import paho.mqtt.client as mqtt
import time
import json
import random

# --- Configuration ---
MQTT_BROKER = "broker.hivemq.com"  # Using a free public broker
MQTT_PORT = 1883
MQTT_TOPIC = "vehicle/tracker/BUS-01"  # The topic to publish data to
SPEED_THRESHOLD = 80  # Speed limit in km/h

# --- Simulation Initial State ---
# Starting coordinates (e.g., near a city)
current_lat = 40.7128  # New York City Latitude
current_lon = -74.0060 # New York City Longitude

def connect_mqtt():
    """Connects to the MQTT broker."""
    client = mqtt.Client(mqtt.CallbackAPIVersion.VERSION1, client_id="vehicle_simulator_01")
    client.connect(MQTT_BROKER, MQTT_PORT, 60)
    client.loop_start()  # Start the loop in a background thread
    return client

def simulate_data():
    """Simulates GPS movement and speed."""
    global current_lat, current_lon

    # 1. Simulate movement by adding a small random "jitter"
    # This makes the vehicle "wander" around the map
    current_lat += random.uniform(-0.0005, 0.0005)
    current_lon += random.uniform(-0.0005, 0.0005)

    # 2. Simulate speed
    # Mostly normal speed, with occasional bursts
    if random.randint(0, 10) > 8:
        speed = random.uniform(85, 100) # Overspeeding burst
    else:
        speed = random.uniform(50, 75)   # Normal speed

    # 3. Check for speed alert
    alert = "none"
    if speed > SPEED_THRESHOLD:
        alert = f"OVERSPEEDING! Speed: {speed:.2f} km/h"

    # 4. Create data payload
    payload = {
        "vehicle_id": "BUS-01",
        "latitude": current_lat,
        "longitude": current_lon,
        "speed_kmh": round(speed, 2),
        "alert_message": alert
    }
    
    return json.dumps(payload)

def publish_data(client):
    """Publishes simulated data every 3 seconds."""
    while True:
        try:
            data = simulate_data()
            result = client.publish(MQTT_TOPIC, data)
            
            # Check if publish was successful
            if result[0] == 0:
                print(f"Published to {MQTT_TOPIC}: {data}")
            else:
                print(f"Failed to publish to {MQTT_TOPIC}")
                
            time.sleep(3)  # Wait for 3 seconds before sending next update

        except KeyboardInterrupt:
            print("Simulation stopped.")
            client.loop_stop()
            client.disconnect()
            break
        except Exception as e:
            print(f"An error occurred: {e}")
            client.loop_stop()
            client.disconnect()
            break

if __name__ == "__main__":
    client = connect_mqtt()
    publish_data(client)