defmodule Unleash.Strategy.Constraint do
  @moduledoc """
  Module that is used to verify
  [constraints](https://www.unleash-hosted.com/docs/strategy-constraints/) are
  met.

  These constraints allow for very complex and specifc strategies to be
  enacted by allowing users to specify context values to include or exclude.
  """

  def verify_all(constraints, context) do
    Enum.all?(constraints, &verify(&1, context))
  end

  defp verify(%{"contextName" => name, "operator" => op, "values" => values}, context) do
    context
    |> find_value(name)
    |> check(op, values)
  end

  defp verify(%{}, _context), do: false

  defp check(value, "IN", values), do: value in values
  defp check(value, "NOT_IN", values), do: value not in values

  defp find_value(nil, _name), do: nil

  defp find_value(ctx, name) do
    Map.get(
      ctx,
      String.to_atom(Recase.to_snake(name)),
      find_value(Map.get(ctx, :properties), name)
    )
  end
end