from rest_framework import serializers
from .models import ContactUs, Composition, Campaign, CompositionImage


class ContactUsSerializer(serializers.ModelSerializer):
    """
    Serializer for ContactUs model.
    """
    class Meta:
        model = ContactUs
        fields = ['id', 'name', 'email_or_phone', 'description', 'category', 
                  'created_at', 'updated_at']
        read_only_fields = ['id', 'created_at', 'updated_at']
    
    def validate_email_or_phone(self, value):
        """Validate that the field contains either email or phone."""
        if not value or len(value.strip()) == 0:
            raise serializers.ValidationError("Email or phone number is required.")
        return value.strip()
    
    def validate_name(self, value):
        """Validate name field."""
        if not value or len(value.strip()) == 0:
            raise serializers.ValidationError("Name is required.")
        return value.strip()
    
    def validate_description(self, value):
        """Validate description field."""
        if not value or len(value.strip()) == 0:
            raise serializers.ValidationError("Description is required.")
        return value.strip()


# Accepted image content types and max upload size (5 MB).
ALLOWED_IMAGE_CONTENT_TYPES = ['image/jpeg', 'image/png', 'image/webp', 'image/gif']
MAX_IMAGE_SIZE = 5 * 1024 * 1024


def validate_uploaded_image(image):
    """Reject anything that is not a real, reasonably sized image file."""
    content_type = getattr(image, 'content_type', None)
    if content_type and content_type not in ALLOWED_IMAGE_CONTENT_TYPES:
        raise serializers.ValidationError(
            f"Unsupported image type '{content_type}'. "
            f"Allowed: {', '.join(ALLOWED_IMAGE_CONTENT_TYPES)}."
        )
    if image.size > MAX_IMAGE_SIZE:
        raise serializers.ValidationError(
            f"Image too large ({image.size} bytes). Max allowed is {MAX_IMAGE_SIZE} bytes."
        )
    return image


class CompositionImageSerializer(serializers.ModelSerializer):
    """
    Serializer for a single image belonging to a Composition.
    """
    image_url = serializers.SerializerMethodField()
    
    class Meta:
        model = CompositionImage
        fields = ['id', 'image', 'image_url', 'is_main', 'created_at']
        read_only_fields = ['id', 'image_url', 'created_at']
    
    def get_image_url(self, obj):
        """Get the full URL of the image."""
        if obj.image:
            request = self.context.get('request')
            if request:
                return request.build_absolute_uri(obj.image.url)
            return obj.image.url
        return None


class CompositionSerializer(serializers.ModelSerializer):
    """
    Serializer for Composition model.

    Read: returns the nested ``images`` list plus ``main_image``.
    Write: accepts ``uploaded_images`` (one or more files) and an optional
    ``main_image_index`` pointing at which uploaded file is the main image.
    """
    # Legacy single image URL (kept for backward compatibility).
    image_url = serializers.SerializerMethodField()
    images = CompositionImageSerializer(many=True, read_only=True)
    main_image = serializers.SerializerMethodField()
    
    # Write-only upload fields.
    uploaded_images = serializers.ListField(
        child=serializers.ImageField(validators=[validate_uploaded_image]),
        write_only=True,
        required=False,
    )
    main_image_index = serializers.IntegerField(
        write_only=True,
        required=False,
        min_value=0,
        help_text='0-based index into uploaded_images marking the main image.'
    )
    
    class Meta:
        model = Composition
        fields = ['id', 'name', 'description', 'image', 'image_url',
                  'images', 'main_image', 'uploaded_images', 'main_image_index',
                  'created_at', 'updated_at']
        read_only_fields = ['id', 'created_at', 'updated_at', 'image_url',
                            'images', 'main_image']
    
    def get_image_url(self, obj):
        """Get the full URL of the legacy image field."""
        if obj.image:
            request = self.context.get('request')
            if request:
                return request.build_absolute_uri(obj.image.url)
            return obj.image.url
        return None
    
    def get_main_image(self, obj):
        """Return the serialized main image, if any."""
        main = obj.main_image
        if main:
            return CompositionImageSerializer(main, context=self.context).data
        return None
    
