from __future__ import unicode_literals

from django.db import IntegrityError
from django.utils.translation import ugettext_lazy as _

from rest_framework import serializers
from rest_framework.exceptions import ValidationError

from .models import DocumentMetadata, MetadataType, DocumentTypeMetadataType


class MetadataTypeSerializer(serializers.ModelSerializer):
    class Meta:
        fields = (
            'id', 'name', 'label', 'default', 'lookup', 'parser', 'validation'
        )
        model = MetadataType


class DocumentMetadataSerializer(serializers.ModelSerializer):
    document = serializers.PrimaryKeyRelatedField(read_only=True)

    class Meta:
        fields = ('document', 'id', 'metadata_type', 'value',)
        model = DocumentMetadata
        read_only_fields = ('metadata_type',)


class DocumentTypeMetadataTypeSerializer(serializers.ModelSerializer):
    class Meta:
        fields = ('metadata_type',)
        model = DocumentTypeMetadataType


class DocumentNewMetadataSerializer(serializers.Serializer):
    metadata_type_pk = serializers.IntegerField(
        help_text=_('Primary key of the metadata type to be added.'),
        write_only=True
    )

    metadata_type = MetadataTypeSerializer(read_only=True)

    pk = serializers.IntegerField(
        help_text=_('Primary key of the document metadata type.'),
        read_only=True
    )

    value = serializers.CharField(
        max_length=255,
        help_text=_('Value of the corresponding metadata type instance.')
    )

    def create(self, validated_data):
        metadata_type = MetadataType.objects.get(
            pk=validated_data['metadata_type_pk']
        )
        try:
            instance = self.document.metadata.create(
                metadata_type=metadata_type, value=validated_data['value']
            )
            return instance
        except IntegrityError:
            detail = 'Metadata type with pk {} is already defined for Document with pk {}'.format(metadata_type.pk,
                                                                                                  self.document.pk)
            raise ValidationError(detail)


class DocumentTypeNewMetadataTypeSerializer(serializers.Serializer):
    metadata_type_pk = serializers.IntegerField(
        help_text=_('Primary key of the metadata type to be added.')
    )