// Reads X-Plane's own navigation data so the FMS can resolve real waypoint /
// VOR / NDB / airport identifiers to coordinates — the same database the sim
// uses. Runs on the X-Plane PC (where the bridge lives), so the files are local.
//
// Everything degrades gracefully: if X-Plane / the files can't be found, the
// FMS still works with map-clicks and raw "LAT,LON" entry.

import fs from 'node:fs';
import path from 'node:path';
import readline from 'node:readline';

// Common install locations to probe. Override with XPLANE_ROOT.
function candidateRoots() {
  const env = process.env.XPLANE_ROOT;
  const home = process.env.HOME || process.env.USERPROFILE || '';
  return [
    env,
    'C:/X-Plane 12', 'D:/X-Plane 12', 'E:/X-Plane 12',
    'C:/X-Plane 11', 'D:/X-Plane 11',
    path.join(home, 'X-Plane 12'),
    path.join(home, 'Desktop', 'X-Plane 12'),
    '/Applications/X-Plane 12',
  ].filter(Boolean);
}

function findRoot() {
  for (const root of candidateRoots()) {
    try {
      if (fs.existsSync(path.join(root, 'Resources', 'default data'))) return root;
    } catch { /* ignore */ }
  }
  return null;
}

// alias -> { lat, lon, type } ; type: WPT | VOR | NDB | APT
const index = new Map();
// Geographic stores for the moving map (bbox queries) and NEAREST search.
// Airports + navaids stay in flat arrays (small enough to scan); the far more
// numerous fixes go into 1°×1° buckets so a bbox query only scans nearby cells.
const airports = [];           // { id, lat, lon, name, elev }
const navaids = [];            // { id, lat, lon, type:'VOR'|'NDB', freq, name }
const fixCells = new Map();    // "ilat,ilon" -> [{ id, lat, lon, type:'FIX' }]
const rwyByApt = new Map();    // ICAO -> [{ n1, la1, lo1, n2, la2, lo2, w }] (runway ends + width m)
const state = { root: null, loaded: false, count: 0 };

function add(id, lat, lon, type) {
  if (!id || !isFinite(lat) || !isFinite(lon)) return;
  const key = id.toUpperCase();
  if (!index.has(key)) index.set(key, { id: key, lat, lon, type });
}

function pushFix(f) {
  const k = `${Math.floor(f.lat)},${Math.floor(f.lon)}`;
  let a = fixCells.get(k);
  if (!a) { a = []; fixCells.set(k, a); }
  a.push(f);
}

const R_NM = 3440.065; // earth radius in nautical miles
const rad = (d) => (d * Math.PI) / 180;
function distNm(la1, lo1, la2, lo2) {
  const dLat = rad(la2 - la1), dLon = rad(lo2 - lo1);
  const a = Math.sin(dLat / 2) ** 2 + Math.cos(rad(la1)) * Math.cos(rad(la2)) * Math.sin(dLon / 2) ** 2;
  return 2 * R_NM * Math.asin(Math.min(1, Math.sqrt(a)));
}
function bearingDeg(la1, lo1, la2, lo2) {
  const y = Math.sin(rad(lo2 - lo1)) * Math.cos(rad(la2));
  const x = Math.cos(rad(la1)) * Math.sin(rad(la2)) - Math.sin(rad(la1)) * Math.cos(rad(la2)) * Math.cos(rad(lo2 - lo1));
  return (Math.atan2(y, x) * 180 / Math.PI + 360) % 360;
}

async function parseFixes(file) {
  if (!fs.existsSync(file)) return;
  const rl = readline.createInterface({ input: fs.createReadStream(file), crlfDelay: Infinity });
  for await (const line of rl) {
    const t = line.trim();
    if (!t || t === '99' || /^[IA]\b/.test(t) || /Version/.test(t)) continue;
    const p = t.split(/\s+/);
    const lat = parseFloat(p[0]), lon = parseFloat(p[1]), id = p[2];
    add(id, lat, lon, 'WPT');
    if (id && isFinite(lat) && isFinite(lon)) pushFix({ id: id.toUpperCase(), lat, lon, type: 'FIX' });
  }
}

async function parseNav(file) {
  if (!fs.existsSync(file)) return;
  const rl = readline.createInterface({ input: fs.createReadStream(file), crlfDelay: Infinity });
  for await (const line of rl) {
    const t = line.trim();
    if (!t || t === '99' || /^[IA]\b/.test(t) || /Version/.test(t)) continue;
    const p = t.split(/\s+/);
    const code = parseInt(p[0], 10);
    if (code !== 2 && code !== 3) continue; // 2 = NDB, 3 = VOR/DME
    const lat = parseFloat(p[1]), lon = parseFloat(p[2]), id = p[7];
    const type = code === 2 ? 'NDB' : 'VOR';
    add(id, lat, lon, type);
    if (id && isFinite(lat) && isFinite(lon)) {
      // p[4] = frequency (VOR in 10 kHz e.g. 11630 → 116.30; NDB in kHz);
      // name is everything after the airport/region columns.
      navaids.push({ id: id.toUpperCase(), lat, lon, type, freq: parseInt(p[4], 10) || 0, name: p.slice(10).join(' ') });
    }
  }
}

