# Simple Calculator using Keypad, OLED & Raspberry Pi Pico
# https://how2electronics.com/simple-calculator-using-keypad-oled-raspberry-pi-pico/

from machine import Pin,Timer,I2C
import utime
from ssd1306 import SSD1306_I2C
import framebuf
import sys

debug=True

WIDTH  = 128
HEIGHT = 64

if(sys.platform=="esp32"):
  led = Pin(2, Pin.OUT)
  I2C_SDA =21 # GPIO21(I2C SDA)
  I2C_SCL =22 # GPIO22(I2C SCL)
  # Initialize I2C
  i2c = I2C(0, scl=Pin(I2C_SCL), sda=Pin(I2C_SDA), freq=400000)     #initializing the I2C method for ESP32
  button_pin = 35

elif(sys.platform=="rp2"):
  led = Pin("LED", Pin.OUT)
  I2C_SDA =16 # GPIO16(I2C SDA)
  I2C_SCL =17 # GPIO17(I2C SCL)
  i2c = I2C(0, scl=Pin(I2C_SCL), sda=Pin(I2C_SDA), freq=400000)
  button_pin = 21

oled = SSD1306_I2C(128, 64, i2c)
 
keyName = [['1','2','3','+'],
           ['4','5','6','-'],
           ['7','8','9','*'],
           ['c','0','=','/']]
keypadRowPins = [13,12,11,10]
keypadColPins = [9,8,7,6]
 
row = []
col = []
keypadState = [];
for i in keypadRowPins:
    row.append(Pin(i,Pin.IN,Pin.PULL_UP))
    keypadState.append([0,0,0,0])
for i in keypadColPins:
    col.append(Pin(i,Pin.OUT))
 
def solve(oprt, oprdA, oprdB):
    if(oprt == "+"):
        return oprdA + oprdB
    elif(oprt == "-"):
        return oprdA - oprdB
    elif(oprt == "*"):
        return oprdA * oprdB
    elif(oprt == "/"):
        return round(oprdA / oprdB , 6)
 
def calc(lst):
    operand = []
    operator = []
    
    for i in lst:
        if(debug):
            print(i)
        if(i=='+'):
            while (len(operator)!=0 and (operator[-1] == '*' or operator[-1] == '/' or operator[-1] == '-' or operator[-1] == '+')):
                b = operand.pop(-1)
                a = operand.pop(-1)
                c = operator.pop(-1)
                operand.append(solve(c,a,b))
            operator.append(i)
        elif(i=='-'):
            while (len(operator)!=0 and (operator[-1] == '*' or operator[-1] == '/' or operator[-1] == '-' or operator[-1] == '+')):
                b = operand.pop(-1)
                a = operand.pop(-1)
                c = operator.pop(-1)
                operand.append(solve(c,a,b))
            operator.append(i)
        elif(i=='*'):
            while (len(operator)!=0 and (operator[-1] == '*' or operator[-1] == '/')):
                b = operand.pop(-1)
                a = operand.pop(-1)
                c = operator.pop(-1)
                operand.append(solve(c,a,b))
            operator.append(i)
        elif(i=='/'):
            while (len(operator)!=0 and (operator[-1] == '*' or operator[-1] == '/')):
                b = operand.pop(-1)
                a = operand.pop(-1)
                c = operator.pop(-1)
                operand.append(solve(c,a,b))
            operator.append(i)
 
        elif(i=='('):
            operator.append(i)
 
        elif(i==')'):
            while(operator[-1] !='('):
                b = operand.pop(-1)
                a = operand.pop(-1)
                c = operator.pop(-1)
                operand.append(solve(c,a,b))
            operator.pop(-1)
        else:
            operand.append(i)
            
    while(len(operator) != 0):
        b = operand.pop(-1)
        a = operand.pop(-1)
        c = operator.pop(-1)
        operand.append(solve(c,a,b))
 
    return operand[0]
 
