from micropython import const
import framebuf
from machine import Pin, I2C

# Minimal SSD1306 driver
_SET_CONTRAST = const(0x81)
_SET_ENTIRE_ON = const(0xA4)
_SET_NORM_INV = const(0xA6)
_SET_DISP = const(0xAE)
_SET_MEM_ADDR = const(0x20)
_SET_COL_ADDR = const(0x21)
_SET_PAGE_ADDR = const(0x22)
_SET_DISP_START_LINE = const(0x40)
_SET_SEG_REMAP = const(0xA0)
_SET_MUX_RATIO = const(0xA8)
_SET_COM_OUT_DIR = const(0xC0)
_SET_DISP_OFFSET = const(0xD3)
_SET_COM_PIN_CFG = const(0xDA)
_SET_DISP_CLK_DIV = const(0xD5)
_SET_PRECHARGE = const(0xD9)
_SET_VCOM_DESEL = const(0xDB)
_SET_CHARGE_PUMP = const(0x8D)

class SSD1306:
    def __init__(self, width, height, external_vcc):
        self.width = width
        self.height = height
        self.external_vcc = external_vcc
        self.pages = height // 8
        self.buffer = bytearray(self.pages * width)
        self.framebuf = framebuf.FrameBuffer(
            self.buffer, width, height, framebuf.MONO_VLSB
        )
        self.init_display()

    def init_display(self):
        for cmd in (
            _SET_DISP | 0x00,  # off
            _SET_DISP_CLK_DIV, 0x80,
            _SET_MUX_RATIO, self.height - 1,
            _SET_DISP_OFFSET, 0x00,
            _SET_DISP_START_LINE | 0x00,
            _SET_CHARGE_PUMP, 0x10 if self.external_vcc else 0x14,
            _SET_MEM_ADDR, 0x00,
            _SET_SEG_REMAP | 0x01,
            _SET_COM_OUT_DIR | 0x08,
            _SET_COM_PIN_CFG, 0x02 if self.height == 32 else 0x12,
            _SET_CONTRAST, 0x9F,
            _SET_PRECHARGE, 0x22 if self.external_vcc else 0xF1,
            _SET_VCOM_DESEL, 0x30,
            _SET_ENTIRE_ON,
            _SET_NORM_INV,
            _SET_DISP | 0x01,  # on
        ):
            self.write_cmd(cmd)
        self.fill(0)
        self.show()

    def write_cmd(self, cmd):
        raise NotImplementedError

    def fill(self, col):
        self.framebuf.fill(col)

    def pixel(self, x, y, col):
        self.framebuf.pixel(x, y, col)

    def text(self, string, x, y, col=1):
        self.framebuf.text(string, x, y, col)

    def rect(self, x, y, w, h, col):
        self.framebuf.rect(x, y, w, h, col)

    def show(self):
        x0 = 0
        x1 = self.width - 1
        self.write_cmd(_SET_COL_ADDR)
        self.write_cmd(x0)
        self.write_cmd(x1)
        self.write_cmd(_SET_PAGE_ADDR)
        self.write_cmd(0)
        self.write_cmd(self.pages - 1)
        self.write_data(self.buffer)

class SSD1306_I2C(SSD1306):
    def __init__(self, width, height, i2c, addr=0x3C, external_vcc=False):
        self.i2c = i2c
        self.addr = addr
        self.temp = bytearray(2)
        super().__init__(width, height, external_vcc)

    def write_cmd(self, cmd):
        self.temp[0] = 0x80  # Co=1, D/C#=0
        self.temp[1] = cmd
        self.i2c.writeto(self.addr, self.temp)

    def write_data(self, buf):
        self.temp[0] = self.addr
        self.temp[1] = 0x40  # Co=0, D/C#=1
        self.i2c.start()
        self.i2c.write(self.temp)
        self.i2c.write(buf)
        self.i2c.stop()

# Your original code
i2c = I2C(0, sda=Pin(21, pull=Pin.PULL_UP),
          scl=Pin(22, pull=Pin.PULL_UP))

oled = SSD1306_I2C(128, 64, i2c)

oled.fill(0)
oled.rect(0, 0, 127, 63, 1)
oled.text('PROGRAMMING the', 5, 12, 1)
oled.text('ESP32', 5, 22, 1)
oled.text('by', 5, 32, 1)
oled.text('Simon Monk', 5, 42, 1)

oled.show()