# -*- coding: utf-8 -*-

'''

Created on Sep 19, 2013

@author: ymh

'''

import logging

from rdflib.namespace import RDF

from rdflib.term import URIRef, Literal, BNode

from collections import OrderedDict

logger = logging.getLogger(__name__)

class BaseSerializer(object):

    creation_counter = 0

    def __init__(self, predicate=None, many=False):

        self.predicate = predicate

        self.creation_counter = BaseSerializer.creation_counter

        self.many = many

        BaseSerializer.creation_counter += 1

        if self.predicate and not isinstance(self.predicate, URIRef):

            self.predicate = URIRef(predicate)

class FieldSerializer(BaseSerializer):

    def __init__(self, predicate=None, convert=None, source=None, many=False):

        super(FieldSerializer, self).__init__(predicate=predicate, many=many)

        self.convert = convert or (lambda x: Literal(unicode(x)) if x else None)

        self.source = source

    def get_rdf_object(self, obj, fieldname):

        raise NotImplemented()

    def to_graph(self, subject, obj, fieldname, graph):

        o = self.get_rdf_object(obj, fieldname)

        if o:

            graph.add((subject, self.predicate, o))

class SimpleFieldSerializer(FieldSerializer):

    def __init__(self, predicate=None, convert=None, source=None, lang_field=None):

        super(SimpleFieldSerializer, self).__init__(predicate=predicate, convert=convert, source=source, many=False)

        self.lang_field = lang_field

    def get_rdf_object(self, obj, fieldname):

        res = self.convert(getattr(obj, self.source or fieldname))

        if res is None:

            return

        if not isinstance(res, Literal):

            res = Literal(unicode(res))        

        lang = getattr(obj, self.lang_field, None) if self.lang_field else None

        return Literal(res.value, lang) if lang else res

class BooleanFieldSerializer(SimpleFieldSerializer):

    def bool_convert(self, value):

        return (Literal('TRUE') if value else Literal('FALSE')) if value is not None else None

    def __init__(self, predicate=None, convert=None, source=None, lang_field=None):

        super(BooleanFieldSerializer, self).__init__( predicate, convert=convert, source=source, lang_field=lang_field)

        self.convert = lambda x: self.bool_convert(x)

class RelatedFieldSerializer(SimpleFieldSerializer):

    def __init__(self, value_field, predicate=None, convert=None, source=None, many=False, lang_field=None):

        super(RelatedFieldSerializer, self).__init__(predicate, convert, source, lang_field=lang_field)

        self.many = many

        self.value_field = value_field

    def to_graph(self, subject, obj, fieldname, graph):

        value = getattr(obj, fieldname, None)

        if not value:

            return

        values_to_add = []

        if self.many:

            for related_obj in value.all():

                values_to_add.append(self.get_rdf_object(related_obj, self.value_field))

        else:

            values_to_add.append(self.get_rdf_object(value, self.value_field))

        for o in values_to_add:

            if o:

                graph.add((subject, self.predicate, o))

# Directly adapted from serializers in rest_framework 

def _get_declared_fields(bases, attrs):

    """

    Create a list of serializer field instances from the passed in 'attrs',

    plus any fields on the base classes (in 'bases').

    Note that all fields from the base classes are used.

    """

    fields = [(field_name, attrs.pop(field_name))

              for field_name, obj in list(attrs.iteritems())

              if isinstance(obj, BaseSerializer)]

    fields.sort(key=lambda x: x[1].creation_counter)

    # If this class is subclassing another Serializer, add that Serializer's

    # fields.  Note that we loop over the bases in *reverse*. This is necessary

    # in order to maintain the correct order of fields.

    for base in bases[::-1]:

        if hasattr(base, 'base_serializers'):

            fields = list(base.base_serializers.items()) + fields

    return OrderedDict(fields)

class SerializerMetaclass(type):

    def __new__(cls, name, bases, attrs):

        attrs['base_serializers'] = _get_declared_fields(bases, attrs)

        return super(SerializerMetaclass, cls).__new__(cls, name, bases, attrs)

class ModelSerializerOptions(object):

    def __init__(self, meta):

        self.type = getattr(meta, 'type', None)

        if self.type and not isinstance(self.type, URIRef):

            self.type = URIRef(self.type)

        self.uri_fieldname = getattr(meta, 'uri_fieldname', None)

class ModelSerializer(BaseSerializer):

    __metaclass__ =  SerializerMetaclass

    class Meta(object):

        pass

    def get_serializers(self):

        return []

    def get_uri(self, obj):

        uri = None

        if self.opts.uri_fieldname:

            uri = getattr(obj, self.opts.uri_fieldname, None)            

        return URIRef(uri) if uri else None

    def object_to_graph(self, subject, uri, obj, graph):

        if self.predicate:

            graph.add((subject, self.predicate, uri))

        for serializer_fieldname, field_serializer in self.base_serializers.iteritems():

            field_serializer.to_graph(uri, obj, serializer_fieldname, graph)

    def to_graph(self, subject, obj, fieldname, graph):        

        uri = self.get_uri(obj)

        if self.opts.type:

            graph.add((uri, RDF.type, self.opts.type))

        obj_to_add = []

        if fieldname:

            field_value = getattr(obj, fieldname, None)

            if field_value:

                if self.many:

                    obj_to_add = [(nested_obj, BNode()) for nested_obj in field_value.all()]

                else:

                    obj_to_add = [(field_value, BNode())]

        else:

            obj_to_add = [(obj, uri)]

        for nested_obj, nested_uri in obj_to_add:

            self.object_to_graph( subject, nested_uri, nested_obj, graph)

    def __init__(self, predicate=None, many=False):

        BaseSerializer.__init__(self, predicate=predicate, many=many)

        self.opts = ModelSerializerOptions(self.Meta)