Adding a form field to validate Processo Numbers

A form field that validates a Legal Process(Processo) number or a Legal Process string.

Author: ffreitasalves

localflavor/br/forms.py

@@ -197,3 +197,51 @@ def clean(self, value):
             raise ValidationError(self.error_messages['invalid'])
 
         return orig_value
+
+
+def mod_97_base10(value):
+    return 98 - ((value * 100 % 97) % 97)
+
+
+class BRProcessoField(CharField):
+    """
+    A form field that validates a Legal Process(Processo) number or a Legal Process string.
+    A Processo number is
+    compounded by NNNNNNN-DD.AAAA.J.TR.OOOO. The two DD digits are check digits.
+    More information:
+    http://www.cnj.jus.br/atos-administrativos/12179:resolucao-no-65-de-16-de-dezembro-de-2008
+    """
+    default_error_messages = {
+        'invalid': _("Invalid Process number."),
+        'max_digits': _("This field requires at most 20 digits or 25 characters."),
+        'digits_only': _("This field requires only numbers."),
+    }
+
+    def __init__(self, max_length=25, min_length=20, *args, **kwargs):
+        super(BRProcessoField, self).__init__(max_length, min_length, *args, **kwargs)
+
+    def clean(self, value):
+        """
+        Value can be either a string in the format NNNNNNN-DD.AAAA.J.TR.OOOO or an
+        20-digit number.
+        """
+        value = super(BRProcessoField, self).clean(value)
+        if value in EMPTY_VALUES:
+            return ''
+        orig_value = value[:]
+        if not value.isdigit():
+            value = re.sub("[-\. ]", "", value)
+        try:
+            int(value)
+        except ValueError:
+            raise ValidationError(self.error_messages['digits_only'])
+        if len(value) != 20:
+            raise ValidationError(self.error_messages['max_digits'])
+        orig_dv = value[7:9]
+
+        value_without_digits = int(value[0:7] + value[9:])
+
+        if str(mod_97_base10(value_without_digits)).zfill(2) != orig_dv:
+            raise ValidationError(self.error_messages['invalid'])
+
+        return orig_value