redefined-designs/backend/tests/unit/imageRotation.test.ts

import { promises as fs } from 'fs';
import os from 'os';
import path from 'path';
import sharp from 'sharp';
import { rotateInPlace } from '../../src/imageProcessing';

let dir = '';

beforeEach(async () => {
  dir = await fs.mkdtemp(path.join(os.tmpdir(), 'rotate-'));
});

afterEach(async () => {
  await fs.rm(dir, { recursive: true, force: true });
});

/**
 * A square image, left half red and right half blue.
 *
 * Square on purpose. Dimensions swap whichever way a quarter turn goes, so a
 * rectangle proves that something rotated but says nothing about which way —
 * only the pixels can say that, and this is the smallest picture that makes
 * the direction visible.
 */
async function halvesPng(): Promise<Buffer> {
  const red = await sharp({
    create: { width: 100, height: 200, channels: 3, background: { r: 255, g: 0, b: 0 } }
  })
    .png()
    .toBuffer();
  const blue = await sharp({
    create: { width: 100, height: 200, channels: 3, background: { r: 0, g: 0, b: 255 } }
  })
    .png()
    .toBuffer();
  return sharp({
    create: { width: 200, height: 200, channels: 3, background: { r: 0, g: 0, b: 0 } }
  })
    .composite([
      { input: red, left: 0, top: 0 },
      { input: blue, left: 100, top: 0 }
    ])
    .png()
    .toBuffer();
}

/** The colour a little way in from the top-left corner, clear of any edge. */
async function topLeft(file: string): Promise<string> {
  const { data, info } = await sharp(file).raw().toBuffer({ resolveWithObject: true });
  const at = (10 * info.width + 10) * info.channels;
  return [data[at], data[at + 1], data[at + 2]].join(',');
}

/**
 * A two-frame animated WebP, built rather than committed as a binary fixture so
 * what it contains is readable here. `pageHeight` is what makes libvips treat
 * one tall buffer as a strip of frames.
 */
async function animatedWebp(): Promise<Buffer> {
  const width = 40;
  const height = 40;
  const raw = Buffer.alloc(width * height * 2 * 4);
  for (let i = 0; i < width * height * 4; i += 4) {
    raw[i] = 255;
    raw[i + 3] = 255;
  }
  for (let i = width * height * 4; i < raw.length; i += 4) {
    raw[i + 2] = 255;
    raw[i + 3] = 255;
  }
  return sharp(raw, { raw: { width, height: height * 2, channels: 4, pageHeight: height } })
    .webp()
    .toBuffer();
}

describe('rotateInPlace', () => {
  it('turns a landscape photo into a portrait one', async () => {
    const file = path.join(dir, 'wide.jpg');
    await fs.writeFile(
      file,
      await sharp({
        create: { width: 400, height: 200, channels: 3, background: { r: 20, g: 60, b: 120 } }
      })
        .jpeg()
        .toBuffer()
    );

    await rotateInPlace(file, 'image/jpeg', 'right');

    const after = await sharp(file).metadata();
    expect(after.width).toBe(200);
    expect(after.height).toBe(400);
  });

  // The direction mapping, which is the one thing here that can be exactly
  // backwards while every dimension assertion still passes. Turning clockwise
  // moves the left edge to the top, so the red half ends up along the top.
  it('turns right clockwise', async () => {
    const file = path.join(dir, 'halves.png');
    await fs.writeFile(file, await halvesPng());

    await rotateInPlace(file, 'image/png', 'right');

    expect(await topLeft(file)).toBe('255,0,0');
  });

  it('turns left anticlockwise', async () => {
    const file = path.join(dir, 'halves.png');
    await fs.writeFile(file, await halvesPng());

    await rotateInPlace(file, 'image/png', 'left');

    expect(await topLeft(file)).toBe('0,0,255');
  });

  // Format is preserved for the reason #226 preserved it: image_path carries
  // the extension, so changing the format here would leave the row pointing at
  // a file that no longer exists.
  it('keeps the file in its own format', async () => {
    const file = path.join(dir, 'halves.png');
    await fs.writeFile(file, await halvesPng());

    await rotateInPlace(file, 'image/png', 'left');

    expect((await sharp(file).metadata()).format).toBe('png');
  });

  // The whole reason for the temp-file-and-rename: a failure must leave the
  // photo exactly as it was, and must not leave a stray file behind either.
  it('leaves the file untouched when sharp cannot read it', async () => {
    const file = path.join(dir, 'broken.jpg');
    await fs.writeFile(file, 'not an image');

    await expect(rotateInPlace(file, 'image/jpeg', 'right')).rejects.toThrow();

    expect(await fs.readFile(file, 'utf8')).toBe('not an image');
    expect(await fs.readdir(dir)).toEqual(['broken.jpg']);
  });

  // The trap this guards. Reading an animated WebP without `animated: true`
  // succeeds and yields the first frame alone, so a rotation that omitted the
  // flag would write back a still and destroy the uploader's animation while
  // reporting success. With the flag, sharp refuses — which is the correct
  // answer, because a quarter turn of a multi-page image is not something it
  // can do.
  it('refuses an animated WebP rather than flattening it', async () => {
    const file = path.join(dir, 'moving.webp');
    await fs.writeFile(file, await animatedWebp());

    await expect(rotateInPlace(file, 'image/webp', 'right')).rejects.toThrow(/multi-page/i);

    expect((await sharp(file, { animated: true }).metadata()).pages).toBe(2);
  });
});