/*
 * 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;

import org.antlr.v4.runtime.atn.LexerATNSimulator;
import org.antlr.v4.runtime.misc.IntegerStack;
import org.antlr.v4.runtime.misc.Interval;
import org.antlr.v4.runtime.misc.Pair;

import java.util.ArrayList;
import java.util.EmptyStackException;
import java.util.List;

A lexer is recognizer that draws input symbols from a character stream.
 lexer grammars result in a subclass of this object. A Lexer object
 uses simplified match() and error recovery mechanisms in the interest
 of speed.
/** A lexer is recognizer that draws input symbols from a character stream.
 *  lexer grammars result in a subclass of this object. A Lexer object
 *  uses simplified match() and error recovery mechanisms in the interest
 *  of speed.
 */
public abstract class Lexer extends Recognizer<Integer, LexerATNSimulator>
	implements TokenSource
{
	public static final int DEFAULT_MODE = 0;
	public static final int MORE = -2;
	public static final int SKIP = -3;

	public static final int DEFAULT_TOKEN_CHANNEL = Token.DEFAULT_CHANNEL;
	public static final int HIDDEN = Token.HIDDEN_CHANNEL;
	public static final int MIN_CHAR_VALUE = 0x0000;
	public static final int MAX_CHAR_VALUE = 0x10FFFF;

	public CharStream _input;
	protected Pair<TokenSource, CharStream> _tokenFactorySourcePair;

	
How to create token objects /** How to create token objects */
	protected TokenFactory<?> _factory = CommonTokenFactory.DEFAULT;

	
The goal of all lexer rules/methods is to create a token object.
 This is an instance variable as multiple rules may collaborate to
 create a single token.  nextToken will return this object after
 matching lexer rule(s).  If you subclass to allow multiple token
 emissions, then set this to the last token to be matched or
 something nonnull so that the auto token emit mechanism will not
 emit another token.
/** The goal of all lexer rules/methods is to create a token object.
	 *  This is an instance variable as multiple rules may collaborate to
	 *  create a single token.  nextToken will return this object after
	 *  matching lexer rule(s).  If you subclass to allow multiple token
	 *  emissions, then set this to the last token to be matched or
	 *  something nonnull so that the auto token emit mechanism will not
	 *  emit another token.
	 */
	public Token _token;

	
What character index in the stream did the current token start at?
 Needed, for example, to get the text for current token.  Set at
 the start of nextToken.
/** What character index in the stream did the current token start at?
	 *  Needed, for example, to get the text for current token.  Set at
	 *  the start of nextToken.
	 */
	public int _tokenStartCharIndex = -1;

	
The line on which the first character of the token resides /** The line on which the first character of the token resides */
	public int _tokenStartLine;

	
The character position of first character within the line /** The character position of first character within the line */
	public int _tokenStartCharPositionInLine;

	
Once we see EOF on char stream, next token will be EOF.
 If you have DONE : EOF ; then you see DONE EOF.
/** Once we see EOF on char stream, next token will be EOF.
	 *  If you have DONE : EOF ; then you see DONE EOF.
	 */
	public boolean _hitEOF;

	
The channel number for the current token /** The channel number for the current token */
	public int _channel;

	
The token type for the current token /** The token type for the current token */
	public int _type;

	public final IntegerStack _modeStack = new IntegerStack();
	public int _mode = Lexer.DEFAULT_MODE;

	
You can set the text for the current token to override what is in
 the input char buffer.  Use setText() or can set this instance var.
/** You can set the text for the current token to override what is in
	 *  the input char buffer.  Use setText() or can set this instance var.
	 */
	public String _text;

	public Lexer() { }

	public Lexer(CharStream input) {
		this._input = input;
		this._tokenFactorySourcePair = new Pair<TokenSource, CharStream>(this, input);
	}

	public void reset() {
		// wack Lexer state variables
		if ( _input !=null ) {
			_input.seek(0); // rewind the input
		}
		_token = null;
		_type = Token.INVALID_TYPE;
		_channel = Token.DEFAULT_CHANNEL;
		_tokenStartCharIndex = -1;
		_tokenStartCharPositionInLine = -1;
		_tokenStartLine = -1;
		_text = null;

		_hitEOF = false;
		_mode = Lexer.DEFAULT_MODE;
		_modeStack.clear();

		getInterpreter().reset();
	}

	
Return a token from this source; i.e., match a token on the char
 stream.
/** Return a token from this source; i.e., match a token on the char
	 *  stream.
	 */
	@Override
	public Token nextToken() {
		if (_input == null) {
			throw new IllegalStateException("nextToken requires a non-null input stream.");
		}

