Add CPF generator

CHANGELOG.md

@@ -50,6 +50,7 @@ Change log itself follows [Keep a CHANGELOG](http://keepachangelog.com) format.
 - `Faker.Aws.PtBr.region_name/0` [[@f-francine](https://github.com/f-francine)]
 - `Faker.Fruit.PtBr` [[@f-francine](https://github.com/f-francine)]
 - `Faker.Commerce.PtBr` [[@f-francine](https://github.com/f-francine)]
+- `Faker.Gov.PtBr.cpf/0` [[@rohlacanna](https://github.com/rohlacanna)]
 
 ### Changed
 

USAGE.md

@@ -60,6 +60,7 @@
   <!-- G -->
 - [Faker.Gov.Us](lib/faker/gov/us.ex)
 - [Faker.Gov.It](lib/faker/gov/it.ex)
+- [Faker.Gov.PtBr](lib/faker/gov/pt_br.ex)
   <!-- H -->
   <!-- I -->
 - [Faker.Industry](lib/faker/industry.ex)

lib/faker/gov/pt_br.ex

@@ -0,0 +1,59 @@
+defmodule Faker.Gov.PtBr do
+  @moduledoc """
+  Generating BR Taxpayer Identification numbers
+  """
+
+  @doc """
+  Returns a random BR CPF number
+
+  ## Examples
+
+      iex> Faker.Gov.PtBr.cpf
+      "396.517.511-55"
+      iex> Faker.Gov.PtBr.cpf
+      "457.899.570-88"
+      iex> Faker.Gov.PtBr.cpf
+      "283.058.997-33"
+      iex> Faker.Gov.PtBr.cpf
+      "294.304.877-66"
+  """
+  @spec cpf() :: String.t()
+  def cpf do
+    "#{area()}.#{group()}.#{serial()}-#{check_digits()}"
+    |> String.replace(~r/(\d{3})(\d{3})(\d{3})(\d{2})/, "\\1.\\2.\\3-\\4")
+  end
+
+  defp area do
+    "#{Faker.random_between(0, 999)}" |> String.pad_leading(3, "0")
+  end
+
+  defp group do
+    "#{Faker.random_between(0, 999)}" |> String.pad_leading(3, "0")
+  end
+
+  defp serial do
+    "#{Faker.random_between(0, 999)}" |> String.pad_leading(3, "0")
+  end
+
+  defp check_digits do
+    base = "#{area()}#{group()}#{serial()}"
+
+    first_check_digit = calculate_cpf_check_digit(base)
+    second_check_digit = calculate_cpf_check_digit("#{base}#{first_check_digit}")
+
+    "#{first_check_digit}#{second_check_digit}"
+  end
+
+  defp calculate_cpf_check_digit(base) do
+    digits = base |> String.graphemes() |> Enum.map(&String.to_integer/1)
+
+    sum =
+      Enum.zip(digits, [10, 9, 8, 7, 6, 5, 4, 3, 2])
+      |> Enum.map(fn {digit, weight} -> digit * weight end)
+      |> Enum.reduce(&+/2)
+
+    remainder = rem(sum, 11)
+
+    if remainder < 2, do: 0, else: 11 - remainder
+  end
+end

test/faker/gov/pt_br.exs

@@ -0,0 +1,37 @@
+defmodule Faker.Gov.PtBrTest do
+  use ExUnit.Case, async: true
+
+  import Faker.Gov.PtBr
+
+  doctest Faker.Gov.PtBr
+
+  describe "cpf" do
+    test "returns a valid cpf" do
+      assert Regex.match?(~r/^\d{3}\.\d{3}\.\d{3}\-\d{2}$/, Faker.Gov.PtBr.cpf())
+    end
+  end
+
+  describe "area" do
+    test "returns a three-digit number" do
+      assert String.length(Faker.Gov.PtBr.area()) == 3
+    end
+  end
+
+  describe "group" do
+    test "returns a three-digit number" do
+      assert String.length(Faker.Gov.PtBr.group()) == 3
+    end
+  end
+
+  describe "serial" do
+    test "returns a three-digit number" do
+      assert String.length(Faker.Gov.PtBr.serial()) == 3
+    end
+  end
+
+  describe "check_digits" do
+    test "returns a two-digit number" do
+      assert String.length(Faker.Gov.PtBr.check_digits()) == 2
+    end
+  end
+end