#!/usr/bin/python3
"""Check the temperature of a drive.
Functions:
    verify_device_node(query)
        - Check if query is a device node
    retrieve_smart_temp(device_node)
        - Retrieve specified drive temperature in mKelvin
    convert_to_celsius(mkel_temp)
        - Given mkel_temp, convert it into °C
"""

import argparse
import pathlib
import subprocess

# ========== Constants ==========
DUMP_CMD = ["skdump", "--temperature"]


# ========== Functions ==========
def verify_device_node(query):
    """Check if query is a device node.
    :param query: input that refers to a device
    :type query: a path-like object
    :returns: True if query is a device node, False if otherwise
    :rtype: bool
    """
    return pathlib.Path(query).is_block_device()


def retrieve_smart_temp(device_node):
    """Retrieve specified drive's temperature.
    :param device_node: device to retrieve temperature for
    :type device_node: str
    :returns: output of skdump in mKelvin
    :rtype: float
    """
    temp = subprocess.run(
        DUMP_CMD + [device_node], capture_output=True, text=True
    ).stdout
    return float(temp)


def convert_to_celsius(mkel_temp):
    """Given mkel_temp, convert it into °C.
    :param mkel_temp: the temperature in mKelvin
    :type mkel_temp: str
    :returns: temperature converted into degrees celsius
    :rtype: str
    """
    return (mkel_temp / 1000) - 273.15


# ========== Main Script ==========
parser = argparse.ArgumentParser()
parser.add_argument(
    "device", help="device node to retrieve the temperature for", metavar="dev"
)
args = parser.parse_args()

dev = args.device

if verify_device_node(dev):
    mkel = retrieve_smart_temp(dev)
    print(f"{dev}: {convert_to_celsius(mkel)}°C")
else:
    print("Not a device node.")
    exit(1)