styler

# Copyright 2023 Adobe. All rights reserved.
# This file is licensed to you under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License. You may obtain a copy
# of the License at http://www.apache.org/licenses/LICENSE-2.0

# Unless required by applicable law or agreed to in writing, software distributed under
# the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR REPRESENTATIONS
# OF ANY KIND, either express or implied. See the License for the specific language
# governing permissions and limitations under the License.

defmodule Mix.Tasks.Style do
  @shortdoc "Rewrites (styles!) and formats your code as a drop in replacement for `mix format`"
  @moduledoc """
  Formats and rewrites the given files and patterns.

    mix style mix.exs "lib/**/*.{ex,exs}" "test/**/*.{ex,exs}"

  If `-` is one of the files, input is read from stdin and written to stdout.

  `mix style` uses the same options as `mix format` specified in `.formatter.exs` to
  format the code, and to determine which files to style if you don't pass any as arguments

  ## Task-specific options

  * `--check-formatted` - an alias for `--check-styled`, included for compatibility with `mix format`

  * `--check-styled` - checks that the file is already styled rather than styling it.
    useful for CI.
  """

  use Mix.Task

  @impl Mix.Task
  def run(args) do
    # we take `check_formatted` so we can easily replace `mix format`
    {opts, files} = OptionParser.parse!(args, strict: [check_styled: :boolean, check_formatted: :boolean])
    check_styled? = opts[:check_styled] || opts[:check_formatted] || false

    {_, formatter_opts} = Mix.Tasks.Format.formatter_for_file("mix.exs")

    files =
      if Enum.empty?(files) do
        case Keyword.fetch(formatter_opts, :inputs) do
          :error -> Mix.raise("you must pass file arguments or run `mix style` from the project's root directory")
          {:ok, inputs} -> inputs
        end
      else
        files
      end

    files
    |> Stream.flat_map(fn
      "-" ->
        [:stdin]

      path ->
        path |> Path.expand() |> Path.wildcard(match_dot: true) |> Enum.filter(&String.ends_with?(&1, [".ex", "exs"]))
    end)
    |> Task.async_stream(&style_file(&1, formatter_opts, check_styled?),
      ordered: false,
      timeout: :timer.seconds(30)
    )
    |> Enum.reduce({[], []}, fn
      {:ok, :ok}, acc -> acc
      {:ok, {:exit, exit}}, {exits, not_styled} -> {[exit | exits], not_styled}
      {:ok, {:not_styled, file}}, {exits, not_styled} -> {exits, [file | not_styled]}
    end)
    |> check!()
  end

  defp check!({[], []}) do
    :ok
  end

  defp check!({[{:stdin, exception, stacktrace} | _], _not_styled}) do
    Mix.shell().error("mix style failed for stdin:")
    reraise exception, stacktrace
  end

  defp check!({[{file, exception, stacktrace} | _], _not_styled}) do
    Mix.shell().error("mix style failed for file: #{Path.relative_to_cwd(file)}")
    reraise exception, stacktrace
  end

  defp check!({_exits, [_ | _] = not_styled}) do
    Mix.raise("""
    mix style failed due to --check-styled.
    The following files are not styled:
    #{Enum.join(not_styled, "\n")}
    """)
  end

  defp style_file(file, formatter_opts, check_styled?) do
    input =
      if file == :stdin,
        do: IO.stream() |> Enum.to_list() |> IO.iodata_to_binary(),
        else: file |> File.read!() |> String.trim()

    styled = Styler.format(input, formatter_opts, on_error: :raise)
    changed? = input != styled

    cond do
      check_styled? and changed? -> {:not_styled, file}
      file == :stdin -> IO.write(styled)
      changed? -> File.write!(file, styled)
      true -> :ok
    end
  rescue
    exception -> {:exit, {file, exception, __STACKTRACE__}}
  end
end