def keypadRead():
    global row
    j_ifPressed = -1
    i_ifPressed = -1
    for i in range(0,len(col)):
        col[i].low()
        utime.sleep(0.005) #settling time
        for j in range(0,len(row)):
            pressed = not row[j].value()
            if(pressed and (keypadState[j][i] != pressed)): #state changed to high
                keypadState[j][i] = pressed
            elif(not pressed and (keypadState[j][i] != pressed)): # state changed to low
                keypadState[j][i] = pressed
                j_ifPressed = j
                i_ifPressed = i
        col[i].high()
    if(j_ifPressed != -1 and i_ifPressed != -1):
        return keyName[j_ifPressed][i_ifPressed]
    else:
        return -1
 
def printOled(lst):
    oledPos = {
            "x" : 0,
            "y" : 0
          }
    
    oled.fill(0)
    string = ''
    for i in lst:
        string += str(i)
    l = 0
    while(l<len(string)):
        oled.text(string[l:l+16],oledPos["x"], oledPos["y"])
        oledPos["y"] =oledPos["y"] + 10
        l = l+16
    oled.show()
    
shiftFlag = False
signFlag = False
inputList = ['']
 
oled.show()
oled.fill(0)
oled.show()
oled.text("Simple",35,15,1)
oled.text("Calculator",18,30,1)
oled.show()
 
if __name__ == '__main__':
    while True:
        key = keypadRead()
 
        if(key != -1):
            if((key <= '9' and key >='0') or key == '.'):
                inputList[-1] = inputList[-1] + key            
            elif(key == '+' or key == '-' or key == '*' or key == '/'):
                if(inputList != ['']):
                    if(inputList[-1] == '' and (inputList[-2] == '+' or inputList[-2] == '-' or inputList[-2] == '*' or inputList[-2] == '/')):
                        inputList[-2] = key
                    elif(inputList[-1]==''):
                        inputList[-1]=key
                        inputList.append('')
                    else:
                        inputList[-1] = float(inputList[-1])
                        inputList.append(key)
                        inputList.append('')
                    
            elif(key == 's'):
                shiftFlag = not shiftFlag
            elif(key == 'a'):
                if(shiftFlag):      
                    if(inputList[-1] != ''):
                        inputList[-1] = float(inputList[-1])
                        inputList.append(')')
                        inputList.append('')
                    else:
                        inputList[-1] = ')'
                        inputList.append('')
                    shiftFlag = False
                else:              
                    signFlag = not signFlag
                    if(inputList[-1] == ''):
                        inputList[-1] = '-'
                    else:
                        if(inputList[-1][0] == '-'):
                           inputList[-1]  = inputList[-1][1:]
                        else:
                            inputList[-1] = '-' + inputList[-1]
                
            elif(key == 'b'):
                if(shiftFlag):      
                    if(inputList[-1] == ''):
                        inputList[-1] = '('
                    else:
                        inputList.append('(')
                    inputList.append('')
                    shiftFlag = False
                else:               
                    if(inputList[-1] == ''):
                        inputList[-1] = 3.14
                    else:
                        inputList.append(3.14)
                    inputList.append('')
            elif(key == 'c'):
                if(shiftFlag):      
                    inputList = ['']
                    shiftFlag = False
                else:               
                    if(inputList == ["error"]):
                        inputList = ['']
                    if(inputList != ['']):   
                        if(inputList[-1] == ''):
                            inputList.pop()
                            inputList[-1] = str(inputList[-1])[:-1]
                        else:
                            inputList[-1] = str(inputList[-1])[:-1]
            elif(key == '='):
                if(inputList[-1] == ''):
                    inputList.pop(-1)
                elif(inputList[-1] != ')'):
                    inputList[-1] = float(inputList[-1])
                try:
                    ans = calc(inputList)
                    inputList = [str(ans)]
                except:
                    ans = ''
                    inputList = []
                    inputList.append("error")
                
            printOled(inputList)
            print(inputList)