#!/usr/bin/env python3

# https://pimylifeup.com/raspberry-pi-temperature/

import logging
import os
import time
import subprocess
import sys

from prometheus_client import start_http_server, Gauge, REGISTRY, GC_COLLECTOR, PLATFORM_COLLECTOR, PROCESS_COLLECTOR

REGISTRY.unregister(GC_COLLECTOR)
REGISTRY.unregister(PLATFORM_COLLECTOR)
REGISTRY.unregister(PROCESS_COLLECTOR)

logging.basicConfig(stream=sys.stdout, level=logging.DEBUG)


def setup_gauge():
    logging.info('Setting up Gauge')
    g = Gauge(f'sys_cpu_temp_celsius_degrees', 'CPU Temperature', ['node_name'])
    logging.info(f'Created Gauge: {g}')

    node_name_label = _get_node_name()
    logging.info(f'Retrieved node_name label {node_name_label}')
    # Why call `.set()` here? Because, without it, I get "gauge metric is missing label values"
    g.labels(node_name=node_name_label).set(_get_temp())

    logging.info('Setting function for Gauge')
    g.set_function(_get_temp)


def _get_temp():
    temp = float(subprocess.run(['/usr/bin/vcgencmd', 'measure_temp'], capture_output=True).stdout.decode('utf-8')
                 .replace('temp=', '').replace("'C\n", ''))
    logging.info(f'Got temp: {temp}')
    return temp


def _get_node_name():
    # https://kubernetes.io/docs/tasks/inject-data-application/environment-variable-expose-pod-information/
    try:
        return os.environ['NODE_NAME']
    except:
        return 'unknown-node'


if __name__ == '__main__':
    setup_gauge()
    start_http_server(8555)
    while True:
        # Stay alive!
        time.sleep(1)