/*
 * 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.misc.Pair;

import java.util.List;

Provides an implementation of TokenSource as a wrapper around a list of Token objects. 
If the final token in the list is an Token.EOF token, it will be used as the EOF token for every call to nextToken after the end of the list is reached. Otherwise, an EOF token will be created.
/**
 * Provides an implementation of {@link TokenSource} as a wrapper around a list
 * of {@link Token} objects.
 *
 * <p>If the final token in the list is an {@link Token#EOF} token, it will be used
 * as the EOF token for every call to {@link #nextToken} after the end of the
 * list is reached. Otherwise, an EOF token will be created.</p>
 */
public class ListTokenSource implements TokenSource {
	
The wrapped collection of Token objects to return. /**
	 * The wrapped collection of {@link Token} objects to return.
	 */
	protected final List<? extends Token> tokens;

	
The name of the input source. If this value is null, a call to getSourceName should return the source name used to create the the next token in tokens (or the previous token if the end of the input has been reached). /**
	 * The name of the input source. If this value is {@code null}, a call to
	 * {@link #getSourceName} should return the source name used to create the
	 * the next token in {@link #tokens} (or the previous token if the end of
	 * the input has been reached).
	 */
	private final String sourceName;

	
The index into tokens of token to return by the next call to nextToken. The end of the input is indicated by this value being greater than or equal to the number of items in tokens. /**
	 * The index into {@link #tokens} of token to return by the next call to
	 * {@link #nextToken}. The end of the input is indicated by this value
	 * being greater than or equal to the number of items in {@link #tokens}.
	 */
	protected int i;

	
This field caches the EOF token for the token source.
/**
	 * This field caches the EOF token for the token source.
	 */
	protected Token eofToken;

	
This is the backing field for getTokenFactory and setTokenFactory. /**
	 * This is the backing field for {@link #getTokenFactory} and
	 * {@link setTokenFactory}.
	 */
	private TokenFactory<?> _factory = CommonTokenFactory.DEFAULT;

	
Constructs a new ListTokenSource instance from the specified collection of Token objects. 
Params:
tokens – The collection of Token objects to provide as a TokenSource.
Throws:
NullPointerException – if tokens is null/**
	 * Constructs a new {@link ListTokenSource} instance from the specified
	 * collection of {@link Token} objects.
	 *
	 * @param tokens The collection of {@link Token} objects to provide as a
	 * {@link TokenSource}.
	 * @exception NullPointerException if {@code tokens} is {@code null}
	 */
	public ListTokenSource(List<? extends Token> tokens) {
		this(tokens, null);
	}

	
Constructs a new ListTokenSource instance from the specified collection of Token objects and source name. 
Params:
tokens – The collection of Token objects to provide as a TokenSource.
sourceName – The name of the TokenSource. If this value is null, getSourceName will attempt to infer the name from the next Token (or the previous token if the end of the input has been reached).
Throws:
NullPointerException – if tokens is null/**
	 * Constructs a new {@link ListTokenSource} instance from the specified
	 * collection of {@link Token} objects and source name.
	 *
	 * @param tokens The collection of {@link Token} objects to provide as a
	 * {@link TokenSource}.
	 * @param sourceName The name of the {@link TokenSource}. If this value is
	 * {@code null}, {@link #getSourceName} will attempt to infer the name from
	 * the next {@link Token} (or the previous token if the end of the input has
	 * been reached).
	 *
	 * @exception NullPointerException if {@code tokens} is {@code null}
	 */
	public ListTokenSource(List<? extends Token> tokens, String sourceName) {
		if (tokens == null) {
			throw new NullPointerException("tokens cannot be null");
		}

		this.tokens = tokens;
		this.sourceName = sourceName;
	}

	
{@inheritDoc}
/**
	 * {@inheritDoc}
	 */
	@Override
	public int getCharPositionInLine() {
		if (i < tokens.size()) {
			return tokens.get(i).getCharPositionInLine();
		}
		else if (eofToken != null) {
			return eofToken.getCharPositionInLine();
		}
		else if (tokens.size() > 0) {
			// have to calculate the result from the line/column of the previous
			// token, along with the text of the token.
			Token lastToken = tokens.get(tokens.size() - 1);
			String tokenText = lastToken.getText();
			if (tokenText != null) {
				int lastNewLine = tokenText.lastIndexOf('\n');
				if (lastNewLine >= 0) {
					return tokenText.length() - lastNewLine - 1;
				}
			}

			return lastToken.getCharPositionInLine() + lastToken.getStopIndex() - lastToken.getStartIndex() + 1;
		}

		// only reach this if tokens is empty, meaning EOF occurs at the first
		// position in the input
		return 0;
	}

	
{@inheritDoc}
/**
	 * {@inheritDoc}
	 */
	@Override
	public Token nextToken() {
		if (i >= tokens.size()) {
			if (eofToken == null) {
				int start = -1;
				if (tokens.size() > 0) {
					int previousStop = tokens.get(tokens.size() - 1).getStopIndex();
					if (previousStop != -1) {
						start = previousStop + 1;
					}
				}

				int stop = Math.max(-1, start - 1);
				eofToken = _factory.create(new Pair<TokenSource, CharStream>(this, getInputStream()), Token.EOF, "EOF", Token.DEFAULT_CHANNEL, start, stop, getLine(), getCharPositionInLine());
			}

			return eofToken;
		}

		Token t = tokens.get(i);
		if (i == tokens.size() - 1 && t.getType() == Token.EOF) {
			eofToken = t;
		}

		i++;
		return t;
	}

	
{@inheritDoc}
/**
	 * {@inheritDoc}
	 */
	@Override
	public int getLine() {
		if (i < tokens.size()) {
			return tokens.get(i).getLine();
		}
		else if (eofToken != null) {
			return eofToken.getLine();
		}
		else if (tokens.size() > 0) {
			// have to calculate the result from the line/column of the previous
			// token, along with the text of the token.
			Token lastToken = tokens.get(tokens.size() - 1);
			int line = lastToken.getLine();

			String tokenText = lastToken.getText();
			if (tokenText != null) {
				for (int i = 0; i < tokenText.length(); i++) {
					if (tokenText.charAt(i) == '\n') {
						line++;
					}
				}
			}

			// if no text is available, assume the token did not contain any newline characters.
			return line;
		}

		// only reach this if tokens is empty, meaning EOF occurs at the first
		// position in the input
		return 1;
	}

	
{@inheritDoc}
/**
	 * {@inheritDoc}
	 */
	@Override
	public CharStream getInputStream() {
		if (i < tokens.size()) {
			return tokens.get(i).getInputStream();
		}
		else if (eofToken != null) {
			return eofToken.getInputStream();
		}
		else if (tokens.size() > 0) {
			return tokens.get(tokens.size() - 1).getInputStream();
		}

		// no input stream information is available
		return null;
	}

	
{@inheritDoc}
/**
	 * {@inheritDoc}
	 */
	@Override
	public String getSourceName() {
		if (sourceName != null) {
			return sourceName;
		}

		CharStream inputStream = getInputStream();
		if (inputStream != null) {
			return inputStream.getSourceName();
		}

		return "List";
	}

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

	
{@inheritDoc}
/**
	 * {@inheritDoc}
	 */
	@Override
	public TokenFactory<?> getTokenFactory() {
		return _factory;
	}
}