Add GS1 capability (#38)

checkdigit/gs1.py

@@ -0,0 +1,90 @@
+# /usr/bin/env python
+
+# This file is part of checkdigit.
+
+# checkdigit is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+# checkdigit is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# You should have received a copy of the GNU General Public License
+# along with checkdigit.  If not, see <http://www.gnu.org/licenses/>.
+
+"""GS1 Validation Functions."""
+
+import math
+
+from checkdigit._data import cleanse, convert
+
+
+# WARNING: Data beginning with 0 must be as a string due to PEP 3127
+
+
+def calculate(data: str) -> str:
+    """Calculates GS1 Check Digit.
+
+    This method works for all fixed length numeric GS1 data structures
+    (including GDTI, GLN, GRAI, etc.) that require a check digit.
+
+    Args:
+        data: A string of characters
+
+    Returns:
+        str: The check digit that was missing
+    """
+    data = cleanse(data)
+    data = data[::-1]  # Reverse the barcode, as last digit is always multiplied by 3
+    total_sum = 0
+    for index, value in enumerate(data):
+        if index % 2 == 0:
+            total_sum += int(value) * 3
+        else:
+            total_sum += int(value)
+    next_multiple_of_ten = int(math.ceil(total_sum / 10.0)) * 10
+    check_digit = next_multiple_of_ten - total_sum
+    return convert(check_digit, "gs1")
+
+
+def validate(data: str) -> bool:
+    """Validates GS1.
+
+    This method works for all fixed length numeric GS1 data structures
+    (including GDTI, GLN, GRAI, etc.) that require a check digit.
+
+    Args:
+        data: A string of characters representing a full GS1 code
+
+    Returns:
+        bool: A boolean representing whether the
+            check digit validates the data or not
+
+    """
+    data = cleanse(data)
+    return calculate(data[:-1]) == data[-1]
+
+
+def missing(data: str) -> str:
+    """Calculates a missing digit in a GS1 Code.
+
+    This method works for all fixed length numeric GS1 data structures
+    (including GDTI, GLN, GRAI, etc.) that require a check digit.
+
+    Args:
+        data: A string of characters representing a full ISBN code
+            with a question mark representing a missing character
+
+    Returns:
+        str: The missing value that should've been where the question mark was
+
+    """
+    data = cleanse(data)
+    for poss_digit in range(10):  # Brute Force the 10 options
+        option = convert(poss_digit)
+        # tests it with the generated number
+        # If this fails, the next number is tried
+        if validate(data.replace("?", option)):
+            return option
+    return "Invalid"

tests.py

@@ -30,6 +30,7 @@
 import checkdigit.luhn as luhn
 import checkdigit.parity as parity
 import checkdigit.upc as upc
+import checkdigit.gs1 as gs1
 
 # Even parity
 test(parity.calculate("0110"), "01100")
@@ -142,3 +143,69 @@
 test(luhn.missing("515853022?76176"), "1")
 test(luhn.missing("?72098369216316"), "3")
 test(luhn.missing("78369216316"), "Invalid")
+
+# Determine Check Digit
+test(gs1.calculate("9894552"), "8")
+test(gs1.calculate("7384553"), "9")
+test(gs1.calculate("6095011"), "6")
+test(gs1.calculate("24497088432"), "5")
+test(gs1.calculate("97379430662"), "0")
+test(gs1.calculate("82778161993"), "7")
+test(gs1.calculate("992802203539"), "2")
+test(gs1.calculate("484614659301"), "5")
+test(gs1.calculate("508533792649"), "5")
+test(gs1.calculate("1268148598279"), "8")
+test(gs1.calculate("2943824610504"), "6")
+test(gs1.calculate("2839112640382"), "7")
+test(gs1.calculate("4314789452907127"), "9")
+test(gs1.calculate("6427894156382299"), "3")
+test(gs1.calculate("9770280892681722"), "8")
+test(gs1.calculate("08408575249213173"), "1")
+test(gs1.calculate("84668430275000727"), "9")
+test(gs1.calculate("67368623738347505"), "1")
+
+# Determine Check Digit
+test(gs1.validate("45649554"))
+test(gs1.validate("53089328"))
+test(gs1.validate("026229133848"))
+test(gs1.validate("791364257635"))
+test(gs1.validate("1396057123946"))
+test(gs1.validate("3832293285225"))
+test(gs1.validate("97781402171203"))
+test(gs1.validate("02146346514943"))
+test(gs1.validate("25020757663329968"))
+test(gs1.validate("82648071988131734"))
+test(gs1.validate("321609478518371973"))
+test(gs1.validate("961552634342856982"))
+test(gs1.validate("97673485"), False)
+test(gs1.validate("52186777"), False)
+test(gs1.validate("548785535769"), False)
+test(gs1.validate("753963090728"), False)
+test(gs1.validate("3293497160526"), False)
+test(gs1.validate("6806652313775"), False)
+test(gs1.validate("02370607330031"), False)
+test(gs1.validate("52262887213914"), False)
+test(gs1.validate("83494889067993460"), False)
+test(gs1.validate("93976703183564468"), False)
+test(gs1.validate("501469249184000304"), False)
+test(gs1.validate("224245438987081447"), False)
+
+# Missing Digit
+test(gs1.missing("?8945528"), "9")
+test(gs1.missing("7?845539"), "3")
+test(gs1.missing("60?50116"), "9")
+test(gs1.missing("244?70884325"), "9")
+test(gs1.missing("9737?4306620"), "9")
+test(gs1.missing("82778?619937"), "1")
+test(gs1.missing("992802?035392"), "2")
+test(gs1.missing("4846146?93015"), "5")
+test(gs1.missing("50853379?6495"), "2")
+test(gs1.missing("126814859?2798"), "8")
+test(gs1.missing("2943824610?046"), "5")
+test(gs1.missing("28391126403?27"), "8")
+test(gs1.missing("431478945290?1279"), "7")
+test(gs1.missing("6427894156382?993"), "2")
+test(gs1.missing("97702808926817?28"), "2")
+test(gs1.missing("084085752492131?31"), "7")
+test(gs1.missing("846684302750007275"), "Invalid")
+test(gs1.missing("?73686237383475059"), "0")