require 'shellwords'

# ref. https://github.com/thoughtbot/hound/blob/d2f3933/app/services/build_runner.rb
class RuboCop::Git::Runner
  def initialize(exit_on_offence: true)
    @exit_on_offence = exit_on_offence
  end

  def run(options = {})
    unless options.is_a?(RuboCop::Git::Options)
      options = RuboCop::Git::Options.new(options)
    end

    @options = options
    @files = RuboCop::Git::DiffParser.parse(git_diff(options))

    display_violations($stdout)

    ok = violations_with_valid_offences.none?
    exit(1) if @exit_on_offence && !ok
    ok
  end

  private

  def violations
    @violations ||= style_checker.violations
  end

  def violations_with_valid_offences
    @violations_with_valid_offences ||= violations.select { |v| valid_offences(v).any? }
  end

  def valid_offences(violation)
    offenses = violation.offenses
    offenses = offenses.reject(&:disabled?) if offenses.first.respond_to?(:disabled?)
    offenses.compact.sort.freeze
  end

  def style_checker
    RuboCop::Git::StyleChecker.new(
      pull_request.pull_request_files,
      @options.rubocop,
      @options.config_file,
      pull_request.config
    )
  end

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

  def git_diff(options)
    args = %w[diff --diff-filter=AMCR --find-renames --find-copies]

    args << '--cached' if options.cached
    args << options.commit_first.shellescape if options.commit_first
    args << options.commit_last.shellescape if options.commit_last

    `git #{args.join(' ')}`
  end

  def display_violations(io)
    formatter = @options.format.new(io)
    formatter.started(@files)

    violations.map do |violation|
      formatter.file_finished(violation.filename, valid_offences(violation))
    end

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