library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity code_lock_simple is
    port(
        enter, clk, reset: in   std_logic;
        code : in   std_logic_vector(3 downto 0);
        LED : out   std_logic_vector(3 downto 0);
        lock , err : out    std_logic
    );
end entity;

architecture fsm of code_lock_simple is
    type state_type is (idle, ECode1, GCode2, ECode2, unlocked, going_idle, wrong_code, perm_locked);
    signal state, next_state : state_type;
    signal err_event, failed : std_logic;
    signal retry_errors, next_retry_errors : unsigned(2 downto 0):= "000";
begin
    process (clk)
    begin
        if reset = '0' then
            state <= idle;
            retry_errors <= "000";
        elsif rising_edge(clk) then
            state <= next_state;
            retry_errors <= next_retry_errors;
        end if;
    end process;

    process (state, enter)
    begin
            case state is
                when idle =>
                    if enter = '0' then
                        next_state <= ECode1;
                    else
                        next_state <= state;
                    end if;
                when ECode1 =>
                    if code = "1010" and enter = '1' then
                        next_state <= GCode2;
                    elsif code = "1010" and enter = '0' then
                        next_state <= state;
                    else
                        next_state <= wrong_code;
                    end if;
                when GCode2 =>
                    if enter = '0' then
                        next_state <= ECode2;
                    else
                        next_state <= state;
                    end if;
                when ECode2 =>
                    if code = "0101" and enter = '1' then
                        next_state <= unlocked;
                    elsif code = "0101" and enter = '0' then
                        next_state <= state;
                    else
                        next_state <= wrong_code;
                    end if;
                when unlocked =>
                    if enter = '0' then
                        next_state <= going_idle;
                    else
                        next_state <= state;
                    end if;
                when going_idle =>
                    if enter = '1' then
                        next_state <= idle;
                    else
                        next_state <= state;
                    end if;
                when wrong_code =>
                    if enter = '0' then
                        next_state <= going_idle;
                        next_retry_errors <= retry_errors + 1;
                        if (retry_errors > 3) then
                        next_state <= perm_locked;
                        end if;
                    else
                        next_state <= state;
                    end if;
                when perm_locked =>
                        next_state <= perm_locked;
            end case;
    end process;


    process (state, reset)
    begin
        if reset = '0' then
            err <= '0';
        else
        case state is
            when idle =>
                lock <= '1';
                err <= '0';
                LED(0) <= '0';
            when ECode1 =>
                lock <= '1';
                err <= '0';
                LED(0) <= '0';
            when GCode2 =>
                lock <= '1';
                err <= '0';
                LED(0) <= '0';
            when ECode2 =>
                lock <= '1';
                err <= '0';
                LED(0) <= '0';
            when unlocked =>
                lock <= '0';
                err <= '0';
                LED(0) <= '0';
            when going_idle =>
                lock <= '1';
                err <= '0';
                LED(0) <= '0';
            when wrong_code =>
                lock <= '1';
                err <= '1';
                LED(0) <= '0';
            when perm_locked =>
                lock <= '1';
                err <= '0';
                LED(0) <= '1';
        end case;
        end if;
    end process;

end fsm;