Class: Worlds::Terminal::Runner

Inherits:
Object
  • Object
show all
Defined in:
lib/worlds/terminal/runner.rb

Overview

A container for the input loop, which is needed because input is read in a non-blocking way, i.e. input is read while new output is displayed.

Constant Summary collapse

PASTEL = 
Pastel.new
CURSOR = 
'█'
BACKSPACE = 
"\x7F"
CTRL_BACKSPACE =

or Cmd+Backspace on MacOS

"\x17"
INTERRUPT =

Ctrl+C

"\x03"

Class Method Summary collapse

Class Method Details

.io_loop ⇒ Object

Loops continuously, reading input and allowing Worlds to update and output.



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# File 'lib/worlds/terminal/runner.rb', line 17

def self.io_loop
  loop do
    # We need our own input buffer here because the terminal input buffer is
    # disabled due to Helper::io_mode_raw!
    @input_buffer ||= ''

    new_input = Helper.read_nonblock

    if new_input
      return if new_input.include?(INTERRUPT)

      # Handle Enter.
      new_input_has_newline = new_input.include?("\n") || new_input.include?("\r")
      new_input = new_input.split(/[\n\r]/).first if new_input_has_newline

      # Add new input to buffer (or add nothing, if no new input).
      @input_buffer << (new_input || '')

      # Handle deletion: Ctrl + Backspace (line), or Backspace (character).
      # In either case, re-print the input buffer with spaces at the end
      # to cover over the deleted characters.
      if @input_buffer.include?(CTRL_BACKSPACE)
        print "#{CURSOR}#{' ' * @input_buffer.length}\r"
        @input_buffer = ''
      else
        backspace_count = @input_buffer.count(BACKSPACE)

        while @input_buffer.length > 0 && @input_buffer.include?(BACKSPACE)
          @input_buffer.sub!(/[^#{BACKSPACE}]#{BACKSPACE}/, '')
          @input_buffer = '' if @input_buffer.chars.uniq == [BACKSPACE]
        end

        print "#{@input_buffer}#{CURSOR}#{' ' * backspace_count}\r"
      end

      # Echo input. The \r is to make the line replaceable by new output,
      # while the input line will re-appear below the new output; in effect,
      # to allow output above the input line.
      print "#{@input_buffer}#{CURSOR}\r"
    end

    # Empty the input buffer if Enter was pressed.
    if new_input_has_newline
      input_line = @input_buffer.strip
      @input_buffer = ''
    end

    # If a line was just inputted, set up an input hash as either a number
    # selection (if a selection menu was just shown) or else a new command.
    if input_line
      if @select_for && input_line.match?(/\A\d+\z/)
        input = { type: :select, command: @select_for, selection: input_line.to_i }
        @select_for = nil
      else
        input = { type: :command, command: input_line }
      end
    end

    # Allow Worlds to loop, and print outputs if any.
    if outputs = Worlds::Updater.tick(input)
      outputs.each do |output|
        case output[:type]
        when :exit
          return
        when :select # selection menu
          Helper.puts PASTEL.white(output[:heading])
          output[:options].each.with_index do |option, i|
            Helper.puts PASTEL.blue("#{i + 1}. ") + PASTEL.white(option)
          end

          @select_for = input_line
        else # informational
          Helper.puts PASTEL.send(output[:color], output[:content])
        end
      end
    end

    # Reset input, to remain empty until next time Enter is pressed.
    input_line = nil && input = nil if input_line
  end
end