"""
DRF Serializers — validation, representation, and nested relations.
"""

from django.contrib.auth import get_user_model
from django.utils import timezone
from rest_framework import serializers
from rest_framework_simplejwt.serializers import TokenObtainPairSerializer

from api.models import (
    Caregiver, CaregiverService, Pet, Service,
    Booking, BookingStatus, Conversation, Message, Role,
)

User = get_user_model()


# ─────────────────────────────────────────────────────────────────────────────
# JWT Custom Claims
# ─────────────────────────────────────────────────────────────────────────────
class CustomTokenObtainPairSerializer(TokenObtainPairSerializer):
    @classmethod
    def get_token(cls, user):
        token = super().get_token(user)
        token['email'] = user.email
        token['role'] = user.role
        token['full_name'] = user.full_name
        return token

    def validate(self, attrs):
        data = super().validate(attrs)
        data['user'] = {
            'id': str(self.user.id),
            'email': self.user.email,
            'role': self.user.role,
            'full_name': self.user.full_name,
            'avatar_url': self.user.avatar_url,
        }
        return data


# ─────────────────────────────────────────────────────────────────────────────
# Auth Serializers
# ─────────────────────────────────────────────────────────────────────────────
class RegisterSerializer(serializers.ModelSerializer):
    password = serializers.CharField(write_only=True, min_length=10)
    password_confirm = serializers.CharField(write_only=True)

    class Meta:
        model = User
        fields = ['email', 'first_name', 'last_name', 'password', 'password_confirm']

    def validate(self, data):
        if data['password'] != data['password_confirm']:
            raise serializers.ValidationError({'password_confirm': 'Passwords do not match.'})
        return data

    def create(self, validated_data):
        validated_data.pop('password_confirm')
        return User.objects.create_user(
            role=Role.USER,
            **validated_data,
        )


class UserProfileSerializer(serializers.ModelSerializer):
    full_name = serializers.ReadOnlyField()

    class Meta:
        model = User
        fields = [
            'id', 'email', 'first_name', 'last_name', 'full_name',
            'role', 'phone', 'address', 'avatar_url', 'date_joined',
        ]
        read_only_fields = ['id', 'role', 'date_joined']


class UserPublicSerializer(serializers.ModelSerializer):
    """Minimal public view — no PII."""
    full_name = serializers.ReadOnlyField()

    class Meta:
        model = User
        fields = ['id', 'full_name', 'avatar_url']


# ─────────────────────────────────────────────────────────────────────────────
# Service
# ─────────────────────────────────────────────────────────────────────────────
class ServiceSerializer(serializers.ModelSerializer):
    class Meta:
        model = Service
        fields = '__all__'


# ─────────────────────────────────────────────────────────────────────────────
# Caregiver
# ─────────────────────────────────────────────────────────────────────────────
class CaregiverServiceSerializer(serializers.ModelSerializer):
    service_name = serializers.ReadOnlyField(source='service.name')
    service_icon = serializers.ReadOnlyField(source='service.icon')

    class Meta:
        model = CaregiverService
        fields = ['service', 'service_name', 'service_icon', 'price_per_hour', 'is_active']


class CaregiverListSerializer(serializers.ModelSerializer):
    """Lightweight serializer for list views / search."""
    full_name = serializers.ReadOnlyField(source='user.full_name')
    avatar_url = serializers.ReadOnlyField(source='user.avatar_url')

    class Meta:
        model = Caregiver
        fields = [
            'id', 'full_name', 'avatar_url', 'profile_image_url',
            'city', 'country', 'rating', 'total_reviews', 'total_bookings',
            'years_of_experience', 'specializations', 'is_available',
            'is_verified', 'is_featured',
        ]


class CaregiverDetailSerializer(serializers.ModelSerializer):
    """Full detail including services and user profile."""
    full_name = serializers.ReadOnlyField(source='user.full_name')
    email = serializers.ReadOnlyField(source='user.email')
    avatar_url = serializers.ReadOnlyField(source='user.avatar_url')
    caregiver_services = CaregiverServiceSerializer(
        source='caregiverservice_set', many=True, read_only=True
    )

    class Meta:
        model = Caregiver
        fields = [
            'id', 'full_name', 'email', 'avatar_url',
            'profile_image_url', 'gallery_images', 'bio',
            'years_of_experience', 'specializations', 'certifications', 'languages',
            'city', 'country', 'latitude', 'longitude',
            'rating', 'total_reviews', 'total_bookings',
            'is_available', 'is_verified', 'is_featured', 'background_check_passed',
            'caregiver_services', 'created_at',
        ]
        read_only_fields = ['rating', 'total_reviews', 'total_bookings', 'created_at']


class CaregiverWriteSerializer(serializers.ModelSerializer):
    """Admin-only — create/update caregiver profiles."""
    email = serializers.EmailField(write_only=True)
    first_name = serializers.CharField(write_only=True, max_length=100)
    last_name = serializers.CharField(write_only=True, max_length=100)
    password = serializers.CharField(write_only=True, min_length=10, required=False)

    class Meta:
        model = Caregiver
        fields = [
            'email', 'first_name', 'last_name', 'password',
            'bio', 'years_of_experience', 'specializations', 'certifications',
            'languages', 'city', 'country', 'latitude', 'longitude',
            'is_available', 'is_verified', 'is_featured', 'background_check_passed',
            'emergency_contact',
        ]

    def create(self, validated_data):
        email = validated_data.pop('email')
        first_name = validated_data.pop('first_name')
        last_name = validated_data.pop('last_name')
        password = validated_data.pop('password', User.objects.make_random_password(16))

        user = User.objects.create_user(
            email=email,
            first_name=first_name,
            last_name=last_name,
            password=password,
            role=Role.CAREGIVER,
        )
        return Caregiver.objects.create(user=user, **validated_data)

    def update(self, instance, validated_data):
        # Update nested user fields if provided
        for field in ('email', 'first_name', 'last_name'):
            val = validated_data.pop(field, None)
            if val:
                setattr(instance.user, field, val)
        password = validated_data.pop('password', None)
        if password:
            instance.user.set_password(password)
        instance.user.save()

        for attr, val in validated_data.items():
            setattr(instance, attr, val)
        instance.save()
        return instance


