"""Utilities to assess basic hardware health metrics for the diagnostic tool."""

from __future__ import annotations

import psutil


def _safe_disk_usage_percent(path: str) -> float | None:
    """Return disk usage percent for path or None when path is unavailable."""
    try:
        return psutil.disk_usage(path).percent
    except FileNotFoundError:
        return None
    except PermissionError:
        return None


def _cpu_temperature_celsius() -> float | None:
    """Return the current CPU temperature in Celsius if available."""
    temps = psutil.sensors_temperatures()
    if not temps:
        return None

    # Sensors differ by platform; look for common CPU entries first.
    for label in ("coretemp", "cpu-thermal", "cpu-therm", "k10temp", "acpitz"):
        entries = temps.get(label)
        if entries:
            for entry in entries:
                if entry.current is not None:
                    return float(entry.current)

    # Fallback: return the first available temperature reading.
    for entries in temps.values():
        for entry in entries:
            if entry.current is not None:
                return float(entry.current)

    return None


def check_hardware() -> dict[str, float | None]:
    """
    Gather key hardware health metrics via psutil.

    Returns:
        A dictionary containing:
            - cpu_usage_percent: overall CPU utilization
            - ram_usage_percent: RAM utilization
            - disk_usage_percent_ssd: disk usage on /mnt/ssd or None if unavailable
            - disk_usage_percent_backup: disk usage on /mnt/backup-hdd or None if unavailable
            - cpu_temperature_celsius: current CPU temp or None if sensors unavailable
    """

    return {
        "cpu_usage_percent": psutil.cpu_percent(interval=1.0),
        "ram_usage_percent": psutil.virtual_memory().percent,
        "disk_usage_percent_ssd": _safe_disk_usage_percent("/mnt/ssd"),
        "disk_usage_percent_backup": _safe_disk_usage_percent("/mnt/backup-hdd"),
        "cpu_temperature_celsius": _cpu_temperature_celsius(),
    }