defmodule Manganese.CoreKit.Structs.Version do
  @moduledoc """

  A SemVer version.

  ## Deserialization

  *See `from_string/1`*

  ## Serialization

  The version struct implements the `String.Chars` protocol.

  ## Manipulation

  - see `increment/2`

  """

  alias Manganese.CoreKit.Structs
  alias Manganese.CoreKit.Enumerations

  @typedoc """

  """
  @type t :: %Structs.Version{
    major: non_neg_integer,
    minor: non_neg_integer,
    patch: non_neg_integer
  }
  defstruct [
    major: 0,
    minor: 0,
    patch: 0
  ]


  # Deserialization

  @doc """

  """
  @spec from_string(String.t) :: t
  def from_string(string) do
    components =
      String.split(string, ".")
      |> Enum.map(&Integer.parse/1)

    [ major, minor, patch ] = components

    %Structs.Version{
      major: major,
      minor: minor,
      patch: patch
    }
  end


  # Serialization
  @type t_external :: String.t


  # Manipulation

  @doc """

  """
  @spec increment(t, Enumerations.VersionType.t) :: t
  def increment(version, version_type \\ :patch) do
    case version_type do
      :major ->
        %Structs.Version{
          major: version.major + 1
        }
      :minor ->
        %Structs.Version{
          major: version.major,
          minor: version.minor + 1
        }
      :patch ->
        %Structs.Version{
          major: version.major,
          minor: version.minor,
          patch: version.patch + 1
        }
    end
  end


  # Ecto type
  @behaviour Ecto.Type

  @doc """

  The PostgreSQL type used to represent a version.

  """
  @spec type :: :string
  def type, do: :string

  @doc false
  def cast(%Structs.Version{} = version) do
    { :ok, version }
  end

  @doc false
  def cast(string) when is_binary(string) do
    { :ok, from_string string }
  end

  @doc false
  def cast(nil) do
    { :ok, nil }
  end

  @doc false
  def cast(_), do: :error

  @doc false
  def load(string) when is_binary(string) do
    { :ok, from_string string }
  end

  @doc false
  def dump(%Structs.Version{} = version) do
    { :ok, to_string version }
  end
end


defimpl String.Chars, for: Manganese.CoreKit.Structs.Version do
  def to_string(version) do
    "#{version.major}.#{version.minor}.#{version.patch}"
  end
end