/*
 * [The "BSD license"]
 *  Copyright (c) 2012 Terence Parr
 *  Copyright (c) 2012 Sam Harwell
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions
 *  are met:
 *
 *  1. Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *  3. The name of the author may not be used to endorse or promote products
 *     derived from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 *  IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 *  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 *  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 *  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 *  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 *  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 *  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 *  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 *  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.antlr.v4.runtime.atn;

import org.antlr.v4.runtime.RuleContext;
import org.antlr.v4.runtime.misc.IntervalSet;
import org.antlr.v4.runtime.misc.NotNull;
import org.antlr.v4.runtime.misc.Nullable;

import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

/** */
public class ATN {
	public static final int INVALID_ALT_NUMBER = 0;

	@NotNull
	public final List<ATNState> states = new ArrayList<ATNState>();

	/** Each subrule/rule is a decision point and we must track them so we
	 *  can go back later and build DFA predictors for them.  This includes
	 *  all the rules, subrules, optional blocks, ()+, ()* etc...
	 */
	@NotNull
	public final List<DecisionState> decisionToState = new ArrayList<DecisionState>();

	public RuleStartState[] ruleToStartState;
	public RuleStopState[] ruleToStopState;

	@NotNull
	public final Map<String, TokensStartState> modeNameToStartState =
		new LinkedHashMap<String, TokensStartState>();

	/**
	 * The type of the ATN.
	 */
	public ATNType grammarType;

	public int maxTokenType;

	// runtime for lexer only
	public int[] ruleToTokenType;
	public int[] ruleToActionIndex;

	@NotNull
	public final List<TokensStartState> modeToStartState = new ArrayList<TokensStartState>();

	/** used during construction from grammar AST */
	int stateNumber = 0;

	/** Used for runtime deserialization of ATNs from strings */
	public ATN() { }

	/** Compute the set of valid tokens that can occur starting in s.
	 *  If ctx is null, the set of tokens will not include what can follow
	 *  the rule surrounding s. In other words, the set will be
	 *  restricted to tokens reachable staying within s's rule.
	 */
	public IntervalSet nextTokens(ATNState s, RuleContext ctx) {
		LL1Analyzer anal = new LL1Analyzer(this);
		IntervalSet next = anal.LOOK(s, ctx);
		return next;
	}

    /** Compute the set of valid tokens that can occur starting in s and staying in same rule.
     *  EPSILON is in set if we reach end of rule.
     */
    public IntervalSet nextTokens(ATNState s) {
        if ( s.nextTokenWithinRule != null ) return s.nextTokenWithinRule;
        s.nextTokenWithinRule = nextTokens(s, null);
        s.nextTokenWithinRule.setReadonly(true);
        return s.nextTokenWithinRule;
    }

	public void addState(@Nullable ATNState state) {
		if ( state==null ) { states.add(null); stateNumber++; return; }
		state.atn = this;
		states.add(state);
		state.stateNumber = stateNumber++;
	}

	public void removeState(@NotNull ATNState state) {
		states.set(state.stateNumber, null); // just free mem, don't shift states in list
	}

	public int defineDecisionState(@NotNull DecisionState s) {
		decisionToState.add(s);
		s.decision = decisionToState.size()-1;
		return s.decision;
	}

    public DecisionState getDecisionState(int decision) {
        if ( !decisionToState.isEmpty() ) {
            return decisionToState.get(decision);
        }
        return null;
    }

	public int getNumberOfDecisions() {
		return decisionToState.size();
	}
}

@@ -2821,81 +2821,8 @@
 );%0A%0A
-%09/** used during construction from grammar AST */%0A%09int stateNumber = 0;%0A%0A
 %09/**
@@ -3813,68 +3813,26 @@
 if (
- 
 state
-==
+ != 
 null
- 
 ) %7B
- states.add(null); stateNumber++; return; %7D
 %0A
+%09
 %09%09st
@@ -3853,62 +3853,68 @@
 ;%0A%09%09
+%09
 state
-s.add(state);%0A%09%09state.stateNumber = stateNumber++
+.stateNumber = states.size();%0A%09%09%7D%0A%0A%09%09states.add(state)
 ;%0A%09%7D

Remove unnecessary field ATN.stateNumber