import os.path
from PIL import Image
try:
    from cStringIO import StringIO
except:
    from StringIO import StringIO

from django.core.files.uploadedfile import InMemoryUploadedFile
from django.http import HttpResponseNotFound, HttpResponseRedirect
from django.shortcuts import get_object_or_404

from . import IMAGE_SIZES
from . import models

# this neat function is based on easy-thumbnails
def scale_and_crop(image, size, crop=False, upscale=False):
    image.open()
    im = Image.open(image)
    # Force PIL to load image data.
    im.load()

    source_x, source_y = [float(v) for v in im.size]
    target_x, target_y = [float(v) for v in size]

    if crop or not target_x or not target_y:
        scale = max(target_x / source_x, target_y / source_y)
    else:
        scale = min(target_x / source_x, target_y / source_y)

    # Handle one-dimensional targets.
    if not target_x:
        target_x = source_x * scale
    elif not target_y:
        target_y = source_y * scale

    if scale < 1.0 or (scale > 1.0 and upscale):
        im = im.resize((int(source_x * scale), int(source_y * scale)),
                       resample=Image.ANTIALIAS)

    if crop:
        # Use integer values now.
        source_x, source_y = im.size
        # Difference between new image size and requested size.
        diff_x = int(source_x - min(source_x, target_x))
        diff_y = int(source_y - min(source_y, target_y))
        if diff_x or diff_y:
            # Center cropping (default).
            halfdiff_x, halfdiff_y = diff_x // 2, diff_y // 2
            box = [halfdiff_x, halfdiff_y,
                   min(source_x, int(target_x) + halfdiff_x),
                   min(source_y, int(target_y) + halfdiff_y)]
            # Finally, crop the image!
            im = im.crop(box)
    image.close()
    return im

def thumbnail(request, image_id, size):
    image = get_object_or_404(models.Image, id=image_id)
    if not size in IMAGE_SIZES:
        return HttpResponseNotFound()
    try:
        thumbnail = image.get_by_size(size)
    except models.Thumbnail.DoesNotExist:
        img = scale_and_crop(image.image, **IMAGE_SIZES[size])
        # save to memory
        buf = StringIO()
        img.save(buf, 'JPEG')
        # and save to storage
        original_dir, original_file = os.path.split(image.image.name)
        thumb_file = InMemoryUploadedFile(buf, "image", original_file, None, buf.tell(), None)
        thumbnail = image.thumbnail_set.create(size=size, image=thumb_file)
    return HttpResponseRedirect(thumbnail.image.url)
