import json
import os
import paho.mqtt.publish as publish
import sys

# Retrieve broker parameters from shared config or environment variables
MQTT_HOST = os.getenv("MQTT_HOST", "localhost")
MQTT_PORT = int(os.getenv("MQTT_PORT", 8884))
MQTT_USER = os.getenv("MQTT_USER", None)
MQTT_PASS = os.getenv("MQTT_PASS", None)


def send_command(topic: str = "cmd/all", payload: dict | str = None):
    """
    Publishes an MQTT command payload to a given topic.
    """
    if payload is None:
        payload = {}

    if isinstance(payload, dict):
        payload_str = json.dumps(payload)
    else:
        payload_str = str(payload)

    auth = None
    if MQTT_USER:
        auth = {"username": MQTT_USER, "password": MQTT_PASS or ""}

    publish.single(
        topic=topic,
        payload=payload_str,
        hostname=MQTT_HOST,
        port=MQTT_PORT,
        auth=auth
    )
    print(f"[MQTT] Published command to '{topic}': {payload_str}")