#!/usr/bin/env python3
"""
Raspberry Pi DHT22 Temperature Publisher to MQTT Broker
Author: Your Name
Date: 2026-09-11
"""

import time
import json
import sys
import Adafruit_DHT
import paho.mqtt.client as mqtt

# ------------------ CONFIGURATION ------------------
# DHT Sensor type and GPIO pin
DHT_SENSOR = Adafruit_DHT.DHT22
DHT_PIN = 4  # GPIO4 (Pin 7 on Raspberry Pi header)

# MQTT Broker settings
MQTT_BROKER = "broker.hivemq.com"  # Public broker for testing
MQTT_PORT = 1883
MQTT_TOPIC = "raspberrypi/temperature"

# Publish interval in seconds
PUBLISH_INTERVAL = 5
# -----------------------------------------------------

def read_temperature():
    """Reads temperature from DHT22 sensor."""
    humidity, temperature = Adafruit_DHT.read_retry(DHT_SENSOR, DHT_PIN)
    if temperature is None:
        raise ValueError("Failed to read from DHT22 sensor.")
    return round(temperature, 2), round(humidity, 2) if humidity else None

def on_connect(client, userdata, flags, rc):
    """Callback when connected to MQTT broker."""
    if rc == 0:
        print("✅ Connected to MQTT Broker")
    else:
        print(f"❌ Failed to connect, return code {rc}")

def main():
    # Initialize MQTT client
    client = mqtt.Client()
    client.on_connect = on_connect

    try:
        client.connect(MQTT_BROKER, MQTT_PORT, keepalive=60)
    except Exception as e:
        print(f"Error connecting to MQTT broker: {e}")
        sys.exit(1)

    client.loop_start()

    try:
        while True:
            try:
                temp, hum = read_temperature()
                payload = {
                    "temperature": temp,
                    "humidity": hum,
                    "unit": "C"
                }
                client.publish(MQTT_TOPIC, json.dumps(payload))
                print(f"📤 Published: {payload}")
            except ValueError as ve:
                print(f"Sensor error: {ve}")
            except Exception as e:
                print(f"Unexpected error: {e}")

            time.sleep(PUBLISH_INTERVAL)

    except KeyboardInterrupt:
        print("\nStopping publisher...")
    finally:
        client.loop_stop()
        client.disconnect()

if __name__ == "__main__":
    main()