-- The Electronic Gardener
--
-- Mark Kudryk, Kim Ellis
--
-- Module Name: session.vhd
-- Author: Kim Ellis
-- Date: November 07, 1998
-- Status: Completed
----------------------------------------------------------------
-- Description:
--   Determine the state of the watering session,
--   then compare the set start/stop times to the 24-hour clock
--   and Control the watering device
--   If the start time is equal to the 24-hour clock,
--   the device is turned on until the end time is reached
----------------------------------------------------------------
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;

entity session is
    port( clk           : in std_logic;
          reset         : in std_logic;

          hour          : in std_logic_vector( 7 downto 0 );
          minute        : in std_logic_vector( 7 downto 0 );

          water_session : in std_logic;
          moist_start_h : in std_logic_vector( 7 downto 0 );
          moist_start_m : in std_logic_vector( 7 downto 0 );
          moist_end_h   : in std_logic_vector( 7 downto 0 );
          moist_end_m   : in std_logic_vector( 7 downto 0 );

          water_status  : out std_logic;
          valve_on      : buffer std_logic     );
end session;

architecture behaviour of session is
begin

    process(reset, clk)
    begin

        if reset = '1' then
            valve_on <= '0';
            water_status <= '0';

        elsif rising_edge(clk) then

--water
              if water_session = '1' then

                   if moist_end_h < moist_start_h then                --change in hour

                       if moist_end_m < moist_start_m then            --change in minutes

                          if hour >= moist_start_h and minute >= moist_start_m then
                              valve_on <= '1';                         --turn on the water valve
                              water_status <= '1';
                          elsif hour <= moist_end_h and minute < moist_end_m then
                              valve_on <= '1';                         --turn on the water valve
                              water_status <= '1';
                          else
                              valve_on <= '0';                              --turn valve off
                              water_status <= '0';
                          end if;
                       end if;

                   else

                       if moist_end_m < moist_start_m then              --change in minutes, no change in hour

                          if hour >= moist_start_h and minute >= moist_start_m then
                              valve_on <= '1';                         --turn on the water valve
                              water_status <= '1';
                          elsif hour <= moist_end_h and minute < moist_end_m then
                              valve_on <= '1';                         --turn on water valve
                              water_status <= '1';
                          else
                              valve_on <= '0';                              --turn valve on
                              water_status <= '0';
                          end if;

                       else       --no change in minutes & hour
 
                          if hour >= moist_start_h and minute >= moist_start_m and
                             hour <= moist_end_h and minute <= moist_end_m - 1 then
 
                              valve_on <= '1';                         --turn on water valve
                              water_status <= '1';
                          else
                              valve_on <= '0';                              --turn valve off
                              water_status <= '0';
                          end if;
                       end if;
      
                   end if;

               else
                   valve_on <= '0';                              --turn valve off
                   water_status <= '0';
               end if;

        end if;
    end process;
end behaviour;