-- file light_control.vhd
-------------------------------------------------------
-- This file is used to determine the direction and speed
-- of the car for different light directions
--
-- Novemeber 13, 1999

library ieee;
use ieee.std_logic_1164.all;
use IEEE.std_logic_arith.all;
use IEEE.std_logic_unsigned.all;

entity light_control is
	port(reset, enable : in std_logic;
		light_dir: in std_logic_vector(2 downto 0);
		obj_ahead: in std_logic;

		fwd_back, left_right: out std_logic_vector(3 downto 0)
	);
end light_control;

architecture behavioural of light_control is
-- define constants for direction
constant left		: std_logic_vector(3 downto 0) := "0000";
constant slight_left: std_logic_vector(3 downto 0) := "0011";

constant right		: std_logic_vector(3 downto 0) := "1111";
constant slight_right:std_logic_vector(3 downto 0) := "1100";

--define constants for speed
constant forward		: std_logic_vector(3 downto 0) := "0011";
constant back		: std_logic_vector(3 downto 0) := "1010";

-- define zero constant for both direction and speed
constant zero		: std_logic_vector(3 downto 0) := "0111";

begin

	process (reset, enable)
	begin
		if reset = '0' then
			fwd_back <= zero;
			left_right <= zero;
		elsif enable = '1' then
			-- if the sonar detects an object 
			-- hirra should slow down and turn hard 
			-- in the appropriate direction
			if obj_ahead = '1' then
				case light_dir is
					--light in front
					when "000" =>
						left_right <= right;
						fwd_back <= forward;	
					--light in front right
					when "001" =>
						left_right <= right;
						fwd_back <= forward;
					-- light on right
					when "010" =>
						left_right <= right;
						fwd_back <= forward;
					-- light in back right
					when "011" => 
						left_right <= right;
						fwd_back <= back;
					-- light in back
					when "100" =>
						left_right <= back;
						fwd_back <= back;
					-- light in back left
					when "101" =>
						left_right <= left;
						fwd_back <= back;
					-- light on left
					when "110" =>
						left_right <= left;
						fwd_back <= forward;
					-- light in front left
					when "111" =>
						left_right <= left;
						fwd_back <= forward;
					when others =>
						left_right <= zero;
						fwd_back <= forward;
				end case;
			-- otherwise it should respond to the light
			-- if light is equal stop = 1 and hirra should stop
			else
				-- drive forward
				case light_dir is
					-- light in front
					when "000" =>
						left_right <= zero;
						fwd_back <= forward;
					-- light in front right
					when "001" =>
						left_right <= slight_right;
						fwd_back <= forward;
					-- light on right
					when "010" =>
						left_right <= right;
						fwd_back <= forward;
					-- light in back right
					when "011" => 
						left_right <= left;
						fwd_back <= back;
					-- light in back
					when "100" =>
						fwd_back <= back;
						left_right <= zero;
					-- light in back left
					when "101" =>
						left_right <= right;
						fwd_back <= back;
					-- light on left
					when "110" =>
						left_right <= left;
						fwd_back <= forward;
					-- light in front left
					when "111" =>
						left_right <= slight_left;
						fwd_back <= forward;
					when others =>
						left_right <= zero;
				end case;
			end if;
		end if;
	end process;
end behavioural;