		// Mark start location in char stream so unbuffered streams are
		// guaranteed at least have text of current token
		int tokenStartMarker = _input.mark();
		try{
			outer:
			while (true) {
				if (_hitEOF) {
					emitEOF();
					return _token;
				}

				_token = null;
				_channel = Token.DEFAULT_CHANNEL;
				_tokenStartCharIndex = _input.index();
				_tokenStartCharPositionInLine = getInterpreter().getCharPositionInLine();
				_tokenStartLine = getInterpreter().getLine();
				_text = null;
				do {
					_type = Token.INVALID_TYPE;
//				System.out.println("nextToken line "+tokenStartLine+" at "+((char)input.LA(1))+
//								   " in mode "+mode+
//								   " at index "+input.index());
					int ttype;
					try {
						ttype = getInterpreter().match(_input, _mode);
					}
					catch (LexerNoViableAltException e) {
						notifyListeners(e);		// report error
						recover(e);
						ttype = SKIP;
					}
					if ( _input.LA(1)==IntStream.EOF ) {
						_hitEOF = true;
					}
					if ( _type == Token.INVALID_TYPE ) _type = ttype;
					if ( _type ==SKIP ) {
						continue outer;
					}
				} while ( _type ==MORE );
				if ( _token == null ) emit();
				return _token;
			}
		}
		finally {
			// make sure we release marker after match or
			// unbuffered char stream will keep buffering
			_input.release(tokenStartMarker);
		}
	}

	
Instruct the lexer to skip creating a token for current lexer rule
 and look for another token.  nextToken() knows to keep looking when
 a lexer rule finishes with token set to SKIP_TOKEN.  Recall that
 if token==null at end of any token rule, it creates one for you
 and emits it.
/** Instruct the lexer to skip creating a token for current lexer rule
	 *  and look for another token.  nextToken() knows to keep looking when
	 *  a lexer rule finishes with token set to SKIP_TOKEN.  Recall that
	 *  if token==null at end of any token rule, it creates one for you
	 *  and emits it.
	 */
	public void skip() {
		_type = SKIP;
	}

	public void more() {
		_type = MORE;
	}

	public void mode(int m) {
		_mode = m;
	}

	public void pushMode(int m) {
		if ( LexerATNSimulator.debug ) System.out.println("pushMode "+m);
		_modeStack.push(_mode);
		mode(m);
	}

	public int popMode() {
		if ( _modeStack.isEmpty() ) throw new EmptyStackException();
		if ( LexerATNSimulator.debug ) System.out.println("popMode back to "+ _modeStack.peek());
		mode( _modeStack.pop() );
		return _mode;
	}

	@Override
	public void setTokenFactory(TokenFactory<?> factory) {
		this._factory = factory;
	}

	@Override
	public TokenFactory<? extends Token> getTokenFactory() {
		return _factory;
	}

	
Set the char stream and reset the lexer /** Set the char stream and reset the lexer */
	@Override
	public void setInputStream(IntStream input) {
		this._input = null;
		this._tokenFactorySourcePair = new Pair<TokenSource, CharStream>(this, _input);
		reset();
		this._input = (CharStream)input;
		this._tokenFactorySourcePair = new Pair<TokenSource, CharStream>(this, _input);
	}

	@Override
	public String getSourceName() {
		return _input.getSourceName();
	}

	@Override
	public CharStream getInputStream() {
		return _input;
	}

	
By default does not support multiple emits per nextToken invocation
 for efficiency reasons.  Subclass and override this method, nextToken,
 and getToken (to push tokens into a list and pull from that list
 rather than a single variable as this implementation does).
/** By default does not support multiple emits per nextToken invocation
	 *  for efficiency reasons.  Subclass and override this method, nextToken,
	 *  and getToken (to push tokens into a list and pull from that list
	 *  rather than a single variable as this implementation does).
	 */
	public void emit(Token token) {
		//System.err.println("emit "+token);
		this._token = token;
	}

	
The standard method called to automatically emit a token at the
 outermost lexical rule.  The token object should point into the
 char buffer start..stop.  If there is a text override in 'text',
 use that to set the token's text.  Override this method to emit
 custom Token objects or provide a new factory.
/** The standard method called to automatically emit a token at the
	 *  outermost lexical rule.  The token object should point into the
	 *  char buffer start..stop.  If there is a text override in 'text',
	 *  use that to set the token's text.  Override this method to emit
	 *  custom Token objects or provide a new factory.
	 */
	public Token emit() {
		Token t = _factory.create(_tokenFactorySourcePair, _type, _text, _channel, _tokenStartCharIndex, getCharIndex()-1,
								  _tokenStartLine, _tokenStartCharPositionInLine);
		emit(t);
		return t;
	}

	public Token emitEOF() {
		int cpos = getCharPositionInLine();
		int line = getLine();
		Token eof = _factory.create(_tokenFactorySourcePair, Token.EOF, null, Token.DEFAULT_CHANNEL, _input.index(), _input.index()-1,
									line, cpos);
		emit(eof);
		return eof;
	}

