/*
 * 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.misc.IntervalSet;

import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

An ATN transition between any two ATN states.  Subclasses define
 atom, set, epsilon, action, predicate, rule transitions.
 
This is a one way link.  It emanates from a state (usually via a list of
 transitions) and has a target state.
 
Since we never have to change the ATN transitions once we construct it,
 we can fix these transitions as specific classes. The DFA transitions
 on the other hand need to update the labels as it adds transitions to
 the states. We'll use the term Edge for the DFA to distinguish them from
 ATN transitions.
/** An ATN transition between any two ATN states.  Subclasses define
 *  atom, set, epsilon, action, predicate, rule transitions.
 *
 *  <p>This is a one way link.  It emanates from a state (usually via a list of
 *  transitions) and has a target state.</p>
 *
 *  <p>Since we never have to change the ATN transitions once we construct it,
 *  we can fix these transitions as specific classes. The DFA transitions
 *  on the other hand need to update the labels as it adds transitions to
 *  the states. We'll use the term Edge for the DFA to distinguish them from
 *  ATN transitions.</p>
 */
public abstract class Transition {
	// constants for serialization
	public static final int EPSILON			= 1;
	public static final int RANGE			= 2;
	public static final int RULE			= 3;
	public static final int PREDICATE		= 4; // e.g., {isType(input.LT(1))}?
	public static final int ATOM			= 5;
	public static final int ACTION			= 6;
	public static final int SET				= 7; // ~(A|B) or ~atom, wildcard, which convert to next 2
	public static final int NOT_SET			= 8;
	public static final int WILDCARD		= 9;
	public static final int PRECEDENCE		= 10;


	public static final List<String> serializationNames =
		Collections.unmodifiableList(Arrays.asList(
			"INVALID",
			"EPSILON",
			"RANGE",
			"RULE",
			"PREDICATE",
			"ATOM",
			"ACTION",
			"SET",
			"NOT_SET",
			"WILDCARD",
			"PRECEDENCE"
		));

	public static final Map<Class<? extends Transition>, Integer> serializationTypes =
		Collections.unmodifiableMap(new HashMap<Class<? extends Transition>, Integer>() {{
			put(EpsilonTransition.class, EPSILON);
			put(RangeTransition.class, RANGE);
			put(RuleTransition.class, RULE);
			put(PredicateTransition.class, PREDICATE);
			put(AtomTransition.class, ATOM);
			put(ActionTransition.class, ACTION);
			put(SetTransition.class, SET);
			put(NotSetTransition.class, NOT_SET);
			put(WildcardTransition.class, WILDCARD);
			put(PrecedencePredicateTransition.class, PRECEDENCE);
		}});

	
The target of this transition. /** The target of this transition. */

	public ATNState target;

	protected Transition(ATNState target) {
		if (target == null) {
			throw new NullPointerException("target cannot be null.");
		}

		this.target = target;
	}

	public abstract int getSerializationType();

	
Determines if the transition is an "epsilon" transition.
The default implementation returns false.
Returns:
true if traversing this transition in the ATN does not consume an input symbol; otherwise, false if traversing this transition consumes (matches) an input symbol./**
	 * Determines if the transition is an "epsilon" transition.
	 *
	 * <p>The default implementation returns {@code false}.</p>
	 *
	 * @return {@code true} if traversing this transition in the ATN does not
	 * consume an input symbol; otherwise, {@code false} if traversing this
	 * transition consumes (matches) an input symbol.
	 */
	public boolean isEpsilon() {
		return false;
	}


	public IntervalSet label() { return null; }

	public abstract boolean matches(int symbol, int minVocabSymbol, int maxVocabSymbol);
}