"""
image_utils.py
==============

Shared image processing utilities.
"""

from __future__ import annotations

import io
import logging
from pathlib import Path

try:
    from PIL import Image as _PILImage
    _HAS_PIL = True
except ImportError:
    _HAS_PIL = False

logger = logging.getLogger(__name__)

DISCORD_MAX_BYTES = 8 * 1024 * 1024  # 8 MiB Discord free-tier upload limit


def compress_to_discord_limit(data: bytes, filename: str) -> tuple[bytes, str]:
    """
    Compress image bytes to fit within Discord's 8 MiB upload limit.

    Tries quality reduction first, then progressive downsizing.
    Converts to JPEG if the source format (e.g. PNG) cannot be quality-compressed.
    Returns (data, filename) — filename may change if format conversion is needed.
    No-op if data is already within the limit.
    """
    if len(data) <= DISCORD_MAX_BYTES:
        logger.info(f"Image size is less than {DISCORD_MAX_BYTES}")
        return data, filename

    if not _HAS_PIL:
        logger.warning("Pillow not installed — cannot compress %s (%d bytes), uploading as-is", filename, len(data))
        return data, filename

    suffix = Path(filename).suffix.lower()
    stem   = Path(filename).stem

    img = _PILImage.open(io.BytesIO(data))

    # PNG/GIF/BMP don't support lossy quality — convert to JPEG
    logger.info("Checking file extension for convert to jpeg")
    if suffix in (".jpg", ".jpeg"):
        fmt, out_name = "JPEG", filename
    elif suffix == ".webp":
        fmt, out_name = "WEBP", filename
    else:
        fmt, out_name = "JPEG", stem + ".jpg"
        if img.mode in ("RGBA", "P", "LA"):
            img = img.convert("RGB")
    logger.info("File extension checked")

    # Round 1: quality reduction only
    logger.info("# Round 1: quality reduction only")
    for quality in (85, 70, 55, 40, 25, 15):
        logger.info(f"# Round 1: Trying quality: {quality}")
        buf = io.BytesIO()
        img.save(buf, format=fmt, quality=quality)
        if buf.tell() <= DISCORD_MAX_BYTES:
            logger.info("Compressed %s at quality=%d: %d → %d bytes", filename, quality, len(data), buf.tell())
            return buf.getvalue(), out_name

    # Round 2: resize + low quality
    logger.info("# Round 2: resize + low quality")
    for scale in (0.75, 0.5, 0.35, 0.25):
        w, h = img.size
        resized = img.resize((int(w * scale), int(h * scale)), _PILImage.LANCZOS)
        logger.info(f"# Round 2: Trying to resize: {resized.size}")
        buf = io.BytesIO()
        resized.save(buf, format=fmt, quality=15)
        if buf.tell() <= DISCORD_MAX_BYTES:
            logger.info("Compressed %s at scale=%.2f: %d → %d bytes", filename, scale, len(data), buf.tell())
            return buf.getvalue(), out_name

    logger.warning("Could not compress %s under %d bytes — uploading best effort", filename, DISCORD_MAX_BYTES)
    buf = io.BytesIO()
    img.save(buf, format=fmt, quality=10)
    return buf.getvalue(), out_name