refactor models, change map package storage and map package loading

src/c3nav/mapdata/models/level.py

@@ -1,3 +1,5 @@
+from collections import OrderedDict
+
 from django.db import models
 from django.utils.translation import ugettext_lazy as _
 
@@ -12,5 +14,25 @@ class Level(models.Model):
     package = models.ForeignKey('Package', on_delete=models.CASCADE, related_name='levels',
                                 verbose_name=_('map package'))
 
+    def jsonize(self):
+        return OrderedDict((
+            ('name', self.name),
+            ('altitude', float(self.altitude)),
+        ))
+
+    @classmethod
+    def fromfile(cls, data, package, name):
+        if 'altitude' not in data:
+            raise ValueError('%s.json: missing altitude.' % name)
+
+        if not isinstance(data['altitude'], (int, float)):
+            raise ValueError('%s.json: altitude has to be in or float.')
+
+        return {
+            'package': package,
+            'name': name,
+            'altitude': data['altitude'],
+        }
+
     class Meta:
         ordering = ['altitude']