from time import sleep_ms 
from machine import Pin, SoftI2C
from i2c_lcd import I2cLcd 

######## Definitions ########

# Define LCD params
AddressOfLcd = 0x27
i2c = SoftI2C(scl=Pin(22), sda=Pin(21), freq=400000) # connect scl to GPIO 22, sda to GPIO 21
lcd = I2cLcd(i2c, AddressOfLcd, 4, 20)

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

# Define the row and column pins
row_pins = [Pin(13, Pin.OUT), Pin(12, Pin.OUT), Pin(14, Pin.OUT), Pin(27, Pin.OUT)]
col_pins = [Pin(26, Pin.IN, Pin.PULL_UP), Pin(25, Pin.IN, Pin.PULL_UP), Pin(33, Pin.IN, Pin.PULL_UP), Pin(32, Pin.IN, Pin.PULL_UP)]

# Initialize the row pins to HIGH
for row_pin in row_pins:
    row_pin.value(1)

# Initialize the col pins to LOW
for col_pin in col_pins:
    col_pin.value(0)

# Variables to store user input and calculation
user_input = ""
result = None
math_sign = ""
sign_applied = False    # When sign button has not been clicked

######## Methods ########
# Pad String
def pad_string(input_string, desired_length = 15):
    current_length = len(input_string)
    if current_length >= desired_length:
        return input_string  # No need to pad if it's long enough

    # Calculate the number of spaces needed
    spaces_needed = desired_length - current_length

    # Append the required spaces to the string
    padded_string = input_string + " " * spaces_needed

    return padded_string

# Print user input
def lcd_print(row, value, start_col = 1, space_padding = True):
    print("move to : " + str(row))
    lcd.move_to(start_col,row)
    if space_padding:
        lcd.putstr(pad_string(str(value)))
    else:
        lcd.putstr(str(value))

# Get Key Pressed value
def get_key():
    keys_detected = []
    for i, row_pin in enumerate(row_pins):
        # Drive the current row LOW
        row_pin.value(0)

        for j, col_pin in enumerate(col_pins):
            if col_pin.value() == 0:
                keys_detected.append(keypad[i][j])
                # Key is pressed, return the corresponding character
                return keypad[i][j]


        # Release the row
        row_pin.value(1)

    return None

# Evaluate Math Expression
def evaluate_expression():
    global user_input
    global result
    global math_sign

    try:
        calc_result = float(result)
    except ValueError:
        calc_result = 0.0
        print("Invalid Result float format: " + result)

    try:
        calc_user_input = float(user_input)
    except ValueError:
        calc_user_input = 0.0
        print("Invalid User Input format: " + user_input)

    try:
        return str(eval(str(calc_result) + " " + str(math_sign) + " " + str(user_input)))
    except:
        return "Error"


# Run keyboard scan
def keyboard_scan():
    global user_input
    global result
    global math_sign
    global sign_applied

    key = get_key()
    if key is not None:
        if key == 'C':
            # Clear the input and result
            user_input = ''
            result = None
            lcd.clear()
            math_sign = ""
            sign_applied = False
            lcd_print(2, "-----", 0, False)
        elif key == '=':
            # Calculate the result
            try:
                if user_input:
                    result = evaluate_expression()
                    #result = evaluate_expression(result if result is not None else "" + math_sign + user_input)
                    lcd_print(3, " " if result is None else str(result))
                    user_input = ""     # Clear input after result is calculated
            except Exception as e:
                print("Error Occured: ", e)

        elif key == '+' or key == '-' or key == '*' or key == '/':
            # save and print sign
            math_sign = key     # store sign
            lcd_print(1, key, 0, False)     # Print current sign
            result = user_input if sign_applied == False else result
            user_input = ""
            sign_applied = True
            
        else:
            # Append the key to the user input
            user_input += key
            lcd_input_row = 0 if sign_applied == False else 1
            lcd_print(lcd_input_row, str(user_input))

    # Add a small delay to debounce the keypad
    sleep_ms(100)


lcd_print(2, "-----", 0, False)

while True:
    keyboard_scan()