import hashlib
import io
from pathlib import Path
import warnings

from dateutil import parser as date_parser
from django.core.files.base import ContentFile
from django.db import transaction
from django.utils import timezone
from PIL import Image, ImageOps

from commerce.integrations.moysklad import MoySkladClient
from commerce.models import IntegrationConnection, ProductImage


PRODUCT_THUMBNAIL_SIZE = (480, 480)
MAX_PRODUCT_IMAGE_PIXELS = 40_000_000
IMAGE_SUFFIXES = {".jpg", ".jpeg", ".png", ".webp", ".gif", ".bmp"}


def _source_updated_at(value: str):
    if not value:
        return None
    try:
        parsed = date_parser.parse(value)
    except (TypeError, ValueError, OverflowError):
        return None
    if timezone.is_naive(parsed):
        parsed = timezone.make_aware(parsed)
    return parsed


def _validated_image_and_thumbnail(content: bytes) -> tuple[bytes, str]:
    with warnings.catch_warnings():
        warnings.simplefilter("error", Image.DecompressionBombWarning)
        with Image.open(io.BytesIO(content)) as probe:
            if probe.width * probe.height > MAX_PRODUCT_IMAGE_PIXELS:
                raise ValueError("Изображение превышает лимит 40 мегапикселей.")
            image_format = (probe.format or "").upper()
            probe.verify()
    with Image.open(io.BytesIO(content)) as source:
        source.seek(0)
        image = ImageOps.exif_transpose(source)
        if image.mode not in {"RGB", "RGBA"}:
            image = image.convert("RGBA" if "transparency" in image.info else "RGB")
        image.thumbnail(PRODUCT_THUMBNAIL_SIZE, Image.Resampling.LANCZOS)
        output = io.BytesIO()
        image.save(output, format="WEBP", quality=84, method=5)
        suffix = {
            "JPEG": ".jpg",
            "PNG": ".png",
            "WEBP": ".webp",
            "GIF": ".gif",
            "BMP": ".bmp",
        }.get(image_format, ".img")
        return output.getvalue(), suffix


def _storage_filename(
    external_id: str,
    source_name: str,
    content: bytes,
    detected_suffix: str,
) -> str:
    suffix = Path(source_name).suffix.lower()
    if suffix not in IMAGE_SUFFIXES:
        suffix = detected_suffix
    digest = hashlib.sha256(content).hexdigest()[:16]
    return f"{external_id}-{digest}{suffix}"


def _delete_replaced_files(image, old_names):
    for field_name, old_name in old_names.items():
        field = getattr(image, field_name)
        if old_name and old_name != field.name:
            field.storage.delete(old_name)


def sync_moysklad_product_images(
    *,
    connection: IntegrationConnection,
    row: dict,
    client: MoySkladClient,
) -> int:
    external_product_id = str(row.get("id") or "").strip()
    if not external_product_id:
        return 0
    binding = connection.source.product_bindings.select_related("product").get(
        external_id=external_product_id
    )
    product = binding.product
    images_meta = row.get("images") if isinstance(row.get("images"), dict) else {}
    collection_meta = (
        images_meta.get("meta") if isinstance(images_meta.get("meta"), dict) else {}
    )
    image_count = max(0, int(collection_meta.get("size") or 0))
    if image_count == 0:
        product.images.filter(source=connection.source).delete()
        return 0

    entity_meta = row.get("meta") if isinstance(row.get("meta"), dict) else {}
    entity_type = str(entity_meta.get("type") or "")
    embedded_rows = images_meta.get("rows")
    remote_images = (
        client.parse_product_images(embedded_rows)
        if isinstance(embedded_rows, list)
        else client.product_images(entity_type, external_product_id)
    )
    retained_ids = []

    for position, remote in enumerate(remote_images):
        source_updated_at = _source_updated_at(remote.updated)
        image = ProductImage.objects.filter(
            product=product,
            source=connection.source,
            external_id=remote.external_id,
        ).first()
        unchanged = bool(
            image
            and image.source_size == remote.size
            and image.source_updated_at == source_updated_at
            and image.file
            and image.file.storage.exists(image.file.name)
            and image.thumbnail
            and image.thumbnail.storage.exists(image.thumbnail.name)
        )
        if unchanged:
            image.product = product
            image.filename = remote.filename
            image.title = remote.title
            image.position = position
            image.is_primary = position == 0
            image.save(
                update_fields=[
                    "product",
                    "filename",
                    "title",
                    "position",
                    "is_primary",
                    "updated_at",
                ]
            )
            retained_ids.append(remote.external_id)
            continue

        content, _content_type = client.download_image(remote.download_href)
        thumbnail, detected_suffix = _validated_image_and_thumbnail(content)
        storage_name = _storage_filename(
            remote.external_id,
            remote.filename,
            content,
            detected_suffix,
        )
        if image is None:
            image = ProductImage(
                source=connection.source,
                external_id=remote.external_id,
            )
        old_names = {
            "file": image.file.name if image.file else "",
            "thumbnail": image.thumbnail.name if image.thumbnail else "",
        }
        image.product = product
        image.filename = remote.filename
        image.title = remote.title
        image.source_size = remote.size
        image.source_updated_at = source_updated_at
        image.position = position
        image.is_primary = position == 0
        image.file.save(storage_name, ContentFile(content), save=False)
        image.thumbnail.save(
            f"{remote.external_id}-{hashlib.sha256(content).hexdigest()[:16]}.webp",
            ContentFile(thumbnail),
            save=False,
        )
        with transaction.atomic():
            image.save()
            transaction.on_commit(
                lambda current=image, previous=old_names: _delete_replaced_files(
                    current,
                    previous,
                )
            )
        retained_ids.append(remote.external_id)

    product.images.filter(source=connection.source).exclude(
        external_id__in=retained_ids
    ).delete()
    return len(retained_ids)