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/*
 * [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.misc.IntervalSet;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

/**
 * The following images show the relation of states and
 * {@link ATNState#transitions} for various grammar constructs.
 *
 * 
 *
 * Solid edges marked with an ε indicate a required
 * {@link EpsilonTransition}.
 *
 * Dashed edges indicate locations where any transition derived from
 * {@link Transition} might appear.
 *
 * Dashed nodes are place holders for either a sequence of linked
 * {@link BasicState} states or the inclusion of a block representing a nested
 * construct in one of the forms below.
 *
 * Nodes showing multiple outgoing alternatives with a {@code ...} support
 * any number of alternatives (one or more). Nodes without the {@code ...} only
 * support the exact number of alternatives shown in the diagram.
 *
 * 
 *
 * Basic Blocks
 *
 * Rule
 *
 * 
 *
 * Block of 1 or more alternatives
 *
 * 
 *
 * Greedy Loops
 *
 * Greedy Closure: {@code (...)*}
 *
 * 
 *
 * Greedy Positive Closure: {@code (...)+}
 *
 * 
 *
 * Greedy Optional: {@code (...)?}
 *
 * 
 *
 * Non-Greedy Loops
 *
 * Non-Greedy Closure: {@code (...)*?}
 *
 * 
 *
 * Non-Greedy Positive Closure: {@code (...)+?}
 *
 * 
 *
 * Non-Greedy Optional: {@code (...)??}
 *
 * 
 */
public abstract class ATNState {
	public static final int INITIAL_NUM_TRANSITIONS = 4;

	// constants for serialization
	public static final int INVALID_TYPE = 0;
	public static final int BASIC = 1;
	public static final int RULE_START = 2;
	public static final int BLOCK_START = 3;
	public static final int PLUS_BLOCK_START = 4;
	public static final int STAR_BLOCK_START = 5;
	public static final int TOKEN_START = 6;
	public static final int RULE_STOP = 7;
	public static final int BLOCK_END = 8;
	public static final int STAR_LOOP_BACK = 9;
	public static final int STAR_LOOP_ENTRY = 10;
	public static final int PLUS_LOOP_BACK = 11;
	public static final int LOOP_END = 12;

	public static final List serializationNames =
		Collections.unmodifiableList(Arrays.asList(
			"INVALID",
			"BASIC",
			"RULE_START",
			"BLOCK_START",
			"PLUS_BLOCK_START",
			"STAR_BLOCK_START",
			"TOKEN_START",
			"RULE_STOP",
			"BLOCK_END",
			"STAR_LOOP_BACK",
			"STAR_LOOP_ENTRY",
			"PLUS_LOOP_BACK",
			"LOOP_END"
		));

	public static final int INVALID_STATE_NUMBER = -1;

    /** Which ATN are we in? */
   	public ATN atn = null;

	public int stateNumber = INVALID_STATE_NUMBER;

	public int ruleIndex; // at runtime, we don't have Rule objects

	public boolean epsilonOnlyTransitions = false;

	/** Track the transitions emanating from this ATN state. */
	protected final List transitions =
		new ArrayList(INITIAL_NUM_TRANSITIONS);

	/** Used to cache lookahead during parsing, not used during construction */
    public IntervalSet nextTokenWithinRule;

	@Override
	public int hashCode() { return stateNumber; }

	@Override
	public boolean equals(Object o) {
		// are these states same object?
		if ( o instanceof ATNState ) return stateNumber==((ATNState)o).stateNumber;
		return false;
	}

	public boolean isNonGreedyExitState() {
		return false;
	}

	@Override
	public String toString() {
		return String.valueOf(stateNumber);
	}

	public Transition[] getTransitions() {
		return transitions.toArray(new Transition[transitions.size()]);
	}

	public int getNumberOfTransitions() {
		return transitions.size();
	}

	public void addTransition(Transition e) {
		if (transitions.isEmpty()) {
			epsilonOnlyTransitions = e.isEpsilon();
		}
		else if (epsilonOnlyTransitions != e.isEpsilon()) {
			System.err.format("ATN state %d has both epsilon and non-epsilon transitions.\n", stateNumber);
			epsilonOnlyTransitions = false;
		}

		transitions.add(e);
	}

	public Transition transition(int i) { return transitions.get(i); }

	public void setTransition(int i, Transition e) {
		transitions.set(i, e);
	}

	public Transition removeTransition(int index) {
		return transitions.remove(index);
	}

	public abstract int getStateType();

	public final boolean onlyHasEpsilonTransitions() {
		return epsilonOnlyTransitions;
	}

	public void setRuleIndex(int ruleIndex) { this.ruleIndex = ruleIndex; }
}