module Solve

def engine=(selected_engine)
  engine_class = solver_for_engine(selected_engine)
  if engine_class.nil?
    raise Errors::InvalidEngine, "Engine `#{selected_engine}` is not supported. Valid values are `:ruby`, `:gecode`"
  else
    engine_class.activate
  end
  @engine = selected_engine
end

def it!(graph, demands, options = {})
  solver_for_engine(engine).new(graph, demands, options).resolve(options)
end

def solver_for_engine(engine_name)
  case engine_name
  when :ruby
    RubySolver
  when :gecode
    GecodeSolver
  end
end