cinny/src/app/utils/stripImageMetadata.test.ts

/* eslint-disable no-bitwise -- byte-level container parsing */
import { describe, it } from 'node:test';
import assert from 'node:assert/strict';
import fs from 'node:fs';
import path from 'node:path';
import { fileURLToPath } from 'node:url';
import {
  buildOrientationApp1,
  readJpegOrientation,
  stripJpeg,
  stripPng,
  stripWebp,
  stripImageMetadataBytes,
} from './stripImageMetadata';

const here = path.dirname(fileURLToPath(import.meta.url));
const fixture = (name: string) =>
  new Uint8Array(fs.readFileSync(path.join(here, '__fixtures__', name)));
const has = (bytes: Uint8Array, text: string) =>
  Buffer.from(bytes).includes(Buffer.from(text, 'latin1'));

/** Walk JPEG segments up to SOS; returns marker list (sanity: structure intact). */
const jpegMarkers = (b: Uint8Array): string[] => {
  const out: string[] = [];
  let pos = 2;
  while (pos + 4 <= b.length && b[pos] === 0xff) {
    const m = b[pos + 1];
    out.push(m.toString(16));
    if (m === 0xda) break;
    pos += 2 + ((b[pos + 2] << 8) | b[pos + 3]);
  }
  return out;
};

describe('stripJpeg', () => {
  it('removes GPS, model and timestamp, keeps a valid JPEG', () => {
    const src = fixture('gps.jpg');
    assert.ok(has(src, 'LotusPhone 9'));
    const { out, stripped } = stripJpeg(src);
    assert.equal(stripped, true);
    assert.ok(!has(out, 'LotusPhone 9'));
    assert.ok(!has(out, '2026:09:20'));
    assert.ok(out.length < src.length);
    assert.deepEqual([out[0], out[1]], [0xff, 0xd8]);
    assert.deepEqual([out[out.length - 2], out[out.length - 1]], [0xff, 0xd9]);
    assert.ok(jpegMarkers(out).includes('da'));
    // Pixel data untouched: everything from SOS on is byte-identical.
    const sos = (b: Uint8Array) => Buffer.from(b).indexOf(Buffer.from([0xff, 0xda]));
    assert.deepEqual(Buffer.from(out.subarray(sos(out))), Buffer.from(src.subarray(sos(src))));
  });

  it('keeps a non-default orientation in a minimal EXIF block', () => {
    const { out, orientation } = stripJpeg(fixture('gps.jpg'));
    assert.equal(orientation, 6);
    const markers = jpegMarkers(out);
    assert.ok(markers.includes('e1'));
    // Find the APP1 we wrote and read the orientation back.
    let pos = 2;
    let found: number | undefined;
    while (pos + 4 <= out.length && out[pos] === 0xff) {
      const len = (out[pos + 2] << 8) | out[pos + 3];
      if (out[pos + 1] === 0xe1) {
        found = readJpegOrientation(out.subarray(pos + 4, pos + 2 + len));
        assert.equal(len, buildOrientationApp1(6).length - 2);
      }
      if (out[pos + 1] === 0xda) break;
      pos += 2 + len;
    }
    assert.equal(found, 6);
    assert.ok(!has(out, 'LotusPhone 9'));
  });

  it('drops EXIF and the comment segment when orientation is 1 (no EXIF written back)', () => {
    const src = fixture('plain.jpg');
    assert.ok(has(src, 'made with love'));
    const { out, stripped, orientation } = stripJpeg(src);
    assert.equal(stripped, true);
    assert.equal(orientation, undefined);
    assert.ok(!has(out, 'made with love'));
    assert.ok(!has(out, 'Cam'));
    assert.ok(!jpegMarkers(out).includes('e1'));
  });

  it('returns the input untouched when there is nothing to strip', () => {
    const src = fixture('clean.jpg');
    const { out, stripped } = stripJpeg(src);
    assert.equal(stripped, false);
    assert.equal(out, src);
  });
});

describe('stripPng', () => {
  it('drops eXIf and text chunks, keeps IHDR/IDAT/IEND', () => {
    const src = fixture('meta.png');
    assert.ok(has(src, 'xmpmeta'));
    const { out, stripped } = stripPng(src);
    assert.equal(stripped, true);
    assert.ok(!has(out, 'xmpmeta'));
    assert.ok(!has(out, 'LotusPhone'));
    assert.ok(!has(out, 'eXIf'));
    assert.ok(has(out, 'IHDR') && has(out, 'IDAT') && has(out, 'IEND'));
  });
});

describe('stripWebp', () => {
  it('drops the EXIF chunk, clears the VP8X flag and fixes the RIFF size', () => {
    const src = fixture('meta.webp');
    assert.ok(has(src, 'LotusPhone'));
    const { out, stripped } = stripWebp(src);
    assert.equal(stripped, true);
    assert.ok(!has(out, 'LotusPhone'));
    assert.ok(!has(out, 'EXIF'));
    const riff = out[4] | (out[5] << 8) | (out[6] << 16) | (out[7] << 24);
    assert.equal(riff, out.length - 8);
    const vp8x = Buffer.from(out).indexOf(Buffer.from('VP8X'));
    if (vp8x !== -1) assert.equal(out[vp8x + 8] & 0x0c, 0);
  });
});

describe('stripImageMetadataBytes', () => {
  it('passes unknown types through', () => {
    const b = new Uint8Array([1, 2, 3]);
    assert.deepEqual(stripImageMetadataBytes(b, 'image/gif'), { out: b, stripped: false });
  });
});