from adrf.serializers import (
    ModelSerializer, CharField, SerializerMethodField,
)
from django.contrib.auth import get_user_model
from django.core.exceptions import SynchronousOnlyOperation
from .models import Message, SystemMessage, SystemMessageRead

User = get_user_model()


async def _load_sender(obj):
    """优先命中 select_related 预加载缓存；未预加载时异步回源，避免外键懒加载"""
    try:
        return obj.sender
    except SynchronousOnlyOperation:
        if not obj.sender_id:
            return None
        return await User.objects.aget(pk=obj.sender_id)


class MessageListSerializer(ModelSerializer):
    sender_name = SerializerMethodField()
    sender_avatar = SerializerMethodField()
    time = SerializerMethodField()
    is_comment = SerializerMethodField()
    comment_id = SerializerMethodField()
    article_id = SerializerMethodField()
    type = CharField(source='msg_type', read_only=True)
    extra = CharField(source='extra_info', read_only=True)
    link = CharField(source='target_link', read_only=True)

    class Meta:
        model = Message
        fields = [
            'id', 'type', 'title', 'content', 'time', 'is_read',
            'sender_name', 'sender_avatar', 'extra', 'link',
            'is_comment', 'comment_id', 'article_id',
        ]

    async def get_sender_name(self, obj):
        sender = await _load_sender(obj)
        if sender:
            return sender.nickname or sender.username
        return '系统'

    async def get_sender_avatar(self, obj):
        sender = await _load_sender(obj)
        if sender and sender.avatar:
            request = self.context.get('request')
            if request:
                return request.build_absolute_uri(sender.avatar.url)
            return sender.avatar.url
        return ''

    async def get_time(self, obj):
        return obj.created_at.strftime('%Y-%m-%d %H:%M')

    async def get_is_comment(self, obj):
        return obj.target_type == 'comment'

    async def get_comment_id(self, obj):
        if obj.target_type == 'comment' and obj.target_id:
            return str(obj.target_id)
        return ''

    async def get_article_id(self, obj):
        if obj.target_link:
            import re
            match = re.search(r'/article/(\d+)', obj.target_link)
            if match:
                return match.group(1)
        if obj.extra_info:
            import re
            match = re.search(r'/article/(\d+)', obj.extra_info)
            if match:
                return match.group(1)
        return None


class SystemMessageSerializer(ModelSerializer):
    is_read = SerializerMethodField()

    class Meta:
        model = SystemMessage
        fields = ['id', 'title', 'content', 'category', 'icon_name', 'icon_color', 'created_at', 'is_read']

    async def get_is_read(self, obj):
        read_ids = self.context.get('read_ids', set())
        return obj.id in read_ids


class SystemMessageDetailSerializer(ModelSerializer):
    is_read = SerializerMethodField()

    class Meta:
        model = SystemMessage
        fields = ['id', 'title', 'content', 'detail', 'category', 'icon_name', 'icon_color', 'created_at', 'is_read']

    async def get_is_read(self, obj):
        request = self.context.get('request')
        if request and request.user.is_authenticated:
            return await SystemMessageRead.objects.filter(
                user=request.user,
                system_message=obj
            ).aexists()
        return False