from rest_framework import serializers
from django.contrib.auth import get_user_model
from django.contrib.auth.password_validation import validate_password
from django.core.exceptions import ValidationError
from django.utils.crypto import get_random_string
from django.utils import timezone
from datetime import timedelta
from django.contrib.sites.shortcuts import get_current_site
from .models import User, PasswordReset
from apps.email_service.services import EmailService
from django.template.loader import render_to_string

UserModel = get_user_model()


class UserSerializer(serializers.ModelSerializer):
    """
    User serializer for API responses
    """
    avatar_url = serializers.SerializerMethodField()

    class Meta:
        model = User
        fields = [
            'id', 'username', 'email', 'first_name', 'last_name',
            'date_joined', 'is_active', 'avatar_url'
        ]
        read_only_fields = ['id', 'date_joined', 'is_active']

    def get_avatar_url(self, obj):
        """Get user avatar URL"""
        if hasattr(obj, 'profile') and obj.profile.avatar:
            return obj.profile.avatar.url
        return None


class LoginSerializer(serializers.Serializer):
    """
    Serializer for user login
    """
    username = serializers.CharField(
        max_length=254,
        help_text="Username or email address"
    )
    password = serializers.CharField(
        max_length=128,
        style={'input_type': 'password'},
        trim_whitespace=False
    )

    def validate(self, attrs):
        username = attrs.get('username')
        password = attrs.get('password')

        if username and password:
            return attrs

        raise serializers.ValidationError(
            'Must include username/email and password.'
        )


class SignupSerializer(serializers.ModelSerializer):
    """
    Serializer for user registration
    """
    password = serializers.CharField(
        write_only=True,
        validators=[validate_password],
        style={'input_type': 'password'}
    )
    password_confirm = serializers.CharField(
        write_only=True,
        style={'input_type': 'password'}
    )

    class Meta:
        model = User
        fields = [
            'username', 'email', 'first_name', 'last_name',
            'password', 'password_confirm'
        ]
        extra_kwargs = {
            'password': {'write_only': True},
            'email': {'required': True},
        }

    def validate_email(self, value):
        """Validate email is unique"""
        if UserModel.objects.filter(email=value).exists():
            raise serializers.ValidationError(
                "A user with this email already exists."
            )
        return value

    def validate_username(self, value):
        """Validate username is unique"""
        if UserModel.objects.filter(username=value).exists():
            raise serializers.ValidationError(
                "A user with this username already exists."
            )
        return value

    def validate(self, attrs):
        """Validate passwords match"""
        password = attrs.get('password')
        password_confirm = attrs.get('password_confirm')

        if password != password_confirm:
            raise serializers.ValidationError({
                'password_confirm': 'Passwords do not match.'
            })

        return attrs

    def create(self, validated_data):
        """Create user with validated data"""
        validated_data.pop('password_confirm', None)
        password = validated_data.pop('password')

        user = UserModel.objects.create(
            **validated_data
        )
        user.set_password(password)
        user.save()

        return user


class PasswordResetSerializer(serializers.Serializer):
    """
    Serializer for password reset request
    """
    email = serializers.EmailField()

    def validate_email(self, value):
        """Validate email exists"""
        try:
            user = UserModel.objects.get(email=value)
            self.user = user
            return value
        except UserModel.DoesNotExist:
            # Don't reveal if email exists or not for security
            return value

    def save(self, **kwargs):
        """Send password reset email if user exists"""
        if hasattr(self, 'user'):
            # Create password reset token
            token = get_random_string(64)
            PasswordReset.objects.update_or_create(
                user=self.user,
                defaults={
                    'token': token,
                    'expires_at': timezone.now() + timedelta(hours=24),
                    'used': False
                }
            )

            # Send reset email
            request = self.context.get('request')
            if request:
                site = get_current_site(request)
                reset_url = f"{request.scheme}://{site.domain}/reset-password/{token}/"

                context = {
                    'user': self.user,
                    'reset_url': reset_url,
                    'site_name': site.name,
                }

                email_html = render_to_string(
                    'accounts/email/password_reset.html',
                    context
                )

                EmailService.send_email(
                    to=getattr(self.user, 'email', None),
                    subject="Reset your password",
                    text=f"Click the link to reset your password: {reset_url}",
                    site=site,
                    html=email_html,
                )


class PasswordChangeSerializer(serializers.Serializer):
    """
    Serializer for password change
    """
    old_password = serializers.CharField(
        max_length=128,
        style={'input_type': 'password'}
    )
    new_password = serializers.CharField(
        max_length=128,
        validators=[validate_password],
        style={'input_type': 'password'}
    )
    new_password_confirm = serializers.CharField(
        max_length=128,
        style={'input_type': 'password'}
    )

    def validate_old_password(self, value):
        """Validate old password is correct"""
        user = self.context['request'].user
        if not user.check_password(value):
            raise serializers.ValidationError(
                'Old password is incorrect.'
            )
        return value

    def validate(self, attrs):
        """Validate new passwords match"""
        new_password = attrs.get('new_password')
        new_password_confirm = attrs.get('new_password_confirm')

        if new_password != new_password_confirm:
            raise serializers.ValidationError({
                'new_password_confirm': 'New passwords do not match.'
            })

        return attrs

    def save(self, **kwargs):
        """Change user password"""
        user = self.context['request'].user
        new_password = self.initial_data.get(
            'new_password') if self.initial_data else None

        if new_password is None:
            raise serializers.ValidationError('New password is required.')

        user.set_password(new_password)
        user.save()

        return user


class SocialProviderSerializer(serializers.Serializer):
    """
    Serializer for social authentication providers
    """
    id = serializers.CharField()
    name = serializers.CharField()
    login_url = serializers.URLField()