	@Override
	public int getLine() {
		return getInterpreter().getLine();
	}

	@Override
	public int getCharPositionInLine() {
		return getInterpreter().getCharPositionInLine();
	}

	public void setLine(int line) {
		getInterpreter().setLine(line);
	}

	public void setCharPositionInLine(int charPositionInLine) {
		getInterpreter().setCharPositionInLine(charPositionInLine);
	}

	
What is the index of the current character of lookahead? /** What is the index of the current character of lookahead? */
	public int getCharIndex() {
		return _input.index();
	}

	
Return the text matched so far for the current token or any
 text override.
/** Return the text matched so far for the current token or any
	 *  text override.
	 */
	public String getText() {
		if ( _text !=null ) {
			return _text;
		}
		return getInterpreter().getText(_input);
	}

	
Set the complete text of this token; it wipes any previous
 changes to the text.
/** Set the complete text of this token; it wipes any previous
	 *  changes to the text.
	 */
	public void setText(String text) {
		this._text = text;
	}

	
Override if emitting multiple tokens. /** Override if emitting multiple tokens. */
	public Token getToken() { return _token; }

	public void setToken(Token _token) {
		this._token = _token;
	}

	public void setType(int ttype) {
		_type = ttype;
	}

	public int getType() {
		return _type;
	}

	public void setChannel(int channel) {
		_channel = channel;
	}

	public int getChannel() {
		return _channel;
	}

	public String[] getChannelNames() { return null; }

	public String[] getModeNames() {
		return null;
	}

	
Used to print out token names like ID during debugging and
 error reporting.  The generated parsers implement a method
 that overrides this to point to their String[] tokenNames.
/** Used to print out token names like ID during debugging and
	 *  error reporting.  The generated parsers implement a method
	 *  that overrides this to point to their String[] tokenNames.
	 */
	@Override
	@Deprecated
	public String[] getTokenNames() {
		return null;
	}

	
Return a list of all Token objects in input char stream.
 Forces load of all tokens. Does not include EOF token.
/** Return a list of all Token objects in input char stream.
	 *  Forces load of all tokens. Does not include EOF token.
	 */
	public List<? extends Token> getAllTokens() {
		List<Token> tokens = new ArrayList<Token>();
		Token t = nextToken();
		while ( t.getType()!=Token.EOF ) {
			tokens.add(t);
			t = nextToken();
		}
		return tokens;
	}

	public void recover(LexerNoViableAltException e) {
		if (_input.LA(1) != IntStream.EOF) {
			// skip a char and try again
			getInterpreter().consume(_input);
		}
	}

	public void notifyListeners(LexerNoViableAltException e) {
		String text = _input.getText(Interval.of(_tokenStartCharIndex, _input.index()));
		String msg = "token recognition error at: '"+ getErrorDisplay(text) + "'";

		ANTLRErrorListener listener = getErrorListenerDispatch();
		listener.syntaxError(this, null, _tokenStartLine, _tokenStartCharPositionInLine, msg, e);
	}

	public String getErrorDisplay(String s) {
		StringBuilder buf = new StringBuilder();
		for (char c : s.toCharArray()) {
			buf.append(getErrorDisplay(c));
		}
		return buf.toString();
	}

	public String getErrorDisplay(int c) {
		String s = String.valueOf((char)c);
		switch ( c ) {
			case Token.EOF :
				s = "<EOF>";
				break;
			case '\n' :
				s = "\\n";
				break;
			case '\t' :
				s = "\\t";
				break;
			case '\r' :
				s = "\\r";
				break;
		}
		return s;
	}

	public String getCharErrorDisplay(int c) {
		String s = getErrorDisplay(c);
		return "'"+s+"'";
	}

	
Lexers can normally match any char in it's vocabulary after matching
 a token, so do the easy thing and just kill a character and hope
 it all works out.  You can instead use the rule invocation stack
 to do sophisticated error recovery if you are in a fragment rule.
/** Lexers can normally match any char in it's vocabulary after matching
	 *  a token, so do the easy thing and just kill a character and hope
	 *  it all works out.  You can instead use the rule invocation stack
	 *  to do sophisticated error recovery if you are in a fragment rule.
	 */
	public void recover(RecognitionException re) {
		//System.out.println("consuming char "+(char)input.LA(1)+" during recovery");
		//re.printStackTrace();
		// TODO: Do we lose character or line position information?
		_input.consume();
	}
}