class Pagination(object):

    def __init__(self, data_num, current_page, url_prefix, per_page=10,  max_show=11):

        """

        进行初始化.

        :param data_num: 数据总数

        :param current_page: 当前页

        :param url_prefix: 生成的页码的链接前缀

        :param per_page: 每页显示多少条数据

        :param max_show: 页面最多显示多少个页码

        """

        self.data_num = data_num

        self.per_page = per_page

        self.max_show = max_show

        self.url_prefix = url_prefix

        # 把页码数算出来

        self.page_num, more = divmod(data_num, per_page)

        if more:

            self.page_num += 1

        try:

            self.current_page = int(current_page)

        except Exception as e:

            self.current_page = 1

            # 如果URL传过来的页码数是负数

        if self.current_page <= 0:

            self.current_page = 1

            # 如果URL传过来的页码数超过了最大页码数

        elif self.current_page > self.page_num:

            self.current_page = self.page_num  # 默认展示最后一页

        # 页码数的一半 算出来

        self.half_show = max_show // 2

        # 页码最左边显示多少

        if self.current_page - self.half_show <= 1:

            self.page_start = 1

            self.page_end = self.max_show

        elif self.current_page + self.half_show >= self.page_num:  # 如果右边越界

            self.page_end = self.page_num

            self.page_start = self.page_num - self.max_show

        else:

            self.page_start = self.current_page - self.half_show

            # 页码最右边显示

            self.page_end = self.current_page + self.half_show

    @property

    def start(self):

        # 数据从哪儿开始切

        return (self.current_page - 1) * self.per_page

    @property

    def end(self):

        # 数据切片切到哪儿

        return self.current_page * self.per_page

    def page_html(self):

        # 生成页码

        l = []

        # 加一个首页

        l.append('<li><a href="{}?page=1">首页</a></li>'.format(self.url_prefix))

        # 加一个上一页

        if self.current_page == 1:

            l.append('<li class="disabled" ><a href="#">«</a></li>'.format(self.current_page))

        else:

            l.append('<li><a href="{}?page={}">«</a></li>'.format(self.url_prefix, self.current_page - 1))

        for i in range(self.page_start, self.page_end + 1):

            if i == self.current_page:

                tmp = '<li class="active"><a href="{0}?page={1}">{1}</a></li>'.format(self.url_prefix, i)

            else:

                tmp = '<li><a href="{0}?page={1}">{1}</a></li>'.format(self.url_prefix, i)

            l.append(tmp)

        # 加一个下一页

        if self.current_page == self.page_num:

            l.append('<li class="disabled"><a href="#">»</a></li>'.format(self.current_page))

        else:

            l.append('<li><a href="{}?page={}">»</a></li>'.format(self.url_prefix, self.current_page + 1))

        # 加一个尾页

        l.append('<li><a href="{}?page={}">尾页</a></li>'.format(self.url_prefix, self.page_num))

        return "".join(l)

# 出版社

@check_login

def publishing_list(request):

    pubishing = Press.objects.all()  # 取出数据库数据

    count_s = pubishing.count()  # 统计出版社有多少数据

    current_page = request.GET.get("page", 1)  # 获取当前页 找不到返回1

    from utils import mypage  # 导入分页文件

    obj = mypage.Pagination(count_s, current_page, "/publishing_list/")  # 把数据传进去

    pubishing_lists = pubishing[obj.start:obj.end]

    page_html = obj.page_html()     # 分页 的导航的 html  类似:上一页 1 2 3 4 5 6  下一页

    return render(request, "publishing_list.html", {"pubishing_lists": pubishing_lists, "page_html": page_html})