from io import BytesIO
from django.db import models
import logging
from django.core.files.uploadedfile import SimpleUploadedFile


class ExtendedImageField(models.ImageField):
    """Extended ImageField that can resize image before saving it."""

    def __init__(self, *args, **kwargs):
        self.width = kwargs.pop('width', None)
        self.height = kwargs.pop('height', None)
        super(ExtendedImageField, self).__init__(*args, **kwargs)

    def save_form_data(self, instance, data):
        if data is not None and data != self.default:
            if not data:
                data = self.default
                if instance.avatar != self.default:
                    instance.avatar.delete()
            else:
                if hasattr(data, 'read') and self.width and self.height:
                    content = self.resize_image(
                        data.read(), width=self.width, height=self.height)
                    data = SimpleUploadedFile(
                        instance.user.username + '.png', content, 'image/png')
            super(ExtendedImageField, self).save_form_data(instance, data)

    def resize_image(self, rawdata, width, height):
        """Resize image to fit it into (width, height) box."""
        from PIL import Image

        image = Image.open(BytesIO(rawdata))
        try:
            oldw, oldh = image.size

            if oldw > width or oldh > height:
                if oldw >= oldh:
                    x = int(round((oldw - oldh) / 2.0))
                    image = image.crop((x, 0, (x + oldh) - 1, oldh - 1))
                else:
                    y = int(round((oldh - oldw) / 2.0))
                    image = image.crop((0, y, oldw - 1, (y + oldw) - 1))
                image = image.resize((width, height), resample=Image.ANTIALIAS)
        except Exception as err:
            logging.error(err)
            return ''

        string = BytesIO()
        image.save(string, format='PNG')
        return string.getvalue()