// Airports: derive a reference point from each airport's first runway (row 100)
// in apt.dat. The "1" header row carries the ICAO but no coordinates.
async function parseAirports(file) {
  if (!fs.existsSync(file)) return;
  const rl = readline.createInterface({ input: fs.createReadStream(file), crlfDelay: Infinity });
  let icao = null, name = '', elev = 0, placed = false;
  const place = (lat, lon) => {
    if (!isFinite(lat) || !isFinite(lon)) return;
    add(icao, lat, lon, 'APT');
    airports.push({ id: icao.toUpperCase(), lat, lon, name, elev });
    placed = true;
  };
  for await (const line of rl) {
    const p = line.trim().split(/\s+/);
    const code = parseInt(p[0], 10);
    if (code === 1 || code === 16 || code === 17) {        // land/sea/heliport header
      icao = p[4]; elev = parseInt(p[1], 10) || 0; name = p.slice(5).join(' '); placed = false;
    } else if (icao && code === 100) {                      // land runway (both ends)
      const r = { n1: p[8], la1: parseFloat(p[9]), lo1: parseFloat(p[10]), n2: p[17], la2: parseFloat(p[18]), lo2: parseFloat(p[19]), w: parseFloat(p[1]) };
      if (isFinite(r.la1) && isFinite(r.lo1) && isFinite(r.la2) && isFinite(r.lo2)) {
        const key = icao.toUpperCase();
        let a = rwyByApt.get(key); if (!a) { a = []; rwyByApt.set(key, a); } a.push(r);
        if (!placed) place((r.la1 + r.la2) / 2, (r.lo1 + r.lo2) / 2);
      }
    } else if (!placed && icao && (code === 101 || code === 102)) { // water/heli pad
      place(parseFloat(p[code === 101 ? 4 : 5]), parseFloat(p[code === 101 ? 5 : 6]));
    }
  }
}

export async function loadNavData() {
  const root = findRoot();
  state.root = root;
  if (!root) {
    console.log('navdata: X-Plane root not found (set XPLANE_ROOT) — FMS works with map-clicks / LAT,LON only');
    state.loaded = true;
    return;
  }
  console.log(`navdata: X-Plane at ${root} — parsing nav data ...`);
  const dd = path.join(root, 'Resources', 'default data');
  const cd = path.join(root, 'Custom Data'); // user nav data overrides if present
  const pick = (name) => (fs.existsSync(path.join(cd, name)) ? path.join(cd, name) : path.join(dd, name));
  try {
    await parseFixes(pick('earth_fix.dat'));
    await parseNav(pick('earth_nav.dat'));
    // apt.dat is large; parse the global airports file in the background.
    parseAirports(path.join(root, 'Global Scenery', 'Global Airports', 'Earth nav data', 'apt.dat'))
      .then(() => { state.count = index.size; console.log(`navdata: airports done (${index.size} total entries)`); })
      .catch((e) => console.log('navdata: airport parse skipped:', e.message));
  } catch (e) {
    console.log('navdata: parse error:', e.message);
  }
  state.count = index.size;
  state.loaded = true;
  console.log(`navdata: ${index.size} fixes/navaids ready`);
}

export function lookup(id) {
  return index.get(String(id).toUpperCase()) || null;
}

export function search(q, limit = 20) {
  const needle = String(q || '').toUpperCase().trim();
  if (!needle) return [];
  const exact = [], prefix = [];
  for (const v of index.values()) {
    if (v.id === needle) exact.push(v);
    else if (v.id.startsWith(needle)) prefix.push(v);
    if (exact.length + prefix.length > 400) break;
  }
  return [...exact, ...prefix].slice(0, limit);
}

// NEAREST: closest airports (default) or navaids to a point, with range/bearing.
export function nearest(lat, lon, { count = 15, type = 'apt' } = {}) {
  if (!isFinite(lat) || !isFinite(lon)) return [];
  const src = (type === 'vor' || type === 'ndb' || type === 'nav') ? navaids : airports;
  return src
    .filter((f) => (type === 'vor' || type === 'ndb') ? f.type.toLowerCase() === type : true)
    .map((f) => ({ ...f, dist: distNm(lat, lon, f.lat, f.lon), brg: Math.round(bearingDeg(lat, lon, f.lat, f.lon)) }))
    .sort((a, b) => a.dist - b.dist)
    .slice(0, count)
    .map((f) => ({ ...f, dist: +f.dist.toFixed(1) }));
}

// BBOX: every feature inside a lat/lon window, for the moving map to draw.
// types ⊆ { apt, vor, ndb, fix }. Output is capped so a wide view stays light.
export function bbox(s, w, n, e, types = ['apt', 'vor', 'ndb'], limit = 800) {
  const out = [];
  const inB = (f) => f.lat >= s && f.lat <= n && f.lon >= w && f.lon <= e;
  if (types.includes('apt')) for (const f of airports) { if (inB(f)) { out.push({ ...f, type: 'APT' }); if (out.length >= limit) return out; } }
  for (const f of navaids) { if (types.includes(f.type.toLowerCase()) && inB(f)) { out.push(f); if (out.length >= limit) return out; } }
  if (types.includes('fix')) {
    for (let la = Math.floor(s); la <= Math.floor(n); la++)
      for (let lo = Math.floor(w); lo <= Math.floor(e); lo++) {
        const a = fixCells.get(`${la},${lo}`);
        if (!a) continue;
        for (const f of a) { if (inB(f)) { out.push(f); if (out.length >= limit) return out; } }
      }
  }
  return out;
}

// Runways of every airport within radiusNm — for the PFD's synthetic-vision view.
export function runwaysNear(lat, lon, radiusNm = 12) {
  if (!isFinite(lat) || !isFinite(lon)) return [];
  const out = [];
  for (const a of airports) {
    if (distNm(lat, lon, a.lat, a.lon) > radiusNm) continue;
    const rs = rwyByApt.get(a.id);
    if (rs) for (const r of rs) out.push({ apt: a.id, ...r });
  }
  return out;
}

export function navStatus() {
  return { root: state.root, loaded: state.loaded, entries: index.size, airports: airports.length, navaids: navaids.length };
}

export function xplaneRoot() {
  return state.root;
}