defmodule Mix.Tasks.Version.Next do
  use Mix.Task
  use VersionTasks.FnExpr

  @shortdoc "The next version (e.g v0.9.2)"
  def run(args) do
    args
    |> calc
    |> IO.puts
  end

  def calc([]), do: calc(["patch"])
  def calc([mode]) do
    Mix.Project.config[:version]
    |> String.split(".")
    |> uptick(mode)
  end

  def uptick([major, minor, patch], "patch") do
    {new_val, ""} = Integer.parse(patch)
    "#{major}.#{minor}.#{new_val + 1}"
  end

  def uptick([major, minor, _patch], "minor") do
    {new_val, ""} = Integer.parse(minor)
    "#{major}.#{new_val + 1}.0"
  end

  def uptick([major, _minor, _patch], "major") do
    {new_val, ""} = Integer.parse(major)
    "#{new_val + 1}.0.0"
  end

end