# ─────────────────────────────────────────────────────────────────────────────
# Pet
# ─────────────────────────────────────────────────────────────────────────────
class PetSerializer(serializers.ModelSerializer):
    class Meta:
        model = Pet
        fields = '__all__'
        read_only_fields = ['id', 'owner', 'created_at', 'updated_at']


# ─────────────────────────────────────────────────────────────────────────────
# Booking
# ─────────────────────────────────────────────────────────────────────────────
class BookingCreateSerializer(serializers.ModelSerializer):
    class Meta:
        model = Booking
        fields = [
            'caregiver', 'pet', 'service',
            'scheduled_start', 'scheduled_end',
            'notes', 'service_address',
        ]

    def validate(self, data):
        if data['scheduled_end'] <= data['scheduled_start']:
            raise serializers.ValidationError('End time must be after start time.')
        # Ensure pet belongs to the requesting user
        request = self.context['request']
        if data['pet'].owner != request.user:
            raise serializers.ValidationError({'pet': 'You can only book for your own pets.'})
        return data

    def create(self, validated_data):
        user = self.context['request'].user
        service = validated_data['service']
        caregiver = validated_data['caregiver']

        # Calculate pricing
        hours = (
            validated_data['scheduled_end'] - validated_data['scheduled_start']
        ).total_seconds() / 3600
        try:
            cs = CaregiverService.objects.get(
                caregiver=caregiver, service=service, is_active=True
            )
            subtotal = cs.price_per_hour * hours
        except CaregiverService.DoesNotExist:
            subtotal = service.base_price * hours

        fees = subtotal * 0.05   # 5% platform fee
        total = subtotal + fees

        return Booking.objects.create(
            user=user,
            price_subtotal=round(subtotal, 2),
            price_fees=round(fees, 2),
            price_total=round(total, 2),
            **validated_data,
        )


class BookingSerializer(serializers.ModelSerializer):
    user = UserPublicSerializer(read_only=True)
    caregiver = CaregiverListSerializer(read_only=True)
    service = ServiceSerializer(read_only=True)
    pet = PetSerializer(read_only=True)

    class Meta:
        model = Booking
        fields = '__all__'
        read_only_fields = [
            'id', 'user', 'price_subtotal', 'price_fees', 'price_total',
            'created_at', 'updated_at',
        ]


class BookingStatusUpdateSerializer(serializers.Serializer):
    status = serializers.ChoiceField(choices=BookingStatus.choices)
    cancellation_reason = serializers.CharField(required=False, allow_blank=True)


class BookingReviewSerializer(serializers.Serializer):
    rating = serializers.IntegerField(min_value=1, max_value=5)
    review = serializers.CharField(max_length=1000, allow_blank=True)

    def update(self, instance, validated_data):
        instance.rating = validated_data['rating']
        instance.review = validated_data.get('review', '')
        instance.reviewed_at = timezone.now()
        instance.save()

        # Update caregiver aggregate rating
        caregiver = instance.caregiver
        bookings_with_reviews = Booking.objects.filter(
            caregiver=caregiver, rating__isnull=False
        )
        count = bookings_with_reviews.count()
        if count:
            avg = sum(b.rating for b in bookings_with_reviews) / count
            caregiver.rating = round(avg, 2)
            caregiver.total_reviews = count
            caregiver.save(update_fields=['rating', 'total_reviews'])
        return instance


# ─────────────────────────────────────────────────────────────────────────────
# Messaging
# ─────────────────────────────────────────────────────────────────────────────
class MessageSerializer(serializers.ModelSerializer):
    sender = UserPublicSerializer(read_only=True)

    class Meta:
        model = Message
        fields = [
            'id', 'conversation', 'sender', 'message_type',
            'content', 'image_url', 'is_read', 'read_at', 'created_at',
        ]
        read_only_fields = ['id', 'sender', 'is_read', 'read_at', 'created_at']


class ConversationSerializer(serializers.ModelSerializer):
    participants = UserPublicSerializer(many=True, read_only=True)
    last_message = serializers.SerializerMethodField()
    unread_count = serializers.SerializerMethodField()

    class Meta:
        model = Conversation
        fields = [
            'id', 'participants', 'booking', 'last_message',
            'unread_count', 'created_at', 'updated_at',
        ]

    def get_last_message(self, obj):
        msg = obj.messages.last()
        if msg:
            return {'content': msg.content[:80], 'created_at': msg.created_at}
        return None

    def get_unread_count(self, obj):
        user = self.context['request'].user
        return obj.messages.filter(is_read=False).exclude(sender=user).count()


# ─────────────────────────────────────────────────────────────────────────────
# Image Upload
# ─────────────────────────────────────────────────────────────────────────────
class ImageUploadSerializer(serializers.Serializer):
    image = serializers.ImageField()
    folder = serializers.ChoiceField(
        choices=['caregivers', 'pets', 'messages'],
        default='caregivers',
    )