import io
import logging
import sys
from pathlib import Path
from typing import Optional

from PIL import Image

logger = logging.getLogger(__name__)
DEBUG_PREFIX = "[image-compression]"


def _load_imgcompress():
    try:
        from imgcompress import (  # type: ignore
            CompressionMode,
            CompressionSettings,
            ImageCompressor,
        )
        print(f"{DEBUG_PREFIX} imported imgcompress from installed environment")
        return ImageCompressor, CompressionSettings, CompressionMode
    except ImportError as exc:
        print(f"{DEBUG_PREFIX} installed import failed: {exc}")
        repo_root = Path(__file__).resolve().parents[2]
        src_path = repo_root / "image-compressor" / "src"
        if src_path.exists():
            sys.path.insert(0, str(src_path))
            print(f"{DEBUG_PREFIX} trying local source path: {src_path}")
            from imgcompress import (  # type: ignore
                CompressionMode,
                CompressionSettings,
                ImageCompressor,
            )
            print(f"{DEBUG_PREFIX} imported imgcompress from local source")
            return ImageCompressor, CompressionSettings, CompressionMode
        raise


def is_compressible_image(filename: str, content_type: Optional[str] = None) -> bool:
    name = (filename or "").lower()
    ctype = (content_type or "").lower()

    if name.endswith(".gif") or name.endswith(".svg"):
        return False
    if ctype in {"image/gif", "image/svg+xml"}:
        return False

    compressible_exts = (".jpg", ".jpeg", ".png", ".webp", ".bmp", ".tif", ".tiff", ".avif")
    return name.endswith(compressible_exts) or ctype.startswith("image/")


def compress_image_bytes(data: bytes, filename: str) -> bytes:
    if not data:
        return data

    print(f"{DEBUG_PREFIX} compress_image_bytes start file={filename} size={len(data)}")
    ImageCompressor, CompressionSettings, CompressionMode = _load_imgcompress()
    settings = CompressionSettings(
        mode=CompressionMode.VISUALLY_LOSSLESS,
        allow_format_switch=False,
        strip_metadata=False,
        png_use_zopfli=False,
    )
    compressor = ImageCompressor(settings=settings)
    result = compressor.compress_bytes(data, Path(filename))
    final_bytes = result.payload or data
    print(
        f"{DEBUG_PREFIX} compress_image_bytes done file={filename} "
        f"original={len(data)} final={len(final_bytes)} skipped={getattr(result, 'skipped', False)} "
        f"note={getattr(result, 'note', '')}"
    )
    return final_bytes


def maybe_compress_uploaded_file(file_obj):
    filename = getattr(file_obj, "name", "upload")
    content_type = getattr(file_obj, "content_type", None)
    print(
        f"{DEBUG_PREFIX} received upload file={filename} "
        f"content_type={content_type} size={getattr(file_obj, 'size', 'unknown')}"
    )

    if not is_compressible_image(filename, content_type):
        print(f"{DEBUG_PREFIX} skip non-compressible file={filename}")
        if hasattr(file_obj, "seek"):
            file_obj.seek(0)
        return None

    try:
        raw_bytes = file_obj.read()
        if hasattr(file_obj, "seek"):
            file_obj.seek(0)

        if not raw_bytes:
            print(f"{DEBUG_PREFIX} skip empty payload file={filename}")
            return None

        with Image.open(io.BytesIO(raw_bytes)) as img:
            img.verify()

        compressed = compress_image_bytes(raw_bytes, filename)
        if compressed and len(compressed) <= len(raw_bytes):
            print(
                f"{DEBUG_PREFIX} accepted file={filename} "
                f"original={len(raw_bytes)} compressed={len(compressed)}"
            )
            return compressed

        print(
            f"{DEBUG_PREFIX} keeping original file={filename} "
            f"original={len(raw_bytes)} candidate={len(compressed) if compressed else 'none'}"
        )
        return raw_bytes
    except Exception as exc:
        print(f"{DEBUG_PREFIX} failed file={filename} error={exc}")
        logger.warning("Image compression skipped for %s: %s", filename, exc)
        if hasattr(file_obj, "seek"):
            file_obj.seek(0)
        return None