module StreamWrapper
  class GzipMultiFile

    def initialize (paths = [], filters = {})
      @paths = paths.is_a?(Array) ? paths.dup : [paths]
      @filters = filters
      if @paths.empty?
        @current_line = 0
        @current_file = $stdin
        @current_path = '<stdin>'
      end
    end

    def gets
      if file = current_stream
        @current_line += 1
        file.gets
      else
        nil
      end
    end

    def eof?
      ! current_stream
    end

    def close
      @current_file.close unless @current_file.nil?
    end

    def current_position
      "#{@current_path}:#{@current_line}"
    end

    def debug= (bool)
      @debug = bool
    end

    def debug?
      @debug
    end

    protected

    def log (message)
      $stderr.puts message if debug?
    end
    
    def current_stream
      if @current_file.nil? || @current_file.eof?
        close
        @current_file = next_available_file
      end
      @current_file
    end

    def next_available_file
      if @current_path
        log "Closed #{@current_path} after reading #{@current_line} lines"
      end
      @current_line = 0
      @current_path = @paths.shift or return nil
      log "Switching to #{@current_path}"
      file = IO.popen(shell_command(@current_path))
      file.eof? ? next_available_file : file
    end

    # Use whitelist to be sure. Observation filters is applied after anyways.
    SHOP_AND_ACCOUNT_ID_FILTER = /^[a-zA-Z0-9._]+$/

    def shell_command (path)
      if path =~ /\.gz/
        command = "gunzip -c #{path.gsub(' ','\\ ')}"
      else
        command = "cat #{path.gsub(' ','\\ ')}"
      end
      if @filters[:shop_id] && @filters[:shop_id] =~ SHOP_AND_ACCOUNT_ID_FILTER  
        command += " | grep -F sid=#{@filters[:shop_id]}"
      end
      if @filters[:account_id] && @filters[:account_id] =~ SHOP_AND_ACCOUNT_ID_FILTER
        command += " | grep -F aid=#{@filters[:account_id]}"
      end
      if @filters[:observation_type]
        command += " | grep -F o=#{@filters[:observation_type]}"
      end
      command
    end
    
  end
end