defmodule Panty.String do

  @moduledoc """
  String utilities
  """

  @doc """
  Return camel-case from a given string.

  ## Examples
      iex> String.camel_case("ha noi")
      "haNoi"
      iex> String.camel_case("Ha noi")
      "haNoi"
      iex> String.camel_case("ha-noi")
      "haNoi"

  """

  @spec camel_case(String.t) :: String.t

  def camel_case(string) do
    string
    |> String.split(~r"[^a-zA-Z]", trim: true)
    |> Enum.with_index()
    |> Enum.map(
      fn
        {el, 0} -> String.downcase(el)

        {el, _idx} -> String.capitalize(el)
      end
    )
    |> Enum.join("")
  end

  @doc """
  Return kebab-case from a given string.

  ## Examples
      iex> String.keybab_case("ha noi")
      "ha-noi"
      iex> String.kebab_case("Panty Utilities")
      "panty-utilities"

  """

  @spec kebab_case(String.t) :: String.t

  def kebab_case(string) do
    string
    |> String.split()
    |> Enum.join("-")
    |> String.downcase
  end


  @doc """
  Get index of a substring from a pattern.

  ## Examples
      iex> Collection.string_find_index("abcdef", "cde")
      2
      iex> Collection.string_find_index("{% sections 'header' %}", "{% endschema %}")
      nil

  """

  @spec substring_index(String.t, String.t) :: integer() | nil

  def substring_index(pattern, substring) do
    case String.split(pattern, substring, parts: 2) do
      [left, _] -> String.length(left)
      [_] -> nil
    end
  end
end