defmodule Exoddic.Converter.Uk do
  @behaviour Exoddic.Converter
  @moduledoc """
    .uk-style traditional odds
  """

  def from_prob(amount), do: (1/amount) - 1

  def to_prob(amount), do: 1/(amount+1);

  @doc "Formatted as the nearest integer ratio with a denominator not larger than 1000"
  def for_display(amount) do
    biggest = 1000
    num = amount * biggest |> round
    denom = gcd(num,biggest)
    "#{Float.to_string(num/denom, [decimals: 0])}/#{Float.to_string(biggest/denom, [decimals: 0])}"
  end

  defp gcd(a,0), do: a
  defp gcd(a,b), do: gcd(b,rem(a,b))

end