import json

from django.contrib.auth.password_validation import validate_password
from django.db import transaction
from rest_framework import serializers

from .migration_service import migration_summary
from .models import InviteCode, InviteCodeUsage, User, VisitorMigration


class UserSerializer(serializers.ModelSerializer):
    class Meta:
        model = User
        fields = (
            "id",
            "username",
            "nickname",
            "avatar_url",
            "bio",
            "track",
            "rating",
            "is_staff",
        )
        read_only_fields = ("id", "rating", "is_staff")


class RegisterSerializer(serializers.Serializer):
    invite_code = serializers.CharField(max_length=32)
    username = serializers.RegexField(r"^[A-Za-z0-9_]{3,30}$")
    password = serializers.CharField(write_only=True, min_length=8)
    nickname = serializers.CharField(max_length=40)
    track = serializers.ChoiceField(choices=User.Track.choices, default=User.Track.STANDARD)
    visitor_data = serializers.JSONField(required=False, default=dict, write_only=True)

    def validate_username(self, value):
        if User.objects.filter(username__iexact=value).exists():
            raise serializers.ValidationError("用户名已存在")
        return value

    def validate_password(self, value):
        validate_password(value)
        return value

    def validate_visitor_data(self, value):
        if not isinstance(value, dict):
            raise serializers.ValidationError("游客数据必须是对象")
        for field in ("story_saves", "favorites", "cards"):
            if field in value and not isinstance(value[field], list):
                raise serializers.ValidationError(f"{field} 必须是数组")
        if "mathbti" in value and not isinstance(value["mathbti"], dict):
            raise serializers.ValidationError("mathbti 必须是对象")
        if len(json.dumps(value, ensure_ascii=False).encode("utf-8")) > 256 * 1024:
            raise serializers.ValidationError("游客数据不能超过 256KB")
        return value

    @transaction.atomic
    def create(self, validated_data):
        code_text = validated_data.pop("invite_code")
        visitor_data = validated_data.pop("visitor_data", {})
        try:
            invite = InviteCode.objects.select_for_update().get(code__iexact=code_text)
        except InviteCode.DoesNotExist as exc:
            raise serializers.ValidationError({"invite_code": "邀请码无效"}) from exc
        if not invite.is_available:
            raise serializers.ValidationError({"invite_code": "邀请码已过期或已用完"})

        user = User.objects.create_user(**validated_data)
        InviteCodeUsage.objects.create(
            invite_code=invite,
            user=user,
            ip_address=self.context.get("ip_address"),
        )
        invite.used_count += 1
        invite.save(update_fields=["used_count"])
        if visitor_data:
            VisitorMigration.objects.create(
                user=user,
                payload=visitor_data,
                summary=migration_summary(visitor_data),
            )
        return user