/*
 * 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;

A token has properties: text, type, line, character position in the line
 (so we can ignore tabs), token channel, index, and source from which
 we obtained this token.
/** A token has properties: text, type, line, character position in the line
 *  (so we can ignore tabs), token channel, index, and source from which
 *  we obtained this token.
 */
public interface Token {
	public static final int INVALID_TYPE = 0;

    
During lookahead operations, this "token" signifies we hit rule end ATN state
 and did not follow it despite needing to.
/** During lookahead operations, this "token" signifies we hit rule end ATN state
     *  and did not follow it despite needing to.
     */
    public static final int EPSILON = -2;

	public static final int MIN_USER_TOKEN_TYPE = 1;

    public static final int EOF = IntStream.EOF;

	
All tokens go to the parser (unless skip() is called in that rule)
 on a particular "channel".  The parser tunes to a particular channel
 so that whitespace etc... can go to the parser on a "hidden" channel.
/** All tokens go to the parser (unless skip() is called in that rule)
	 *  on a particular "channel".  The parser tunes to a particular channel
	 *  so that whitespace etc... can go to the parser on a "hidden" channel.
	 */
	public static final int DEFAULT_CHANNEL = 0;

	
Anything on different channel than DEFAULT_CHANNEL is not parsed
 by parser.
/** Anything on different channel than DEFAULT_CHANNEL is not parsed
	 *  by parser.
	 */
	public static final int HIDDEN_CHANNEL = 1;

	
This is the minimum constant value which can be assigned to a
user-defined token channel.
 The non-negative numbers less than MIN_USER_CHANNEL_VALUE are assigned to the predefined channels DEFAULT_CHANNEL and HIDDEN_CHANNEL.
See Also:
getChannel()/**
	 * This is the minimum constant value which can be assigned to a
	 * user-defined token channel.
	 *
	 * <p>
	 * The non-negative numbers less than {@link #MIN_USER_CHANNEL_VALUE} are
	 * assigned to the predefined channels {@link #DEFAULT_CHANNEL} and
	 * {@link #HIDDEN_CHANNEL}.</p>
	 *
	 * @see Token#getChannel()
	 */
	public static final int MIN_USER_CHANNEL_VALUE = 2;

	
Get the text of the token.
/**
	 * Get the text of the token.
	 */
	String getText();

	
Get the token type of the token /** Get the token type of the token */
	int getType();

	
The line number on which the 1st character of this token was matched,
 line=1..n
/** The line number on which the 1st character of this token was matched,
	 *  line=1..n
	 */
	int getLine();

	
The index of the first character of this token relative to the
 beginning of the line at which it occurs, 0..n-1
/** The index of the first character of this token relative to the
	 *  beginning of the line at which it occurs, 0..n-1
	 */
	int getCharPositionInLine();

	
Return the channel this token. Each token can arrive at the parser
 on a different channel, but the parser only "tunes" to a single channel.
 The parser ignores everything not on DEFAULT_CHANNEL.
/** Return the channel this token. Each token can arrive at the parser
	 *  on a different channel, but the parser only "tunes" to a single channel.
	 *  The parser ignores everything not on DEFAULT_CHANNEL.
	 */
	int getChannel();

	
An index from 0..n-1 of the token object in the input stream.
 This must be valid in order to print token streams and
 use TokenRewriteStream.
 Return -1 to indicate that this token was conjured up since
 it doesn't have a valid index.
/** An index from 0..n-1 of the token object in the input stream.
	 *  This must be valid in order to print token streams and
	 *  use TokenRewriteStream.
	 *
	 *  Return -1 to indicate that this token was conjured up since
	 *  it doesn't have a valid index.
	 */
	int getTokenIndex();

	
The starting character index of the token
 This method is optional; return -1 if not implemented.
/** The starting character index of the token
	 *  This method is optional; return -1 if not implemented.
	 */
	int getStartIndex();

	
The last character index of the token.
 This method is optional; return -1 if not implemented.
/** The last character index of the token.
	 *  This method is optional; return -1 if not implemented.
	 */
	int getStopIndex();

	
Gets the TokenSource which created this token. /** Gets the {@link TokenSource} which created this token.
	 */
	TokenSource getTokenSource();

	
Gets the CharStream from which this token was derived. /**
	 * Gets the {@link CharStream} from which this token was derived.
	 */
	CharStream getInputStream();
}