# Used to see if a specified TML structure (given in the form of a Hash) resembles the
# overall structure of the given TML document.
#
# This is used to validate that the document conforms to a particular set of expectations
# without the overhead of loading it into the simulator.
#
# This class is tied into RSpec with the #resemble_tml method, as well as into Test::Unit
# with the #assert_tml_resembles method:
#
# RSpec Example
#
#   get :index
#   response.should resemble_tml(:tml => { :screen => [ :setvar, :submit => { :getvar } ] })
#
#   response.should_not resemble_tml(. . .) # negative test
#
# Test::Unit Examples
#
#   get :index
#   assert_tml_resembles(:tml => { :screen => [ :setvar, :submit => { :getvar } ] }, response)
#   
#   assert_tml_not_resemble(. . .) # negative test
#
class Rtml::Test::ResemblanceTest
  attr_reader :tml, :expectation

  def pass?
    pass_recursively?
  end

  def initialize(expectation, tml)
    build_expectation(expectation)
    find_tml(tml)
    @xml = Hpricot::XML(@tml).root
  end

  private
  def pass_recursively?(exp = @expectation.deep_dup, level = @xml)
    case exp
      when Hash
        pass_recursively_with_hash?(exp, level)
      when Array
        pass_with_array?(exp, level)
      else
        pass_with_object?(exp, level)
    end
  end

  def pass_recursively_with_hash?(exp, level)
    if key_matches = pass_with_array?(exp.keys, level)
      key_matches.each do |match|
        if array = pass_with_array?(exp.values, match)
          return array
        end
      end
    end
    false
  end

  def pass_with_array?(exp, level)
    matches = []
    exp.each do |item|
      return false unless object_matches = pass_recursively?(item, level)
      matches.concat object_matches
    end
    matches
  end

  def pass_with_object?(exp, level)
    if exp.to_s == level.name
      [level]
    elsif (matches = (level / exp)) && !matches.empty?
      matches
    else
      false
    end
  end

  def build_expectation(hash)
    @expectation = hash
  end

  def find_tml(object)
    @tml = case object
      when ActionController::TestResponse
        object.body
      when String
        object
      when Hpricot::Doc, Hpricot::Elem
        object.to_s
      when ActiveRecord::Base, Rtml::DocumentModelObject
        object.to_tml
      else
        object.to_s
    end
  end
end