defmodule Mix.Tasks.Clje.Run do
  @moduledoc """
  Compile and run a CljElixir file.

  ## Usage

      mix clje.run examples/chat_room.clje
      mix clje.run -e '(println "hello")' script.clje

  Like `elixir script.exs` or `bb script.clj`. The file is compiled and
  evaluated. Modules defined in the file become available.

  ## Options

    * `-e` / `--eval` - evaluate expression before running the file
    * `--no-halt` - keep the system running after execution (useful for spawned processes)

  Arguments after `--` are available via `System.argv()`.
  """

  use Mix.Task

  @shortdoc "Run a CljElixir file"

  @impl Mix.Task
  def run(args) do
    # Split on "--" to separate mix opts from script args
    {before_dashdash, script_args} = split_on_dashdash(args)

    {opts, positional, _} =
      OptionParser.parse(before_dashdash,
        switches: [eval: :keep, no_halt: :boolean],
        aliases: [e: :eval]
      )

    Mix.Task.run("compile")
    Mix.Task.run("app.start")

    # Make script args available via System.argv()
    System.argv(script_args)

    # Evaluate any -e expressions first
    bindings =
      opts
      |> Keyword.get_values(:eval)
      |> Enum.reduce([], fn expr, bindings ->
        case CljElixir.Compiler.eval_string(expr, bindings: bindings) do
          {:ok, result, new_bindings} ->
            IO.puts(CljElixir.Printer.pr_str(result))
            new_bindings

          {:error, diagnostics} ->
            print_diagnostics(diagnostics)
            System.halt(1)
        end
      end)

    # Run file(s)
    case positional do
      [] ->
        unless Keyword.has_key?(opts, :eval) do
          Mix.shell().error("Usage: mix clje.run [options] <file.clje>")
          System.halt(1)
        end

      files ->
        Enum.reduce(files, bindings, fn file, bindings ->
          case CljElixir.Compiler.eval_file(file, bindings: bindings) do
            {:ok, _result, new_bindings} ->
              new_bindings

            {:error, diagnostics} ->
              print_diagnostics(diagnostics)
              System.halt(1)
          end
        end)
    end

    if opts[:no_halt] do
      Process.sleep(:infinity)
    end
  end

  defp split_on_dashdash(args) do
    case Enum.split_while(args, &(&1 != "--")) do
      {before, ["--" | rest]} -> {before, rest}
      {before, []} -> {before, []}
    end
  end

  defp print_diagnostics(diagnostics) do
    Enum.each(diagnostics, fn diag ->
      loc =
        case {Map.get(diag, :file), Map.get(diag, :line, 0)} do
          {nil, _} -> ""
          {_f, 0} -> "#{diag.file}: "
          {_f, l} -> "#{diag.file}:#{l}: "
        end

      Mix.shell().error("#{loc}#{diag.severity}: #{diag.message}")
    end)
  end
end