Initial upload

elixir/city-office/lib/form.ex

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+defmodule Form do
+  @moduledoc """
+  A collection of loosely related functions helpful for filling out various forms at the city office.
+  """
+
+  @doc """
+  Generates a string of a given length.
+
+  This string can be used to fill out a form field that is supposed to have no value.
+  Such fields cannot be left empty because a malicious third party could fill them out with false data.
+  """
+  @spec blanks(non_neg_integer) :: String.t()
+  def blanks(n) do
+    String.duplicate("X", n)
+  end
+
+  @doc """
+  Splits the string into a list of uppercase letters.
+
+  This is needed for form fields that don't offer a single input for the whole string,
+  but instead require splitting the string into a predefined number of single-letter inputs.
+  """
+  @spec letters(String.t()) :: [String.t()]
+  def letters(word) do
+    word
+    |> String.upcase()
+    |> String.split("", trim: true)
+  end
+
+  @doc """
+  Checks if the value has no more than the maximum allowed number of letters.
+
+  This is needed to check that the values of fields do not exceed the maximum allowed length.
+  It also tells you by how much the value exceeds the maximum.
+  """
+  @spec check_length(String.t(), non_neg_integer()) :: :ok | {:error, pos_integer()}
+  def check_length(word, length) do
+    diff = String.length(word) - length
+
+    if diff <= 0 do
+      :ok
+    else
+      {:error, diff}
+    end
+  end
+
+  @type address_map :: %{street: String.t(), postal_code: String.t(), city: String.t()}
+  @type address_tuple :: {street :: String.t(), postal_code :: String.t(), city :: String.t()}
+  @type address :: address_map() | address_tuple()
+
+  @doc """
+  Formats the address as an uppercase multiline string.
+  """
+  @spec format_address(address()) :: String.t()
+  def format_address(%{street: street, postal_code: postal_code, city: city}) do
+    format_address({street, postal_code, city})
+  end
+
+  def format_address({street, postal_code, city}) do
+    """
+    #{String.upcase(street)}
+    #{String.upcase(postal_code)} #{String.upcase(city)}
+    """
+  end
+end