"""
Images Pipeline

See documentation in topics/media-pipeline.rst
"""
import functools
import hashlib
from contextlib import suppress
from io import BytesIO

from itemadapter import ItemAdapter
from PIL import Image

from scrapy.exceptions import DropItem
from scrapy.http import Request
from scrapy.pipelines.files import FileException, FilesPipeline
# TODO: from scrapy.pipelines.media import MediaPipeline
from scrapy.settings import Settings
from scrapy.utils.misc import md5sum
from scrapy.utils.python import to_bytes


class NoimagesDrop(DropItem):
    """Product with no images exception"""


class ImageException(FileException):
    """General image error exception"""


class ImagesPipeline(FilesPipeline):
    """Abstract pipeline that implement the image thumbnail generation logic

    """

    MEDIA_NAME = 'image'

    # Uppercase attributes kept for backward compatibility with code that subclasses
    # ImagesPipeline. They may be overridden by settings.
    MIN_WIDTH = 0
    MIN_HEIGHT = 0
    EXPIRES = 90
    THUMBS = {}
    DEFAULT_IMAGES_URLS_FIELD = 'image_urls'
    DEFAULT_IMAGES_RESULT_FIELD = 'images'

    def __init__(self, store_uri, download_func=None, settings=None):
        super(ImagesPipeline, self).__init__(store_uri, settings=settings,
                                             download_func=download_func)

        if isinstance(settings, dict) or settings is None:
            settings = Settings(settings)

        resolve = functools.partial(self._key_for_pipe,
                                    base_class_name="ImagesPipeline",
                                    settings=settings)
        self.expires = settings.getint(
            resolve("IMAGES_EXPIRES"), self.EXPIRES
        )

        if not hasattr(self, "IMAGES_RESULT_FIELD"):
            self.IMAGES_RESULT_FIELD = self.DEFAULT_IMAGES_RESULT_FIELD
        if not hasattr(self, "IMAGES_URLS_FIELD"):
            self.IMAGES_URLS_FIELD = self.DEFAULT_IMAGES_URLS_FIELD

        self.images_urls_field = settings.get(
            resolve('IMAGES_URLS_FIELD'),
            self.IMAGES_URLS_FIELD
        )
        self.images_result_field = settings.get(
            resolve('IMAGES_RESULT_FIELD'),
            self.IMAGES_RESULT_FIELD
        )
        self.min_width = settings.getint(
            resolve('IMAGES_MIN_WIDTH'), self.MIN_WIDTH
        )
        self.min_height = settings.getint(
            resolve('IMAGES_MIN_HEIGHT'), self.MIN_HEIGHT
        )
        self.thumbs = settings.get(
            resolve('IMAGES_THUMBS'), self.THUMBS
        )

    @classmethod
    def from_settings(cls, settings):
        s3store = cls.STORE_SCHEMES['s3']
        s3store.AWS_ACCESS_KEY_ID = settings['AWS_ACCESS_KEY_ID']
        s3store.AWS_SECRET_ACCESS_KEY = settings['AWS_SECRET_ACCESS_KEY']
        s3store.AWS_ENDPOINT_URL = settings['AWS_ENDPOINT_URL']
        s3store.AWS_REGION_NAME = settings['AWS_REGION_NAME']
        s3store.AWS_USE_SSL = settings['AWS_USE_SSL']
        s3store.AWS_VERIFY = settings['AWS_VERIFY']
        s3store.POLICY = settings['IMAGES_STORE_S3_ACL']

        gcs_store = cls.STORE_SCHEMES['gs']
        gcs_store.GCS_PROJECT_ID = settings['GCS_PROJECT_ID']
        gcs_store.POLICY = settings['IMAGES_STORE_GCS_ACL'] or None

        ftp_store = cls.STORE_SCHEMES['ftp']
        ftp_store.FTP_USERNAME = settings['FTP_USER']
        ftp_store.FTP_PASSWORD = settings['FTP_PASSWORD']
        ftp_store.USE_ACTIVE_MODE = settings.getbool('FEED_STORAGE_FTP_ACTIVE')

        store_uri = settings['IMAGES_STORE']
        return cls(store_uri, settings=settings)

    def file_downloaded(self, response, request, info):
        return self.image_downloaded(response, request, info)

    def image_downloaded(self, response, request, info):
        checksum = None
        for path, image, buf in self.get_images(response, request, info):
            if checksum is None:
                buf.seek(0)
                checksum = md5sum(buf)
            width, height = image.size
            self.store.persist_file(
                path, buf, info,
                meta={'width': width, 'height': height},
                headers={'Content-Type': 'image/jpeg'})
        return checksum

    def get_images(self, response, request, info):
        path = self.file_path(request, response=response, info=info)
        orig_image = Image.open(BytesIO(response.body))

        width, height = orig_image.size
        if width < self.min_width or height < self.min_height:
            raise ImageException("Image too small (%dx%d < %dx%d)" %
                                 (width, height, self.min_width, self.min_height))

        image, buf = self.convert_image(orig_image)
        yield path, image, buf

        for thumb_id, size in self.thumbs.items():
            thumb_path = self.thumb_path(request, thumb_id, response=response, info=info)
            thumb_image, thumb_buf = self.convert_image(image, size)
            yield thumb_path, thumb_image, thumb_buf

    def convert_image(self, image, size=None):
        if image.format == 'PNG' and image.mode == 'RGBA':
            background = Image.new('RGBA', image.size, (255, 255, 255))
            background.paste(image, image)
            image = background.convert('RGB')
        elif image.mode == 'P':
            image = image.convert("RGBA")
            background = Image.new('RGBA', image.size, (255, 255, 255))
            background.paste(image, image)
            image = background.convert('RGB')
        elif image.mode != 'RGB':
            image = image.convert('RGB')

        if size:
            image = image.copy()
            image.thumbnail(size, Image.ANTIALIAS)

        buf = BytesIO()
        image.save(buf, 'JPEG')
        return image, buf

    def get_media_requests(self, item, info):
        urls = ItemAdapter(item).get(self.images_urls_field, [])
        return [Request(u) for u in urls]

    def item_completed(self, results, item, info):
        with suppress(KeyError):
            ItemAdapter(item)[self.images_result_field] = [x for ok, x in results if ok]
        return item

    def file_path(self, request, response=None, info=None):
        image_guid = hashlib.sha1(to_bytes(request.url)).hexdigest()
        return 'full/%s.jpg' % (image_guid)

    def thumb_path(self, request, thumb_id, response=None, info=None):
        thumb_guid = hashlib.sha1(to_bytes(request.url)).hexdigest()
        return 'thumbs/%s/%s.jpg' % (thumb_id, thumb_guid)
