library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

Entity Mealy_SM IS Port
(
 clk_input, rst_n, x_motion, x_LT, x_ET, x_GT, ext_out      : IN std_logic;
 clk_en, UD_en, ext_en, error                                           : OUT std_logic
 );
END ENTITY;


 Architecture SM of Mealy_SM is


 TYPE STATE_NAMES IS (STILL, MOVING, ERROR_STATE);   -- list all the STATE_NAMES values but use more meaningful names


 SIGNAL current_state, next_state   :  STATE_NAMES;         -- signals of type STATE_NAMES
 signal input_signals : std_logic_vector(4 downto 0);


 BEGIN

 input_signals(4) <= x_motion;
 input_signals(3) <=    x_LT;
 input_signals(2) <= x_ET;
 input_signals(1) <= x_GT;
 input_signals(0) <= ext_out;


 --------------------------------------------------------------------------------
 --State Machine:
 --------------------------------------------------------------------------------

 -- REGISTER_LOGIC PROCESS:

Register_Section: PROCESS (clk_input, rst_n)  -- this process synchronizes the activity to a clock
BEGIN
    IF (rst_n = '0') THEN
        current_state <= STILL;
    ELSIF(rising_edge(clk_input)) THEN
        current_state <= next_State;
    END IF;
END PROCESS;



-- TRANSITION LOGIC PROCESS

Transition_Section: PROCESS (input_signals, current_state)

BEGIN
     CASE current_state IS
          WHEN STILL =>
                IF(input_signals = "0-0-0") THEN -- pb is pressed ,  not equal, not extended
                    next_state <= MOVING;
                ELSIF(input_signals = "0-0-1") THEN -- pb is pressed, target is not equal, extended
                    next_state <= ERROR_STATE;
                ELSE
                    next_state <= STILL;  -- stay in the same state otherwise
                END IF;

             WHEN MOVING =>
                IF(input_signals = "1-0-0") THEN -- pb is not pressed and less than or greater than, not extended
                    next_state <= STILL;
                ELSIF(input_signals = "-0100") THEN -- don't care if pressed or not, value is equal, not extended
                    next_state <= STILL;
                ELSE
                    next_state <= MOVING;
                END IF;

             WHEN ERROR_STATE =>
                IF(input_signals = "----0") THEN -- the only way to exit the error state is when you toggle the extender OFF
                    next_state <= STILL;
                ELSE
                    next_state <= ERROR_STATE; -- otherwise stay
                END IF;

                WHEN OTHERS =>
               next_state <= STILL;
        END CASE;


 END PROCESS;

-- DECODER SECTION PROCESS

Decoder_Section: PROCESS (input_signals,current_state)

BEGIN
     CASE current_state IS
         WHEN STILL =>
                IF(input_signals = "1-0-0") THEN -- if pb not pressed, and val is greater than or less than, extender is not out, do nothing
                    clk_en <= '0';
                    UD_en  <= '-';
                    ext_en <= '0';
                    error    <= '0';
                ELSIF(input_signals = "-0100") THEN -- don't care if pb is pressed or not, if current equals target, extender is not out, enable extender
                    clk_en <= '0';
                    UD_en  <= '-';
                    ext_en <= '1';
                    error    <= '0';
                ELSIF(input_signals = "10101") THEN-- if the pb is not pressed and current equals target, and extender is out, disable extender
                    clk_en <= '0';
                    UD_en  <= '-';
                    ext_en <= '0';
                    error    <= '0';
                ELSIF(input_signals = "01000") THEN -- if the push button pressed and extender is retracted, inputs less than
                    clk_en <= '1';                          -- enable clock and count up
                    UD_en  <= '1';
                    ext_en <= '0';
                    error    <= '0';
                ELSIF(input_signals = "00010") THEN -- if the push button pressed and extender is retracted, inputs are  greater than
                    clk_en <= '1';                          -- enable clock and count down
                    UD_en  <= '0';
                    ext_en <= '0';
                    error    <= '0';
                END IF;

            WHEN MOVING =>
                IF(input_signals= "01000") THEN  -- if the push button is pressed and the value is less than, not extended, enable clock, count up
                    clk_en <= '1';
                    UD_en  <= '1';
                    ext_en <= '0';
                    error    <= '0';
                ELsIF(input_signals= "000010") THEN  -- if the push button is pressed and the value is greater than,and not extended, then enable clock, count down
                    clk_en <= '1';
                    UD_en  <= '0';
                    ext_en <= '0';
                    error    <= '0';
                END IF;

            WHEN ERROR_STATE =>
                IF(input_signals = "----1") THEN--once in the error state, input with the extender toggle on  gets an error output
                    clk_en <= '0';
                    UD_en  <= '-';
                    ext_en <= '0';
                    error    <= '1';
                END IF;

      END CASE;

 END PROCESS;

 END ARCHITECTURE SM;