import { describe, it, expect } from 'vitest';
import { estimateHomography, applyHomography, invertMat3 } from './homography';
import type { Vec2, Mat3 } from '../types';

const close = (a: Vec2, b: Vec2, eps = 1e-6) =>
  Math.abs(a[0] - b[0]) < eps && Math.abs(a[1] - b[1]) < eps;

describe('homography', () => {
  it('recovers the identity from coincident point sets', () => {
    const pts: Vec2[] = [[0, 0], [1, 0], [1, 1], [0, 1]];
    const H = estimateHomography(pts, pts);
    expect(close(applyHomography(H, [0.3, 0.7]), [0.3, 0.7])).toBe(true);
  });

  it('recovers a known perspective transform', () => {
    const H: Mat3 = [1.1, 0.2, 5, -0.1, 0.9, 3, 0.001, 0.002, 1];
    const src: Vec2[] = [[0, 0], [100, 0], [100, 100], [0, 100], [40, 60]];
    const dst = src.map((p) => applyHomography(H, p));
    const est = estimateHomography(src, dst);
    for (const p of [[10, 20], [70, 30], [55, 90]] as Vec2[]) {
      expect(close(applyHomography(est, p), applyHomography(H, p), 1e-4)).toBe(true);
    }
  });

  it('invertMat3 round-trips a point', () => {
    const H: Mat3 = [1.1, 0.2, 5, -0.1, 0.9, 3, 0.001, 0.002, 1];
    const inv = invertMat3(H);
    const p: Vec2 = [37, 91];
    expect(close(applyHomography(inv, applyHomography(H, p)), p, 1e-6)).toBe(true);
  });
});