import { describe, expect, it } from 'vitest';
import { haversineKm, initialBearingDeg } from './geo';

describe('initialBearingDeg', () => {
  it('is due north (0) for a point directly above', () => {
    expect(initialBearingDeg(0, 0, 10, 0)).toBe(0);
  });

  it('is due east (90) along the equator', () => {
    expect(initialBearingDeg(0, -10, 0, 10)).toBeCloseTo(90, 9);
  });

  it('is due south (180) for a point directly below', () => {
    expect(initialBearingDeg(10, 0, 0, 0)).toBeCloseTo(180, 9);
  });

  it('is due west (270) along the equator — normalized into [0, 360)', () => {
    expect(initialBearingDeg(0, 10, 0, -10)).toBeCloseTo(270, 9);
  });

  it('always normalizes to [0, 360) for arbitrary pairs', () => {
    const pairs: Array<[number, number, number, number]> = [
      [50.03, 8.57, 40.47, -3.56], // FRA → MAD (southwest-ish)
      [40.47, -3.56, 50.03, 8.57], // reverse: northeast-ish
      [65.66, -18.07, 50.03, 8.57], // far north → south-east wrap case
    ];
    for (const [a1, a2, b1, b2] of pairs) {
      const brg = initialBearingDeg(a1, a2, b1, b2);
      expect(brg).toBeGreaterThanOrEqual(0);
      expect(brg).toBeLessThan(360);
    }
  });

  it('FRA → MAD points roughly south-southwest (between 180 and 270)', () => {
    const brg = initialBearingDeg(50.03, 8.57, 40.47, -3.56);
    expect(brg).toBeGreaterThan(180);
    expect(brg).toBeLessThan(270);
  });
});

describe('haversineKm', () => {
  it('returns 0 for identical points', () => {
    expect(haversineKm(50.03, 8.57, 50.03, 8.57)).toBeCloseTo(0, 10);
  });

  it('computes the London → Paris great-circle distance (~343 km)', () => {
    const km = haversineKm(51.47, -0.454, 49.0097, 2.5479); // LHR → CDG
    expect(km).toBeGreaterThan(330);
    expect(km).toBeLessThan(360);
  });

  it('is symmetric', () => {
    const a = haversineKm(50.03, 8.57, 40.47, -3.56); // FRA → MAD
    const b = haversineKm(40.47, -3.56, 50.03, 8.57);
    expect(a).toBeCloseTo(b, 10);
  });
});