ilm-labs/ilm

module Ilm
  module Chemistry
    # This class has functionality for compounds
    # Ex: constituent elements, molecular mass, etc
    class Compound
      COMPOUND_REGEXP =
        /[A-Z][a-z]{0,2}\d*|\((?:[^()]*(?:\(.*\))?[^()]*)+\)\d*/.freeze

      attr_accessor :molecular_mass, :constituents, :formula, :molar_mass

      def initialize(arg)
        @formula = arg
        build_constituents
        calculate_mass
      end

      private

      def calculate_mass
        @molecular_mass = 0.0.u
        @constituents.each do |_symbol, info|
          @molecular_mass += info[:element].atomic_mass * info[:atom_count]
        end
        @molar_mass = (@molecular_mass.value / 1000.0).kg / 1.mol
      end

      def build_constituents
        @constituents = {}
        get_const_atoms.each do |symbol, count|
          @constituents[symbol] = {
            element: Element.get_by_symbol(symbol),
            atom_count: count
          }
        end
        @constituents
      end

      def get_const_atoms(formula = @formula, r = {})
        formula.scan(COMPOUND_REGEXP).each do |const|
          multipler = get_multipler const
          if const[0] != '(' && multipler.zero?
            r[const] = r[const] ? r[const] + 1 : 1
          else
            (multipler.zero? ? 1 : multipler).times do
              sub_const = const.match(/^\(?(.*?)\)?($|\d*$)/).to_a
              get_const_atoms sub_const[const == sub_const.first ? 1 : 0], r
            end
          end
        end
        r
      end

      def get_multipler(const)
        multipler = const.match(/\d*$/).to_a.first.to_i
        multipler
      end
    end
  end
end