import { describe, expect, it } from 'vitest';

import { clampCrop, initialCrop, outputSize } from './crop';

/**
 * The crop arithmetic (issue #306). Pure functions on purpose: the canvas
 * work is a thin shell around these, and getting the bounds wrong is what
 * would let a number input produce a rectangle outside the image.
 */
describe('initialCrop', () => {
  it('takes the whole image when the aspect is free', () => {
    expect(initialCrop({ width: 900, height: 300 }, false)).toEqual({
      x: 0,
      y: 0,
      width: 900,
      height: 300,
    });
  });

  it('centres the largest square that fits', () => {
    expect(initialCrop({ width: 900, height: 300 }, true)).toEqual({
      x: 300,
      y: 0,
      width: 300,
      height: 300,
    });
  });
});

describe('outputSize', () => {
  it('scales the long edge down to the bound and keeps the ratio', () => {
    expect(outputSize({ x: 0, y: 0, width: 900, height: 300 }, 512)).toEqual({
      width: 512,
      height: 171,
    });
  });

  it('never scales UP — enlarging would only invent pixels', () => {
    expect(outputSize({ x: 0, y: 0, width: 120, height: 40 }, 512)).toEqual({
      width: 120,
      height: 40,
    });
  });
});

describe('clampCrop', () => {
  const source = { width: 200, height: 100 };

  it('keeps the rectangle inside the image', () => {
    expect(clampCrop({ x: 190, y: 90, width: 50, height: 50 }, source)).toEqual({
      x: 150,
      y: 50,
      width: 50,
      height: 50,
    });
  });

  it('never lets a size fall below one pixel or exceed the source', () => {
    expect(clampCrop({ x: 0, y: 0, width: 0, height: 999 }, source)).toEqual({
      x: 0,
      y: 0,
      width: 1,
      height: 100,
    });
  });

  it('accepts a negative offset by pulling it back to the edge', () => {
    expect(clampCrop({ x: -30, y: -5, width: 20, height: 20 }, source)).toMatchObject({
      x: 0,
      y: 0,
    });
  });
});