/*
 * Copyright 2017 Real Logic Ltd.
 *
 * 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 io.aeron.logbuffer;

import org.agrona.concurrent.UnsafeBuffer;

import static io.aeron.logbuffer.FrameDescriptor.*;
import static io.aeron.logbuffer.LogBufferDescriptor.applyDefaultHeader;
import static io.aeron.protocol.HeaderFlyweight.HDR_TYPE_PAD;

/**
 * Fills a gap in a term with a padding record.
 */
public class TermGapFiller
{
    /**
     * Try to gap fill the current term at a given offset if the gap contains no data.
     *
     * Note: the gap offset plus gap length must end on a {@link FrameDescriptor#FRAME_ALIGNMENT} boundary.
     *
     * @param logMetaDataBuffer containing the default headers
     * @param termBuffer        to gap fill
     * @param termId            for the current term.
     * @param gapOffset         to fill from
     * @param gapLength         to length of the gap.
     * @return true if the gap has been filled with a padding record or false if data found.
     */
    public static boolean tryFillGap(
        final UnsafeBuffer logMetaDataBuffer,
        final UnsafeBuffer termBuffer,
        final int termId,
        final int gapOffset,
        final int gapLength)
    {
        int offset = (gapOffset + gapLength) - FRAME_ALIGNMENT;

        while (offset >= gapOffset)
        {
            if (0 != termBuffer.getInt(offset))
            {
                return false;
            }

            offset -= FRAME_ALIGNMENT;
        }

        applyDefaultHeader(logMetaDataBuffer, termBuffer, gapOffset);
        frameType(termBuffer, gapOffset, HDR_TYPE_PAD);
        frameTermOffset(termBuffer, gapOffset);
        frameTermId(termBuffer, gapOffset, termId);
        frameLengthOrdered(termBuffer, gapOffset, gapLength);

        return true;
    }
}