A DSL to get you through the first 6 levels of http://bitsquest.bitbucket.org/index.html

bitquest.rb

class Dsl
  Change = Struct.new(:state, :new_directions)
  def initialize
    @state_count = 0
    @sensor_changes = {}
  end

  def start(directions)
    @start_directions = [directions].flatten
    @state_count = 1
  end

  def after(sensor_direction, directions_to_go)
    @sensor_changes[sensor_direction] ||= []
    @sensor_changes[sensor_direction] << Change.new(@state_count, [directions_to_go].flatten)
    @state_count += 1
  end

  def print
    [
      complete_stop_function,
      initialize_state_variable,
      start_direction,
      sensor_directions,
    ].join("\n")
  end

  def complete_stop_function
    <<-EOF
    function completeStop(thrusters) {
      thrusters.left(false);
      thrusters.top(false);
      thrusters.right(false);
      thrusters.bottom(false);
    }
    EOF
  end

  def start_direction
    <<-EOF
    this.on('start', function() {
      #{start_thrusters(@start_directions)}
      this.state += 1;
    });
    EOF
  end

  def sensor_directions
    output = @sensor_changes.map do |sensor_change|
      key, changes = sensor_change
      sensor_direction(key, changes)
    end

    output.join("\n\n")
  end

  def sensor_direction(direction, changes)
    start_out = <<-EOF
    this.on('sensor:#{direction}', function() {
    EOF

    content = ""
    changes.each do |change|
      content += <<-EOF
      if(this.state == #{change.state}) {
        completeStop(this.thrusters);
        #{start_thrusters(change.new_directions)}
        this.state += 1;
      }
      EOF
    end

    end_out = <<-EOF
    });
    EOF

    [start_out, content, end_out].join("\n")
  end

  def start_thrusters(directions)
    directions.map do |direction|
      "this.thrusters.#{thruster_for_direction(direction)}(true);"
    end.join("\n")
  end

  def thruster_for_direction(direction)
    case direction
    when :up then :bottom
    when :down then :top
    when :left then :right
    when :right then :left
    else raise "WHAT IS #{direction}"
    end
  end

  def initialize_state_variable
    "this.state = 0;"
  end
end

def run(&block)
  dsl = Dsl.new
  dsl.instance_eval(&block)
  puts dsl.print
end

# Level 6:
run do
  start :down
  after :bottom, :right
  after :right, :up
  after :left, :right
  after :right, :down
  after :bottom, :left
  after :left, :up
  after :top, :right
  after :right, :down
  after :left, :right
  after :right, :up
  after :top, :right
  after :right, [:right, :down]
end

# Level 5:
# run do
#   start :down
#   after :bottom, :right
#   after :right, :up
#   after :top, :left
#   after :left, :down
#   after :bottom, :right
#   after :right, :up
#   after :top, :left
#   after :left, :down
#   after :bottom, :right
#   after :right, :up
# end