"""
captcha - 验证码

Author: Hao
Date: 2021/8/24
"""
import os
import random
import string
from io import BytesIO

from PIL import Image
from PIL import ImageFilter
from PIL.ImageDraw import Draw
from PIL.ImageFont import truetype


class Bezier:
    """贝塞尔曲线"""

    def __init__(self):
        self.tsequence = tuple([t / 20.0 for t in range(21)])
        self.beziers = {}

    def make_bezier(self, n):
        """绘制贝塞尔曲线"""
        try:
            return self.beziers[n]
        except KeyError:
            combinations = pascal_row(n - 1)
            result = []
            for t in self.tsequence:
                tpowers = (t ** i for i in range(n))
                upowers = ((1 - t) ** i for i in range(n - 1, -1, -1))
                coefs = [c * a * b for c, a, b in zip(combinations,
                                                      tpowers, upowers)]
                result.append(coefs)
            self.beziers[n] = result
            return result


class Captcha:
    """验证码"""

    def __init__(self, width, height, fonts=None, color=None):
        self._image = None
        self._fonts = fonts if fonts else \
            [os.path.join('./fonts', font)
             for font in ['Arial.ttf', 'Georgia.ttf', 'Action.ttf']]
        self._color = color if color else random_color(0, 200, random.randint(220, 255))
        self._width, self._height = width, height

    @classmethod
    def instance(cls, width=200, height=75):
        prop_name = f'_instance_{width}_{height}'
        if not hasattr(cls, prop_name):
            setattr(cls, prop_name, cls(width, height))
        return getattr(cls, prop_name)

    def _background(self):
        """绘制背景"""
        Draw(self._image).rectangle([(0, 0), self._image.size],
                                    fill=random_color(230, 255))

    def _smooth(self):
        """平滑图像"""
        return self._image.filter(ImageFilter.SMOOTH)

    def _curve(self, width=4, number=6, color=None):
        """绘制曲线"""
        dx, height = self._image.size
        dx /= number
        path = [(dx * i, random.randint(0, height))
                for i in range(1, number)]
        bcoefs = Bezier().make_bezier(number - 1)
        points = []
        for coefs in bcoefs:
            points.append(tuple(sum([coef * p for coef, p in zip(coefs, ps)])
                                for ps in zip(*path)))
        Draw(self._image).line(points, fill=color if color else self._color, width=width)

    def _noise(self, number=50, level=2, color=None):
        """绘制扰码"""
        width, height = self._image.size
        dx, dy = width / 10, height / 10
        width, height = width - dx, height - dy
        draw = Draw(self._image)
        for i in range(number):
            x = int(random.uniform(dx, width))
            y = int(random.uniform(dy, height))
            draw.line(((x, y), (x + level, y)),
                      fill=color if color else self._color, width=level)

    def _text(self, captcha_text, fonts, font_sizes=None, drawings=None, squeeze_factor=0.75, color=None):
        """绘制文本"""
        color = color if color else self._color
        fonts = tuple([truetype(name, size)
                       for name in fonts
                       for size in font_sizes or (65, 70, 75)])
        draw = Draw(self._image)
        char_images = []
        for c in captcha_text:
            font = random.choice(fonts)
            c_width, c_height = draw.textsize(c, font=font)
            char_image = Image.new('RGB', (c_width, c_height), (0, 0, 0))
            char_draw = Draw(char_image)
            char_draw.text((0, 0), c, font=font, fill=color)
            char_image = char_image.crop(char_image.getbbox())
            for drawing in drawings:
                d = getattr(self, drawing)
                char_image = d(char_image)
            char_images.append(char_image)
        width, height = self._image.size
        offset = int((width - sum(int(i.size[0] * squeeze_factor)
                                  for i in char_images[:-1]) -
                      char_images[-1].size[0]) / 2)
        for char_image in char_images:
            c_width, c_height = char_image.size
            mask = char_image.convert('L').point(lambda i: i * 1.97)
            self._image.paste(char_image,
                              (offset, int((height - c_height) / 2)),
                              mask)
            offset += int(c_width * squeeze_factor)

    @staticmethod
    def _warp(image, dx_factor=0.3, dy_factor=0.3):
        """图像扭曲"""
        width, height = image.size
        dx = width * dx_factor
        dy = height * dy_factor
        x1 = int(random.uniform(-dx, dx))
        y1 = int(random.uniform(-dy, dy))
        x2 = int(random.uniform(-dx, dx))
        y2 = int(random.uniform(-dy, dy))
        warp_image = Image.new(
            'RGB',
            (width + abs(x1) + abs(x2), height + abs(y1) + abs(y2)))
        warp_image.paste(image, (abs(x1), abs(y1)))
        width2, height2 = warp_image.size
        return warp_image.transform(
            (width, height),
            Image.QUAD,
            (x1, y1, -x1, height2 - y2, width2 + x2, height2 + y2, width2 - x2, -y1))

    @staticmethod
    def _offset(image, dx_factor=0.1, dy_factor=0.2):
        """图像偏移"""
        width, height = image.size
        dx = int(random.random() * width * dx_factor)
        dy = int(random.random() * height * dy_factor)
        offset_image = Image.new('RGB', (width + dx, height + dy))
        offset_image.paste(image, (dx, dy))
        return offset_image

    @staticmethod
    def _rotate(image, angle=25):
        """图像旋转"""
        return image.rotate(random.uniform(-angle, angle),
                            Image.BILINEAR, expand=1)

    def generate(self, captcha_text='', fmt='PNG'):
        """生成验证码(文字和图片)"""
        self._image = Image.new('RGB', (self._width, self._height), (255, 255, 255))
        self._background()
        self._text(captcha_text, self._fonts,
                   drawings=['_warp', '_rotate', '_offset'])
        self._curve()
        self._noise()
        self._smooth()
        image_bytes = BytesIO()
        self._image.save(image_bytes, format=fmt)
        return image_bytes.getvalue()


def pascal_row(n=0):
    """生成毕达哥拉斯三角形（杨辉三角）"""
    result = [1]
    x, numerator = 1, n
    for denominator in range(1, n // 2 + 1):
        x *= numerator
        x /= denominator
        result.append(x)
        numerator -= 1
    if n & 1 == 0:
        result.extend(reversed(result[:-1]))
    else:
        result.extend(reversed(result))
    return result


def random_color(start=0, end=255, opacity=255):
    """获得随机颜色"""
    red = random.randint(start, end)
    green = random.randint(start, end)
    blue = random.randint(start, end)
    if opacity is None:
        return red, green, blue
    return red, green, blue, opacity


def random_code(length=4):
    return ''.join(random.choices(string.ascii_letters + string.digits, k=length))


if __name__ == '__main__':
    captcha = Captcha.instance()
    image_data = captcha.generate(random_code())
    with open('resources/captcha.png', 'wb') as file:
        file.write(image_data)