require 'csv'

# Responsible for running the `cloc` system command and handling any resulting errors
class CLOCScanner
  class Exception < StandardError; end
  class ArgumentError < RuntimeError; end
  class Unavailable < RuntimeError; end
  class NoDirectory < RuntimeError; end
  class CSVError < RuntimeError; end

  def initialize(system_cloc = SystemCloc.new)
    @system_cloc = system_cloc
  end

  def scan(directory)
    fail ArgumentError, "directory must must be a string (or quack like a string)" unless directory.respond_to?(:to_str)
    fail Unavailable, "The 'cloc' command is unavailable. Is it installed and in your path?" unless cloc_available?
    fail NoDirectory, "No such directory: '#{directory}'" unless Dir.exist?(directory)

    result, status = @system_cloc.call(directory)

    if status.success?
      CLOC.new(cloc_csv(result))
    else
      raise Exception, "CLOC raised an error we didn't recognise. Here's the output:\n#{result}"
    end
  end

  private

  def cloc_csv(cloc_result)
    CSV.parse(cloc_result.lstrip, headers: true)
  rescue CSV::MalformedCSVError => e
    raise CSVError, "The CSV generated by CLOC was malformed: #{e}"
  end

  def cloc_available?
    _result, status = @system_cloc.which
    status.success?
  end
end