defmodule Faker.Date do
  import Faker.Util, only: [pick: 1]

  @moduledoc """
  Functions for generating dates
  """

  @doc """
  Returns a random date of birth for a person with an age specified by a number or range
  """
  @spec date_of_birth(integer | Range.t()) :: Date.t()
  def date_of_birth(age_or_range \\ 18..99)

  def date_of_birth(age) when is_integer(age) do
    {date, _time} = :calendar.local_time()

    today = Date.from_erl!(date)

    earliest_year = today.year - (age + 1)

    {:ok, earliest_date} = safe_date(earliest_year, today.month, today.day)
    earliest_date = Date.add(earliest_date, 1)

    {:ok, latest_date} = safe_date(earliest_year + 1, today.month, today.day)

    date_range = Date.range(earliest_date, latest_date)

    pick(date_range)
  end

  def date_of_birth(age_range) do
    age_range
    |> pick()
    |> date_of_birth()
  end

  @doc """
  Returns a random date in the past up to N days, today not included
  """
  @spec backward(integer) :: Date.t()
  def backward(days) do
    forward(-days)
  end

  @doc """
  Returns a random date in the future up to N days, today not included
  """
  @spec forward(integer) :: Date.t()
  def forward(days) do
    days
    |> Faker.DateTime.forward()
    |> DateTime.to_date()
  end

  @doc """
  Returns a random date between two dates

  ## Examples

      iex> Faker.Date.between(~D[2010-12-10], ~D[2016-12-25])
      ~D[2013-06-07]
      iex> Faker.Date.between(~D[2000-12-20], ~D[2000-12-25])
      ~D[2000-12-20]
      iex> Faker.Date.between(~D[2000-02-02], ~D[2016-02-05])
      ~D[2014-10-23]
      iex> Faker.Date.between(~D[2010-12-20], ~D[2010-12-25])
      ~D[2010-12-21]
  """
  @spec between(Date.t(), Date.t()) :: Date.t()
  def between(from, to) do
    from
    |> Faker.DateTime.between(to)
    |> DateTime.to_date()
  end

  defp safe_date(year, month, day) do
    case Date.new(year, month, day) do
      {:ok, date} -> {:ok, date}
      {:error, :invalid_date} -> safe_date(year, month, day - 1)
    end
  end
end