import errno
import struct

import usb.core
import usb.util
from usb.core import USBError

VENDOR_ID = 0x191A
PRODUCT_ID = 0x8003
ENDPOINT = 1


class PatliteDevice:
    def __init__(self):
        self._dev = None

    def connect(self):
        dev = usb.core.find(idVendor=VENDOR_ID, idProduct=PRODUCT_ID)
        if dev is None:
            raise RuntimeError(
                f"Patlite not found (vendor={VENDOR_ID:#06x}, product={PRODUCT_ID:#06x})"
            )

        try:
            if dev.is_kernel_driver_active(0):
                dev.detach_kernel_driver(0)
            dev.set_configuration()
        except USBError as exc:
            if exc.errno == errno.EACCES:
                raise RuntimeError(
                    "USB access denied. On headless hosts, run ./scripts/install-udev.sh, "
                    "then 'newgrp patlite' (or re-login), unplug/replug the Patlite, and retry."
                ) from exc
            raise

        self._dev = dev

    def close(self):
        if self._dev is not None:
            self.send(0x00, 0x00, 0x00)
            usb.util.dispose_resources(self._dev)
            self._dev = None

    def send(self, ry: int, gb: int, w: int):
        if self._dev is None:
            return
        data = struct.pack(
            "BBBBBBBx",
            0x00,
            0x00,
            0x0F,
            0x00,
            ry & 0xFF,
            gb & 0xFF,
            w & 0xFF,
        )
        self._dev.write(ENDPOINT, data)