"""
SMART disk health monitoring for WROLPi Controller.
"""

import subprocess
from typing import Optional

# Import pySMART only if available
try:
    from pySMART import DeviceList, Device

    SMART_AVAILABLE = True
except ImportError:
    SMART_AVAILABLE = False

from controller.lib.config import is_docker_mode

# Warning thresholds for hard-drive temperature, in Celsius.  Unlike CPU
# temperature, neither SMART nor psutil reports a recommended limit, so we
# carry sensible spinning-disk defaults in the payload (warn 55, critical 65)
# and let the frontend stay dumb.
HDD_HIGH_TEMPERATURE = 55
HDD_CRITICAL_TEMPERATURE = 65

SMARTCTL_SCAN_TIMEOUT = 10
SMARTCTL_STANDBY_TIMEOUT = 5


def is_smart_available() -> bool:
    """Check if SMART monitoring is available."""
    if is_docker_mode():
        return False
    return SMART_AVAILABLE


def get_all_smart_status() -> list[dict]:
    """
    Get SMART status for all drives.

    Returns:
        list of SMART status dicts
    """
    if not is_smart_available():
        return []

    try:
        devices = DeviceList()
        results = []

        for device in devices.devices:
            results.append(_get_device_smart(device))

        return results
    except Exception:
        return []


def _get_device_smart(device) -> dict:
    """Extract SMART data from a pySMART device."""
    return {
        "device": device.name,
        "path": f"/dev/{device.name}",
        "model": device.model,
        "serial": device.serial,
        "capacity": device.capacity,
        "assessment": device.assessment,  # PASS, FAIL, WARN
        "temperature": _get_temperature(device),
        "power_on_hours": _get_attribute(device, "Power_On_Hours"),
        "reallocated_sectors": _get_attribute(device, "Reallocated_Sector_Ct"),
        "pending_sectors": _get_attribute(device, "Current_Pending_Sector"),
        "smart_enabled": device.smart_enabled,
    }


def _get_temperature(device) -> Optional[int]:
    """Get drive temperature.

    Prefer pySMART's `temperature` property: it parses real-world raw
    values like "52 (Min/Max 16/57)" that int() cannot, and works for
    NVMe devices which have no ATA attribute table.  Fall back to the
    plain attributes for devices where the property is unavailable.
    """
    temp = getattr(device, "temperature", None)
    if isinstance(temp, int):
        return temp
    temp = _get_attribute(device, "Temperature_Celsius")
    if temp is None:
        temp = _get_attribute(device, "Airflow_Temperature_Cel")
    return temp


def _get_attribute(device, name: str) -> Optional[int]:
    """Get a specific SMART attribute value."""
    if not hasattr(device, 'attributes') or device.attributes is None:
        return None

    for attr in device.attributes:
        if attr and attr.name == name:
            try:
                return int(attr.raw)
            except (ValueError, TypeError):
                return None
    return None


def _scan_devices() -> list[tuple[str, Optional[str]]]:
    """List SMART-capable devices via ``smartctl --scan``.

    ``--scan`` only enumerates devices; it does not read SMART data, so it
    does not wake a drive that has spun down.  Returns (path, interface)
    tuples, where interface is the ``-d`` type smartctl detected (e.g.
    "sat") or None.
    """
    try:
        result = subprocess.run(
            ["smartctl", "--scan"],
            capture_output=True, text=True, timeout=SMARTCTL_SCAN_TIMEOUT,
        )
    except (subprocess.SubprocessError, OSError):
        return []

    devices = []
    for line in result.stdout.splitlines():
        line = line.strip()
        if not line or line.startswith("#"):
            continue
        # Format: "/dev/sda -d sat # /dev/sda [SAT], ATA device"
        parts = line.split()
        path = parts[0]
        if not path.startswith("/dev/"):
            continue
        interface = None
        if "-d" in parts:
            idx = parts.index("-d")
            if idx + 1 < len(parts):
                interface = parts[idx + 1]
        devices.append((path, interface))
    return devices


def _drive_is_asleep(path: str) -> bool:
    """Return True if the drive at ``path`` is in standby/sleep.

    Uses ``smartctl -n standby``, which checks the drive's power mode and
    exits WITHOUT waking it when it is in standby.  This goes through the
    same SAT translation smartctl already uses to read these drives, so it
    works on the USB-SATA bridges where ``hdparm -C`` only reports
    "unknown".  On any error we return False so the caller falls back to a
    normal SMART read (better to read an awake drive than to never read it).
    """
    try:
        result = subprocess.run(
            ["smartctl", "-n", "standby", "-i", path],
            capture_output=True, text=True, timeout=SMARTCTL_STANDBY_TIMEOUT,
        )
    except (subprocess.SubprocessError, OSError):
        return False
    # In a low-power mode smartctl prints e.g. "Device is in STANDBY mode,
    # exit(2)" (or "SLEEP" for the deeper mode) and skips the data read.  An
    # awake -i read mentions neither.
    output = result.stdout.upper()
    return "STANDBY" in output or "SLEEP" in output


def build_smart_stats(previous: Optional[dict] = None) -> dict:
    """Collect SMART status for the navbar/Disk Management warning.

    Reading SMART wakes a sleeping drive, so any drive in standby is NOT
    read: instead we reuse its last-known data from ``previous`` (matched by
    path).  A spun-down drive is not hot, so this is safe.  The warning
    thresholds travel in the payload alongside the per-drive list so the
    frontend does not hardcode them.

    Returns ``{"drives": [...], "high_temperature": int,
    "critical_temperature": int}``.  In Docker mode or without pySMART the
    drive list is empty.
    """
    stats = {
        "drives": [],
        "high_temperature": HDD_HIGH_TEMPERATURE,
        "critical_temperature": HDD_CRITICAL_TEMPERATURE,
    }
    if not is_smart_available():
        return stats

    previous_by_path = {}
    if previous:
        for drive in previous.get("drives", []):
            previous_by_path[drive.get("path")] = drive

    try:
        for path, interface in _scan_devices():
            if _drive_is_asleep(path):
                # Don't wake it; reuse the last reading if we have one.
                prior = previous_by_path.get(path)
                if prior is not None:
                    stats["drives"].append(prior)
                continue
            try:
                device = Device(path, interface=interface)
            except Exception:
                continue
            stats["drives"].append(_get_device_smart(device))
    except Exception:
        # Never let a status-collection failure blank the whole payload.
        pass

    return stats