expression_parser.rb

require 'method_source'

module ChristmasTree
  class WrappingPaper
    class ExpressionParser

      attr_reader :block

      ExpressionOptions = Struct.new(:expression, :line_number) do
        def range
          line_number..(expression.split("\n").length + line_number)
        end
      end

      def initialize(options)
        @block = options.fetch(:block)
        @expression_counter = 0
      end

      def expression_counter
        @expression_counter ||= 0
      end

      def accumulator
        @accumulator ||= {}
      end

      def length
        @length ||= block.source.split("\n").length
      end

      def location
        block.source_location[0]
      end

      def starting_line
        block.source_location[1]
      end

      def extract_expression_from(line_number)
        expression  = MethodSource.expression_at(File.read(location),line_number).strip

        self.accumulator[expression_counter] = ExpressionOptions.new(expression, line_number)
        @expression_counter += 1
      rescue SyntaxError
        true
      end

      def collect_expression
        (source_range).each do |line_number|
          extract_expression_from(line_number)
        end

        accumulator
      end

      def source_range
        starting_line..(starting_line + length)
      end

      def self.expression_from_block(block)
        new(block: block).collect_expression
      end

    end
  end
end