const KNOT_TO_MPS = 0.514444;
const FOOT_TO_M = 0.3048;
const FPM_TO_MPS = 0.00508;

function finiteNumber(value) {
  if (value === null || value === undefined || value === '') return null;
  const number = Number(value);
  return Number.isFinite(number) ? number : null;
}

function emitterCategory(value) {
  const category = String(value || '')
    .trim()
    .toUpperCase();
  const categories = {
    A1: 2,
    A2: 3,
    A3: 4,
    A4: 5,
    A5: 6,
    A6: 7,
    A7: 8,
    B1: 9,
    B2: 10,
    B3: 11,
    B4: 12,
    B6: 14,
    B7: 15,
  };
  return categories[category] || 0;
}

/**
 * Convert one adsb.lol v2 aircraft record into the OpenSky state-vector shape
 * consumed by the existing Flights renderer.
 * @param {object} aircraft adsb.lol aircraft record.
 * @param {number} nowSeconds Feed response time in epoch seconds.
 * @returns {Array|null} OpenSky-compatible state vector, or null when invalid.
 */
export function normalizeAdsbLolAircraftState(aircraft, nowSeconds) {
  const hex = String(aircraft?.hex || '')
    .trim()
    .toLowerCase();
  const latitude = finiteNumber(aircraft?.lat);
  const longitude = finiteNumber(aircraft?.lon);
  if (
    !hex ||
    latitude === null ||
    longitude === null ||
    Math.abs(latitude) > 90 ||
    Math.abs(longitude) > 180
  )
    return null;

  const seenPosition = Math.max(
    0,
    finiteNumber(aircraft?.seen_pos) ?? finiteNumber(aircraft?.seen) ?? NaN,
  );
  const seen = Math.max(0, finiteNumber(aircraft?.seen) ?? seenPosition);
  const onGround = aircraft?.alt_baro === 'ground';
  const barometricFeet = onGround ? null : finiteNumber(aircraft?.alt_baro);
  const geometricFeet = finiteNumber(aircraft?.alt_geom);
  const groundSpeedKnots = finiteNumber(aircraft?.gs);
  const verticalRateFpm =
    finiteNumber(aircraft?.baro_rate) ?? finiteNumber(aircraft?.geom_rate);
  const track = finiteNumber(aircraft?.track);

  return [
    hex,
    String(aircraft?.flight || aircraft?.r || '').trim() || null,
    null,
    Number.isFinite(seenPosition)
      ? Math.max(0, nowSeconds - seenPosition)
      : null,
    Number.isFinite(seen) ? Math.max(0, nowSeconds - seen) : null,
    longitude,
    latitude,
    barometricFeet === null ? null : barometricFeet * FOOT_TO_M,
    onGround,
    groundSpeedKnots === null ? null : groundSpeedKnots * KNOT_TO_MPS,
    track,
    verticalRateFpm === null ? null : verticalRateFpm * FPM_TO_MPS,
    null,
    geometricFeet === null ? null : geometricFeet * FOOT_TO_M,
    aircraft?.squawk || null,
    aircraft?.spi === 1,
    0,
    emitterCategory(aircraft?.category),
  ];
}

/**
 * Normalize an adsb.lol point response to an OpenSky-compatible response.
 * Invalid rows and positionless contacts are intentionally excluded.
 * @param {object} payload adsb.lol v2 response.
 * @returns {{time:number,states:Array[]}}
 */
export function normalizeAdsbLolPointResponse(payload) {
  const responseNow = finiteNumber(payload?.now);
  const nowSeconds =
    responseNow === null
      ? Math.floor(Date.now() / 1000)
      : Math.floor(
          responseNow > 10_000_000_000 ? responseNow / 1000 : responseNow,
        );
  const aircraft = Array.isArray(payload?.ac) ? payload.ac : [];
  const states = [];
  // Keep the OpenSky vectors unchanged. The regional fallback's extra readsb
  // status travels alongside them, keyed only to admitted aircraft.
  const admitted = new Set();
  const statuses = [];
  for (const row of aircraft) {
    const state = normalizeAdsbLolAircraftState(row, nowSeconds);
    if (!state) continue;
    states.push(state);
    // The live contract admits the first valid vector for each ICAO. Its
    // status must come from that same row, never an invalid or later duplicate.
    const id = state[0];
    if (admitted.has(id)) continue;
    admitted.add(id);
    if (typeof row.emergency === 'string')
      statuses.push([id, row.emergency.trim().toLowerCase()]);
  }
  const emergencyByIcao = Object.fromEntries(statuses);
  return {
    time: nowSeconds,
    states,
    ...(Object.keys(emergencyByIcao).length ? { emergencyByIcao } : {}),
  };
}