implemented is_valid()

facturx/facturx.py

@@ -128,7 +128,48 @@ def is_valid(self):
 
         Returns: true/false (validation passed/failed)
         """
-        pass
+        # Check XSD
+        try:
+            self.flavor.check_xsd(self.xml)
+            check_pass = True
+        except Exception:
+            check_pass = False
+
+        # Check required field is present
+        self.__make_dict()
+
+        if self.flavor.name == 'factur-x':
+            flavor_dict = self.factx
+            ns = {'xsi': 'http://www.w3.org/2001/XMLSchema-instance',
+                  'udt': 'urn:un:unece:uncefact:data:standard:UnqualifiedDataType:100',
+                  'rsm': 'urn:un:unece:uncefact:data:standard:CrossIndustryInvoice:100',
+                  'ram': 'urn:un:unece:uncefact:data:standard:ReusableAggregateBusinessInformationEntity:100',
+                  'qdt': 'urn:un:unece:uncefact:data:standard:QualifiedDataType:100'
+                  }
+        elif self.flavor.name == 'zugferd':
+            flavor_dict = self.zugf
+            ns = {'udt': 'urn:un:unece:uncefact:data:standard:UnqualifiedDataType:15',
+                  'ram': 'urn:un:unece:uncefact:data:standard:ReusableAggregateBusinessInformationEntity:12',
+                  'rsm': 'urn:ferd:CrossIndustryDocument:invoice:1p0',
+                  'xsi': 'http://www.w3.org/2001/XMLSchema-instance'
+                  }
+
+        tree = self._xml_from_file(self.pdf)
+
+        if tree is not None:
+            for k, v in flavor_dict.items():
+                try:
+                    r = tree.xpath(v, namespaces=ns)
+                    if r[0].text is None:
+                        check_pass = False
+                except IndexError:
+                    logger.error("Required field %s is empty", k)
+                    check_pass = False
+
+        if check_pass:
+            return True
+        else:
+            return False
 
     def write_pdf(self, path):
         pdfwriter = FacturXPDFWriter(self)