from django.contrib.auth import get_user_model
from django.contrib.auth.password_validation import validate_password
from rest_framework import serializers

User = get_user_model()


class RegisterSerializer(serializers.Serializer):
    username = serializers.CharField(max_length=150)
    email = serializers.EmailField(required=False, allow_blank=True)
    password = serializers.CharField(write_only=True, min_length=8)

    def validate_username(self, value):
        username = value.strip()
        if not username:
            raise serializers.ValidationError('Укажите имя пользователя.')
        if User.objects.filter(username__iexact=username).exists():
            raise serializers.ValidationError('Это имя пользователя уже занято.')
        return username

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

    def create(self, validated_data):
        email = (validated_data.get('email') or '').strip()
        return User.objects.create_user(
            username=validated_data['username'],
            email=email,
            password=validated_data['password'],
        )


class UserSerializer(serializers.ModelSerializer):
    class Meta:
        model = User
        fields = ['id', 'username', 'email']
        read_only_fields = fields


class UpdateProfileSerializer(serializers.Serializer):
    username = serializers.CharField(max_length=150, required=False)
    email = serializers.EmailField(required=False, allow_blank=True)
    current_password = serializers.CharField(write_only=True)

    def validate_current_password(self, value):
        user = self.context['request'].user
        if not user.check_password(value):
            raise serializers.ValidationError('Неверный текущий пароль.')
        return value

    def validate_username(self, value):
        username = value.strip()
        if not username:
            raise serializers.ValidationError('Укажите имя пользователя.')
        user = self.context['request'].user
        if User.objects.filter(username__iexact=username).exclude(pk=user.pk).exists():
            raise serializers.ValidationError('Это имя пользователя уже занято.')
        return username

    def validate(self, data):
        if 'username' not in data and 'email' not in data:
            raise serializers.ValidationError('Укажите новое имя пользователя или email.')
        return data

    def save(self):
        user = self.context['request'].user
        if 'username' in self.validated_data:
            user.username = self.validated_data['username']
        if 'email' in self.validated_data:
            user.email = (self.validated_data.get('email') or '').strip()
        user.save(update_fields=['username', 'email'])
        return user


class ChangePasswordSerializer(serializers.Serializer):
    current_password = serializers.CharField(write_only=True)
    new_password = serializers.CharField(write_only=True, min_length=8)

    def validate_current_password(self, value):
        user = self.context['request'].user
        if not user.check_password(value):
            raise serializers.ValidationError('Неверный текущий пароль.')
        return value

    def validate_new_password(self, value):
        validate_password(value, self.context['request'].user)
        return value

    def save(self):
        user = self.context['request'].user
        user.set_password(self.validated_data['new_password'])
        user.save(update_fields=['password'])
        return user