boards/models/signature.py

import xml.etree.ElementTree as et
from django.db import models


ATTR_KEY = 'key'
ATTR_KEY_TYPE = 'type'
ATTR_LOCAL_ID = 'local-id'


class GlobalId(models.Model):
    class Meta:
        app_label = 'boards'

    def __init__(self, *args, **kwargs):
        models.Model.__init__(self, *args, **kwargs)

        if 'key' in kwargs and 'key_type' in kwargs and 'local_id' in kwargs:
            self.key = kwargs['key']
            self.key_type = kwargs['key_type']
            self.local_id = kwargs['local_id']

    key = models.TextField()
    key_type = models.TextField()
    local_id = models.IntegerField()

    def __str__(self):
        return '%s | %s | %d' % (self.key_type, self.key, self.local_id)

    def to_xml_element(self, element: et.Element):
        """
        Exports global id to an XML element.
        """

        element.set(ATTR_KEY, self.key)
        element.set(ATTR_KEY_TYPE, self.key_type)
        element.set(ATTR_LOCAL_ID, str(self.local_id))

    @staticmethod
    def from_xml_element(element: et.Element, existing=False):
        """
        Parses XML id tag and gets global id from it.

        Arguments:
        element -- the XML 'id' element
        existing -- if this is False, a new instance of GlobalId will be
         created. Otherwise, we will search for an existing GlobalId instance
         and throw DoesNotExist if there isn't one.
        """

        if existing:
            return GlobalId.objects.get(key=element.get(ATTR_KEY),
                                        key_type=element.get(ATTR_KEY_TYPE),
                                        local_id=int(element.get(
                                            ATTR_LOCAL_ID)))
        else:
            return GlobalId(key=element.get(ATTR_KEY),
                            key_type=element.get(ATTR_KEY_TYPE),
                            local_id=int(element.get(ATTR_LOCAL_ID)))


class Signature(models.Model):
    class Meta:
        app_label = 'boards'

    key_type = models.TextField()
    key = models.TextField()
    signature = models.TextField()