module Neo4j::Embedded

  # Wraps the Cypher query result.
  # Loads the node and relationships wrapper if possible and use symbol as column keys.
  # This is typically used in the native neo4j bindings since result does is not a Ruby enumerable with symbols as keys.
  # @note The result is a once forward read only Enumerable, work if you need to read the result twice - use #to_a
  #
  class ResultWrapper
    class ResultsAlreadyConsumedException < Exception;
    end

    include Enumerable

    # @return the original result from the Neo4j Cypher Engine, once forward read only !
    attr_reader :source

    def initialize(source, query)
      @source = source
      @struct = Struct.new(*source.columns.to_a.map(&:to_sym))
      @unread = true
      @query = query
    end

    def to_s
      @query
    end

    def inspect
      "Enumerable query: '#{@query}'"
    end

    # @return [Array<Symbol>] the columns in the query result
    def columns
      @source.columns.map(&:to_sym)
    end

    def each
      raise ResultsAlreadyConsumedException unless @unread

      if block_given?
        @source.each do |row|
          yield(row.each_with_object(@struct.new) do |(column, value), result|
            result[column.to_sym] = (value.respond_to?(:wrapper) ? value.wrapper : value)
          end)
        end
      else
        Enumerator.new(self)
      end
    end

  end
end