from django.conf import settings
from django.contrib.auth import get_user_model
from rest_framework import serializers
from drf_spectacular.utils import extend_schema_field

from apps.chat.models.chat import ChatRoom, ChatMessage
from apps.profiles.models.institution import Institution

User = get_user_model()


class CentrifugoTokenResponseSerializer(serializers.Serializer):
    token = serializers.CharField(help_text="Signed HMAC-SHA256 JWT for Centrifugo WebSocket connection")
    ws_url = serializers.CharField(help_text="WebSocket endpoint URL for frontend client")
    user_id = serializers.IntegerField(help_text="Authenticated user ID")
    expires_in = serializers.IntegerField(help_text="Token lifetime in seconds")


class ChatUserMiniSerializer(serializers.ModelSerializer):
    class Meta:
        model = User
        fields = ['id', 'email', 'fullname', 'avatar', 'user_type']
        read_only_fields = fields


class ChatInstitutionMiniSerializer(serializers.ModelSerializer):
    type_display = serializers.CharField(source='get_type_display', read_only=True)

    class Meta:
        model = Institution
        fields = ['id', 'name', 'slug', 'type', 'type_display', 'avatar', 'city', 'country']
        read_only_fields = fields


class ChatMessageSerializer(serializers.ModelSerializer):
    sender = ChatUserMiniSerializer(read_only=True)
    sender_institution = ChatInstitutionMiniSerializer(read_only=True)
    is_read_by_me = serializers.SerializerMethodField()
    read_by_count = serializers.SerializerMethodField()

    class Meta:
        model = ChatMessage
        fields = [
            'id',
            'room',
            'sender',
            'sender_institution',
            'content',
            'attachment',
            'attachment_name',
            'is_read_by_me',
            'read_by_count',
            'created_at',
        ]
        read_only_fields = fields

    @extend_schema_field(serializers.BooleanField)
    def get_is_read_by_me(self, obj) -> bool:
        request = self.context.get('request')
        if not request or not request.user.is_authenticated:
            return False
        return obj.read_by.filter(id=request.user.id).exists()

    @extend_schema_field(serializers.IntegerField)
    def get_read_by_count(self, obj) -> int:
        return obj.read_by.count()


class ChatMessageCreateSerializer(serializers.Serializer):
    content = serializers.CharField(required=False, allow_blank=True)
    attachment = serializers.FileField(required=False, allow_null=True)
    sender_institution_id = serializers.IntegerField(required=False, allow_null=True)

    def validate(self, attrs):
        if not attrs.get('content') and not attrs.get('attachment'):
            raise serializers.ValidationError("Message must contain either text content or an attachment.")
        return attrs


class ChatRoomListSerializer(serializers.ModelSerializer):
    display_title = serializers.SerializerMethodField()
    participant_users = ChatUserMiniSerializer(many=True, read_only=True)
    participant_institutions = ChatInstitutionMiniSerializer(many=True, read_only=True)
    last_message = serializers.SerializerMethodField()
    unread_count = serializers.SerializerMethodField()
    centrifugo_channel = serializers.CharField(read_only=True)

    class Meta:
        model = ChatRoom
        fields = [
            'id',
            'room_type',
            'title',
            'display_title',
            'participant_users',
            'participant_institutions',
            'last_message',
            'unread_count',
            'centrifugo_channel',
            'updated_at',
        ]
        read_only_fields = fields

    @extend_schema_field(serializers.CharField)
    def get_display_title(self, obj) -> str:
        request = self.context.get('request')
        user = request.user if request else None
        return obj.get_display_title(user)

    @extend_schema_field(ChatMessageSerializer(allow_null=True))
    def get_last_message(self, obj):
        last_msg = obj.get_last_message()
        if not last_msg:
            return None
        return ChatMessageSerializer(last_msg, context=self.context).data

    @extend_schema_field(serializers.IntegerField)
    def get_unread_count(self, obj) -> int:
        request = self.context.get('request')
        if not request or not request.user.is_authenticated:
            return 0
        return obj.get_unread_count(request.user)


class ChatRoomDetailSerializer(serializers.ModelSerializer):
    display_title = serializers.SerializerMethodField()
    participant_users = ChatUserMiniSerializer(many=True, read_only=True)
    participant_institutions = ChatInstitutionMiniSerializer(many=True, read_only=True)
    centrifugo_channel = serializers.CharField(read_only=True)
    unread_count = serializers.SerializerMethodField()

    class Meta:
        model = ChatRoom
        fields = [
            'id',
            'room_type',
            'title',
            'display_title',
            'participant_users',
            'participant_institutions',
            'unread_count',
            'centrifugo_channel',
            'created_at',
            'updated_at',
        ]
        read_only_fields = fields

    @extend_schema_field(serializers.CharField)
    def get_display_title(self, obj) -> str:
        request = self.context.get('request')
        user = request.user if request else None
        return obj.get_display_title(user)

    @extend_schema_field(serializers.IntegerField)
    def get_unread_count(self, obj) -> int:
        request = self.context.get('request')
        if not request or not request.user.is_authenticated:
            return 0
        return obj.get_unread_count(request.user)


class ChatRoomCreateSerializer(serializers.Serializer):
    room_type = serializers.ChoiceField(
        choices=ChatRoom.RoomType.choices,
        default=ChatRoom.RoomType.DIRECT
    )
    title = serializers.CharField(required=False, allow_blank=True, max_length=255)
    target_user_id = serializers.IntegerField(required=False, allow_null=True)
    target_institution_id = serializers.IntegerField(required=False, allow_null=True)
    participant_user_ids = serializers.ListField(
        child=serializers.IntegerField(),
        required=False,
        default=list
    )
    participant_institution_ids = serializers.ListField(
        child=serializers.IntegerField(),
        required=False,
        default=list
    )
    initial_message = serializers.CharField(required=False, allow_blank=True)