from machine import Pin, I2C
import utime
from ssd1306 import SSD1306_I2C

debug = False

i2c = I2C(0, scl=Pin(1), sda=Pin(0), freq=200000)
oled = SSD1306_I2C(128, 64, i2c)

keyName = [['1', '2', '3', '+'], ['4', '5', '6', '-'], ['7', '8', '9', '*'], ['c', '0', '=', '/']]
keyDescriptions = [['1', '2', '3', 'Addition (+)'], ['4', '5', '6', 'Subtraction (-)'], ['7', '8', '9', 'Multiplication (*)'], ['Clear (c)', '0', 'Equals (=)', 'Division (/)']]
keypadRowPins = [13, 12, 11, 10]
keypadColPins = [9, 8, 7, 6]

row = [Pin(i, Pin.IN, Pin.PULL_UP) for i in keypadRowPins]
col = [Pin(i, Pin.OUT) for i in keypadColPins]
keypadState = [[0] * 4 for _ in range(4)]

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 in ('+', '-', '*', '/'):
            while operator and operator[-1] in ('*', '/', '-', '+'):
                b, a, c = operand.pop(), operand.pop(), operator.pop()
                operand.append(solve(c, a, b))
            operator.append(i)
        elif i == '(':
            operator.append(i)
        elif i == ')':
            while operator[-1] != '(':
                b, a, c = operand.pop(), operand.pop(), operator.pop()
                operand.append(solve(c, a, b))
            operator.pop()
        else:
            operand.append(i)

    while operator:
        b, a, c = operand.pop(), operand.pop(), operator.pop()
        operand.append(solve(c, a, b))

    return operand[0]

def keypadRead():
    global row
    j_ifPressed = i_ifPressed = -1

    for i in range(len(col)):
        col[i].low()
        utime.sleep(0.005)  # settling time
        for j in range(len(row)):
            pressed = not row[j].value()
            if pressed and (keypadState[j][i] != pressed):
                keypadState[j][i] = pressed
            elif not pressed and (keypadState[j][i] != pressed):
                keypadState[j][i] = pressed
                j_ifPressed, i_ifPressed = j, i
        col[i].high()

    return keyName[j_ifPressed][i_ifPressed] if j_ifPressed != -1 and i_ifPressed != -1 else -1

def printOled(lst):
    oledPos = {"x": 0, "y": 0}

    oled.fill(0)
    string = ''.join(map(str, lst))
    for l in range(0, len(string), 16):
        oled.text(string[l:l + 16], oledPos["x"], oledPos["y"])
        oledPos["y"] += 10
    oled.show()

shiftFlag, signFlag, inputList = False, False, ['']

oled.show()
oled.fill(0)
oled.show()
oled.text("Simple", 35, 15, 1)
oled.text("Calculator", 18, 30, 1)
oled.show()

# Print keybindings to console
print("Key Bindings:")
for i in range(len(keyName)):
    for j in range(len(keyName[i])):
        print(f"Key '{keyName[i][j]}' - {keyDescriptions[i][j]}")

while True:
    key = keypadRead()

    if key != -1:
        if '0' <= key <= '9' or key == '.':
            inputList[-1] += key
        elif key in ('+', '-', '*', '/'):
            if inputList and inputList[-1] and inputList[-1][-1] in ('+', '-', '*', '/'):
                inputList[-1] = key
            else:
                inputList[-1] = float(inputList[-1]) if inputList[-1] else ''
                inputList.extend([key, ''])
        elif key == 's':
            shiftFlag = not shiftFlag
        elif key == 'a':
            if shiftFlag:
                if inputList[-1]:
                    inputList[-1] = float(inputList[-1])
                    inputList.extend([')', ''])
                else:
                    inputList[-1] = ')'
                    inputList.append('')
                shiftFlag = False
            else:
                signFlag = not signFlag
                inputList[-1] = '-' + inputList[-1] if inputList[-1] and inputList[-1][0] != '-' else inputList[-1][1:]
        elif key == 'b':
            if shiftFlag:
                inputList[-1] = '(' if not inputList[-1] else inputList[-1]
                inputList.extend(['(', ''])
                shiftFlag = False
            else:
                inputList[-1] = 3.14 if not inputList[-1] else inputList[-1]
                inputList.extend([3.14, ''])
        elif key == 'c':
            if shiftFlag:
                inputList = ['']
                shiftFlag = False
            else:
                if inputList == ["error"]:
                    inputList = ['']
                if inputList[-1]:
                    inputList[-1] = inputList[-1][:-1]
                    if not inputList[-1]:
                        inputList.pop(-1)
        elif key == '=':
            if not 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)