"""Hashing: byte identity vs normalized-pixel identity."""

import numpy as np
from PIL import Image

from photo_pipeline.services import hashing


def _write(path, seed, size=(48, 32)):
    rng = np.random.default_rng(seed)
    arr = rng.integers(0, 256, (size[1], size[0], 3), dtype=np.uint8)
    Image.fromarray(arr).save(path, quality=95)


def test_sha256_is_deterministic_and_distinct(tmp_path):
    a, b = tmp_path / "a.jpg", tmp_path / "b.jpg"
    _write(a, 1)
    _write(b, 2)
    assert hashing.sha256_file(a) == hashing.sha256_file(a)
    assert hashing.sha256_file(a) != hashing.sha256_file(b)


def test_trailing_bytes_change_sha_but_not_pixels(tmp_path):
    """Appending bytes after a JPEG (an EXIF-only-style edit) changes the file
    hash while decoded pixels — and the pixel hash — stay the same."""
    img = tmp_path / "a.jpg"
    _write(img, 1)
    sha_before = hashing.sha256_file(img)
    pix_before = hashing.pixel_sha256(img)

    with open(img, "ab") as handle:
        handle.write(b"\xff\xfe trailing comment bytes")

    assert hashing.sha256_file(img) != sha_before
    assert hashing.pixel_sha256(img) == pix_before


def test_different_images_have_different_pixel_hashes(tmp_path):
    a, b = tmp_path / "a.jpg", tmp_path / "b.jpg"
    _write(a, 1)
    _write(b, 2)
    assert hashing.pixel_sha256(a) != hashing.pixel_sha256(b)


def test_safe_pixel_sha256_returns_none_for_garbage(tmp_path):
    bad = tmp_path / "bad.jpg"
    bad.write_bytes(b"not an image")
    assert hashing.safe_pixel_sha256(bad) is None