@ -461,6 +501,8 @@ int main()
   testlog->info("TEST \"proc\" finished successfully\n\n");
   TESTASSERT(test_nas_fsm() == SRSLTE_SUCCESS);
   testlog->info("TEST \"nas fsm\" finished successfully\n\n");
+  TESTASSERT(test_fsm_self_trigger() == SRSLTE_SUCCESS);
+  testlog->info("TEST \"fsm self trigger\" finished successfully\n\n");
 
   return SRSLTE_SUCCESS;
 }