defmodule Mix.Tasks.Compile.ElixirMake do
  use Mix.Task

  @moduledoc """
  Runs `make` in the current project.

  This task runs `make` in the current project; any output coming from `make` is
  printed in real-time on stdout.

  ## Configuration

  The configuration options need to be added to the `project` function in the
  `mix.exs` file, as in this example:

      def project do
        [app: :myapp,
         make_executable: "make",
         make_makefile: "Othermakefile",
         compilers: [:elixir_make] ++ Mix.compilers,
         deps: deps]
      end

  The following options are available:

    * `:make_executable` - (binary or `:default`) it's the executable to use as the
      `make` program. If not provided or if `:default`, it defaults to `"nmake"`
      on Windows, `"gmake"` on FreeBSD and OpenBSD, and `"make"` on everything
      else. You can, for example, customize which executable to use on a
      specific OS and use `:default` for every other OS.

    * `:make_makefile` - (binary or `:default`) it's the Makefile to
      use. Defaults to `"Makefile"` for Unix systems and `"Makefile.win"` for
      Windows systems if not provided or if `:default`.

    * `:make_targets` - (list of binaries) it's the list of Make targets that
      should be run. Defaults to `[]`, meaning `make` will run the first target.

    * `:make_clean` - (list of binaries) it's a list of Make targets to be run
      when `mix clean` is run. It's only run if a non-`nil` value for
      `:make_clean` is provided. Defaults to `nil`.

    * `:make_cwd` - (binary) it's the directory where `make` will be run,
      relative to the root of the project.

    * `:make_env` - (map of binary to binary) it's a map of extra environment
      variables to be passed to `make`.

    * `:make_error_message` - (binary or `:default`) it's a custom error message
      that can be used to give instructions as of how to fix the error (e.g., it
      can be used to suggest installing `gcc` if you're compiling a C
      dependency).

  """

  @unix_error_msg """
  Depending on your OS, make sure to follow these instructions:

    * Mac OS X: You need to have gcc and make installed. Try running the
      commands `gcc --version` and / or `make --version`. If these programs
      are not installed, you will be prompted to install them.

    * Linux: You need to have gcc and make installed. If you are using
      Ubuntu or any other Debian-based system, install the packages
      `build-essential`. Also install `erlang-dev` package if not
      included in your Erlang/OTP version. If you're on Fedora, run
      `dnf group install 'Development Tools'`.
  """

  @windows_error_msg """
  One option is to install a recent version of Visual Studio (you can download
  the community edition for free). When you install Visual Studio, make sure
  you also install the C/C++ tools.

  After installing VS, look in the `Program Files (x86)` folder and search
  for `Microsoft Visual Studio`. Note down the full path of the folder with
  the highest version number. Open the `run` command and type in the following
  command (make sure that the path and version number are correct):

      cmd /K "C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat" amd64

  This should open up a command prompt with the necessary environment variables
  set, and from which you will be able to run the `mix compile`, `mix deps.compile`,
  and `mix test` commands.
  """

  @spec run(OptionParser.argv) :: :ok | no_return
  def run(args) do
    config = Mix.Project.config()
    Mix.shell.print_app()
    build(config, args)
    Mix.Project.build_structure()
    :ok
  end

  # This is called by Elixir when `mix clean` is run and `:elixir_make` is in
  # the list of compilers.
  def clean() do
    config = Mix.Project.config()
    {clean_targets, config} = Keyword.pop(config, :make_clean)

    if clean_targets do
      config
      |> Keyword.put(:make_targets, clean_targets)
      |> build([])
    end
  end

  defp build(config, task_args) do
    exec      = Keyword.get(config, :make_executable, :default) |> os_specific_executable()
    makefile  = Keyword.get(config, :make_makefile, :default)
    targets   = Keyword.get(config, :make_targets, [])
    env       = Keyword.get(config, :make_env, %{})
    cwd       = Keyword.get(config, :make_cwd, ".")
    error_msg = Keyword.get(config, :make_error_message, :default) |> os_specific_error_msg()

    args = args_for_makefile(exec, makefile) ++ targets

    case cmd(exec, args, cwd, env, "--verbose" in task_args) do
      0 ->
        :ok
      exit_status ->
        raise_build_error(exec, exit_status, error_msg)
    end
  end

  # Runs `exec [args]` in `cwd` and prints the stdout and stderr in real time,
  # as soon as `exec` prints them (using `IO.Stream`).
  defp cmd(exec, args, cwd, env, verbose?) do
    opts = [
      into: IO.stream(:stdio, :line),
      stderr_to_stdout: true,
      cd: cwd,
      env: env
    ]

    if verbose? do
      print_verbose_info(exec, args)
    end

    {%IO.Stream{}, status} = System.cmd(find_executable(exec), args, opts)
    status
  end

  defp find_executable(exec) do
    System.find_executable(exec) || Mix.raise("`#{exec}` not found in the current path")
  end

  defp raise_build_error(exec, exit_status, error_msg) do
    Mix.raise("Could not compile with `#{exec}` (exit status: #{exit_status}).\n" <> error_msg)
  end

  defp os_specific_executable(exec) when is_binary(exec) do
    exec
  end

  defp os_specific_executable(:default) do
    case :os.type() do
      {:win32, _} ->
        "nmake"
      {:unix, type} when type in [:freebsd, :openbsd] ->
        "gmake"
      _ ->
        "make"
    end
  end

  defp os_specific_error_msg(msg) when is_binary(msg) do
    msg
  end

  defp os_specific_error_msg(:default) do
    case :os.type() do
      {:unix, _} -> @unix_error_msg
      {:win32, _} -> @windows_error_msg
      _ -> ""
    end
  end

  # Returns a list of command-line args to pass to make (or nmake/gmake) in
  # order to specify the makefile to use.
  defp args_for_makefile("nmake", :default), do: ["/F", "Makefile.win"]
  defp args_for_makefile("nmake", makefile), do: ["/F", makefile]
  defp args_for_makefile(_, :default), do: []
  defp args_for_makefile(_, makefile), do: ["-f", makefile]

  defp print_verbose_info(exec, args) do
    args = Enum.map_join(args, " ", fn(arg) ->
      if String.contains?(arg, " "), do: inspect(arg), else: arg
    end)

    Mix.shell.info "Compiling with make: #{exec} #{args}"
  end
end