cache.rb

# frozen_string_literal: true

require 'pathname'

#
# This code is based on https://github.com/fohte/rubocop-daemon.
#
# Copyright (c) 2018 Hayato Kawai
#
# The MIT License (MIT)
#
# https://github.com/fohte/rubocop-daemon/blob/master/LICENSE.txt
#
module RuboCop
  module Server
    # Caches the states of server process.
    # @api private
    class Cache
      GEMFILE_NAMES = %w[Gemfile gems.rb].freeze

      class << self
        attr_accessor :cache_root_path

        # Searches for Gemfile or gems.rb in the current dir or any parent dirs
        def project_dir
          current_dir = Dir.pwd
          while current_dir != '/'
            return current_dir if GEMFILE_NAMES.any? do |gemfile|
              File.exist?(File.join(current_dir, gemfile))
            end

            current_dir = File.expand_path('..', current_dir)
          end
          # If we can't find a Gemfile, just use the current directory
          Dir.pwd
        end

        def project_dir_cache_key
          @project_dir_cache_key ||= project_dir[1..].tr('/', '+')
        end

        def dir
          Pathname.new(File.join(cache_path, project_dir_cache_key)).tap do |d|
            d.mkpath unless d.exist?
          end
        end

        def cache_path
          cache_root_dir = cache_root_path || File.join(Dir.home, '.cache')

          File.expand_path(File.join(cache_root_dir, 'rubocop_cache', 'server'))
        end

        def port_path
          dir.join('port')
        end

        def token_path
          dir.join('token')
        end

        def pid_path
          dir.join('pid')
        end

        def lock_path
          dir.join('lock')
        end

        def status_path
          dir.join('status')
        end

        def version_path
          dir.join('version')
        end

        def pid_running?
          Process.kill(0, pid_path.read.to_i) == 1
        rescue Errno::ESRCH
          false
        end

        def acquire_lock
          lock_file = File.open(lock_path, File::CREAT)
          # flock returns 0 if successful, and false if not.
          flock_result = lock_file.flock(File::LOCK_EX | File::LOCK_NB)
          yield flock_result != false
        ensure
          lock_file.flock(File::LOCK_UN)
          lock_file.close
        end

        def write_port_and_token_files(port:, token:)
          port_path.write(port)
          token_path.write(token)
        end

        def write_pid_file
          pid_path.write(Process.pid)
          yield
        ensure
          dir.rmtree
        end

        def write_status_file(status)
          status_path.write(status)
        end

        def write_version_file(version)
          version_path.write(version)
        end
      end
    end
  end
end