"""Image pipeline. Validates, re-encodes (drops EXIF), thumbnails, saves to media.

Re-encoding through Pillow strips metadata and neutralizes polyglot/malicious
payloads. Filenames are randomized. Returns a ListingImage (uncommitted).
"""
import io
import os
import secrets
from PIL import Image
from flask import current_app
from app.models.listing import ListingImage

MAX_BYTES = 8 * 1024 * 1024          # 8 MB per upload
MAX_DIM = 1600                        # longest edge for the full image
THUMB_DIM = 400
ALLOWED = {"JPEG", "PNG", "WEBP"}


class ImageError(ValueError):
    pass


def _media_root():
    root = current_app.config.get("MEDIA_ROOT") or os.path.join(
        current_app.instance_path, "media")
    os.makedirs(root, exist_ok=True)
    return root


def process_upload(file_storage, listing_id, sort_order=0):
    data = file_storage.read()
    if not data:
        raise ImageError("empty file")
    if len(data) > MAX_BYTES:
        raise ImageError("file too large")

    try:
        img = Image.open(io.BytesIO(data))
        img.verify()                       # detect truncated/corrupt
        img = Image.open(io.BytesIO(data))  # re-open after verify
    except Exception:
        raise ImageError("not a valid image")

    if img.format not in ALLOWED:
        raise ImageError("unsupported format")

    img = img.convert("RGB")               # normalize, drop alpha/EXIF
    img.thumbnail((MAX_DIM, MAX_DIM))

    root = _media_root()
    sub = os.path.join(root, str(listing_id))
    os.makedirs(sub, exist_ok=True)
    name = secrets.token_hex(16)

    full_rel = os.path.join(str(listing_id), f"{name}.jpg")
    thumb_rel = os.path.join(str(listing_id), f"{name}_t.jpg")
    img.save(os.path.join(root, full_rel), "JPEG", quality=85, optimize=True)

    thumb = img.copy()
    thumb.thumbnail((THUMB_DIM, THUMB_DIM))
    thumb.save(os.path.join(root, thumb_rel), "JPEG", quality=80, optimize=True)

    return ListingImage(
        listing_id=listing_id, path=full_rel, thumb_path=thumb_rel,
        sort_order=sort_order, width=img.width, height=img.height,
    )


def delete_image_files(image):
    root = _media_root()
    for rel in (image.path, image.thumb_path):
        if rel:
            try:
                os.remove(os.path.join(root, rel))
            except OSError:
                pass