/*
 * 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.codehaus.groovy.eclipse.core.impl;

import org.codehaus.groovy.eclipse.core.ISourceBuffer;

/**
 * A buffer useful for reverse regex.
 *
 * @author empovazan
 */
public class ReverseSourceBuffer implements ISourceBuffer {
    private ISourceBuffer buffer;

    private int origin;

    public ReverseSourceBuffer(ISourceBuffer buffer, int origin) {
        this.buffer = buffer;
        this.origin = origin;
    }

    public char charAt(int offset) {
        char ch = buffer.charAt(origin - offset);
        return ch;
    }

    public int length() {
        return origin + 1;
    }

    public CharSequence subSequence(int start, int end) {
        return buffer.subSequence(origin - end + 1, origin - start + 1);
    }

    public int[] toLineColumn(int offset) {
        throw new UnsupportedOperationException();
    }

    public int toOffset(int line, int column) {
        throw new UnsupportedOperationException();
    }
}