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path: root/lib/pry/terminal.rb
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# frozen_string_literal: true

class Pry
  class Terminal
    class << self
      # Return a pair of [rows, columns] which gives the size of the window.
      #
      # If the window size cannot be determined, return nil.
      def screen_size
        rows, cols = actual_screen_size
        [rows.to_i, cols.to_i] if rows.to_i != 0 && cols.to_i != 0
      end

      # Return a screen size or a default if that fails.
      def size!(default = [27, 80])
        screen_size || default
      end

      # Return a screen width or the default if that fails.
      def width!
        size![1]
      end

      # Return a screen height or the default if that fails.
      def height!
        size![0]
      end

      def actual_screen_size
        # The best way, if possible (requires non-jruby >=1.9 or io-console gem)
        screen_size_according_to_io_console ||
          # Fall back to the old standby, though it might be stale:
          screen_size_according_to_env ||
          # Fall further back, though this one is also out of date without something
          # calling Readline.set_screen_size
          screen_size_according_to_readline ||
          # Windows users can otherwise run ansicon and get a decent answer:
          screen_size_according_to_ansicon_env
      end

      def screen_size_according_to_io_console
        return if Pry::Helpers::Platform.jruby?

        begin
          require 'io/console'

          begin
            if $stdout.respond_to?(:tty?) && $stdout.tty? && $stdout.respond_to?(:winsize)
              $stdout.winsize
            end
          rescue Errno::EOPNOTSUPP # rubocop:disable Lint/HandleExceptions
            # $stdout is probably a socket, which doesn't support #winsize.
          end
        rescue LoadError # rubocop:disable Lint/HandleExceptions
          # They probably don't have the io/console stdlib or the io-console gem.
          # We'll keep trying.
        end
      end

      def screen_size_according_to_env
        size = [ENV['LINES'] || ENV['ROWS'], ENV['COLUMNS']]
        size if nonzero_column?(size)
      end

      def screen_size_according_to_readline
        if defined?(Readline) && Readline.respond_to?(:get_screen_size)
          size = Readline.get_screen_size
          size if nonzero_column?(size)
        end
      rescue Java::JavaLang::NullPointerException
        # This rescue won't happen on jrubies later than:
        #     https://github.com/jruby/jruby/pull/436
        nil
      end

      def screen_size_according_to_ansicon_env
        return unless ENV['ANSICON'] =~ /\((.*)x(.*)\)/

        size = [Regexp.last_match(2), Regexp.last_match(1)]
        size if nonzero_column?(size)
      end

      private

      def nonzero_column?(size)
        size[1].to_i > 0
      end
    end
  end
end