from rest_framework import serializers
from .models import FriendRequest, Friendship, Conversation, ConversationParticipant, ChatMessage
from django.conf import settings


class UserBriefSerializer(serializers.Serializer):
    id = serializers.IntegerField()
    username = serializers.CharField()
    nickname = serializers.SerializerMethodField()
    avatar = serializers.SerializerMethodField()

    def get_nickname(self, obj):
        return getattr(obj, 'nickname', '') or obj.username

    def get_avatar(self, obj):
        avatar = getattr(obj, 'avatar', None)
        if avatar and hasattr(avatar, 'url'):
            request = self.context.get('request')
            if request:
                return request.build_absolute_uri(avatar.url)
            return avatar.url
        return ''


class FriendRequestSerializer(serializers.ModelSerializer):
    from_user = UserBriefSerializer(read_only=True)
    to_user = UserBriefSerializer(read_only=True)
    from_user_id = serializers.IntegerField(write_only=True, required=False)
    to_user_id = serializers.IntegerField(write_only=True, required=False)

    class Meta:
        model = FriendRequest
        fields = ['id', 'from_user', 'to_user', 'from_user_id', 'to_user_id', 'status', 'message', 'created_at', 'updated_at']


class FriendshipSerializer(serializers.ModelSerializer):
    friend = serializers.SerializerMethodField()

    class Meta:
        model = Friendship
        fields = ['id', 'friend', 'created_at']

    def get_friend(self, obj):
        request = self.context.get('request')
        if not request:
            return None
        friend_user = obj.user2 if obj.user1 == request.user else obj.user1
        return UserBriefSerializer(friend_user, context=self.context).data


class ConversationSerializer(serializers.ModelSerializer):
    other_user = serializers.SerializerMethodField()
    last_message = serializers.SerializerMethodField()
    unread_count = serializers.SerializerMethodField()

    class Meta:
        model = Conversation
        fields = ['id', 'type', 'other_user', 'last_message', 'unread_count', 'created_at']

    def get_other_user(self, obj):
        request = self.context.get('request')
        if not request:
            return None
        participant = obj.participants.exclude(user=request.user).first()
        if participant:
            return UserBriefSerializer(participant.user, context=self.context).data
        return None

    def get_last_message(self, obj):
        last_msg = obj.messages.order_by('-created_at').first()
        if last_msg:
            return ChatMessageSerializer(last_msg, context=self.context).data
        return None

    def get_unread_count(self, obj):
        request = self.context.get('request')
        if not request:
            return 0
        try:
            participant = ConversationParticipant.objects.get(conversation=obj, user=request.user)
            if participant.last_read_at:
                return obj.messages.filter(created_at__gt=participant.last_read_at).exclude(sender=request.user).count()
            return obj.messages.exclude(sender=request.user).count()
        except ConversationParticipant.DoesNotExist:
            return 0


class ChatMessageSerializer(serializers.ModelSerializer):
    sender_info = UserBriefSerializer(source='sender', read_only=True)
    is_own = serializers.SerializerMethodField()
    reply_to_message = serializers.SerializerMethodField()

    class Meta:
        model = ChatMessage
        fields = ['id', 'conversation', 'sender', 'sender_info', 'content', 'msg_type', 'file_url', 'reply_to', 'reply_to_message', 'is_recalled', 'is_own', 'created_at']
        read_only_fields = ['sender', 'conversation']

    def get_is_own(self, obj):
        request = self.context.get('request')
        if request and hasattr(request, 'user'):
            return obj.sender == request.user
        return False

    def get_reply_to_message(self, obj):
        if obj.reply_to and not obj.reply_to.is_recalled:
            return {
                'id': obj.reply_to.id,
                'content': obj.reply_to.content[:50],
                'sender_name': getattr(obj.reply_to.sender, 'nickname', '') or obj.reply_to.sender.username,
                'msg_type': obj.reply_to.msg_type,
            }
        return None