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

entity Zadatak4 is
    Port ( inOK : in  STD_LOGIC;
           inHAZ : in  STD_LOGIC;
           inRST : in  STD_LOGIC;
           iCLK : in  STD_LOGIC;
           oRED : out  STD_LOGIC_VECTOR (1 downto 0);
           oYELLOW : out  STD_LOGIC_VECTOR (1 downto 0);
           oGREEN : out  STD_LOGIC_VECTOR (1 downto 0));
end Zadatak4;

architecture Behavioral of Zadatak4 is

type tSTATE is (IDLE, RED, RED_YELLOW, GREEN, YELLOW, HAZARD);
signal state, state_next : tSTATE;
signal sTC : STD_LOGIC;
signal sCNT : STD_LOGIC_VECTOR (3 downto 0); --(23 downto 0)
signal sGO : STD_LOGIC;
signal sSTOP : STD_LOGIC;

begin

    --COUNTER
    process (iCLK, inRST) begin
        if (inRST = '0') then
            sCNT <= (others => '0');
        elsif (iCLK'event and iCLK = '1') then
            if (sCNT = 11) then --11999999
                sCNT <= (others => '0');
            else
                sCNT <= sCNT + 1;
            end if;
        end if;
    end process;

    sTC <= '1' when sCNT = 11 else '0'; --11999999

    --SEMAFOR:
    --FLIPFLOP
    process (iCLK, inRST) begin
        if (inRST = '0') then
            state <= IDLE;
        elsif (iCLK'event and iCLK = '1') then
            state <= state_next;
        end if;
    end process;

    --fp
    process (state, sTC, sGO, sSTOP) begin
        case (state) is
            when IDLE =>
                if (sTC = '1') then
                    if (sGO = '1') then
                        state_next <= RED;
                    elsif (sSTOP = '1') then
                        state_next <= HAZARD;
                    else
                        state_next <= IDLE;
                    end if;
                else
                    state_next <= IDLE;
                end if;
            when RED =>
                if (sTC = '1') then
                    if (sGO = '1') then
                        state_next <= RED_YELLOW;
                    else
                        state_next <= HAZARD;
                    end if;
                else
                    state_next <= RED;
                end if;
            when RED_YELLOW =>
                if (sTC = '1') then
                    if (sGO = '1') then
                        state_next <= GREEN;
                    else
                        state_next <= HAZARD;
                    end if;
                else
                    state_next <= RED_YELLOW;
                end if;
            when GREEN =>
                if (sTC = '1') then
                    if (sGO = '1') then
                        state_next <= YELLOW;
                    else
                        state_next <= HAZARD;
                    end if;
                else
                    state_next <= GREEN;
                end if;
            when YELLOW =>
                if (sTC = '1') then
                    if (sGO = '1') then
                        state_next <= RED;
                    else
                        state_next <= HAZARD;
                    end if;
                else
                    state_next <= YELLOW;
                end if;
            when others =>
                if (sTC = '1') then
                    if (sGO = '1') then
                        state_next <= RED;
                    else
                        state_next <= HAZARD;
                    end if;
                else
                    state_next <= HAZARD;
                end if;
        end case;
    end process;

    --pomocni signali
    process (iCLK, inRST) begin
        if (inRST = '0') then
            sGO <= '0';
        elsif (iCLK'event and iCLK = '1') then
            if (inOK = '0') then
                sGO <= '1';
            elsif (inHAZ = '0') then
                sGO <= '0';
            else
                sGO <= sGO;
            end if;
        end if;
    end process;

    process (iCLK, inRST) begin
        if (inRST = '0') then
            sSTOP <= '0';
        elsif (iCLK'event and iCLK = '1') then
            if (inOK = '1' and inHAZ = '0') then
                sSTOP <= '1';
            elsif (inOK = '0') then
                sSTOP <= '0';
            else
                sSTOP <= sSTOP;
            end if;
        end if;
    end process;

    --fi
    process (state) begin
        case (state) is
            when IDLE =>
                oRED <= "00";
                oYELLOW <= "00";
                oGREEN <= "00";
            when RED  =>
                oRED <= "11";
                oYELLOW <= "00";
                oGREEN <= "00";
            when RED_YELLOW  =>
                oRED <= "11";
                oYELLOW <= "11";
                oGREEN <= "00";
            when GREEN  =>
                oRED <= "00";
                oYELLOW <= "00";
                oGREEN <= "11";
            when YELLOW  =>
                oRED <= "00";
                oYELLOW <= "11";
                oGREEN <= "00";
            when others =>
                oRED <= "11";
                oYELLOW <= "11";
                oGREEN <= "11";
        end case;
    end process;


end Behavioral;