from machine import Pin, time_pulse_us
import time
import network
from umqtt.simple import MQTTClient

# WiFi Credentials
SSID = "Wokwi-GUEST"
PASSWORD = ""

# MQTT Config
BROKER = "broker.emqx.io"
PORT = 1883
TOPIC = b"sensor/distance"
CLIENT_ID = b"ultrasonic-publisher"

# Ultrasonic Pins
TRIG = Pin(5, Pin.OUT)
ECHO = Pin(18, Pin.IN)

# WiFi Connection
def connect_wifi():
    wlan = network.WLAN(network.STA_IF)
    wlan.active(True)
    wlan.connect(SSID, PASSWORD)
    print("🔌 Connecting WiFi...", end="")
    while not wlan.isconnected():
        print(".", end="")
        time.sleep(0.5)
    print("\n✅ Connected:", wlan.ifconfig())

# Measure distance
def get_distance():
    TRIG.value(0)
    time.sleep_us(2)
    TRIG.value(1)
    time.sleep_us(10)
    TRIG.value(0)
    duration = time_pulse_us(ECHO, 1, 30000)  # wait max 30ms
    distance = (duration / 2) * 0.0343  # speed of sound = 343 m/s
    return round(distance, 2)

# Publish loop
def publish_loop():
    client = MQTTClient(CLIENT_ID, BROKER, PORT)
    client.connect()
    print("✅ Connected to MQTT Broker")
    
    try:
        while True:
            dist = get_distance()
            msg = str(dist).encode()  # convert to bytes
            client.publish(TOPIC, msg)
            print(f"📡 Published distance: {dist} cm")
            time.sleep(2)
    finally:
        client.disconnect()

# Run program
connect_wifi()
publish_loop()