import serial


class LCDScreen(object):
    def _command(self, command):
        self.serial.write("\xFE" + chr(command))
        self.serial.flush()

    def clear(self):
        self._command(1)

    def home(self):
        self._command(2)

    def blank(self):
        self._command(8)

    def unblank(self):
        self._command(12)

    def location(self, x, y):
        self._command(128 + 0x40*y + x)

    def text(self, text):
        sanitized = "".join(c for c in text if c.lower() in "1234567890abcdefghjiklmnopqrstuvwxyz{}[]/+-_. ")
        self.serial.write(sanitized)
        self.serial.flush()

    def text_at(self, x, y, text):
        self.location(x, y)
        self.text(text)

    def __init__(self):
        self.serial = serial.Serial("/dev/ttyS1", 2400)
        self.clear()
        self.home()

    def close(self):
        self.serial.close()