module Flydata
  # Directory structure
  #  log_dir
  #    - log_path
  #    + .flydata
  #      + [log_file_name]
  #        + trash  <- temprary directory
  #          - [log_archived_files]
  #        + backup <- backup archive files when initialize
  #          - [log_archived_files]
  class LogMonitor
    FLYDATA_DIR = '.flydata'
    TRASH_DIR = 'trash'
    BACKUP_DIR = 'backup'
    DEFAULT_DAYS_TO_TRASH = 7 #days
    DEFAULT_DAYS_TO_DELETE = DEFAULT_DAYS_TO_TRASH + 7 #days

    def initialize(log_path, options={})
      # check arguments
      raise "Cannot access to log path... #{log_path}" unless File.exist?(log_path)
      @log_path = log_path
      @options = options
      @days_to_trash = @options[:days_to_trash] ?
        @options[:days_to_trash] : DEFAULT_DAYS_TO_TRASH
      @days_to_delete = @options[:days_to_delete] ?
        @options[:days_to_delete] : DEFAULT_DAYS_TO_DELETE
      @setup_flag = false
      # initialize paths
      @flydata_path = File.join(File.dirname(@log_path),
                                FLYDATA_DIR,
                                File.basename(@log_path))
      @backup_path = File.join(@flydata_path, BACKUP_DIR)
      @trash_path = File.join(@flydata_path, TRASH_DIR)
    end
    def setup
      # create directories
      FileUtils.mkdir_p(@flydata_path)
      FileUtils.mkdir_p(@backup_path)
      # backup_files to avoid to delete non-uploaded files
      backup_files
      @setup_flag = true
      self
    end
    def rotate
      check_setup_done
      # move files to trash
      trash_files
      # delete trashed files
      delete_files
    end

    private
    def check_setup_done
      raise "Setup hasn't been done, yet." unless @setup_flag
    end
    def archived_files
      Dir::glob("#{@log_path}?*")
    end
    def trashed_files
      Dir::glob("#{File.join(@trash_path, File.basename(@log_path))}?*")
    end
    def backup_files
      # use trash dir as checkpoint to backup initial archive files
      unless File.exist?(@trash_path)
        archived_files.each {|f|
          puts "buckup file: #{f} -> #{@backup_path}"
          FileUtils.mv(f, @backup_path)
        }
        FileUtils.mkdir_p(@trash_path)
      end
    end
    def trash_files
      archived_files.each {|f|
        # check date and trash
        if @days_to_trash.days.ago > File.stat(f).mtime
          to_path = File.join(@trash_path, File.basename(f))
          to_path = "#{to_path}_#{Time.now.strftime('%Y%m%d_%H%M%S')}" if File.exist?(to_path)
          puts "trash file: #{f} -> #{to_path}"
          FileUtils.mv(f, File.join(@trash_path, File.basename(f)))
        end
      }
    end
    def delete_files
      trashed_files.each {|f|
        if @days_to_delete.days.ago > File.stat(f).mtime
          file_path = File.join(@trash_path, File.basename(f))
          puts "delete file: #{file_path}"
          FileUtils.rm(file_path)
        end
      }
    end
  end
end