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

ENTITY fsm_C IS
        PORT (
                key: in integer range 0 to 255;
                clk: in std_logic;
                number: out integer range -1000000000 to 1000000000;
                memPos: out integer range 0 to 31;
                ff_write, ff_calc: out std_logic
        );
END fsm_C;

ARCHITECTURE fsm_C of fsm_C IS
    signal state: integer range 0 to 7 := 0;
    signal memory: integer range 0 to 31 := 0;
    signal last_key: integer range 0 to 255 := 0;
    signal neg: std_logic := '0';
    signal n, degree: integer range -1000000000 to 1000000000 := 0;

BEGIN

PROCESS (clk, key)
BEGIN
    IF (clk'event AND clk = '1') THEN
        CASE state IS
            WHEN 0 =>
                IF (last_key /= key) THEN
                    IF (key = 45) THEN
                        state <= 1;
                    ELSIF (key >= 48 AND key <= 57) THEN
                        state <= 2;
                    ELSIF (key = 10) THEN
                        IF (neg = '0') THEN
                            state <= 3;
                        ELSE
                            state <= 4;
                        END IF;
                    END IF;
                    last_key <= key;
                END IF;

            WHEN 1 =>
                neg <= '1';
                state <= 0;

            WHEN 2 =>
                n <= (n * 10) + key - 48;
                state <= 0;

            WHEN 3 =>
                ff_write <= '1';
                state <= 5;

            WHEN 4 =>
                n <= (-1) * n;
                state <= 3;

            WHEN 5 =>
                IF (memory = 0) THEN
                    degree <= n;
                END IF;
                ff_write <= '0';
                neg <= '0';
                n <= 0;
                memory <= memory + 1;
                IF (memory <= degree) THEN
                    state <= 0;
                ELSE
                    state <= 6;
                END IF;

            WHEN 6 =>
                ff_calc <= '1';
                state <= 7;

            WHEN 7 =>
                memory <= 0;
                ff_calc <= '0';
        END CASE;
    END IF;

    memPos <= memory;
    number <= n;
END PROCESS;


END fsm_C;