# Libraries
from machine import I2C, Pin
from time import sleep
from pico_i2c_lcd import I2cLcd
import time
import utime

# Pin Initialization
button = Pin(17, Pin.IN, Pin.PULL_DOWN)
clear = Pin(19, Pin.IN, Pin.PULL_DOWN)
i2c = I2C(0, sda=Pin(0), scl=Pin(1), freq=400000)
I2C_ADDR = i2c.scan()[0]
lcd = I2cLcd(i2c, I2C_ADDR, 4, 20)

# Variable Initialization
display = "I2C Address:"+str(I2C_ADDR)+"\n"
previous_display = ""
calc = ""
result = ""
# CONSTANTS
KEY_UP   = const(0)
KEY_DOWN = const(1)
keys = [['1', '2', '3', '+'], ['4', '5', '6', '-'], [7, 8, 9, '*'], ['.', 0, '=', '/']]
# RPi Pico pin assignments
rows = [8,9,10,11]
cols = [12,13,15,16]
# Set pins for rows as outputs
row_pins = [Pin(pin_name, mode=Pin.OUT) for pin_name in rows]
# Set pins for columns as inputs
col_pins = [Pin(pin_name, mode=Pin.IN, pull=Pin.PULL_DOWN) for pin_name in cols]

# Keypad Functions
def InitKeypad():
    for row in range(0,4):
        for col in range(0,4):
            row_pins[row].low()
def PollKeypad():
    key = None
    keys_down = []
    for row in range(4):
        for col in range(4):
            # Set the current row to high
            row_pins[row].high()
            # Check for key pressed events
            if col_pins[col].value() == KEY_DOWN:
                key = KEY_DOWN
            if col_pins[col].value() == KEY_UP:
                key = KEY_UP
            row_pins[row].low()
            if key == KEY_DOWN:
              keys_down.append(keys[row][col])
    return keys_down
# Initialize and set all the rows to low
InitKeypad()
# UPDATE DISPLAY FUNCTION
def update_display(txt):
  global previous_display
  if(previous_display!=txt):
    lcd.clear()
    lcd.putstr(txt)
  previous_display = txt

# Main Loop
while True:
  # LED and Button
  if button.value():
    led.toggle()
    time.sleep(0.5)

  if clear.value():
    calc = ""
    result = ""
    time.sleep(0.5)
  # LCD
  to_display = ""
  if PollKeypad() != []:
    if '=' in PollKeypad():
        result = '\n = ' + str(eval(calc))
        to_display = calc + result
    else:
        result = ""
        calc += str(PollKeypad()).replace('[','').replace(']','').replace("'",'')
        to_display = calc + result
    time.sleep(0.5)
  else: to_display = calc + result
  update_display(to_display)