module RuboCop
  module Git
    # ref. https://github.com/thoughtbot/hound/blob/be2dd34/app/services/build_runner.rb
    class Runner
      DEFAULT_CONFIG_FILE = '.rubocop.yml'
      HOUND_DEFAULT_CONFIG_FILE =
        File.expand_path('../../../../hound.yml', __FILE__)

      def run(options)
        if options[:hound] && RuboCop::Version.version != '0.22.0'
          warn 'Hound compatibility mode require rubocop 0.22.0'
          exit 1
        end

        @options = options
        @files = parse_diff(git_diff(options[:cached]))

        display_violations($stdout)
      end

      private

      def violations
        @violations ||= style_checker.violations
      end

      def style_checker
        StyleChecker.new(pull_request.pull_request_files,
                         @options[:rubocop],
                         config_path,
                         pull_request.config)
      end

      def pull_request
        @pull_request ||= PseudoPullRequest.new(@files, @options)
      end

      def git_diff(cached)
        if cached
          `git diff --diff-filter=AMCR --cached --find-renames --find-copies`
        else
          `git diff --diff-filter=AM`
        end
      end

      def parse_diff(diff)
        files    = []
        in_patch = false

        diff.each_line do |line|
          case line
          when /^diff --git/
            in_patch = false
          when %r{^\+{3} b/([^\t\n\r]+)}
            files << PseudoResource.new($1, 'modified', '')
          when /^@@/
            in_patch = true
          end

          files.last.patch << line if in_patch
        end

        files
      end

      def config_path
        if @options[:hound]
          HOUND_DEFAULT_CONFIG_FILE
        else
          @options[:config] || DEFAULT_CONFIG_FILE
        end
      end

      def display_violations(io)
        formatter = RuboCop::Formatter::ClangStyleFormatter.new(io)
        formatter.started(nil)

        violations.map do |violation|
          formatter.file_finished(
            violation.filename,
            violation.offenses.compact.sort.freeze
          )
        end

        formatter.finished(@files.map(&:filename).freeze)
      end
    end
  end
end