import os
import random
from io import BytesIO

from PIL import Image, ImageDraw, ImageFont, ImageFilter
from django.http import HttpResponse, JsonResponse
from django.views import View
from django.urls import reverse
from django.utils import timezone

from pingcap_sso.models import CaptchaStore


# Distance of the drawn text from the top of the captcha image
DISTANCE_FROM_TOP = 4

CAPTCHA_FONT_PATH = os.path.normpath(
    os.path.join(
        os.path.dirname(__file__),
        'Vera.ttf',
    )
)
CAPTCHA_PUNCTUATION = """_"',.;:-"""
CAPTCHA_LETTER_ROTATION = (-35, 35)
CAPTCHA_FOREGROUND_COLOR = "#0b3c01"
CAPTCHA_BACKGROUND_COLOR = "#ffffff"


def get_letter_color(index, challenge):
    return CAPTCHA_FOREGROUND_COLOR


def getsize(font, text):
    if hasattr(font, "getbbox"):
        _top, _left, _right, _bottom = font.getbbox(text)
        return _right - _left, _bottom - _top
    elif hasattr(font, "getoffset"):
        return tuple([x + y for x, y in zip(font.getsize(text), font.getoffset(text))])
    else:
        return font.getsize(text)


def makeimg(size):
    if CAPTCHA_BACKGROUND_COLOR == "transparent":
        image = Image.new("RGBA", size)
    else:
        image = Image.new("RGB", size, CAPTCHA_BACKGROUND_COLOR)
    return image


def post_smooth(image):
    return image.filter(ImageFilter.SMOOTH)


def noise_arcs(draw, image):
    size = image.size
    draw.arc([-20, -20, size[0], 20], 0, 295, fill=CAPTCHA_FOREGROUND_COLOR)
    draw.line(
        [-20, 20, size[0] + 20, size[1] - 20], fill=CAPTCHA_FOREGROUND_COLOR
    )
    draw.line([-20, 0, size[0] + 20, size[1]], fill=CAPTCHA_FOREGROUND_COLOR)
    return draw


def noise_dots(draw, image):
    size = image.size
    for p in range(int(size[0] * size[1] * 0.1)):
        draw.point(
            (random.randint(0, size[0]), random.randint(0, size[1])),
            fill=CAPTCHA_FOREGROUND_COLOR,
        )
    return draw


class CaptchaImageView(View):

    def get(self, request, identifier, *args, **kwargs):
        try:
            store = CaptchaStore.objects.get(
                identifier=identifier,
                expires_at__gt=timezone.now()
            )
        except CaptchaStore.DoesNotExist:
            # HTTP 410 Gone status so that crawlers don't index these expired urls.
            return HttpResponse(status=410)

        random.seed(identifier)  # Do not generate different images for the same key

        text = store.challenge

        font = ImageFont.truetype(CAPTCHA_FONT_PATH, 44)

        size = getsize(font, text)
        size = (size[0] * 2, int(size[1] * 1.4))

        image = makeimg(size)
        xpos = 2

        charlist = []
        for char in text:
            if char in CAPTCHA_PUNCTUATION and len(charlist) >= 1:
                charlist[-1] += char
            else:
                charlist.append(char)

        for index, char in enumerate(charlist):
            fgimage = Image.new(
                "RGB", size, get_letter_color(index, "".join(charlist))
            )
            charimage = Image.new("L", getsize(font, " %s " % char), "#000000")
            chardraw = ImageDraw.Draw(charimage)
            chardraw.text((0, 0), " %s " % char, font=font, fill="#ffffff")
            if CAPTCHA_LETTER_ROTATION:
                charimage = charimage.rotate(
                    random.randrange(*CAPTCHA_LETTER_ROTATION),
                    expand=0,
                    resample=Image.BICUBIC,
                )
            charimage = charimage.crop(charimage.getbbox())
            maskimage = Image.new("L", size)

            maskimage.paste(
                charimage,
                (
                    xpos,
                    DISTANCE_FROM_TOP,
                    xpos + charimage.size[0],
                    DISTANCE_FROM_TOP + charimage.size[1],
                ),
            )
            size = maskimage.size
            image = Image.composite(fgimage, image, maskimage)
            xpos = xpos + 2 + charimage.size[0]

        image = image.crop((0, 0, xpos + 1, size[1]))
        draw = ImageDraw.Draw(image)

        for f in (noise_arcs, noise_dots):
            draw = f(draw, image)
        for f in (post_smooth,):
            image = f(image)

        out = BytesIO()
        image.save(out, "PNG")
        out.seek(0)

        response = HttpResponse(content_type="image/png")
        response.write(out.read())
        response["Content-length"] = out.tell()

        # At line :50 above we fixed the random seed so that we always generate the
        # same image, see: https://github.com/mbi/django-simple-captcha/pull/194
        # This is a problem though, because knowledge of the seed will let an attacker
        # predict the next random (globally). We therefore reset the random here.
        # Reported in https://github.com/mbi/django-simple-captcha/pull/221
        random.seed()

        return response