holidays

defmodule Holidays.Definitions.Us do
  import Holidays.Define

  alias Holidays.DateCalculator.DateMath

  @moduledoc """

  United States holiday definitions.



  """
  def init() do
    holiday "Good Friday",
      %{regions: [:us],
        function: {Holidays, :easter, [:year], -2},
        type: :informal}

    holiday "Easter Sunday",
      %{regions: [:us],
        function: {Holidays, :easter, [:year]},
        type: :informal}

    holiday "New Year's Day",
      %{month: 1,
        regions: [:us],
        day: 1,
        observed: {:to_weekday_if_weekend, [:date]}}

    holiday "Martin Luther King, Jr. Day",
      %{month: 1,
        week: :third,
        regions: [:us],
        weekday: :monday}

    holiday "Inauguration Day",
      %{month: 1,
        function: {Holidays.Definitions.Us, :inauguration_day, [:year]},
        regions: [:us_dc]}

    holiday "Presidents' Day",
      %{month: 2,
        week: :third,
        regions: [:us],
        weekday: :monday}

    holiday "Cesar Chavez Day",
      %{month: 3,
        regions: [:us_ca],
        day: 31}

    holiday "Memorial Day",
      %{month: 5,
        week: :last,
        regions: [:us],
        weekday: :monday}

    holiday "Independence Day",
      %{month: 7,
        regions: [:us],
        day: 4,
        observed: {:to_weekday_if_weekend, [:date]}}

    holiday "Labor Day",
      %{month: 9,
        week: :first,
        regions: [:us],
        weekday: :monday}

    holiday "Columbus Day",
      %{month: 10,
        week: :second,
        regions: [:us],
        weekday: :monday}

    holiday "Veterans Day",
      %{month: 11,
        regions: [:us],
        day: 11,
        observed: {:to_weekday_if_weekend, [:date]}}

    holiday "Thanksgiving",
      %{month: 11,
        week: :fourth,
        regions: [:us],
        weekday: :thursday}

    holiday "Day after Thanksgiving",
      %{month: 11,
        function: {Holidays.Definitions.Us, :day_after_thanksgiving, [:year]},
        regions: [:us]}

    holiday "Christmas Day",
      %{month: 12,
        regions: [:us],
        day: 25,
        observed: {:to_weekday_if_weekend, [:date]}}
  end

  @doc """

  January 20, every fourth year, following Presidential election.



  ## Examples



      iex> Holidays.Defenitions.Us.inauguration_day(2016)

      :none



      iex> Holidays.Defenitions.Us.inauguration_day(2017)

      {2017, 1, 20}



      iex> Holidays.Defenitions.Us.inauguration_day(2018)

      :none

  """
  def inauguration_day(year) when rem(year, 4) == 1, do: {:ok, {year, 1, 20}}
  def inauguration_day(_year), do: :none

  def day_after_thanksgiving(year) do
    DateMath.get_weekth_day(year, 11, :fourth, :thursday)
    |> DateMath.add_days(1)
  end
end