from time import sleep_ms

from machine import Pin

pins: list[int] = [19, 18, 5, 17]
LEDS = [Pin(p, Pin.OUT, value=0) for p in pins]

reg: list[int] = [1, 0, 0, 0]
direction: int = 1  # 1 = right; -1 = left

# extras
extra = False  # off by-default. set to True to see the extra functionality
first_run = True
pattern: list[int] = [1, 0, 0, 1, 1, 0, 1, 1, 1]
pos: int = 0  # current bit position in pattern


def shift_right(reg: list[int], val: int):
    """shift all bits to the right and insert new value in the start"""
    for i in range(len(reg) - 1, 0, -1):
        reg[i] = reg[i - 1]
    reg[0] = val


def shift_left(reg: list[int], val: int):
    """shift all bits to the left and insert new value to the end"""
    for i in range(len(reg) - 1):
        reg[i] = reg[i + 1]
    reg[len(reg) - 1] = val


def write_leds():
    """maps the items of register to leds"""
    for i, led in enumerate(LEDS):
        led.value(reg[i])


def main_loop():
    """the main activity loop"""
    global direction

    write_leds()

    sleep_ms(200)

    if reg == [0, 0, 0, 1]:
        direction = -1  # go left
    elif reg == [1, 0, 0, 0]:
        direction = 1  # go right

    if direction == 1:
        shift_right(reg, 0)
    else:
        shift_left(reg, 0)


def extra_loop():
    """extra functionality"""

    global reg
    global first_run
    global pos

    # extra requires the register to be empty
    if first_run:
        reg = [0, 0, 0, 0]  # reset reg
        first_run = False


    if pos == len(pattern) - 1:
        pos = 0

    print(pos, reg)
    shift_right(reg, pattern[pos])

    pos += 1

    write_leds()
    sleep_ms(750) # longer period to notice the pattern


while True:
    if extra:
        extra_loop()
    else:
        main_loop()