From 8efa47f3da52112381bb7626cdb0dfaf8dea6ad2 Mon Sep 17 00:00:00 2001
From: John Wellbelove <github@wellbelove.co.uk>
Date: Wed, 5 Sep 2018 18:49:37 +0100
Subject: [PATCH] First draft

---
 include/etl/lwfsm.h | 154 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 154 insertions(+)
 create mode 100644 include/etl/lwfsm.h

diff --git a/include/etl/lwfsm.h b/include/etl/lwfsm.h
new file mode 100644
index 00000000..99f11c8d
--- /dev/null
+++ b/include/etl/lwfsm.h
@@ -0,0 +1,154 @@
+/******************************************************************************
+The MIT License(MIT)
+
+Embedded Template Library.
+https://github.com/ETLCPP/etl
+https://www.etlcpp.com
+
+Copyright(c) 2017 jwellbelove
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files(the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions :
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+******************************************************************************/
+
+#ifndef ETL_LWFSM_INCLUDED
+#define ETL_LWFSM_INCLUDED
+
+#include <stdint.h>
+
+#include "etl/nullptr.h"
+
+namespace etl
+{
+  //***************************************************************************
+  /// Light Weight Finite State Machine
+  //***************************************************************************
+  template <typename TObject>
+  class state_machine
+  {
+  public:
+
+    typedef uint32_t state_id_t;
+    typedef uint32_t event_id_t;
+
+    //*************************************************************************
+    /// Transition definition
+    //*************************************************************************
+    struct transition
+    {
+      transition(event_id_t event_,
+                 state_id_t current_state_,
+                 state_id_t next_state_,
+                 void (TObject::*action_)(),
+                 bool (TObject::*condition_)()  = nullptr)
+        : event(event_),
+          current_state(current_state_),
+          nextState(next_state_),
+          action(action_),
+          condition(condition_)
+      {
+      }
+
+      event_id_t event;
+      state_id_t current_state;
+      state_id_t nextState;
+      void (TObject::*action)();
+      bool (TObject::*condition)();
+    };
+
+    //*************************************************************************
+    ///
+    //*************************************************************************
+    state_machine(TObject& object_)
+      : object(object_)
+    {
+    }
+
+    //*************************************************************************
+    ///
+    //*************************************************************************
+    state_machine(TObject& object_, state_id_t state_)
+      : object(object_),
+        current_state(state_)
+    {
+    }
+
+    //*************************************************************************
+    ///
+    //*************************************************************************
+    template <const uint32_t TRANSITION_TABLE_SIZE>
+    void set_transition_table(transition<TObject>(&transition_table_)[TRANSITION_TABLE_SIZE])
+    {
+      transition_table      = &transition_table_[0];
+      transition_table_size = TRANSITION_TABLE_SIZE;
+    }
+
+    //*************************************************************************
+    ///
+    //*************************************************************************
+    void set_initial_state(state_id_t state)
+    {
+      current_state = state;
+    }
+
+    //*************************************************************************
+    ///
+    //*************************************************************************
+    state_id_t get_state() const
+    {
+      return current_state;
+    }
+
+    //*************************************************************************
+    ///
+    //*************************************************************************
+    void process_event(event_id_t event)
+    {
+      bool handled = false;
+
+      // Scan the transition table.
+      for (uint32_t i = 0; (i < transition_table_size) && (handled == false); ++i)
+      {
+        transition<TObject>& transition = transition_table[i];
+
+        // Matching event and state?
+        if ((transition.event == event) && (transition.current_state == current_state))
+        {
+          // Shall we execute the transition?
+          bool do_transition = (transition.condition == nullptr) || ((object.*transition.condition)());
+
+          if (do_transition)
+          {
+            (object.*transition.action)();
+            current_state = transition.next_state;
+            handled = true;
+          }
+        }
+      }
+    }
+
+  private:
+
+    state_id_t           current_state;         ///< The current state id.
+    TObject&             object;                ///< The object that supplies codition and action member functions
+    transition<TObject>* transition_table;      ///< The table of transitions.
+    uint32_t             transition_table_size; ///< The size of the transition table.
+  };
+}
+
+#endif
\ No newline at end of file