From d4b2a3f53ba7b123384a3690fc062fcee043bc0a Mon Sep 17 00:00:00 2001
From: meatball <69751659+meatball133@users.noreply.github.com>
Date: Tue, 11 Jul 2023 15:20:52 +0200
Subject: [PATCH] fix luhn (#206)

---
 exercises/practice/luhn/.meta/config.json    |  3 +-
 exercises/practice/luhn/.meta/example.coffee | 63 ++++++--------------
 exercises/practice/luhn/.meta/tests.toml     |  9 +++
 exercises/practice/luhn/luhn.spec.coffee     | 20 ++++++-
 4 files changed, 46 insertions(+), 49 deletions(-)

diff --git a/exercises/practice/luhn/.meta/config.json b/exercises/practice/luhn/.meta/config.json
index 827f78e..f97a57d 100644
--- a/exercises/practice/luhn/.meta/config.json
+++ b/exercises/practice/luhn/.meta/config.json
@@ -7,7 +7,8 @@
     "alxndr",
     "marocchino",
     "meientau",
-    "rootulp"
+    "rootulp",
+    "meatball133"
   ],
   "files": {
     "solution": [
diff --git a/exercises/practice/luhn/.meta/example.coffee b/exercises/practice/luhn/.meta/example.coffee
index 66cc67b..7dfaa54 100644
--- a/exercises/practice/luhn/.meta/example.coffee
+++ b/exercises/practice/luhn/.meta/example.coffee
@@ -1,46 +1,17 @@
-module.exports = class Luhn
-  constructor: (number) ->
-    @checkDigit = number % 10
-    @addends = @calculateAddends(number)
-    @checksum = @calculateChecksum(@addends)
-    @valid = @determineIfValid(@checksum)
-
-  calculateAddends: (number) ->
-
-    numberAsString = "" + number + ""
-    numbers = numberAsString.split('')
-
-    addends = (@calculateAddend(i,numbers) for i in [0..numbers.length-1])
-    addends.reverse()
-
-  calculateAddend: (i,numbers) ->
-    index = numbers.length - 1 - i
-
-    currentAddend = parseInt(numbers[index])
-
-    if (i + 1) % 2 == 0
-      currentAddend = currentAddend * 2
-      if currentAddend > 10
-        currentAddend = currentAddend - 9
-
-    currentAddend
-
-  calculateChecksum: (numbers) ->
-    numbers.reduce (x,y) -> x + y
-
-  determineIfValid: (sum) ->
-    (sum % 10 == 0)
-
-
-  @create = (number) ->
-    finalNumber = number * 10
-    luhnNumber = new Luhn(finalNumber)
-    index = 0
-
-    while(!luhnNumber.valid)
-      finalNumber = number * 10 + index
-      luhnNumber = new Luhn(finalNumber)
-      break if luhnNumber.valid
-      index += 1
-
-    finalNumber
+class Luhn
+  constructor: (@num) ->
+
+  valid: ->
+    @num = @num.replace /\s+/g, ''
+    return false if @num.length < 2
+    return false if @num.match /\D/
+    sum = 0
+    for digit, i in @num.split('').reverse()
+      digit = parseInt digit
+      if i % 2 == 1
+        digit *= 2
+        digit -= 9 if digit > 9
+      sum += digit
+    sum % 10 == 0
+
+module.exports = Luhn
diff --git a/exercises/practice/luhn/.meta/tests.toml b/exercises/practice/luhn/.meta/tests.toml
index 06c2880..c0be0c4 100644
--- a/exercises/practice/luhn/.meta/tests.toml
+++ b/exercises/practice/luhn/.meta/tests.toml
@@ -33,6 +33,9 @@ description = "invalid credit card"
 [20e67fad-2121-43ed-99a8-14b5b856adb9]
 description = "invalid long number with an even remainder"
 
+[7e7c9fc1-d994-457c-811e-d390d52fba5e]
+description = "invalid long number with a remainder divisible by 5"
+
 [ad2a0c5f-84ed-4e5b-95da-6011d6f4f0aa]
 description = "valid number with an even number of digits"
 
@@ -57,6 +60,12 @@ description = "more than a single zero is valid"
 [ab56fa80-5de8-4735-8a4a-14dae588663e]
 description = "input digit 9 is correctly converted to output digit 9"
 
+[b9887ee8-8337-46c5-bc45-3bcab51bc36f]
+description = "very long input is valid"
+
+[8a7c0e24-85ea-4154-9cf1-c2db90eabc08]
+description = "valid luhn with an odd number of digits and non zero first digit"
+
 [39a06a5a-5bad-4e0f-b215-b042d46209b1]
 description = "using ascii value for non-doubled non-digit isn't allowed"
 
diff --git a/exercises/practice/luhn/luhn.spec.coffee b/exercises/practice/luhn/luhn.spec.coffee
index bd10b44..fd1a244 100644
--- a/exercises/practice/luhn/luhn.spec.coffee
+++ b/exercises/practice/luhn/luhn.spec.coffee
@@ -26,8 +26,12 @@ describe 'Luhn', ->
     luhn = new Luhn('8273 1232 7352 0569')
     expect(luhn.valid()).toBe false
 
-  xit 'invalid credit card', ->
-    luhn = new Luhn('8273 1232 7352 0569')
+  xit 'invalid long number with an even remainder', ->
+    luhn = new Luhn('1 2345 6789 1234 5678 9012')
+    expect(luhn.valid()).toBe false
+
+  xit 'invalid long number with a remainder divisible by 5', ->
+    luhn = new Luhn('1 2345 6789 1234 5678 9013')
     expect(luhn.valid()).toBe false
 
   xit 'valid number with an even number of digits', ->
@@ -62,6 +66,14 @@ describe 'Luhn', ->
     luhn = new Luhn('091')
     expect(luhn.valid()).toBe true
 
+  xit 'very long input is valid', ->
+    luhn = new Luhn('9999999999 9999999999 9999999999 9999999999')
+    expect(luhn.valid()).toBe true
+
+  xit 'valid luhn with an odd number of digits and non zero first digit', ->
+    luhn = new Luhn('109')
+    expect(luhn.valid()).toBe true
+
   xit 'using ascii value for non-doubled non-digit isn\'t allowed', ->
     luhn = new Luhn('055b 444 285')
     expect(luhn.valid()).toBe false
@@ -69,3 +81,7 @@ describe 'Luhn', ->
   xit 'using ascii value for doubled non-digit isn\'t allowed', ->
     luhn = new Luhn(':9')
     expect(luhn.valid()).toBe false
+
+  xit 'non-numeric, non-space char in the middle with a sum that\'s divisible by 10 isn\'t allowed', ->
+    luhn = new Luhn('59%59')
+    expect(luhn.valid()).toBe false