differ.rb

class Differ
  attr_reader :data1, :data2

  def initialize(data1, data2)
    if data1 === nil || data2 === nil
      raise ArgumentError.new("Can't diff nil values")
    end
    @data1 = data1
    @data2 = data2
    check_matching_parameters
  end

  def check_matching_parameters
    type_1 = find_matching_type(data1)
    type_2 = find_matching_type(data2)
    if type_1 != type_2
      raise ArgumentError.new("Can't diff parameters that are not of the same type")
    end
  end

  def find_matching_type(data)
    [String, Set, SortedSet, Hash, Array].select do |type|
      data.is_a?(type)
    end.first || ""
  end

  def are_sets?
    @data1.is_a?(Set) && @data2.is_a?(Set)
  end

  def are_hashes?
    @data1.is_a?(Hash) && @data2.is_a?(Hash)
  end

  def are_sorted_sets?
    @data1.is_a?(SortedSet) && @data2.is_a?(SortedSet)
  end

  def are_arrays?
    @data1.is_a?(Array) && @data2.is_a?(Array)
  end

  def are_strings?
    @data1.is_a?(String) && @data2.is_a?(String)
  end

  def diff_sets
    data2.difference(data1)
  end

  def diff_arrays(first = data1, second = data2)
    (second + first) - (second & first)
  end

  def diff_sorted_sets
    diff_arrays(HashWithIndifferentAccess(data1).to_a, HashWithIndifferentAccess(data2).to_a)
  end

  def diff_hashes
    h = {};
    diff_arrays(data1.to_a, data2.to_a).flatten.each do |data|
      if data2[data].present?
        h[data.to_s] = data2[data]
      end
    end
    h
  end

  def diff_strings
    data1_arr = data1.split('').collect(&:strip)
    data2_arr = data2.split('').collect(&:strip)
    diff_arrays(data1_arr, data2_arr).join('')
  end


  def diff
    if are_arrays?
      diff_arrays
    elsif are_hashes?
      diff_hashes
    elsif are_sorted_sets?
      diff_sorted_sets
    elsif are_sets?
      diff_sets
    elsif are_strings?
      diff_strings
    end
  end
end