defmodule Mix.Tasks.Nvim.BuildHost do
  use Mix.Task

  import Mix.Generator
  @shortdoc "Build host with all complided plugins founded in neovim runtime"

  def run(argv) do
    {opts, _argv} = OptionParser.parse!(argv)

    if File.dir?("../host") do
      session_opts = Keyword.take(opts, [:xdg_home_path, :vim_rc_path])
      start_neovim_session(session_opts)

      create_file "mix.exs", host_mixfile, force: true

      System.cmd "mix", ["deps.get"]
      System.cmd "mix", ["escript.build", "--force"]

      update_neovim_remote_plugins
    else
      Mix.shell.info [:red, "host application is required for this task."]
    end
  end

  defp start_neovim_session(args) do
    xdg_home_path = Keyword.get(args, :xdg_home_path)
    vim_rc_path = Keyword.get(args, :vim_rc_path)

    {:ok, _port} = MessagePack.Transports.Port.start_link(
     [link: {:spawn, spawn_command(vim_rc_path)},
      settings: port_settings(xdg_home_path, vim_rc_path),
      session: NVim.Installer.Session],[name: NVim.Installer.Port])

    {:ok, _session} = MessagePack.RPC.Session.start_link(
     [method_handler: NVim.Host.Handler,
      transport: NVim.Installer.Port ],[ name: NVim.Installer.Session ])
  end

  defp spawn_command(vim_rc_path) when is_nil(vim_rc_path) do
    "nvim --embed"
  end

  defp spawn_command(vim_rc_path) do
    "nvim --embed -u #{vim_rc_path}"
  end

  defp port_settings(xdg_home_path, vim_rc_path)
    when is_nil(xdg_home_path) and is_nil(vim_rc_path)
  do
    []
  end

  defp port_settings(xdg_home_path, vim_rc_path) do
    [ env:
      [
        { 'XDG_CONFIG_HOME', String.to_charlist(xdg_home_path) },
        { 'MYVIMRC', String.to_charlist(vim_rc_path) }
      ]
    ]
  end

  defp plugin_apps_in_vim_runtime do
    {:ok, response} = MessagePack.RPC.Session.call(
      NVim.Installer.Session, "vim_eval",
      ["globpath(&rtp, 'rplugin/elixir/apps/*')"]
    )

    String.split(response, "\n")
  end

  defp update_neovim_remote_plugins do
    {:ok, response} = MessagePack.RPC.Session.call(NVim.Installer.Session, "vim_command_output", ["UpdateRemotePlugins"])

    if Regex.match?(~r/elixir host registered plugins/, response) do
      Mix.shell.info [:green, """

      Remote plugins were updated. Restart neovim instances.
      """]
    else
      Mix.shell.info [:red, """

      Problem with updating the remote plugins. See the elixir host log for more information.
      """]
    end
  end

  defp host_mixfile do
    depended_plugins =
      plugin_apps_in_vim_runtime
      |> Enum.filter(fn(app)-> Path.basename(app) != "host" end)
      |> Enum.uniq

    plugin_deps =
      depended_plugins
      |> Enum.map(fn(plugin_path)->
          plugin_name = Path.basename(plugin_path)
          ~s({:#{plugin_name}, path: "#{plugin_path}", in_umbrella: true}) end)
      |> Enum.join(",")

    host_mixfile_template(plugin_deps: plugin_deps, nvim_version: Application.spec(:nvim)[:vsn])
  end

  embed_template :host_mixfile, """
  defmodule Host.Mixfile do
    use Mix.Project

    def project do
      [app: :host,
       version: "<%= @nvim_version %>",
       build_path: "../../_build",
       config_path: "../../config/config.exs",
       deps_path: "../../deps",
       lockfile: "../../mix.lock",
       elixir: "~> 1.3",
       deps: deps,
       escript: escript]
    end

    def application do
      [applications: [:logger, :nvim], env: [plugin_module: NVim.Host.Plugin]]
    end

    def escript do
      [main_module: NVim.Host, emu_args: "-noinput"]
    end

    defp deps do
      [{:nvim, "<%= @nvim_version %>"},
      <%= @plugin_deps %>]
    end
  end
  """
end