module Overcommit::Hook::PreCommit
  # Checks for trailing whitespace in files.
  class TrailingWhitespace < Base
    def message
      "Trailing whitespace detected"
    end

    def lint_split output, message = message
      # Keep lines from the output for files that we actually modified
      error_lines, warning_lines = output.split("\n").partition do |output_line|
        _, file, line = output_line.match(/^([^:]+):(\d+)/).to_a
        modified_lines(file).include?(line.to_i)
      end

      return :bad, message + ":\n" + error_lines.join("\n") unless error_lines.empty?
      return :warn, message + " (on lines you didn't modify):\n" + warning_lines.join("\n")\
          unless warning_lines.empty?

      :good
    end

    def run
      lint_split execute(%w[grep -IHn \s$] + applicable_files).stdout
    end
  end
end