/*
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 Copyright (c) 2005-2009 Terence Parr
 All rights reserved.

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 1. Redistributions of source code must retain the above copyright
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     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
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package org.antlr.runtime;

import java.util.*;

The most common stream of tokens is one where every token is buffered up
 and tokens are prefiltered for a certain channel (the parser will only
 see these tokens and cannot change the filter channel number during the
 parse).
 TODO: how to access the full token stream?  How to track all tokens matched per rule?
/** The most common stream of tokens is one where every token is buffered up
 *  and tokens are prefiltered for a certain channel (the parser will only
 *  see these tokens and cannot change the filter channel number during the
 *  parse).
 *
 *  TODO: how to access the full token stream?  How to track all tokens matched per rule?
 */
public class LegacyCommonTokenStream implements TokenStream {
    protected TokenSource tokenSource;

	
Record every single token pulled from the source so we can reproduce
 chunks of it later.
/** Record every single token pulled from the source so we can reproduce
	 *  chunks of it later.
	 */
	protected List<Token> tokens;

	
Map<tokentype, channel> to override some Tokens' channel numbers /** Map&lt;tokentype, channel&gt; to override some Tokens' channel numbers */
	protected Map<Integer, Integer> channelOverrideMap;

	
Set<tokentype>; discard any tokens with this type /** Set&lt;tokentype&gt;; discard any tokens with this type */
	protected Set<Integer> discardSet;

	
Skip tokens on any channel but this one; this is how we skip whitespace... /** Skip tokens on any channel but this one; this is how we skip whitespace... */
	protected int channel = Token.DEFAULT_CHANNEL;

	
By default, track all incoming tokens /** By default, track all incoming tokens */
	protected boolean discardOffChannelTokens = false;

	
Track the last mark() call result value for use in rewind(). /** Track the last mark() call result value for use in rewind(). */
	protected int lastMarker;

	protected int range = -1; // how deep have we gone?	

	
The index into the tokens list of the current token (next token
 to consume).  p==-1 indicates that the tokens list is empty
/** The index into the tokens list of the current token (next token
     *  to consume).  p==-1 indicates that the tokens list is empty
     */
    protected int p = -1;

	public LegacyCommonTokenStream() {
		tokens = new ArrayList<Token>(500);
	}

	public LegacyCommonTokenStream(TokenSource tokenSource) {
	    this();
		this.tokenSource = tokenSource;
	}

	public LegacyCommonTokenStream(TokenSource tokenSource, int channel) {
		this(tokenSource);
		this.channel = channel;
	}

	
Reset this token stream by setting its token source. /** Reset this token stream by setting its token source. */
	public void setTokenSource(TokenSource tokenSource) {
		this.tokenSource = tokenSource;
		tokens.clear();
		p = -1;
		channel = Token.DEFAULT_CHANNEL;
	}

	
Load all tokens from the token source and put in tokens.
 This is done upon first LT request because you might want to
 set some token type / channel overrides before filling buffer.
/** Load all tokens from the token source and put in tokens.
	 *  This is done upon first LT request because you might want to
	 *  set some token type / channel overrides before filling buffer.
	 */
	protected void fillBuffer() {
		int index = 0;
		Token t = tokenSource.nextToken();
		while ( t!=null && t.getType()!=CharStream.EOF ) {
			boolean discard = false;
			// is there a channel override for token type?
			if ( channelOverrideMap!=null ) {
				Integer channelI = channelOverrideMap.get(t.getType());
				if ( channelI!=null ) {
					t.setChannel(channelI);
				}
			}
			if ( discardSet!=null &&
				 discardSet.contains(new Integer(t.getType())) )
			{
				discard = true;
			}
			else if ( discardOffChannelTokens && t.getChannel()!=this.channel ) {
				discard = true;
			}
			if ( !discard )	{
				t.setTokenIndex(index);
				tokens.add(t);
				index++;
			}
			t = tokenSource.nextToken();
		}
		// leave p pointing at first token on channel
		p = 0;
		p = skipOffTokenChannels(p);
    }

