from machine import Pin, I2C
import ssd1306
import time

# ESP32 Pin assignment 
i2c = I2C(0, scl=Pin(22), sda=Pin(21))

#display
oled_width = 128
oled_height = 64
oled = ssd1306.SSD1306_I2C(oled_width, oled_height, i2c)

# Define the GPIO pins for rows and columns
row_pins = [19, 18, 5, 17]
col_pins = [16, 4, 0, 2]

# Define the keypad matrix
keys = [
    ['1', '2', '3', '+'],
    ['4', '5', '6', '-'],
    ['7', '8', '9', '*'],
    ['C', '0', '=', '/']
]

# Initialize the row pins as input with pull-up
row_pins_objects = [Pin(pin, Pin.IN, Pin.PULL_UP) for pin in row_pins]

# Initialize the column pins as output
col_pins_objects = [Pin(pin, Pin.OUT) for pin in col_pins]

def read_keypad():
    key = None

    # Scan each column
    for i, col_pin in enumerate(col_pins_objects):
        col_pin.value(0)  # Set the current column to low

        # Check each row for a pressed key
        for j, row_pin in enumerate(row_pins_objects):
            if row_pin.value() == 0:
                key = keys[j][i]
                break

        col_pin.value(1)  # Set the current column back to high

    return key
result = 0
num1 = []
num2 = []
operand = ''
secondNum = False
# Main loop
while True:
    key_pressed = read_keypad()
    
    if key_pressed:

        if key_pressed == '=':
            if operand == '+':
                result = int(''.join(num1)) + int(''.join(num2))
            elif operand == '-':
                result = int(''.join(num1)) - int(''.join(num2))
            elif operand == '*':
                result = int(''.join(num1)) * int(''.join(num2))
            elif operand == '/' and int(''.join(num2)) > 0:
                result = int(''.join(num1)) / int(''.join(num2))
            
            oled.text(''.join(num1), 0, 0) 
            oled.text(operand, 0, 10)  
            oled.text(''.join(num2), 0, 20)
            oled.text(key_pressed, 0, 30)
            oled.text(str(result), 0, 40)
            oled.show()
        else:
            if not secondNum:
                # print("Key pressed:", key_pressed)
                if key_pressed not in ['+', '-', '*', '/']:
                    num1.append(str(key_pressed))
                    oled.text(''.join(num1), 0, 0)      
                    oled.show()
                if key_pressed in ['+', '-', '*', '/']:
                    secondNum = True
                    operand = key_pressed
                    oled.text(''.join(num1), 0, 0) 
                    oled.text(operand, 0, 10)     
                    oled.show()
            else:
                num2.append(str(key_pressed))
                oled.text(''.join(num1), 0, 0) 
                oled.text(operand, 0, 10)  
                oled.text(''.join(num2), 0, 20)      
                oled.show()

    if key_pressed == 'C':
        oled.fill(0)
        oled.show()
        num1.clear()
        num2.clear()
        result = 0
        operand = ''
        secondNum = False
        

        
    oled.fill(0)
    

    
    
    
    time.sleep(0.1)  # Add a short delay to avoid rapid key detection

# number1 = int(input('Enter a number: '))
# number2 = int(input('Enter a second number: '))
# #print on the display
# oled.text(str(number1 + number2), 55, 20)      
# oled.show()