/*******************************************************************************
 * Copyright Technophobia Ltd 2012
 * 
 * This file is part of the Substeps Eclipse Plugin.
 * 
 * The Substeps Eclipse Plugin is free software: you can redistribute it and/or modify
 * it under the terms of the Eclipse Public License v1.0.
 * 
 * The Substeps Eclipse Plugin is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * Eclipse Public License for more details.
 * 
 * You should have received a copy of the Eclipse Public License
 * along with the Substeps Eclipse Plugin.  If not, see <http://www.eclipse.org/legal/epl-v10.html>.
 ******************************************************************************/
package com.technophobia.substeps.document.content.feature.partiton;

import org.eclipse.jface.text.rules.ICharacterScanner;
import org.eclipse.jface.text.rules.IToken;

public class CharacterScannerToProcessedTextExtractor implements TextExtractor<ICharacterScanner, IToken> {

    private static final int EOF = -1;
    private static final int NEWLINE = '\n';
    private static final int COMMENT = '#';

    private final TextProcessor<IToken> textProcessor;


    public CharacterScannerToProcessedTextExtractor(final TextProcessor<IToken> textProcessor) {
        this.textProcessor = textProcessor;
    }


    @Override
    public IToken extractText(final ICharacterScanner scanner) {
        final String text = readLine(scanner);
        
        IToken token = null;
        if (text != null){
            token = textProcessor.doWithText(text.trim());
        }

        // Didn't find it, so unread everything
        if (text != null && token == null) {
            unread(scanner, text.length());
        }
        else if (text == null && token == null){
            unread(scanner, 0);
        }
        

        return token;
    }


    private String readLine(final ICharacterScanner scanner) {
        final StringBuilder sb = new StringBuilder();
        int c = scanner.read();
        while (c != EOF && c != COMMENT) {
            sb.append((char) c);
            c = scanner.read();

            if (c == NEWLINE) {
                sb.append((char) c);
                scanWhitespace(scanner, sb);
                break;
            }
        }

        // If we've got a comment, then unread it
        if (c == EOF || c == COMMENT) {
            scanner.unread();
        }
        
        if (sb.length() == 0){
            return null;
        }
        else{
            return sb.toString();
        }
    }


    private void unread(final ICharacterScanner scanner, final int length) {
        for (int i = 0; i < length; i++) {
            scanner.unread();
        }
    }


    // We need to scan any additional whitespace, as the next predicate rule
    // after this needs to start at the 1st char to be matched - no trimming by
    // the framework
    private void scanWhitespace(final ICharacterScanner scanner, final StringBuilder sb) {
        int c = scanner.read();
        while (c != EOF) {
            if (Character.isWhitespace(c)) {
                sb.append((char) c);
                c = scanner.read();
            } else {
                scanner.unread();
                break;
            }
        }

    }
}