#!/usr/bin/env python3
"""ISS live position -> control signals. The space station's motion drifts the timbre.
It circles Earth every ~90 min at ~7.66 km/s; lat/lon sweep continuously while the
computed ground speed wobbles gently around orbital velocity -> a slow, living modulator.
"""
import argparse
import json
import math
import time
import urllib.request
import urllib.error

from pythonosc.udp_client import SimpleUDPClient

URL = "http://api.open-notify.org/iss-now.json"
USER_AGENT = "godstrument-iss/1.0"
EARTH_RADIUS_M = 6371000.0


def haversine_m(lat1, lon1, lat2, lon2):
    """Great-circle ground distance in meters between two lat/lon points."""
    p1 = math.radians(lat1)
    p2 = math.radians(lat2)
    dphi = math.radians(lat2 - lat1)
    dlam = math.radians(lon2 - lon1)
    a = math.sin(dphi / 2) ** 2 + math.cos(p1) * math.cos(p2) * math.sin(dlam / 2) ** 2
    return 2 * EARTH_RADIUS_M * math.asin(math.sqrt(a))


def fetch():
    req = urllib.request.Request(URL, headers={"User-Agent": USER_AGENT})
    with urllib.request.urlopen(req, timeout=10) as resp:
        data = json.loads(resp.read().decode("utf-8"))
    pos = data["iss_position"]
    return float(pos["latitude"]), float(pos["longitude"])


def main():
    ap = argparse.ArgumentParser()
    ap.add_argument("--host", default="127.0.0.1")
    ap.add_argument("--port", type=int, default=9000)
    ap.add_argument("--interval", type=float, default=5.0)
    args = ap.parse_args()

    client = SimpleUDPClient(args.host, args.port)
    print(f"[world_iss] emitting /gs/iss/lat,lon,vel every {args.interval:g}s")

    prev = None          # (lat, lon)
    prev_t = None        # monotonic timestamp of prev fix
    smooth_vel = None    # exponentially smoothed ground speed (m/s)
    backoff = args.interval

    while True:
        try:
            lat, lon = fetch()
            now = time.monotonic()

            client.send_message("/gs/iss/lat", float(lat))
            client.send_message("/gs/iss/lon", float(lon))

            if prev is not None and prev_t is not None:
                dt = now - prev_t
                if dt > 0:
                    dist = haversine_m(prev[0], prev[1], lat, lon)
                    vel = dist / dt  # m/s ground speed
                    if smooth_vel is None:
                        smooth_vel = vel
                    else:
                        smooth_vel = 0.6 * smooth_vel + 0.4 * vel
                    client.send_message("/gs/iss/vel", float(smooth_vel))

            prev = (lat, lon)
            prev_t = now
            backoff = args.interval
        except (urllib.error.URLError, OSError, ValueError, KeyError, json.JSONDecodeError) as e:
            print(f"[world_iss] warning: {e}; retrying in {backoff:g}s")
            time.sleep(backoff)
            backoff = min(backoff * 2, 60.0)
            continue

        time.sleep(args.interval)


if __name__ == "__main__":
    main()