// Shared flight plan: one plan, synced to every connected tablet. Can resolve
// idents via navdata, and export an X-Plane .fms file the sim can load.

import fs from 'node:fs';
import path from 'node:path';
import { lookup, xplaneRoot } from './navdata.js';

// waypoint: { id, lat, lon, type, alt? }
// activeLeg = index of the waypoint the active (magenta) leg flies TO. The leg
// runs from waypoints[activeLeg-1] to waypoints[activeLeg]. Defaults to 1.
let plan = { name: 'ACTIVE', waypoints: [], activeLeg: 1 };

const clampLeg = (i) => Math.max(1, Math.min(plan.waypoints.length - 1, i | 0));

export const getPlan = () => plan;

export function setPlan(next) {
  const wps = Array.isArray(next?.waypoints)
    ? next.waypoints
        .filter((w) => isFinite(w.lat) && isFinite(w.lon))
        .map((w) => ({ id: String(w.id || 'WPT'), lat: +w.lat, lon: +w.lon, type: w.type || 'WPT', alt: w.alt ?? null }))
    : [];
  const wantLeg = Number.isFinite(next?.activeLeg) ? next.activeLeg : 1;
  plan = { name: next?.name || 'ACTIVE', waypoints: wps, activeLeg: Math.max(1, Math.min(wps.length - 1, wantLeg)) || 1 };
  return plan;
}

export function setActiveLeg(index) {
  if (plan.waypoints.length >= 2) plan.activeLeg = clampLeg(index);
  return plan;
}

// Add a waypoint by ident (resolved against navdata) or raw "lat,lon".
export function addWaypoint(input) {
  const raw = String(input || '').trim();
  const m = raw.match(/^(-?\d+(?:\.\d+)?)[ ,]+(-?\d+(?:\.\d+)?)$/);
  if (m) {
    plan.waypoints.push({ id: 'USR', lat: +m[1], lon: +m[2], type: 'USR', alt: null });
    return { ok: true, plan };
  }
  const hit = lookup(raw);
  if (!hit) return { ok: false, error: `unknown ident: ${raw}` };
  plan.waypoints.push({ ...hit, alt: null });
  return { ok: true, plan };
}

export function removeWaypoint(index) {
  if (index >= 0 && index < plan.waypoints.length) plan.waypoints.splice(index, 1);
  if (plan.waypoints.length >= 2) plan.activeLeg = clampLeg(plan.activeLeg);
  return plan;
}

// ---- great-circle helpers (nm + degrees) ----
const R_NM = 3440.065;
const rad = (d) => (d * Math.PI) / 180;
const deg = (r) => (r * 180) / Math.PI;

export function legDistanceNm(a, b) {
  const dLat = rad(b.lat - a.lat), dLon = rad(b.lon - a.lon);
  const s = Math.sin(dLat / 2) ** 2 + Math.cos(rad(a.lat)) * Math.cos(rad(b.lat)) * Math.sin(dLon / 2) ** 2;
  return 2 * R_NM * Math.asin(Math.min(1, Math.sqrt(s)));
}

export function legBearing(a, b) {
  const y = Math.sin(rad(b.lon - a.lon)) * Math.cos(rad(b.lat));
  const x = Math.cos(rad(a.lat)) * Math.sin(rad(b.lat)) -
            Math.sin(rad(a.lat)) * Math.cos(rad(b.lat)) * Math.cos(rad(b.lon - a.lon));
  return (deg(Math.atan2(y, x)) + 360) % 360;
}

// ---- X-Plane .fms (v1100) export ----
function fmsType(t) {
  return { APT: 1, NDB: 2, VOR: 3, WPT: 11, USR: 28 }[t] || 11;
}

export function exportFms(name = 'WEBFPL') {
  const wp = plan.waypoints;
  if (wp.length < 2) return { ok: false, error: 'need at least 2 waypoints' };

  const lines = ['I', '1100 Version', 'CYCLE 2501'];
  lines.push(`ADEP ${wp[0].id}`);
  lines.push(`ADES ${wp[wp.length - 1].id}`);
  lines.push(`NUMENR ${wp.length}`);
  for (const w of wp) {
    const alt = w.alt ?? 0;
    lines.push(`${fmsType(w.type)} ${w.id} ${alt.toFixed(6)} ${w.lat.toFixed(6)} ${w.lon.toFixed(6)}`);
  }
  const content = lines.join('\n') + '\n';

  const root = xplaneRoot();
  const dir = root ? path.join(root, 'Output', 'FMS plans') : path.join(process.cwd(), 'fms-out');
  try {
    fs.mkdirSync(dir, { recursive: true });
    const file = path.join(dir, `${name}.fms`);
    fs.writeFileSync(file, content);
    return { ok: true, file, intoXplane: !!root };
  } catch (e) {
    return { ok: false, error: e.message };
  }
}