snake.rb

require 'glimmer-dsl-libui'

require_relative 'snake/presenter/grid'

class Snake
  include Glimmer
  
  CELL_SIZE = 15
  SNAKE_MOVE_DELAY = 0.1
  
  def initialize
    @game = Model::Game.new
    @grid = Presenter::Grid.new(@game)
    @game.start
    @keypress_queue = []
    create_gui
    register_observers
  end
  
  def launch
    @main_window.show
  end
  
  def register_observers
    observe(@game, :over) do |game_over|
      Glimmer::LibUI.queue_main do
        if game_over
          msg_box('Game Over!', "Score: #{@game.score} | High Score: #{@game.high_score}")
          @game.start
        end
      end
    end
    
    Glimmer::LibUI.timer(SNAKE_MOVE_DELAY) do
      unless @game.paused? || @game.over?
        process_queued_keypress
        @game.snake.move
      end
    end
  end
  
  def process_queued_keypress
    # key press queue ensures one turn per snake move to avoid a double-turn resulting in instant death (due to snake illogically going back against itself)
    key = @keypress_queue.shift
    case [@game.snake.head.orientation, key]
    in [:north, :right] | [:east, :down] | [:south, :left] | [:west, :up]
      @game.snake.turn_right
    in [:north, :left] | [:west, :down] | [:south, :right] | [:east, :up]
      @game.snake.turn_left
    else
      # No Op
    end
  end
  
  def create_gui
    @main_window = window {
      # data-bind window title to game score, converting it to a title string on read from the model
      title <= [@game, :score, on_read: -> (score) {"Snake (Score: #{@game.score})"}]
      content_size @game.width * CELL_SIZE, @game.height * CELL_SIZE
      resizable false
      
      vertical_box {
        padded false
        
        @game.height.times do |row|
          horizontal_box {
            padded false
            
            @game.width.times do |column|
              area {
                square(0, 0, CELL_SIZE) {
                  fill <= [@grid.cells[row][column], :color] # data-bind square fill to grid cell color
                }
                
                on_key_down do |area_key_event|
                  handled = true # assume we will handle the event
                  if area_key_event[:key] == ' '
                    @game.toggle_pause
                  elsif %i[up right down left].include?(area_key_event[:ext_key])
                    @keypress_queue << area_key_event[:ext_key]
                  else
                    handled = false # we won't handle the event after all
                  end
                  handled
                end
              }
            end
          }
        end
      }
    }
  end
end

Snake.new.launch