module Isomorfeus
  module Operation
    module Gherkin
      FIRST_EXCEPTION = "First must be the first one that is used and can only used once!"
      FINALLY_EXCEPTION = "Finally, except for Ensure and Failed, must be the last one to be used and can only be used once!"

      NEWLINE = /\r?\n/
      OPERATION = /^\s*Operation: (.*)$/
      PROCEDURE = /^\s*Procedure: (.*)$/
      STAR = /^\s*\* (.*)$/
      GIVEN = /^\s*Given (.*)$/
      WHEN = /^\s*When (.*)$/
      THEN = /^\s*Then (.*)$/
      AND = /^\s*And (.*)$/
      FIRST = /^\s*First (.*)$/
      ENSURE = /^\s*Ensure (.*)$/
      FINALLY = /^\s*Finally (.*)$/
      IW_FAILING = /^\s*(?:When|If) failing (.*)$/
      IF_ITT_FAILED = /^\s*If (?:that|this|it) failed (.*)$/
      FAILED = /^\s*Failed (.*)$/
      COMMENT = /^\s*# (.*)$/
      WHITE_SPACE = /^\s*$/

      def self.parse(gherkin_text)
        operation = { operation: '', procedure: '', steps: [], failure: [], ensure: [] }
        has_finally = false
        lines = gherkin_text.split(NEWLINE)

        lines.each do |line|
          case line
          when STAR, GIVEN, WHEN, THEN, AND
            raise FINALLY_EXCEPTION if has_finally
            operation[:steps] << $1.strip
          when ENSURE
            operation[:ensure] << $1.strip
          when IW_FAILING, IF_ITT_FAILED, FAILED
            operation[:failure] << $1.strip
          when FIRST
            raise FIRST_EXCEPTION if operation[:steps].size > 0
            operation[:steps] << $1.strip
          when FINALLY
            raise FINALLY_EXCEPTION if has_finally
            operation[:steps] << $1.strip
            has_finally = true
          when PROCEDURE
            raise 'No Operation defined!' if operation[:operation].empty?
            raise 'Procedure already defined!' unless operation[:procedure].empty?
            operation[:procedure] = $1.strip
          when OPERATION
            raise 'Operation already defined!' unless operation[:operation].empty?
            operation[:operation] = $1.strip
          when WHITE_SPACE, COMMENT
            # nothing, just skip
          else
            raise "Unknown key word(s) at the beginning of the line: #{line}" unless operation[:procedure].empty?
            operation[:description] = [] unless operation.key?(:description)
            operation[:description] << line.strip
          end
        end

        operation
      end
    end
  end
end