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/*
 * Copyright (c) 2012 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.TokenStream;
import org.antlr.v4.runtime.misc.NotNull;
import org.antlr.v4.runtime.misc.Nullable;

/**
 * This is the base class for gathering detailed information about prediction
 * events which occur during parsing.
 *
 * Note that we could record the parser call stack at the time this event
 * occurred but in the presence of left recursive rules, the stack is kind of
 * meaningless. It's better to look at the individual configurations for their
 * individual stacks. Of course that is a {@link PredictionContext} object
 * not a parse tree node and so it does not have information about the extent
 * (start...stop) of the various subtrees. Examining the stack tops of all
 * configurations provide the return states for the rule invocations.
 * From there you can get the enclosing rule.
 *
 * @since 4.3
 */
public class DecisionEventInfo {
	/**
	 * The invoked decision number which this event is related to.
	 *
	 * @see ATN#decisionToState
	 */
	public final int decision;
	/**
	 * The simulator state containing additional information relevant to the
	 * prediction state when the current event occurred, or {@code null} if no
	 * additional information is relevant or available.
	 */
	@Nullable
	public final SimulatorState state;
	/**
	 * The input token stream which is being parsed.
	 */
	@NotNull
	public final TokenStream input;
	/**
	 * The token index in the input stream at which the current prediction was
	 * originally invoked.
	 */
	public final int startIndex;
	/**
	 * The token index in the input stream at which the current event occurred.
	 */
	public final int stopIndex;
	/**
	 * {@code true} if the current event occurred during LL prediction;
	 * otherwise, {@code false} if the input occurred during SLL prediction.
	 */
	public final boolean fullCtx;

	public DecisionEventInfo(int decision, @Nullable SimulatorState state,
							 @NotNull TokenStream input, int startIndex,
							 int stopIndex, boolean fullCtx)
	{
		this.decision = decision;
		this.fullCtx = fullCtx;
		this.stopIndex = stopIndex;
		this.input = input;
		this.startIndex = startIndex;
		this.state = state;
	}
}