'''

Voltaat Learn (http://learn.voltaat.com)

Link to the full tutorial:

Tutorial: How to Build a Calculator Using a Raspberry Pi Pico Board

This code is for building a Calculator Using a Raspberry Pi Pico Board

Note: You can use this sketch with any Raspberry Pi Pico.

'''

import machine

from machine import Pin, I2C

import time

from lcd_api import LcdApi

from pico_i2c_lcd import I2cLcd

# -------------------- LCD Setup --------------------

I2C_ADDR = 0x27

I2C_NUM_ROWS = 2

I2C_NUM_COLS = 16

i2c = I2C(0, sda=machine.Pin(0), scl=machine.Pin(1), freq=400000)

lcd = I2cLcd(i2c, I2C_ADDR, I2C_NUM_ROWS, I2C_NUM_COLS)

lcd.clear()

lcd.putstr("  Calculator Ready")

# -------------------- Keypad Setup --------------------

rows = [Pin(26, Pin.OUT), Pin(22, Pin.OUT), Pin(21, Pin.OUT), Pin(20, Pin.OUT)]

cols = [Pin(19, Pin.IN, Pin.PULL_DOWN),

       Pin(18, Pin.IN, Pin.PULL_DOWN),

       Pin(17, Pin.IN, Pin.PULL_DOWN),

       Pin(16, Pin.IN, Pin.PULL_DOWN)]

keys = [['1', '2', '3', 'A'],

       ['4', '5', '6', 'B'],

       ['7', '8', '9', 'C'],

       ['*', '0', '#', 'D']]

def read_keypad():

   """Reads pressed key from the keypad"""

   for i, row in enumerate(rows):

       row.value(1)

       for j, col in enumerate(cols):

           if col.value() == 1:

               row.value(0)

               return keys[i][j]

       row.value(0)

   return None

# -------------------- Calculator Logic --------------------

expression = ""

time.sleep(1)

lcd.clear()

lcd.putstr("Enter:")  # Display on first line

while True:

   key = read_keypad()

   if key:

       if key == '*':  # Clear

           expression = ""

           lcd.clear()

           lcd.putstr("Enter:")

           lcd.move_to(0, 1)

           lcd.putstr("Cleared")

           time.sleep(0.6)

           lcd.move_to(0, 1)

           lcd.putstr(" " * 16)  # Clear second line

           lcd.move_to(0, 1)

       elif key == '#':  # Calculate

           lcd.move_to(0, 1)

           lcd.putstr(" " * 16)  # Clear second line

           lcd.move_to(0, 1)

           try:

               result = eval(expression)

               lcd.putstr("= " + str(result))

               expression = str(result)

               expression = ""

           except:

               lcd.putstr("Error!")

               expression = ""

           time.sleep(1.8)

           lcd.move_to(0, 1)

           lcd.putstr(" " * 16)

           lcd.move_to(0, 1)

       elif key in ['A', 'B', 'C', 'D']:  # Operations

           if key == 'A':

               expression += '+'

           elif key == 'B':

               expression += '-'

           elif key == 'C':

               expression += '*'

           elif key == 'D':

               expression += '/'

           lcd.move_to(0, 1)

           lcd.putstr(" " * 16)

           lcd.move_to(0, 1)

           lcd.putstr(expression)

       else:  # Numbers

           expression += key

           lcd.move_to(0, 1)

           lcd.putstr(" " * 16)  # Clear second line

           lcd.move_to(0, 1)

           lcd.putstr(expression)

       time.sleep(0.25)

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