/*
 * Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
 * Use of this file is governed by the BSD 3-clause license that
 * can be found in the LICENSE.txt file in the project root.
 */

package org.antlr.v4.runtime.atn;

import org.antlr.v4.runtime.ParserRuleContext;
import org.antlr.v4.runtime.RuleContext;
import org.antlr.v4.runtime.Token;
import org.antlr.v4.runtime.misc.IntervalSet;

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;


	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...
/** 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...
	 */
	public final List<DecisionState> decisionToState = new ArrayList<DecisionState>();

	
Maps from rule index to starting state number.
/**
	 * Maps from rule index to starting state number.
	 */
	public RuleStartState[] ruleToStartState;

	
Maps from rule index to stop state number.
/**
	 * Maps from rule index to stop state number.
	 */
	public RuleStopState[] ruleToStopState;


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

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

	
The maximum value for any symbol recognized by a transition in the ATN.
/**
	 * The maximum value for any symbol recognized by a transition in the ATN.
	 */
	public final int maxTokenType;

	
For lexer ATNs, this maps the rule index to the resulting token type. For parser ATNs, this maps the rule index to the generated bypass token type if the ATNDeserializationOptions.isGenerateRuleBypassTransitions deserialization option was specified; otherwise, this is null. /**
	 * For lexer ATNs, this maps the rule index to the resulting token type.
	 * For parser ATNs, this maps the rule index to the generated bypass token
	 * type if the
	 * {@link ATNDeserializationOptions#isGenerateRuleBypassTransitions}
	 * deserialization option was specified; otherwise, this is {@code null}.
	 */
	public int[] ruleToTokenType;

	
For lexer ATNs, this is an array of LexerAction objects which may be referenced by action transitions in the ATN. /**
	 * For lexer ATNs, this is an array of {@link LexerAction} objects which may
	 * be referenced by action transitions in the ATN.
	 */
	public LexerAction[] lexerActions;

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

	
Used for runtime deserialization of ATNs from strings /** Used for runtime deserialization of ATNs from strings */
	public ATN(ATNType grammarType, int maxTokenType) {
		this.grammarType = grammarType;
		this.maxTokenType = maxTokenType;
	}

	
Compute the set of valid tokens that can occur starting in state 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. /** Compute the set of valid tokens that can occur starting in state {@code s}.
	 *  If {@code ctx} is null, the set of tokens will not include what can follow
	 *  the rule surrounding {@code s}. In other words, the set will be
	 *  restricted to tokens reachable staying within {@code 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. Token.EPSILON is in set if we reach end of rule. /**
	 * Compute the set of valid tokens that can occur starting in {@code s} and
	 * staying in same rule. {@link Token#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(ATNState state) {
		if (state != null) {
			state.atn = this;
			state.stateNumber = states.size();
		}

		states.add(state);
	}

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

	public int defineDecisionState(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();
	}

	
Computes the set of input symbols which could follow ATN state number stateNumber in the specified full context. This method considers the complete parser context, but does not evaluate semantic predicates (i.e. all predicates encountered during the calculation are assumed true). If a path in the ATN exists from the starting state to the RuleStopState of the outermost context without matching any symbols, Token.EOF is added to the returned set. 
If context is null, it is treated as RuleContext.EMPTY.
Note that this does NOT give you the set of all tokens that could
appear at a given token position in the input phrase.  In other words,
it does not answer:
  "Given a specific partial input phrase, return the set of all tokens
   that can follow the last token in the input phrase."
The big difference is that with just the input, the parser could
land right in the middle of a lookahead decision. Getting
all *possible* tokens given a partial input stream is a separate
computation. See https://github.com/antlr/antlr4/issues/1428
For this function, we are specifying an ATN state and call stack to compute
what token(s) can come next and specifically: outside of a lookahead decision.
That is what you want for error reporting and recovery upon parse error.
Params:
stateNumber – the ATN state number
context – the full parse context
Throws:
IllegalArgumentException – if the ATN does not contain a state with number stateNumber
Returns:
The set of potentially valid input symbols which could follow the
specified state in the specified context./**
	 * Computes the set of input symbols which could follow ATN state number
	 * {@code stateNumber} in the specified full {@code context}. This method
	 * considers the complete parser context, but does not evaluate semantic
	 * predicates (i.e. all predicates encountered during the calculation are
	 * assumed true). If a path in the ATN exists from the starting state to the
	 * {@link RuleStopState} of the outermost context without matching any
	 * symbols, {@link Token#EOF} is added to the returned set.
	 *
	 * <p>If {@code context} is {@code null}, it is treated as {@link ParserRuleContext#EMPTY}.</p>
	 *
	 * Note that this does NOT give you the set of all tokens that could
	 * appear at a given token position in the input phrase.  In other words,
	 * it does not answer:
	 *
	 *   "Given a specific partial input phrase, return the set of all tokens
	 *    that can follow the last token in the input phrase."
	 *
	 * The big difference is that with just the input, the parser could
	 * land right in the middle of a lookahead decision. Getting
     * all *possible* tokens given a partial input stream is a separate
     * computation. See https://github.com/antlr/antlr4/issues/1428
	 *
	 * For this function, we are specifying an ATN state and call stack to compute
	 * what token(s) can come next and specifically: outside of a lookahead decision.
	 * That is what you want for error reporting and recovery upon parse error.
	 *
	 * @param stateNumber the ATN state number
	 * @param context the full parse context
	 * @return The set of potentially valid input symbols which could follow the
	 * specified state in the specified context.
	 * @throws IllegalArgumentException if the ATN does not contain a state with
	 * number {@code stateNumber}
	 */
	public IntervalSet getExpectedTokens(int stateNumber, RuleContext context) {
		if (stateNumber < 0 || stateNumber >= states.size()) {
			throw new IllegalArgumentException("Invalid state number.");
		}

		RuleContext ctx = context;
		ATNState s = states.get(stateNumber);
		IntervalSet following = nextTokens(s);
		if (!following.contains(Token.EPSILON)) {
			return following;
		}

		IntervalSet expected = new IntervalSet();
		expected.addAll(following);
		expected.remove(Token.EPSILON);
		while (ctx != null && ctx.invokingState >= 0 && following.contains(Token.EPSILON)) {
			ATNState invokingState = states.get(ctx.invokingState);
			RuleTransition rt = (RuleTransition)invokingState.transition(0);
			following = nextTokens(rt.followState);
			expected.addAll(following);
			expected.remove(Token.EPSILON);
			ctx = ctx.parent;
		}

		if (following.contains(Token.EPSILON)) {
			expected.add(Token.EOF);
		}

		return expected;
	}
}