/*
 * Copyright 2009-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.eclipse.jdt.groovy.core.util;

import java.io.Reader;
import java.io.StringReader;

import groovyjarjarantlr.Token;
import groovyjarjarantlr.TokenStream;
import groovyjarjarantlr.TokenStreamException;
import org.codehaus.groovy.antlr.parser.GroovyLexer;
import org.codehaus.groovy.antlr.parser.GroovyRecognizer;
import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.IDocument;

/**
 * A wrapper around an Antlr Groovy Scanner, providing a convenient interface to tokenize a snippet of groovy code.
 *
 * @author kdvolder
 */
public class GroovyScanner {

    private TokenStream stream;
    private GroovyLexer lexer;
    private boolean whiteSpaceIncluded;

    public GroovyScanner(Reader input) {
        this(input, false);
    }

    public GroovyScanner(Reader input, boolean whiteSpaceIncluded) {
        init(input, whiteSpaceIncluded);
    }

    private void init(Reader input, boolean whiteSpaceIncluded) {
        this.whiteSpaceIncluded = whiteSpaceIncluded;
        lexer = new GroovyLexer(input);
        lexer.setWhitespaceIncluded(whiteSpaceIncluded);
        this.stream = lexer.plumb();
        /*
         * TODO Remove ones http://jira.codehaus.org/browse/GROOVY-6608 is fixed Initializes the parser to avoid NPE in Groovy code
         */
        GroovyRecognizer.make(lexer);
    }

    public GroovyScanner(String text) {
        this(new StringReader(text), false);
    }

    public Token nextToken() throws TokenStreamException {
        return stream.nextToken();
    }

    /**
     * Attempt to recover after a scanning error. We will recreate the Antlr lexer one character past the place where we got an
     * error and try to continue scanning from there.
     *
     * @throws BadLocationException
     */
    public void recover(IDocument document) throws BadLocationException {
        int line = lexer.getInputState().getLine(); // Line and
        int col = lexer.getInputState().getColumn(); // column where error happened.
        int offset = getOffset(document, line, col) + 1; // +1 to skip one character.
        line = document.getLineOfOffset(offset);
        int lineStart = document.getLineOffset(line);
        line = line + 1; // antlr lines start at 1
        col = offset - lineStart + 1; // antlr cols start at 1
        String remainingInput = document.get(offset, document.getLength() - offset);
        init(new StringReader(remainingInput), whiteSpaceIncluded); // Reinitialize with remaining input
        lexer.setLine(line); // Fix antlr line and
        lexer.setColumn(col);// column infos because we are not starting at the start
    }

    /**
     * Convert antlr line / col position into a IDocument offset.
     *
     * @param document The reference document
     * @param line antlr style line number (starts at 1)
     * @param col antlr style col number (starts at 1)
     */
    public static int getOffset(IDocument document, int line, int col) throws BadLocationException {
        return document.getLineOffset(line - 1) + col - 1;
    }

}