	
Move the input pointer to the next incoming token.  The stream
 must become active with LT(1) available.  consume() simply
 moves the input pointer so that LT(1) points at the next
 input symbol. Consume at least one token.
 Walk past any token not on the channel the parser is listening to.
/** Move the input pointer to the next incoming token.  The stream
	 *  must become active with LT(1) available.  consume() simply
	 *  moves the input pointer so that LT(1) points at the next
	 *  input symbol. Consume at least one token.
	 *
	 *  Walk past any token not on the channel the parser is listening to.
	 */
	@Override
	public void consume() {
		if ( p<tokens.size() ) {
            p++;
			p = skipOffTokenChannels(p); // leave p on valid token
        }
    }

	
Given a starting index, return the index of the first on-channel
 token.
/** Given a starting index, return the index of the first on-channel
	 *  token.
	 */
	protected int skipOffTokenChannels(int i) {
		int n = tokens.size();
		while ( i<n && tokens.get(i).getChannel()!=channel ) {
			i++;
		}
		return i;
	}

	protected int skipOffTokenChannelsReverse(int i) {
		while ( i>=0 && tokens.get(i).getChannel()!=channel ) {
			i--;
		}
		return i;
	}

	
A simple filter mechanism whereby you can tell this token stream
 to force all tokens of type ttype to be on channel.  For example,
 when interpreting, we cannot exec actions so we need to tell
 the stream to force all WS and NEWLINE to be a different, ignored
 channel.
/** A simple filter mechanism whereby you can tell this token stream
	 *  to force all tokens of type ttype to be on channel.  For example,
	 *  when interpreting, we cannot exec actions so we need to tell
	 *  the stream to force all WS and NEWLINE to be a different, ignored
	 *  channel.
	 */
	public void setTokenTypeChannel(int ttype, int channel) {
		if ( channelOverrideMap==null ) {
			channelOverrideMap = new HashMap<Integer, Integer>();
		}
        channelOverrideMap.put(ttype, channel);
	}

	public void discardTokenType(int ttype) {
		if ( discardSet==null ) {
			discardSet = new HashSet<Integer>();
		}
        discardSet.add(ttype);
	}

	public void discardOffChannelTokens(boolean discardOffChannelTokens) {
		this.discardOffChannelTokens = discardOffChannelTokens;
	}

	public List<? extends Token> getTokens() {
		if ( p == -1 ) {
			fillBuffer();
		}
		return tokens;
	}

	public List<? extends Token> getTokens(int start, int stop) {
		return getTokens(start, stop, (BitSet)null);
	}

	
Given a start and stop index, return a List of all tokens in
 the token type BitSet.  Return null if no tokens were found.  This
 method looks at both on and off channel tokens.
/** Given a start and stop index, return a List of all tokens in
	 *  the token type BitSet.  Return null if no tokens were found.  This
	 *  method looks at both on and off channel tokens.
	 */
	public List<? extends Token> getTokens(int start, int stop, BitSet types) {
		if ( p == -1 ) {
			fillBuffer();
		}
		if ( stop>=tokens.size() ) {
			stop=tokens.size()-1;
		}
		if ( start<0 ) {
			start=0;
		}
		if ( start>stop ) {
			return null;
		}

		// list = tokens[start:stop]:{Token t, t.getType() in types}
		List<Token> filteredTokens = new ArrayList<Token>();
		for (int i=start; i<=stop; i++) {
			Token t = tokens.get(i);
			if ( types==null || types.member(t.getType()) ) {
				filteredTokens.add(t);
			}
		}
		if ( filteredTokens.isEmpty() ) {
			filteredTokens = null;
		}
		return filteredTokens;
	}

	public List<? extends Token> getTokens(int start, int stop, List<Integer> types) {
		return getTokens(start,stop,new BitSet(types));
	}

	public List<? extends Token> getTokens(int start, int stop, int ttype) {
		return getTokens(start,stop,BitSet.of(ttype));
	}

