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

entity Semafor is
    Port ( 
				iCLK    : in  std_logic;
				iRST    : in  std_logic;
				iOK     : in  std_logic;
				iHAZ    : in  std_logic;
				oRED    : out std_logic;
				oYELLOW : out std_logic;
				oGREEN  : out std_logic
			 );
end entity;

architecture Behavioral of Semafor is

type tSTATE is (IDLE, RED, RED_YELLOW, GREEN, YELLOW, HAZARD);
	 signal sSTATE, sNEXT_STATE : tSTATE;
    signal sLED 		: std_logic_vector(7 downto 0);
	-- signal sNEXT_LED : std_logic_vector(7 downto 0);
    signal sCNT 		: std_logic_vector(23 downto 0);
	 signal sEN			: std_logic;

	-- konstanta za maksimalnu vrednost brojača jedne sekunde - za MAX 10
	constant cMAX : std_logic_vector (23 downto 0) := conv_std_logic_vector(12000000, 24); -- 12Mhz
	 
	-- konstanta za maksimalnu vrednost brojača jedne sekunde - za simulaciju
	--constant cMAX : std_logic_vector (23 downto 0) := conv_std_logic_vector(10, 24);
	 
begin
	
-- brojac jedne sekunde
    process (iCLK, iRST) begin
        if (iRST = '1') then
            sCNT <= (others=>'0');
        elsif (iCLK'event and iCLK = '1') then
            if (sCNT = cMAX) then        
                sCNT <= (others=>'0');
            else                        
                sCNT <= sCNT + 1;
            end if;
        end if;
    end process;
	 sEN <= '1' when sCNT = cMAX else '0';
-- registar za pamcenje stanja 
    process (iCLK, iRST) begin
		if (iRST = '1') then
			sSTATE <= IDLE;
      elsif (iCLK'event and iCLK = '1') then
			if(sEN = '1') then
				sSTATE <= sNEXT_STATE;
			end if;
		end if;
	end process;
	
--funkcija prelaza stanja (kombinaciona mreza)
	process (iOK, iHAZ, sSTATE) begin
		case sSTATE is
			when IDLE =>
				if (iOK = '1') then
					sNEXT_STATE <= RED;
				else
					sNEXT_STATE <= IDLE;
				end if;
				
			when RED =>
				if (iHAZ = '1') then
					sNEXT_STATE <= HAZARD;
				else
					sNEXT_STATE <= RED_YELLOW;
				end if;
			
			when RED_YELLOW =>
				if (iOK = '1') then
					sNEXT_STATE <= HAZARD;
				else
					sNEXT_STATE <= GREEN;
				end if;
	
			when GREEN =>
				if (iOK = '1') then
					sNEXT_STATE <= HAZARD;
				else
					sNEXT_STATE <= YELLOW;
				end if;
	
			when YELLOW =>
				if (iOK = '1') then
					sNEXT_STATE <= HAZARD;
				else
					sNEXT_STATE <= RED;
				end if;
	
			when HAZARD =>
				if (iOK = '1') then
					sNEXT_STATE <= RED;
				else
					sNEXT_STATE <= HAZARD;
				end if;
			when others =>
					sNEXT_STATE <= sSTATE;
			end case;
		end process;
		
--registar za izlazno stanje LED diode
	
			oRED <= '1'when (sSTATE = RED or sSTATE = RED_YELLOW or sSTATE = HAZARD) else '0';
			oYELLOW <= '1'when (sSTATE = YELLOW or sSTATE = RED_YELLOW or sSTATE = HAZARD) else '0';
			oGREEN <= '1'when (sSTATE = GREEN or sSTATE = HAZARD) else '0';
	
	
end Behavioral;