"""Raspberry Pi model detection for choosing a WS2812 backend."""

from __future__ import annotations

from functools import lru_cache


@lru_cache(maxsize=1)
def board_model() -> str:
    try:
        with open("/proc/device-tree/model", "rb") as f:
            return f.read().rstrip(b"\x00").decode("ascii")
    except OSError:
        return "Unknown"


@lru_cache(maxsize=1)
def board_family() -> str:
    model = board_model().lower()
    if "raspberry pi 5" in model:
        return "pi5"
    if "raspberry pi 4" in model:
        return "pi4"
    if "zero 2" in model:
        return "pi_zero2"
    if "zero" in model:
        return "pi_zero"
    if "raspberry pi 3" in model:
        return "pi3"
    return "unknown"


def supports_ws281x() -> bool:
    return board_family() != "pi5"


def pio_device(index: int = 0) -> str | None:
    from pathlib import Path

    path = Path(f"/dev/leds{index}")
    return str(path) if path.exists() else None


def pio_available() -> bool:
    return pio_device(0) is not None


def pi5_second_spi_bus() -> int:
    """
    Second strip on Pi 5 SPI — prefer spi1 from dtoverlay=spi1-3cs
    (/dev/spidev1.0, MOSI on GPIO 20). Falls back to built-in spidev10.0.
    """
    from pathlib import Path

    if Path("/dev/spidev1.0").exists():
        return 1
    if Path("/dev/spidev10.0").exists():
        return 10
    raise RuntimeError(
        "No second SPI device found. Add to /boot/firmware/config.txt under [all]:\n"
        "  dtoverlay=spi1-3cs\n"
        "Then reboot. Wire strip 1 DIN to GPIO 20 (SPI1 MOSI).\n"
        "Note: dtparam=spi1=on is ignored on Pi 5; use the overlay in [all], not [cm5]."
    )