"use client";

import { useEffect, useState } from "react";
import { collection, onSnapshot, orderBy, query, where, FirestoreError } from "firebase/firestore";
import { db } from "@/lib/firebase";
import type { AircraftTrailPoint } from "@/lib/types";

// Trail points live at aircraft/{icao}/positions (written by c2-core
// telemetry.py on every position change, TTL-deleted after ~24h). The same
// icao can fly several legs a day, so only the latest continuous stretch is
// "this flight": a gap longer than FLIGHT_GAP_MS starts a new one.
const LOOKBACK_MS = 6 * 60 * 60 * 1000;
const FLIGHT_GAP_MS = 20 * 60 * 1000;

function currentFlight(points: AircraftTrailPoint[]): AircraftTrailPoint[] {
  let start = 0;
  for (let i = 1; i < points.length; i++) {
    if (new Date(points[i].t).getTime() - new Date(points[i - 1].t).getTime() > FLIGHT_GAP_MS) start = i;
  }
  return points.slice(start);
}

/** Live flight path for one aircraft; pass null to subscribe to nothing. */
export function useAircraftTrail(icao: string | null) {
  const [trail, setTrail] = useState<AircraftTrailPoint[]>([]);

  useEffect(() => {
    setTrail([]);
    if (!icao) return;
    // `t` is Python's isoformat() in UTC ("...T17:06:48.755123+00:00"), so it
    // sorts and range-filters correctly as a string against toISOString()'s
    // "...T17:06:48.755Z" down to the second — no composite index needed.
    const since = new Date(Date.now() - LOOKBACK_MS).toISOString();
    const q = query(collection(db, "aircraft", icao, "positions"), where("t", ">=", since), orderBy("t"));
    return onSnapshot(
      q,
      (snap) => setTrail(currentFlight(snap.docs.map((d) => d.data() as AircraftTrailPoint))),
      (err: FirestoreError) => console.error("useAircraftTrail:", err),
    );
  }, [icao]);

  return trail;
}