Day 2

# MQTT publisher and subscriber with paho-mqtt
# pip install paho-mqtt

import json, time, threading
import paho.mqtt.client as mqtt

BROKER = "broker.hivemq.com"  # free public broker for testing
PORT   = 1883
TOPIC_DATA   = "precisionai/demo/sensors"
TOPIC_STATUS = "precisionai/demo/status"
CLIENT_ID    = "demo-sensor-01"

# ── Subscriber (runs in background) ─────────────────────────
def on_connect(client, userdata, flags, rc):
    print(f"Subscriber connected: {rc}")
    client.subscribe(TOPIC_DATA,   qos=1)
    client.subscribe(TOPIC_STATUS, qos=1)

def on_message(client, userdata, msg):
    try:
        payload = json.loads(msg.payload.decode())
        print(f"  [{msg.topic}] temp={payload.get('temp')}°C")
    except:
        print(f"  [{msg.topic}] {msg.payload.decode()}")

sub = mqtt.Client(client_id="demo-subscriber")
sub.on_connect = on_connect
sub.on_message = on_message
sub.connect(BROKER, PORT, keepalive=60)
sub.loop_start()
time.sleep(1)

# ── Publisher ────────────────────────────────────────────────
import random

pub = mqtt.Client(client_id=CLIENT_ID)

# Last Will: auto-publish 'offline' if we disconnect unexpectedly
pub.will_set(TOPIC_STATUS, payload=json.dumps({"status":"offline","id":CLIENT_ID}), qos=1, retain=True)

pub.connect(BROKER, PORT, keepalive=60)
pub.loop_start()

# Announce online (retained so new subscribers see current state)
pub.publish(TOPIC_STATUS, json.dumps({"status":"online","id":CLIENT_ID}), qos=1, retain=True)

print(f"Publishing to {BROKER}:{PORT}/{TOPIC_DATA}")
for i in range(5):
    payload = json.dumps({
        "device": CLIENT_ID,
        "temp":   round(22 + random.gauss(0, 1), 1),
        "hum":    round(50 + random.gauss(0, 5), 1),
        "seq":    i,
    })
    result = pub.publish(TOPIC_DATA, payload, qos=1)
    result.wait_for_publish()
    print(f"Published #{i}: {payload}")
    time.sleep(2)

pub.loop_stop()
sub.loop_stop()
print("Done.")