drill_into.rb

    # This attempts to extract an element from an Array or Hash according to
    # the contents of the second parameter "path_array" which can contain
    # either strings or integers representing array indexes.
    #
    # This is very useful for parsing a URI as a query string
    #
    # Examples:
    #
    #  data = { stuff: { things: [
    #    {foo: "baz", bird: "pink", car: "blue" },
    #    {foo: "blah", bird: "purple", car: "orange"}
    #  ] } },
    #
    # drill_into(data, ["stuff", "things", "0", "car"])
    # => "blue"
    #
    # drill_into(data, ["stuff", "things", "orange", "bird"])
    # => "purple"
    #
    # drill_into(data, ["stuff", "things"]
    # => [ {foo: "baz", bird: "pink", car: "blue" },  {foo: "blah", bird: "purple", car: "orange"} ]
    #
    def drill_into(data, path_array)
      try_find = proc do |p_data, array|
        p_data.find { |a, _b|
          a.find { |_k, v| v == array.first } if a.is_a?(Enumerable)
        }
      end
      if data.is_a?(Enumerable)
        s_array = path_array.map do |s|
          @@index = Integer(s) rescue -1
          (@@index == s.to_i) ? '*' : ".#{s}"
        end
        selector = ':root > ' + s_array.join(' > ')
        match = JSONSelect(selector).match(data)
        result = match ? match : try_find.call(data, path_array)
        unless result
          key = path_array.shift.to_sym
          if data.is_a?(Hash)
            result = drill_into(data[key], path_array) if data.key?(key)
          elsif data.is_a?(Array)
            result = data[@@index] if @@index >= 0
          end
          result ||= try_find.call(data, path_array)
          if result and path_array.size > 1
            path_array.shift
            result = drill_into(result, path_array)
          end
        end
        return result
      end