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/*
 * Copyright 2014-2024 Real Logic Limited.
 *
 * 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
 *
 * https://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 com.fluxtion.agrona.concurrent.errors;

import com.fluxtion.agrona.concurrent.AtomicBuffer;

import static com.fluxtion.agrona.BitUtil.SIZE_OF_INT;
import static com.fluxtion.agrona.BitUtil.align;
import static com.fluxtion.agrona.concurrent.errors.DistinctErrorLog.*;

/**
 * Reader for the log created by a {@link DistinctErrorLog} encoded as UTF-8 errors.
 * 
 * The read methods are thread safe.
 */
public class ErrorLogReader
{
    /**
     * Has the error buffer any recorded errors?
     *
     * @param buffer containing the {@link DistinctErrorLog}.
     * @return true if there is at least one error.
     */
    public static boolean hasErrors(final AtomicBuffer buffer)
    {
        return buffer.capacity() >= SIZE_OF_INT && buffer.getIntVolatile(LENGTH_OFFSET) > 0;
    }

    /**
     * Read all the errors in a log since the creation of the log.
     *
     * @param buffer   containing the {@link DistinctErrorLog}.
     * @param consumer to be called for each exception encountered.
     * @return the number of entries that has been read.
     */
    public static int read(final AtomicBuffer buffer, final ErrorConsumer consumer)
    {
        return read(buffer, consumer, 0);
    }

    /**
     * Read all the errors in a log since a given timestamp.
     *
     * @param buffer         containing the {@link DistinctErrorLog}.
     * @param consumer       to be called for each exception encountered.
     * @param sinceTimestamp for filtering errors that have been recorded since this time.
     * @return the number of entries that has been read.
     */
    public static int read(final AtomicBuffer buffer, final ErrorConsumer consumer, final long sinceTimestamp)
    {
        int entries = 0;
        int offset = 0;
        final int capacity = buffer.capacity();

        while (offset <= capacity - ENCODED_ERROR_OFFSET)
        {
            final int length = Math.min(buffer.getIntVolatile(offset + LENGTH_OFFSET), capacity - offset);
            if (length <= 0)
            {
                break;
            }

            final long lastObservationTimestamp = buffer.getLongVolatile(offset + LAST_OBSERVATION_TIMESTAMP_OFFSET);
            if (lastObservationTimestamp >= sinceTimestamp)
            {
                ++entries;

                consumer.accept(
                    buffer.getInt(offset + OBSERVATION_COUNT_OFFSET),
                    buffer.getLong(offset + FIRST_OBSERVATION_TIMESTAMP_OFFSET),
                    lastObservationTimestamp,
                    buffer.getStringWithoutLengthUtf8(offset + ENCODED_ERROR_OFFSET, length - ENCODED_ERROR_OFFSET));
            }

            offset += align(length, RECORD_ALIGNMENT);
        }

        return entries;
    }
}