"""Driver registry — auto-discovers board drivers from sub-folders.

At application startup call ``registry.discover()``.  Every sub-folder of
``app/drivers/`` that contains a ``driver.py`` with a ``BoardDriver`` subclass
is registered automatically.  No manual imports needed.

Usage
-----
::
    from app.drivers.registry import registry

    driver = registry.get("olimex_esp32_c6_evb")
    driver.set_relay(board, 1, True)

    # All registered drivers (for UI drop-downs):
    all_drivers = registry.all()
"""
from __future__ import annotations

import importlib
import inspect
import logging
import os
from typing import TYPE_CHECKING

from app.drivers.base import BoardDriver

if TYPE_CHECKING:
    pass

logger = logging.getLogger(__name__)

_DRIVERS_DIR = os.path.dirname(__file__)


class DriverRegistry:
    def __init__(self):
        self._drivers: dict[str, BoardDriver] = {}

    # ── discovery ─────────────────────────────────────────────────────────────

    def discover(self) -> None:
        """Scan ``app/drivers/`` sub-folders and register found drivers."""
        for entry in sorted(os.scandir(_DRIVERS_DIR), key=lambda e: e.name):
            if not entry.is_dir() or entry.name.startswith(("_", ".")):
                continue
            driver_module_path = os.path.join(entry.path, "driver.py")
            if not os.path.isfile(driver_module_path):
                logger.debug("Skipping %s — no driver.py found", entry.name)
                continue
            module_name = f"app.drivers.{entry.name}.driver"
            try:
                mod = importlib.import_module(module_name)
                self._register_from_module(mod, entry.name)
            except Exception as exc:
                logger.error("Failed to load driver '%s': %s", entry.name, exc, exc_info=True)

    def _register_from_module(self, mod, folder_name: str) -> None:
        for _name, obj in inspect.getmembers(mod, inspect.isclass):
            if (
                issubclass(obj, BoardDriver)
                and obj is not BoardDriver
                and obj.DRIVER_ID
            ):
                instance = obj()
                self._drivers[obj.DRIVER_ID] = instance
                logger.info(
                    "Board driver registered: '%s' (%s) from folder '%s'",
                    obj.DRIVER_ID, obj.DISPLAY_NAME, folder_name,
                )
                return
        logger.warning(
            "Folder '%s' has driver.py but no BoardDriver subclass with DRIVER_ID found",
            folder_name,
        )

    # ── lookup ────────────────────────────────────────────────────────────────

    def get(self, driver_id: str) -> BoardDriver | None:
        return self._drivers.get(driver_id)

    def get_or_default(self, driver_id: str) -> BoardDriver:
        """Return driver or fall back to the generic_esp32 stub."""
        return self._drivers.get(driver_id) or self._drivers.get("generic_esp32") or next(iter(self._drivers.values()))

    def all(self) -> list[BoardDriver]:
        return list(self._drivers.values())

    def choices(self) -> list[tuple[str, str]]:
        """Return list of (DRIVER_ID, DISPLAY_NAME) for form select fields."""
        return [(d.DRIVER_ID, d.DISPLAY_NAME) for d in self._drivers.values()]

    def is_registered(self, driver_id: str) -> bool:
        return driver_id in self._drivers

    def __len__(self) -> int:
        return len(self._drivers)

    def __repr__(self) -> str:
        return f"<DriverRegistry drivers={list(self._drivers.keys())}>"


# Singleton — import this everywhere
registry = DriverRegistry()