	
Get the ith token from the current position 1..n where k=1 is the
 first symbol of lookahead.
/** Get the ith token from the current position 1..n where k=1 is the
	 *  first symbol of lookahead.
	 */
	@Override
	public Token LT(int k) {
		if ( p == -1 ) {
			fillBuffer();
		}
		if ( k==0 ) {
			return null;
		}
		if ( k<0 ) {
			return LB(-k);
		}
		//System.out.print("LT(p="+p+","+k+")=");
		if ( (p+k-1) >= tokens.size() ) {
            return tokens.get(tokens.size()-1);
		}
		//System.out.println(tokens.get(p+k-1));
		int i = p;
		int n = 1;
		// find k good tokens
		while ( n<k ) {
			// skip off-channel tokens
			i = skipOffTokenChannels(i+1); // leave p on valid token
			n++;
		}
		if ( i>=tokens.size() ) {
            return tokens.get(tokens.size()-1); // must be EOF
		}

		if ( i>range ) range = i;
        return tokens.get(i);
    }

	
Look backwards k tokens on-channel tokens /** Look backwards k tokens on-channel tokens */
	protected Token LB(int k) {
		//System.out.print("LB(p="+p+","+k+") ");
		if ( p == -1 ) {
			fillBuffer();
		}
		if ( k==0 ) {
			return null;
		}
		if ( (p-k)<0 ) {
			return null;
		}

		int i = p;
		int n = 1;
		// find k good tokens looking backwards
		while ( n<=k ) {
			// skip off-channel tokens
			i = skipOffTokenChannelsReverse(i-1); // leave p on valid token
			n++;
		}
		if ( i<0 ) {
			return null;
		}
		return tokens.get(i);
	}

	
Return absolute token i; ignore which channel the tokens are on;
 that is, count all tokens not just on-channel tokens.
/** Return absolute token i; ignore which channel the tokens are on;
	 *  that is, count all tokens not just on-channel tokens.
	 */
	@Override
	public Token get(int i) {
		return tokens.get(i);
	}

	
Get all tokens from start..stop inclusively /** Get all tokens from start..stop inclusively */
	public List<? extends Token> get(int start, int stop) {
		if ( p == -1 ) fillBuffer();
		if ( start<0 || stop<0 ) return null;
		return tokens.subList(start, stop);
	}

	@Override
	public int LA(int i) {
        return LT(i).getType();
    }

	@Override
    public int mark() {
		if ( p == -1 ) {
			fillBuffer();
		}
		lastMarker = index();
		return lastMarker;
	}

	@Override
	public void release(int marker) {
		// no resources to release
	}

	@Override
	public int size() {
		return tokens.size();
	}

	@Override
    public int index() {
        return p;
    }

	@Override
	public int range() {
		return range;
	}

	@Override
	public void rewind(int marker) {
		seek(marker);
	}

	@Override
	public void rewind() {
		seek(lastMarker);
	}

	public void reset() {
		p = 0;
		lastMarker = 0;
	}
	
	@Override
	public void seek(int index) {
		p = index;
	}

	@Override
	public TokenSource getTokenSource() {
		return tokenSource;
	}

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

	@Override
	public String toString() {
		if ( p == -1 ) {
			fillBuffer();
		}
		return toString(0, tokens.size()-1);
	}

	@Override
	public String toString(int start, int stop) {
		if ( start<0 || stop<0 ) {
			return null;
		}
		if ( p == -1 ) {
			fillBuffer();
		}
		if ( stop>=tokens.size() ) {
			stop = tokens.size()-1;
		}
 		StringBuilder buf = new StringBuilder();
		for (int i = start; i <= stop; i++) {
			Token t = tokens.get(i);
			buf.append(t.getText());
		}
		return buf.toString();
	}

	@Override
	public String toString(Token start, Token stop) {
		if ( start!=null && stop!=null ) {
			return toString(start.getTokenIndex(), stop.getTokenIndex());
		}
		return null;
	}
}