library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity Traffic is
    Port ( Reset      : in   STD_LOGIC;
           Clock      : in   STD_LOGIC;

           -- for debug
           debugLED   : out  std_logic;
           LEDs       : out  std_logic_vector(2 downto 0);

           -- Car and pedestrian buttons
           CarEW      : in   STD_LOGIC; -- Car on EW road
           CarNS      : in   STD_LOGIC; -- Car on NS road
           PedEW      : in   STD_LOGIC; -- Pedestrian moving EW (crossing NS road)
           PedNS      : in   STD_LOGIC; -- Pedestrian moving NS (crossing EW road)

           -- Light control
           LightsEW   : out STD_LOGIC_VECTOR (1 downto 0); -- controls EW lights
           LightsNS   : out STD_LOGIC_VECTOR (1 downto 0)  -- controls NS lights
           );
end Traffic;

architecture Behavioral of Traffic is

-- Encoding for lights
constant RED   : std_logic_vector(1 downto 0) := "00";
constant AMBER : std_logic_vector(1 downto 0) := "01";
constant GREEN : std_logic_vector(1 downto 0) := "10";
constant WALK  : std_logic_vector(1 downto 0) := "11";
type StateType is (GreenEW, YellowEW, GreenNS, YellowNS);
signal state, nextState : StateType;
signal t : integer range 0 to 60;

begin

   -- Show reset status on FPGA LED
   debugLed <= Reset;

   -- Threee LEDs for debug
   LEDs     <= "000";

   -- Luck North-south traffic
   LightsEW <= RED;
   LightsNS <= WALK;


sync: -- CLOCK
process(Reset, clock)
begin
		if (Reset = '1') then
					state <= GreenEW;
		elsif rising_edge(clock) then
					state <= nextState;
		end if;
end process;

comb:
process(state, CarNS, CarEW, PedEW, PedNS, reset, t)
begin
		case state is
			when GreenEW =>
				LightsEW <= GREEN;
				LightsNS <= RED;
				t <= '0';
				if rising_edge(clock) then
					t <= t+1;
					if ((t = 60) and (CarEW = '0') and (CarNS = '1') and (t = 59) and (PedEW = 0)) then
						nextState <= YellowEW;
				end if;
			when YellowEW =>
				LightsEW <= AMBER;
				LightsNS <= AMBER;
				nextState <= GreenNS;
			when GreenNS =>
				LightsEW <= RED;
				LightsNS <= GREEN;
				t <= '0';
				if rising_edge(clock) then
					t <= t+1;
					if ((t = 60) and (CarEW = '0') and (CarNS = '1') and (t = 59) and (PedEW = 0))then
						nextState <= YellowEW;
					end if;
			when YellowNS =>
				LightsEW <= AMBER;
				LightsNS <= AMBER;
				nextState <= GreenEW;
		end case;
end process comb;
end architecture Behavioral;