defmodule Carny.Identifier do
  @moduledoc """
  Identifiers are the objects that represent a given resource. i.e. bulwark:my-company:deployments
  """

  alias __MODULE__

  defstruct organization: "", domain: "", resource: ""

  @doc """
  Parse an arn into an identifier struct

  ## Examples

      iex> Carny.Identifier.parse("bulwark:my-company:deployments")
      %Carny.Identifier{domain: "my-company", organization: "bulwark", resource: "deployments"}

  """
  def parse(str) when is_binary(str), do: String.split(str, ":") |> parse()

  def parse([organization, domain, resource]),
    do: %Identifier{
      organization: organization,
      domain: domain,
      resource: resource
    }

  def parse(_), do: {:error, :badmatch}

  @doc """
  Takes an identifier and creates a list of each component. Useful when you're trying to build
  a string to represent the Identifier.
  """
  def parts(%{organization: o, domain: d, resource: r}), do: [o, d, r]

  @doc ~S"""
  Returns a global identifier, aka "*"
  """
  def global(), do: %Identifier{organization: "*", domain: "*", resource: "*"}

  @doc """
  Given two identifiers see if the first matches the second
  """
  def validate_against(identifier, resource) do
    identifier =
      replace_wildcards(identifier, resource) |> Map.take([:organization, :domain, :resource])

    resource = resource |> Map.take([:organization, :domain, :resource])

    # Do a pattern match
    match?(
      ^identifier,
      resource
    )
  end

  @doc ~S"""
  Replaces all the variables in a given resource with "*" if
  the compared to resource has a "*" in that field
  """
  def replace_wildcards(a, b) do
    a = if b.organization == "*", do: Map.put(a, :organization, "*"), else: a
    a = if b.domain == "*", do: Map.put(a, :domain, "*"), else: a
    if b.resource == "*", do: Map.put(a, :resource, "*"), else: a
  end
end