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

entity LIFT is
    port(
        iOUT        : in  std_logic_vector(3 downto 0) := (others => '0'); --outside input
        iIN         : in  std_logic_vector(3 downto 0) := (others => '0'); --inside elevator car input
        DIR         : in  std_logic;    --FPGA button to switch for outside input (if you either want to go up/down)
        -- 0 down, 1 up

        floor       : out std_logic_vector(6 downto 0) := "1111110";
        an          : out std_logic_vector(3 downto 0) := "1110"; --output lcd
        DOOR        : out std_logic                    := '1'; --output door
        WEIGHT      : in  std_logic;
        DOOR_SENSOR : in  std_logic                    := '0';
        CLK         : in  std_logic);
end LIFT;

architecture behavioral of LIFT is

    type lift_states is (initial, waiting, check, openDoor, closeDoor, move); --states that the elevator has

    signal curr_state : lift_states;    -- := initial;
    signal next_state : lift_states;

    signal INTERIOR : std_logic_vector (13 downto 0) := (others => '0'); -- interior commands
    signal UP       : std_logic_vector (13 downto 0) := (others => '0'); -- exterior commands for going up
    signal DOWN     : std_logic_vector (13 downto 0) := (others => '0'); -- exterior commands for going down

    constant empty    : std_logic_vector (13 downto 0) := (others => '0'); -- empty vector used for comparison
    constant iempty : std_logic_vector (3 downto 0) := (others => '0'); -- empty vector used for input comparison

    signal press : natural;             --It's 1 for ext. commands and 2 for interior commands and 0 for no commands

    signal position  : integer   := 0;  --lift's floor
    signal direction : std_logic := '1'; --direction, up = 1 / down = 0;

    signal GOu, GOd : std_logic;        -- checks if there are commands lower/higher relative to position

    signal i, k : natural;              -- used to determine commands relative to position

    signal counter : natural;

    signal freq : std_logic := '0';

begin

    proccy : process(CLK)
    begin
        if (rising_edge(CLK)) then
            curr_state <= next_state;
        end if;
    end process proccy;

    commands : process(freq)
    begin
        if (rising_edge(freq)) then

            if (iIN /= iempty) then
                press <= 2;
            end if;

            if (iOUT /= iempty) then
                press <= 1;
            end if;

            if (press = 1) then
                if (DIR = '1') then
                    UP(to_integer(unsigned(iOUT))) <= '1';
                    press                          <= 0;
                end if;

                if (DIR = '0') then
                    DOWN(to_integer(unsigned(iOUT))) <= '1';
                    press                            <= 0;
                end if;
            elsif (press = 2) then
                INTERIOR(to_integer(unsigned(iIN))) <= '1';
                press                               <= 0;
            end if;

            if (position /= to_integer(unsigned(iOUT)) and position /= to_integer(unsigned(iIN))) then
                UP(position)       <= '0';
                DOWN(position)     <= '0';
                INTERIOR(position) <= '0';
            end if;
        end if;
    end process commands;

    states_lift : process(DOOR_SENSOR, DOWN, GOd, GOu, INTERIOR, UP, WEIGHT, counter, curr_state, direction, i, next_state, position)
    begin
        case curr_state is

            when initial => position <= 0; --initialize everything
                -- +door sensor, weight sensor;

                next_state <= closeDoor;
            --waiting for stuff

            when waiting => if (UP /= empty or DOWN /= empty or INTERIOR /= empty) then
                    next_state <= check;
                end if;

            --rough w8ing process

            when check => GOu <= '0';
                GOd <= '0';
                if (WEIGHT /= '1') then
                    if (UP /= empty) then
                        next_state <= move;
                    end if;

                    if (DOWN /= empty) then
                        next_state <= move;
                    end if;

                    if (INTERIOR /= empty) then
                        next_state <= move;
                    end if;
                end if;
                if (UP(position) = '1' or DOWN(position) = '1' or INTERIOR(position) = '1') then
                    next_state <= openDoor;
                end if;

            --the checking state

            when move => if (direction = '1') then
                    if (i < 14 and GOu /= '1' and GOd /= '1') then
                        if (i > position) then
                            if (UP(i) = '1' or INTERIOR(i) = '1') then
                                GOu <= '1';
                            else
                                i <= i + 1;
                            end if;
                        else
                            if (UP(i) = '1' or DOWN(i) = '1' or INTERIOR(i) = '1') then
                                GOd <= '1';
                            else
                                i <= i + 1;
                            end if;
                        end if;
                    else
                        if (GOu = '1') then

                            if (UP(position) = '1' or INTERIOR(position) = '1') then
                                next_state <= OpenDoor;
                            else
                                if (next_state /= OpenDoor) then
                                    position <= position + 1;
                                end if;
                            end if;

                        else
                            if (GOd = '1') then
                                if (UP(position) = '1' or INTERIOR(position) = '1' or DOWN(position) = '1') then
                                    next_state <= OpenDoor;
                                else
                                    if (next_state /= OpenDoor) then
                                        position <= position - 1;
                                    end if;
                                end if;
                            else
                                direction <= '0';
                                i         <= 13;
                            end if;
                        end if;

                    end if;

                else

                    if (i > 0 and GOd /= '1' and GOu /= '1') then
                        if (i < position) then
                            if (DOWN(i) = '1' or INTERIOR(i) = '1') then
                                GOd <= '1';
                            else
                                i <= i - 1;
                            end if;
                        else
                            if (DOWN(i) = '1' or INTERIOR(i) = '1') then
                                GOu <= '1';
                            else
                                i <= i - 1;
                            end if;
                        end if;

                    else

                        if (GOd = '1') then

                            if (DOWN(position) = '1' or INTERIOR(position) = '1') then
                                next_state <= OpenDoor;
                            else
                                if (next_state /= OpenDoor) then
                                    position <= position - 1;
                                end if;
                            end if;

                        else
                            if (GOu = '1') then
                                if (DOWN(position) = '1' or INTERIOR(position) = '1') then
                                    next_state <= OpenDoor;
                                else
                                    if (next_state /= OpenDoor) then
                                        position <= position + 1;
                                    end if;
                                end if;
                            else
                                direction <= '1';
                            end if;
                        end if;

                    end if;
                end if;

            when openDoor =>            --opens door, checks sensor for weight, waits a period of time

                DOOR <= '1';
                if (counter = 3) then
                    next_state <= closeDoor;
                else
                    counter <= counter + 1;
                end if;

            when closeDoor =>           --closes door

                counter <= 0;
                if (door_sensor = '0') then
                    DOOR       <= '0';
                    next_state <= waiting;
                else
                    next_state <= openDoor;
                end if;

        end case;

    end process states_lift;

    display : process(position)
    begin
        case position is
            when 1      => floor <= "1111110";
            when 2      => floor <= "0110000";
            when 3      => floor <= "1101101";
            when 4      => floor <= "1111001";
            when 5      => floor <= "0110011";
            when 6      => floor <= "1011011";
            when 7      => floor <= "1011111";
            when 8      => floor <= "1110000";
            when 9      => floor <= "1111111";
            when 10     => floor <= "1111011";
            when 11     => floor <= "1110111"; --a
            when 12     => floor <= "0011111"; --b
            when 13     => floor <= "1001110"; --c
            when others => floor <= "1111111";
        end case;
    end process display;

    frequency : process(freq, k)
    begin
        if (k = 200) then
            k    <= 0;
            freq <= not freq;
        else
            k <= k + 1;
        end if;
    end process frequency;

end architecture behavioral;