import computeDestinationPoint from 'geolib/es/computeDestinationPoint';
import Parser from '../parser';
import { computeSpeed } from '../utils/computeSpeed';
import { computeTurnRate } from '../utils/computeTurnRate';

// NOTE: Distance is interpreted as distance and not time
export const TerminatorsHA = (leg: HATerminalEntry, previousFix: NavFix): [NavFix?, LineSegment[]?] => {
  const refFix = {
    latitude: leg.WptLat,
    longitude: leg.WptLon,
  };
  const speed = computeSpeed(leg, previousFix);
  const turnRate = computeTurnRate(speed, Parser.AC_BANK);
  const inboundCrs = leg.Course.toTrue(refFix);
  const outboundCrs = inboundCrs.reciprocalCourse();

  const line: LineSegment[] = [[previousFix.longitude, previousFix.latitude]];

  // Generate top arc
  let currentCrs = inboundCrs;
  while (!currentCrs.equal(outboundCrs)) {
    let time = 0;
    if (leg.TurnDir === 'R') {
      const delta = (outboundCrs - currentCrs).normaliseDegrees();
      const increment = delta < 0.1 ? delta : 0.1;
      currentCrs = (currentCrs + increment).normaliseDegrees();
      time = increment / turnRate;
    } else {
      const delta = (currentCrs - outboundCrs).normaliseDegrees();
      const increment = delta < 0.1 ? delta : 0.1;
      currentCrs = (currentCrs - increment).normaliseDegrees();
      time = increment / turnRate;
    }

    const arcFix = computeDestinationPoint(
      {
        latitude: line.at(-1)![1],
        longitude: line.at(-1)![0],
      },
      ((speed / 3600) * time).toMetre(),
      currentCrs
    );

    line.push([arcFix.longitude, arcFix.latitude]);
  }

  const outboundStart = computeDestinationPoint(
    {
      latitude: line.at(-1)![1],
      longitude: line.at(-1)![0],
    },
    leg.Distance.toMetre(),
    outboundCrs
  );
  line.push([outboundStart.longitude, outboundStart.latitude]);

  // Generate bottom arc
  currentCrs = outboundCrs;
  while (!currentCrs.equal(inboundCrs)) {
    let time = 0;
    if (leg.TurnDir === 'R') {
      const delta = (inboundCrs - currentCrs).normaliseDegrees();
      const increment = delta < 0.1 ? delta : 0.1;
      currentCrs = (currentCrs + increment).normaliseDegrees();
      time = increment / turnRate;
    } else {
      const delta = (currentCrs - inboundCrs).normaliseDegrees();
      const increment = delta < 0.1 ? delta : 0.1;
      currentCrs = (currentCrs - increment).normaliseDegrees();
      time = increment / turnRate;
    }

    const arcFix = computeDestinationPoint(
      {
        latitude: line.at(-1)![1],
        longitude: line.at(-1)![0],
      },
      ((speed / 3600) * time).toMetre(),
      currentCrs
    );

    line.push([arcFix.longitude, arcFix.latitude]);
  }

  line.push([refFix.longitude, refFix.latitude]);

  return [refFix, line];
};