From 5c9090b369440885e2c3a68eba46c6fb8baace97 Mon Sep 17 00:00:00 2001
From: Arthur de Jong <arthur@arthurdejong.org>
Date: Fri, 3 May 2013 22:52:17 +0200
Subject: Implement validate() for the Verhoeff checksum

---
 stdnum/verhoeff.py          | 32 +++++++++++++++++++++++++-------
 tests/test_verhoeff.doctest | 30 +++++++++++++++++-------------
 2 files changed, 42 insertions(+), 20 deletions(-)

diff --git a/stdnum/verhoeff.py b/stdnum/verhoeff.py
index 69fb4b7..4fb9315 100644
--- a/stdnum/verhoeff.py
+++ b/stdnum/verhoeff.py
@@ -1,6 +1,6 @@
 # verhoeff.py - functions for performing the Verhoeff checksum
 #
-# Copyright (C) 2010, 2011, 2012 Arthur de Jong
+# Copyright (C) 2010, 2011, 2012, 2013 Arthur de Jong
 #
 # This library is free software; you can redistribute it and/or
 # modify it under the terms of the GNU Lesser General Public
@@ -22,16 +22,21 @@
 The Verhoeff algorithm uses two tables for permutations and
 multiplications to calculate a checksum.
 
->>> is_valid('1234')
-False
+>>> validate('1234')
+Traceback (most recent call last):
+    ...
+InvalidChecksum: ...
 >>> checksum('1234')
 1
 >>> calc_check_digit('1234')
 '0'
->>> is_valid('12340')
-True
+>>> validate('12340')
+'12340'
 """
 
+from stdnum.exceptions import *
+
+
 # These are the multiplication and permutation tables used in the
 # Verhoeff algorithm.
 
@@ -70,11 +75,24 @@ def checksum(number):
     return check
 
 
-def is_valid(number):
+def validate(number):
     """Checks to see if the number provided passes the Verhoeff checksum."""
+    if not bool(number):
+        raise InvalidFormat()
     try:
-        return bool(number) and checksum(number) == 0
+        valid = checksum(number) == 0
     except:
+        raise InvalidFormat()
+    if not valid:
+        raise InvalidChecksum()
+    return number
+
+
+def is_valid(number):
+    """Checks to see if the number provided passes the Verhoeff checksum."""
+    try:
+        return bool(validate(number))
+    except ValidationError:
         return False
 
 
diff --git a/tests/test_verhoeff.doctest b/tests/test_verhoeff.doctest
index 5e2faa6..4c22e9d 100644
--- a/tests/test_verhoeff.doctest
+++ b/tests/test_verhoeff.doctest
@@ -1,6 +1,6 @@
 test_verhoeff.doctest - more detailed doctests for stdnum.verhoeff module
 
-Copyright (C) 2010 Arthur de Jong
+Copyright (C) 2010, 2011, 2013 Arthur de Jong
 
 This library is free software; you can redistribute it and/or
 modify it under the terms of the GNU Lesser General Public
@@ -37,25 +37,29 @@ These are normal variations that should just work. Calculating checksums:
 
 The same numbers but now simply ask for validation:
 
->>> verhoeff.is_valid('654')
-False
->>> verhoeff.is_valid('1428570')
-True
->>> verhoeff.is_valid('398438246238642378648236487236482734')
-False
+>>> verhoeff.validate('654')
+Traceback (most recent call last):
+    ...
+InvalidChecksum: ...
+>>> verhoeff.validate('1428570')
+'1428570'
+>>> verhoeff.validate('398438246238642378648236487236482734')
+Traceback (most recent call last):
+    ...
+InvalidChecksum: ...
 
 
 Adding a check digit to the numbers so they are all valid:
 
 >>> verhoeff.calc_check_digit('654')
 '8'
->>> verhoeff.is_valid('6548')
-True
+>>> verhoeff.validate('6548')
+'6548'
 >>> verhoeff.calc_check_digit('1428570')
 '8'
->>> verhoeff.is_valid('1428570')
-True
+>>> verhoeff.validate('1428570')
+'1428570'
 >>> verhoeff.calc_check_digit('398438246238642378648236487236482734')
 '7'
->>> verhoeff.is_valid('3984382462386423786482364872364827347')
-True
+>>> verhoeff.validate('3984382462386423786482364872364827347')
+'3984382462386423786482364872364827347'
-- 
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