set correct check digit for generated VINs

CHANGELOG.md

@@ -25,6 +25,7 @@ Change log itself follows [Keep a CHANGELOG](http://keepachangelog.com) format.
 - `Faker.Currency.code/0` remove duplicates/replace old currencies [[@yassinrais](https://github.com/yassinrais)]
 - `Faker.Adress.PtBr` - fix model documentation [[@laraujo7](https://github.com/laraujo7)]
 - `Faker.Address.En/0` corrected formatting for US and Britian [[@atavistock](https://github.com/atavistock)]
+- `Faker.Vehicle.En` - ensure generated VINs have the correct check digit [[@rubysolo](https://github.com/rubysolo)]
 
 ### Security
 

lib/faker/vehicle.ex

@@ -244,20 +244,21 @@ defmodule Faker.Vehicle do
   localize(:transmission)
 
   @doc """
-  Returns a vehicle identification number string
+  Returns a vehicle identification number string with the correct check digit
 
   ## Examples
       iex> Faker.Vehicle.vin()
-      "1C68203VCV0360337"
+      "1C68203V9V0360337"
       iex> Faker.Vehicle.vin()
-      "5190V7FL8YX113016"
+      "5190V7FL3YX113016"
       iex> Faker.Vehicle.vin()
-      "4RSE9035H9JA97940"
+      "4RSE903569JA97940"
       iex> Faker.Vehicle.vin()
-      "59E4A13G890C97377"
+      "59E4A13G190C97377"
   """
   def vin do
-    Util.format("%10x%y%x%5d",
+    "%10x%y%x%5d"
+    |> Util.format(
       x: fn ->
         Util.pick([Util.upper_letter(), "#{Util.digit()}"], ["I", "O", "Q"])
       end,
@@ -268,5 +269,51 @@ defmodule Faker.Vehicle do
         "#{Util.digit()}"
       end
     )
+    |> set_check_digit()
+  end
+
+  @position_weights [8, 7, 6, 5, 4, 3, 2, 10, 0, 9, 8, 7, 6, 5, 4, 3, 2]
+  @character_values %{
+    "A" => 1,
+    "B" => 2,
+    "C" => 3,
+    "D" => 4,
+    "E" => 5,
+    "F" => 6,
+    "G" => 7,
+    "H" => 8,
+    "J" => 1,
+    "K" => 2,
+    "L" => 3,
+    "M" => 4,
+    "N" => 5,
+    "P" => 7,
+    "R" => 9,
+    "S" => 2,
+    "T" => 3,
+    "U" => 4,
+    "V" => 5,
+    "W" => 6,
+    "X" => 7,
+    "Y" => 8,
+    "Z" => 9
+  }
+
+  defp set_check_digit(partial_vin) do
+    checksum =
+      partial_vin
+      |> String.graphemes()
+      |> Enum.with_index()
+      |> Enum.reduce(0, fn {character, position}, sum ->
+        weight = Enum.at(@position_weights, position)
+        value = Map.get_lazy(@character_values, character, fn -> String.to_integer(character) end)
+
+        sum + weight * value
+      end)
+      |> rem(11)
+
+    check_digit = if checksum > 9, do: "X", else: to_string(checksum)
+
+    String.slice(partial_vin, 0..7) <> check_digit <> String.slice(partial_vin, 9..-1)
   end
 end