from django.contrib import admin
from django.contrib.admin.models import DELETION
from django.contrib.contenttypes.models import ContentType
from django.urls import reverse, NoReverseMatch
from django.utils.encoding import force_str
from django.utils.html import escape
from django.utils.safestring import mark_safe
from django.utils.translation import gettext_lazy as _


class LogEntryAdmin(admin.ModelAdmin):
    """Django管理员日志条目的自定义管理界面"""
    
    # 列表页过滤器配置：按内容类型过滤
    list_filter = [
        'content_type'
    ]

    # 搜索字段配置：可按对象表示和变更消息搜索
    search_fields = [
        'object_repr',
        'change_message'
    ]

    # 列表页中可点击的链接字段
    list_display_links = [
        'action_time',
        'get_change_message',
    ]
    
    # 列表页显示的字段
    list_display = [
        'action_time',           # 操作时间
        'user_link',             # 用户链接（自定义）
        'content_type',          # 内容类型
        'object_link',           # 对象链接（自定义）
        'get_change_message',    # 变更消息
    ]

    def has_add_permission(self, request):
        """禁止添加新的日志条目"""
        return False

    def has_change_permission(self, request, obj=None):
        """修改权限控制：只允许超级用户或具有特定权限的用户查看（不允许POST修改）"""
        return (
                request.user.is_superuser or
                request.user.has_perm('admin.change_logentry')
        ) and request.method != 'POST'

    def has_delete_permission(self, request, obj=None):
        """禁止删除日志条目"""
        return False

    def object_link(self, obj):
        """生成对象链接的显示"""
        object_link = escape(obj.object_repr)  # 转义对象表示字符串
        content_type = obj.content_type

        # 如果不是删除操作且内容类型存在，尝试生成可点击的链接
        if obj.action_flag != DELETION and content_type is not None:
            try:
                # 构建管理员修改页面的URL
                url = reverse(
                    'admin:{}_{}_change'.format(content_type.app_label,
                                                content_type.model),
                    args=[obj.object_id]
                )
                # 创建HTML链接
                object_link = '<a href="{}">{}</a>'.format(url, object_link)
            except NoReverseMatch:
                # 如果无法生成URL，保持原样
                pass
        return mark_safe(object_link)  # 标记为安全HTML

    # 设置对象链接字段的排序和显示名称
    object_link.admin_order_field = 'object_repr'
    object_link.short_description = _('object')

    def user_link(self, obj):
        """生成用户链接的显示"""
        content_type = ContentType.objects.get_for_model(type(obj.user))
        user_link = escape(force_str(obj.user))  # 转义用户字符串
        
        try:
            # 构建用户修改页面的URL
            url = reverse(
                'admin:{}_{}_change'.format(content_type.app_label,
                                            content_type.model),
                args=[obj.user.pk]
            )
            # 创建HTML链接
            user_link = '<a href="{}">{}</a>'.format(url, user_link)
        except NoReverseMatch:
            # 如果无法生成URL，保持原样
            pass
        return mark_safe(user_link)  # 标记为安全HTML

    # 设置用户链接字段的排序和显示名称
    user_link.admin_order_field = 'user'
    user_link.short_description = _('user')

    def get_queryset(self, request):
        """获取查询集，预取content_type关系以提高性能"""
        queryset = super(LogEntryAdmin, self).get_queryset(request)
        return queryset.prefetch_related('content_type')

    def get_actions(self, request):
        """获取可用的批量操作，移除删除选中操作"""
        actions = super(LogEntryAdmin, self).get_actions(request)
        if 'delete_selected' in actions:
            del actions['delete_selected']  # 移除批量删除选项
        return actions