import utime
from machine import Pin

# ============================
# SHIFT REGISTER (74HC595)
# ============================

DS = Pin(7, Pin.OUT)     # serial data
STCP = Pin(8, Pin.OUT)   # latch
SHCP = Pin(9, Pin.OUT)   # clock

def shift_out(byte):
    """Send 8 bits to 74HC595"""
    for i in range(8):
        SHCP.value(0)
        DS.value((byte >> (7 - i)) & 1)
        SHCP.value(1)

    STCP.value(0)
    STCP.value(1)


# ============================
# LCD via 74HC595
# ============================

class ShiftLCD:
    # LCD bit positions on 74HC595:
    RS = 0
    E  = 1
    D4 = 2
    D5 = 3
    D6 = 4
    D7 = 5

    def __init__(self):
        self.init_lcd()

    def send_nibble(self, nibble, rs_value):
        """Output 4 bits to LCD through the shift register"""
        byte = 0
        byte |= (rs_value << self.RS)
        byte |= (1 << self.E)  # E HIGH

        byte |= ((nibble >> 0) & 1) << self.D4
        byte |= ((nibble >> 1) & 1) << self.D5
        byte |= ((nibble >> 2) & 1) << self.D6
        byte |= ((nibble >> 3) & 1) << self.D7

        shift_out(byte)

        # Toggle E to latch nibble
        utime.sleep_us(1)
        byte &= ~(1 << self.E)  # E LOW
        shift_out(byte)
        utime.sleep_us(50)

    def send_byte(self, byte, rs):
        self.send_nibble(byte >> 4, rs)
        self.send_nibble(byte & 0x0F, rs)

    def command(self, cmd):
        self.send_byte(cmd, 0)

    def write_char(self, ch):
        self.send_byte(ord(ch), 1)

    def clear(self):
        self.command(0x01)
        utime.sleep_ms(2)

    def putstr(self, text):
        for c in text:
            if c == "\n":
                self.command(0xC0)  # Line 2
            else:
                self.write_char(c)

    def init_lcd(self):
        utime.sleep_ms(20)
        self.send_nibble(0x03, 0)
        utime.sleep_ms(5)
        self.send_nibble(0x03, 0)
        utime.sleep_us(150)
        self.send_nibble(0x03, 0)
        self.send_nibble(0x02, 0)  # 4-bit mode

        self.command(0x28)  # 2-line, 5x8 font
        self.command(0x0C)  # Display ON
        self.command(0x06)  # Entry mode
        self.clear()


# Create LCD Object
lcd = ShiftLCD()

# ============================
# KEYPAD
# ============================

col_list = [4, 14, 15, 17]
row_list = [18, 27, 22, 21]

for x in range(4):
    row_list[x] = Pin(row_list[x], Pin.OUT, value=1)

for x in range(4):
    col_list[x] = Pin(col_list[x], Pin.IN, Pin.PULL_UP)

key_map = [
    ["D", "#", "0", "*"],
    ["C", "9", "8", "7"],
    ["B", "6", "5", "4"],
    ["A", "3", "2", "1"]
]

def Keypad4x4Read(cols, rows):
    for r in rows:
        r.value(0)
        result = [c.value() for c in cols]
        if min(result) == 0:
            key = key_map[rows.index(r)][result.index(0)]
            utime.sleep(0.2)
            r.value(1)
            return key
        r.value(1)
    return None

PINCode = "1234"
invalidPIN = False

def waitForInputPIN():
    global invalidPIN
    while True:
        lcd.clear()
        if invalidPIN:
            lcd.putstr("Wrong PIN,\ntry again:")
        else:
            lcd.putstr("Enter your PIN:")

        inputedPIN = ""
        key = None

        while key != '#':
            key = Keypad4x4Read(col_list, row_list)
            if key and key != "#":
                lcd.write_char("*")
                inputedPIN += key
                utime.sleep(0.2)

        if inputedPIN == PINCode:
            lcd.clear()
            lcd.putstr("Welcome!")
            utime.sleep(1.5)
            return True
        else:
            invalidPIN = True

def getMessageFromKeypad():
    lcd.clear()
    lcd.putstr("Enter text:\n")
    message = ""
    key = None

    while True:
        key = Keypad4x4Read(col_list, row_list)
        if key:
            if key == '#':        
                lcd.clear()
                lcd.putstr("Final Msg:\n" + message)
                break
            
            elif key == '*':     
                if len(message) > 0:
                    message = message[:-1]
                    lcd.clear()
                    lcd.putstr("Enter text:\n" + message)

            else:
                message += key
                lcd.clear()
                lcd.putstr("Enter text:\n" + message)

            utime.sleep(0.2)

# ============================
# RUN PROGRAM
# ============================

if waitForInputPIN():
    getMessageFromKeypad()