Antlr4.Runtime.Atn.ATNDeserializer.OptimizeSets C# (CSharp) Method

        private static int OptimizeSets(ATN atn, bool preserveOrder)
        {
            if (preserveOrder)
            {
                // this optimization currently doesn't preserve edge order.
                return 0;
            }
            int removedPaths = 0;
            IList<DecisionState> decisions = atn.decisionToState;
            foreach (DecisionState decision in decisions)
            {
                IntervalSet setTransitions = new IntervalSet();
                for (int i = 0; i < decision.NumberOfOptimizedTransitions; i++)
                {
                    Transition epsTransition = decision.GetOptimizedTransition(i);
                    if (!(epsTransition is EpsilonTransition))
                    {
                        continue;
                    }
                    if (epsTransition.target.NumberOfOptimizedTransitions != 1)
                    {
                        continue;
                    }
                    Transition transition = epsTransition.target.GetOptimizedTransition(0);
                    if (!(transition.target is BlockEndState))
                    {
                        continue;
                    }
                    if (transition is NotSetTransition)
                    {
                        // TODO: not yet implemented
                        continue;
                    }
                    if (transition is AtomTransition || transition is RangeTransition || transition is SetTransition)
                    {
                        setTransitions.Add(i);
                    }
                }
                if (setTransitions.Count <= 1)
                {
                    continue;
                }
                IList<Transition> optimizedTransitions = new List<Transition>();
                for (int i_1 = 0; i_1 < decision.NumberOfOptimizedTransitions; i_1++)
                {
                    if (!setTransitions.Contains(i_1))
                    {
                        optimizedTransitions.Add(decision.GetOptimizedTransition(i_1));
                    }
                }
                ATNState blockEndState = decision.GetOptimizedTransition(setTransitions.MinElement).target.GetOptimizedTransition(0).target;
                IntervalSet matchSet = new IntervalSet();
                for (int i_2 = 0; i_2 < setTransitions.GetIntervals().Count; i_2++)
                {
                    Interval interval = setTransitions.GetIntervals()[i_2];
                    for (int j = interval.a; j <= interval.b; j++)
                    {
                        Transition matchTransition = decision.GetOptimizedTransition(j).target.GetOptimizedTransition(0);
                        if (matchTransition is NotSetTransition)
                        {
                            throw new NotSupportedException("Not yet implemented.");
                        }
                        else
                        {
                            matchSet.AddAll(matchTransition.Label);
                        }
                    }
                }
                Transition newTransition;
                if (matchSet.GetIntervals().Count == 1)
                {
                    if (matchSet.Count == 1)
                    {
                        newTransition = new AtomTransition(blockEndState, matchSet.MinElement);
                    }
                    else
                    {
                        Interval matchInterval = matchSet.GetIntervals()[0];
                        newTransition = new RangeTransition(blockEndState, matchInterval.a, matchInterval.b);
                    }
                }
                else
                {
                    newTransition = new SetTransition(blockEndState, matchSet);
                }
                ATNState setOptimizedState = new BasicState();
                setOptimizedState.SetRuleIndex(decision.ruleIndex);
                atn.AddState(setOptimizedState);
                setOptimizedState.AddTransition(newTransition);
                optimizedTransitions.Add(new EpsilonTransition(setOptimizedState));
                removedPaths += decision.NumberOfOptimizedTransitions - optimizedTransitions.Count;
                if (decision.IsOptimized)
                {
                    while (decision.NumberOfOptimizedTransitions > 0)
                    {
                        decision.RemoveOptimizedTransition(decision.NumberOfOptimizedTransitions - 1);
                    }
                }
                foreach (Transition transition_1 in optimizedTransitions)
                {
                    decision.AddOptimizedTransition(transition_1);
                }
            }
            return removedPaths;
        }