'''Metadata handling commonalities
'''

from urllib import unquote_plus

from django.shortcuts import get_object_or_404
from django.core.exceptions import ObjectDoesNotExist

from documents.models import DocumentMetadata, MetadataType


def decode_metadata_from_url(url_dict):
    '''Parses a URL query string to a list of metadata
    '''
    metadata_dict = {
        'id': {},
        'value': {}
    }
    metadata_list = []
    #Match out of order metadata_type ids with metadata values from request
    for key, value in url_dict.items():
        if 'metadata' in key:
            index, element = key[8:].split('_')
            metadata_dict[element][index] = value

    #Convert the nested dictionary into a list of id+values dictionaries
    for order, identifier in metadata_dict['id'].items():
        if order in metadata_dict['value'].keys():
            metadata_list.append({
                'id': identifier,
                'value': metadata_dict['value'][order]
            })

    return metadata_list


def save_metadata_list(metadata_list, document):
    '''Takes a list of metadata values and associates a document to it
    '''
    for item in metadata_list:
        if item['value']:
            save_metadata(item, document)
        else:
            #If there is no metadata value, delete the metadata entry
            #completely from the document
            try:
                metadata_type = MetadataType.objects.get(id=item['id'])
                document_metadata = DocumentMetadata.objects.get(
                    document=document,
                    metadata_type=metadata_type
                )
                document_metadata.delete()
            except ObjectDoesNotExist:
                pass


def save_metadata(metadata_dict, document):
    '''save metadata_dict
    '''
    #Use matched metadata now to create document metadata
    document_metadata, created = DocumentMetadata.objects.get_or_create(
        document=document,
        metadata_type=get_object_or_404(
            MetadataType,
            pk=metadata_dict['id']
        ),
    )
    #Handle 'plus sign as space' in the url

    #unquote_plus handles utf-8?!?
    #http://stackoverflow.com/questions/4382875/handling-iri-in-django
    #.decode('utf-8')
    document_metadata.value = unquote_plus(metadata_dict['value'])
    document_metadata.save()


def metadata_repr(metadata_list):
    '''Return a printable representation of a metadata list
    '''
    return ', '.join(metadata_repr_as_list(metadata_list))


def metadata_repr_as_list(metadata_list):
    '''Turn a list of metadata into a list of printable representations
    '''
    output = []
    for metadata_dict in metadata_list:
        try:
            output.append(u'%s - %s' % (MetadataType.objects.get(
                pk=metadata_dict['id']), metadata_dict.get('value', '')))
        except:
            pass

    return output