# ENV: micropython-20231005-v1.21.0
# DOCS: https://docs.micropython.org/en/v1.21.0/index.html

import re
from machine import Pin, I2C

# Tutorials:
# https://newbiely.com/tutorials/esp32-micropython/esp32-micropython-lcd-i2c
# https://newbiely.com/tutorials/esp32-micropython/esp32-micropython-keypad-4x4
from DIYables_MicroPython_LCD_I2C import LCD_I2C
from DIYables_MicroPython_Keypad import Keypad

# I2C LCD Init
I2C_ADDR = 0x27
LCD_ROWS = 4
LCD_COLS = 20
i2c = I2C(0, scl=Pin(22), sda=Pin(21))
lcd = LCD_I2C(i2c, I2C_ADDR, LCD_ROWS, LCD_COLS)
lcd.backlight_on()
lcd.clear()

# Keypad Init
NUM_ROWS = 4
NUM_COLS = 4
ROW_PINS = [19, 18, 5, 17]
COL_PINS = [16, 4, 0, 2]
KEYMAP = ['1', '2', '3', '+',
          '4', '5', '6', '-',
          '7', '8', '9', '*',
          'C', '0', '=', '/']
          

keypad = Keypad(KEYMAP, ROW_PINS, COL_PINS, NUM_ROWS, NUM_COLS)
keypad.set_debounce_time(400) # 400ms, addjust it if it detects twice for single press

# State Init
state = 0 # 0 - ready; 1 - digit; 2 - operator; 3 - result
result = 0 # compute result
seq = [] # number and operatots sequence

dgt = re.compile('[0123456789]')
opr = re.compile('[\+\-\*\/]')

lcd.clear()
lcd.print('0')

"""
# 
def calc(sq):
    for op in ['*', '/', '+', '-']:
        while sq.count(op):
            pos = sq.index(op)
            sq.pop(pos)
            a = int(sq[pos - 1])
            b = int(sq.pop(pos))

            if op == '*': с = a * b
            elif op == '/': с = a / b
            elif op == '+': с = a + b
            elif op == '-': с = a - b

            sq[pos - 1] = с

    return sq[0]

assert calc([]) == 0
assert calc(['123']) == 123
assert calc(['2', '-', '1']) == 1
assert calc(['1', '+', '2', '+', '3', '*', '4', '/', '2']) == 9
assert calc(['1', '/', '0']) == 'error'
assert calc(['xyz']) == 'error'
assert calc(['5', '/', '2']) == 2.5
assert calc(['10', '/', '3']) == 3.3333333333333335
"""


while True:
    # C — clear
    # 0-9 — digit
    # A-D — operator
    # # — compute
    key = keypad.get_key()

    if key:
        if (key == 'C'):
            state = 0
            result = 0
            seq.clear()
            lcd.clear()
            lcd.print('0')

        elif (key == '='):
            if state == 2:
                seq.pop()
                state = 1

            if state == 1:
                try: result = '=' + str(eval(''.join(seq)))
                except: result = 'error'
                lcd.set_cursor(0, 1)
                lcd.print(result)

        elif (opr.match(key)):
            if state < 2:
                if state == 0:
                    seq.append('0')
                seq.append(key)
                state = 2

            elif state == 2:
                seq[len(seq) - 1] = key

        elif (dgt.match(key)):
            if state == 1:
                num = seq.pop()
                if num == '0':
                    num = ''
                seq.append(num + key)

            elif state == 0 or state == 2:
                seq.append(key)
                state = 1

        lcd.set_cursor(0, 0)
        lcd.print(''.join(seq))