    def validate_name(self, value):
        """Validate name field."""
        if not value or len(value.strip()) == 0:
            raise serializers.ValidationError("Name is required.")
        return value.strip()
    
    def validate_description(self, value):
        """Validate description field."""
        if not value or len(value.strip()) == 0:
            raise serializers.ValidationError("Description is required.")
        return value.strip()
    
    def to_internal_value(self, data):
        """
        MultiPartParser stores repeated file fields as a QueryDict where only
        the last value is returned by .get(). Pull the full list explicitly.
        """
        if hasattr(data, 'getlist'):
            uploaded = data.getlist('uploaded_images')
            if uploaded:
                mutable = data.copy()
                mutable.setlist('uploaded_images', uploaded)
                data = mutable
        return super().to_internal_value(data)
    
    def validate(self, data):
        """Ensure main_image_index points at an actually uploaded image."""
        uploaded = data.get('uploaded_images')
        index = data.get('main_image_index')
        if index is not None:
            if not uploaded:
                raise serializers.ValidationError({
                    'main_image_index': 'Cannot set a main image without uploaded_images.'
                })
            if index >= len(uploaded):
                raise serializers.ValidationError({
                    'main_image_index': f'Index out of range (got {index}, '
                                        f'{len(uploaded)} image(s) uploaded).'
                })
        return data
    
    def _save_images(self, composition, uploaded_images, main_index):
        """Persist uploaded images, flagging the chosen one as main."""
        # If the composition has no main image yet, default the first upload to main.
        has_main = composition.images.filter(is_main=True).exists()
        for i, image_file in enumerate(uploaded_images):
            is_main = (i == main_index) if main_index is not None else (
                i == 0 and not has_main
            )
            CompositionImage.objects.create(
                composition=composition,
                image=image_file,
                is_main=is_main,
            )
    
    def create(self, validated_data):
        uploaded_images = validated_data.pop('uploaded_images', [])
        main_index = validated_data.pop('main_image_index', None)
        composition = super().create(validated_data)
        if uploaded_images:
            self._save_images(composition, uploaded_images, main_index)
        return composition
    
    def update(self, instance, validated_data):
        uploaded_images = validated_data.pop('uploaded_images', [])
        main_index = validated_data.pop('main_image_index', None)
        composition = super().update(instance, validated_data)
        if uploaded_images:
            self._save_images(composition, uploaded_images, main_index)
        return composition


class CampaignSerializer(serializers.ModelSerializer):
    """
    Serializer for Campaign model.
    """
    image_url = serializers.SerializerMethodField()
    is_active = serializers.SerializerMethodField()
    is_upcoming = serializers.SerializerMethodField()
    is_ended = serializers.SerializerMethodField()
    
    class Meta:
        model = Campaign
        fields = ['id', 'name', 'description', 'start_time', 'end_time', 
                  'image', 'image_url', 'is_active', 'is_upcoming', 'is_ended',
                  'created_at', 'updated_at']
        read_only_fields = ['id', 'created_at', 'updated_at', 'image_url', 
                           'is_active', 'is_upcoming', 'is_ended']
    
    def get_image_url(self, obj):
        """Get the full URL of the image."""
        if obj.image:
            request = self.context.get('request')
            if request:
                return request.build_absolute_uri(obj.image.url)
            return obj.image.url
        return None
    
    def get_is_active(self, obj):
        """Get campaign active status."""
        return obj.is_active()
    
    def get_is_upcoming(self, obj):
        """Get campaign upcoming status."""
        return obj.is_upcoming()
    
    def get_is_ended(self, obj):
        """Get campaign ended status."""
        return obj.is_ended()
    
    def validate(self, data):
        """Validate that end_time is after start_time."""
        if 'start_time' in data and 'end_time' in data:
            if data['end_time'] <= data['start_time']:
                raise serializers.ValidationError({
                    'end_time': 'End time must be after start time.'
                })
        return data
    
    def validate_name(self, value):
        """Validate name field."""
        if not value or len(value.strip()) == 0:
            raise serializers.ValidationError("Name is required.")
        return value.strip()
    
    def validate_description(self, value):
        """Validate description field."""
        if not value or len(value.strip()) == 0:
            raise serializers.ValidationError("Description is required.")
        return value.strip()