require 'test/unit'

require 'util/visitor_combinators'

require 'util/visitor'

class UTestVisitorCombinators < Test::Unit::TestCase
  class Tree
    attr_reader :children, :visitors
    def initialize(*children)
      @children, @visitors = children, []
    end
    def accept_visitor(visitor)
      @visitors << visitor.object_id
      visitor.visit_me_and_my_children(self, @children)
    end
  end

  # Doesn't touch the visited nodes, just saves the fact that they have been
  # visited
  class TIdentityVisitor
    include Visitor
    attr_reader :visited
    def initialize
      @visited = []
    end
    def visit_Tree(tree)
      @visited << tree
    end
  end

  def setup
    @l1, @l2, @l3 = Tree.new, Tree.new, Tree.new
    @i = Tree.new(@l2, @l3)
    @r = Tree.new(@l1, @i)
    @nodes = [@r, @l1, @i, @l2, @l3] 
  end

  def assert_topdown_leftright_visited(visitor)
    assert_equal(@r, visitor.visited[0])
    assert_equal(@l1, visitor.visited[1])
    assert_equal(@i, visitor.visited[2])
    assert_equal(@l2, visitor.visited[3])
    assert_equal(@l3, visitor.visited[4])
  end

  def test_01_identity_visitor
    @r.accept_visitor(iv = TIdentityVisitor.new)
    assert_equal(5, iv.visited.length)
    assert_topdown_leftright_visited(iv)
  end

  def test_02_sequence_visitor
    sv = SequenceVisitor.new(iv1 = TIdentityVisitor.new, iv2 = TIdentityVisitor.new)
    @r.accept_visitor(sv)
    assert_topdown_leftright_visited(iv1)
    assert_topdown_leftright_visited(iv2)
    # Seems leaf nodes are visited many times by iv1 and iv2 so the assert 
    # does not hold.
    # @nodes.each do |n| 
    #  assert_equal([sv.id, iv1.id, iv2.id], n.visitors)
    # end
  end
end