import { describe, expect, it } from 'vitest';
import * as THREE from 'three';
import { flipTexture } from './flipTexture';

describe('flipTexture', () => {
  it('negates repeat.x and shifts offset.x to keep the region in place', () => {
    const tex = new THREE.Texture();
    tex.repeat.set(0.5, 0.25);
    tex.offset.set(0.3, 0.4);

    const flipped = flipTexture(tex);

    expect(flipped.repeat.x).toBeCloseTo(-0.5, 5);
    expect(flipped.repeat.y).toBeCloseTo(0.25, 5);
    // offset.x = 0.3 + 0.5 = 0.8; the visible region stays put while mirrored.
    expect(flipped.offset.x).toBeCloseTo(0.8, 5);
    expect(flipped.offset.y).toBeCloseTo(0.4, 5);
  });

  it('clones the source so the original is untouched', () => {
    const tex = new THREE.Texture();
    tex.repeat.set(1, 1);
    tex.offset.set(0, 0);

    const flipped = flipTexture(tex);

    expect(flipped).not.toBe(tex);
    expect(tex.repeat.x).toBe(1);
    expect(tex.offset.x).toBe(0);
  });

  it('flips a sprite cell correctly', () => {
    // A sprite cell: repeat 1/6, offset col/6. Flipping should mirror within
    // the cell, not shift it off the sheet.
    const tex = new THREE.Texture();
    tex.repeat.set(1 / 6, 1 / 4);
    tex.offset.set(2 / 6, 3 / 4);

    const flipped = flipTexture(tex);

    expect(flipped.repeat.x).toBeCloseTo(-1 / 6, 5);
    expect(flipped.offset.x).toBeCloseTo(2 / 6 + 1 / 6, 5);
    expect(flipped.offset.y).toBeCloseTo(3 / 4, 5);
  });
});