#!/usr/bin/env python3

import random
import math
import json
from datetime import datetime

def generate_signal_k_data(num_boats, base_coords, nautical_miles):
    signal_k_data = {
        "@context": "https://signalk.org/specification/1.4.0/context.json",
        "vessels": {
            "boat-1": {
                "name": "Boat 1",
                "mmsi": "123456789",
                "navigation": {
                    "position": {
                        "latitude": base_coords[0],
                        "longitude": base_coords[1]
                    }
                },
                "heading": {
                    "trueHeading": 0.0
                },
                "speedOverGround": 0.0,
                "courseOverGroundTrue": 0.0
            }
        }
    }
    for i in range(2, num_boats + 1):
        boat_data = {
            "name": f"Boat {i}",
            "mmsi": str(123456789 + i),
            "navigation": {
                "position": {
                    "latitude": base_coords[0] + (random.random() * 2 - 1) * (nautical_miles / 60),
                    "longitude": base_coords[1] + (random.random() * 2 - 1) * (nautical_miles / 60) / math.cos(base_coords[0] * math.pi / 180)
                }
            },
            "heading": {
                "trueHeading": 0.0
            },
            "speedOverGround": 0.0,
            "courseOverGroundTrue": 0.0
        }
        signal_k_data["vessels"][f"boat-{i}"] = boat_data
    return json.dumps(signal_k_data)


def move_boats(signal_k_data):
    signal_k_data = json.loads(signal_k_data)
    for boat in signal_k_data["vessels"].values():
        # calculate new position based on current position, course over ground true, and speed over ground
        lat = boat["navigation"]["position"]["latitude"]
        lon = boat["navigation"]["position"]["longitude"]
        cog_true = boat["courseOverGroundTrue"]
        sog = boat["speedOverGround"]
        lat += (sog / 60) * math.cos(cog_true * math.pi / 180)
        lon += (sog / 60) * math.sin(cog_true * math.pi / 180) / math.cos(lat * math.pi / 180)
        # update boat position, heading, and speed
        boat["navigation"]["position"]["latitude"] = lat
        boat["navigation"]["position"]["longitude"] = lon
        boat["heading"]["trueHeading"] = random.uniform(0, 360)
        boat["speedOverGround"] = random.randint(1, 15)
        boat["courseOverGroundTrue"] = boat["heading"]["trueHeading"]
    signal_k_data["@timestamp"] = datetime.utcnow().strftime('%Y-%m-%dT%H:%M:%S.%fZ')
    return json.dumps(signal_k_data)

# example usage
num_boats = 5
base_coords = (37.7749, -122.4194) # San Francisco
nautical_miles = 10
data = generate_signal_k_data(num_boats, base_coords, nautical_miles)
print("Initial boat positions:")
print(data)
for i in range(3):
    data = move_boats(data)
    print(f"Boat positions after iteration {i + 1}:")
    print(data)