import struct
import zlib
from pathlib import Path

import pytest

import imagepipeline.modules  # noqa: F401


def make_png(
    path: Path,
    width: int = 2,
    height: int = 2,
    rgb: tuple[int, int, int] = (200, 100, 50),
) -> None:
    """Write a minimal valid PNG without external dependencies."""
    r, g, b = rgb

    def chunk(tag: bytes, data: bytes) -> bytes:
        crc = zlib.crc32(tag + data) & 0xFFFFFFFF
        return struct.pack(">I", len(data)) + tag + data + struct.pack(">I", crc)

    raw = b"".join(
        b"\x00" + bytes([r, g, b] * width)
        for _ in range(height)
    )
    compressed = zlib.compress(raw, 9)
    ihdr = struct.pack(">IIBBBBB", width, height, 8, 2, 0, 0, 0)
    png = (
        b"\x89PNG\r\n\x1a\n"
        + chunk(b"IHDR", ihdr)
        + chunk(b"IDAT", compressed)
        + chunk(b"IEND", b"")
    )
    path.write_bytes(png)


@pytest.fixture(autouse=True)
def _ensure_builtin_modules() -> None:
    import imagepipeline.modules  # noqa: F401


@pytest.fixture
def input_dir(tmp_path: Path) -> Path:
    directory = tmp_path / "input"
    directory.mkdir()
    make_png(directory / "photo_a.png")
    make_png(directory / "photo_b.png", rgb=(10, 20, 30))
    return directory


@pytest.fixture
def output_base(tmp_path: Path) -> Path:
    base = tmp_path / "output"
    base.mkdir()
    return base