import { describe, expect, it } from 'bun:test';
import { computeTrackDistance, haversine, type GeoPoint } from './geo';

// One degree of latitude is ~111_195 m, so these small deltas give
// predictable segment lengths: 0.0001° ≈ 11.12 m, 0.00001° ≈ 1.11 m.
const DEG = 111_195;

function pt(
  lat: number,
  lon: number,
  seconds: number,
  accuracy?: number | null
): GeoPoint {
  return { lat, lon, accuracy, recordedAt: new Date(seconds * 1000) };
}

describe('haversine', () => {
  it('returns 0 for identical points', () => {
    expect(haversine(pt(0, 0, 0), pt(0, 0, 0))).toBe(0);
  });

  it('measures one degree of latitude along a meridian', () => {
    const d = haversine({ lat: 0, lon: 0 }, { lat: 1, lon: 0 });
    expect(Math.abs(d - DEG)).toBeLessThan(1);
  });

  it('measures one degree of longitude along the equator', () => {
    const d = haversine({ lat: 0, lon: 0 }, { lat: 0, lon: 1 });
    expect(Math.abs(d - DEG)).toBeLessThan(1);
  });

  it('is symmetric', () => {
    const a = { lat: 52.5, lon: 13.4 };
    const b = { lat: 52.6, lon: 13.5 };
    expect(haversine(a, b)).toBeCloseTo(haversine(b, a), 6);
  });
});

describe('computeTrackDistance', () => {
  it('returns 0 for empty input', () => {
    expect(computeTrackDistance([])).toBe(0);
  });

  it('returns 0 for a single point', () => {
    expect(computeTrackDistance([pt(0, 0, 0)])).toBe(0);
  });

  it('sums a normal multi-point walk', () => {
    const points = [
      pt(0, 0, 0),
      pt(0.0001, 0, 10),
      pt(0.0002, 0, 20),
      pt(0.0003, 0, 30)
    ];
    // three ~11.12 m segments
    const d = computeTrackDistance(points);
    expect(d).toBeGreaterThan(32);
    expect(d).toBeLessThan(35);
  });

  it('excludes fixes with accuracy worse than 50 m', () => {
    const points = [
      pt(0, 0, 0, 5),
      // far off path, bad accuracy → dropped
      pt(0, 0.001, 10, 100),
      pt(0.0001, 0, 20, 5)
    ];
    const d = computeTrackDistance(points);
    // only the ~11 m A→C segment counts, not the ~222 m detour via B
    expect(d).toBeGreaterThan(10);
    expect(d).toBeLessThan(50);
  });

  it('keeps accuracy of exactly 50 m', () => {
    const points = [pt(0, 0, 0, 50), pt(0.0001, 0, 10, 50)];
    const d = computeTrackDistance(points);
    expect(d).toBeGreaterThan(10);
    expect(d).toBeLessThan(13);
  });

  it('rejects teleport candidates and preserves the anchor', () => {
    const points = [
      pt(0, 0, 0),
      // ~1112 m in 1 s → far above 7 m/s → rejected, anchor stays at A
      pt(0.01, 0, 1),
      // ~11 m from A over 2 s → 5.6 m/s → accepted
      pt(0.0001, 0, 2)
    ];
    const d = computeTrackDistance(points);
    expect(d).toBeGreaterThan(10);
    expect(d).toBeLessThan(13);
  });

  it('ignores stationary jitter below 5 m', () => {
    const jitter = [
      pt(0, 0, 0),
      pt(0.00001, 0, 10), // ~1.1 m
      pt(0.00002, 0, 20) // ~2.2 m from anchor
    ];
    expect(computeTrackDistance(jitter)).toBe(0);

    // a real move after the jitter is still measured from the original anchor
    const withMove = [...jitter, pt(0.0002, 0, 30)];
    const d = computeTrackDistance(withMove);
    expect(d).toBeGreaterThan(21);
    expect(d).toBeLessThan(24);
  });

  it('dedupes and sorts out-of-order points', () => {
    const a = pt(0, 0, 0);
    const b = pt(0.0001, 0, 10);
    const c = pt(0.0002, 0, 20);
    const shuffled = [c, a, b, a, c, b];
    const d = computeTrackDistance(shuffled);
    // two ~11.12 m segments after dedupe + sort
    expect(d).toBeGreaterThan(21);
    expect(d).toBeLessThan(24);
  });

  it('accepts string recordedAt values', () => {
    const points: GeoPoint[] = [
      { lat: 0, lon: 0, recordedAt: new Date(0).toISOString() },
      { lat: 0.0001, lon: 0, recordedAt: new Date(10_000).toISOString() }
    ];
    const d = computeTrackDistance(points);
    expect(d).toBeGreaterThan(10);
    expect(d).toBeLessThan(13);
  });

  it('returns an integer number of meters', () => {
    const points = [pt(0, 0, 0), pt(0.0001, 0, 10), pt(0.0002, 0, 20)];
    expect(Number.isInteger(computeTrackDistance(points))).toBeTrue();
  });
});