/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.skywalking.generator;

import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
import lombok.Data;

import java.util.concurrent.atomic.AtomicLong;

@JsonDeserialize(builder = TimeGenerator.Builder.class)
public class TimeGenerator implements Generator<Object, Long> {

    private final Long stepMillisecond;
    private final Long waitMillisecond;
    private AtomicLong last;
    private AtomicLong lastSync;

    public TimeGenerator(Builder builder) {
        this.waitMillisecond = builder.waitMillisecond;
        this.stepMillisecond = builder.stepMillisecond;
        reset();
    }

    @Override
    public Long next(Object ignored) {
        long current = System.currentTimeMillis();
        if (current - lastSync.longValue() < waitMillisecond) {
            // in case of the time is not sync
            return last.incrementAndGet();
        }
        lastSync.set(current);
        return last.addAndGet(stepMillisecond);
    }

    @Override
    public void reset() {
        last = new AtomicLong(System.currentTimeMillis());
        lastSync = new AtomicLong(last.longValue());
    }

    @Data
    public static class Builder {
        private Long stepMillisecond;
        private Long waitMillisecond;

        public TimeGenerator build() {
            if (stepMillisecond == null) {
                stepMillisecond = 1000L;
            }
            if (waitMillisecond == null) {
                waitMillisecond = 0L;
            }
            return new TimeGenerator(this);
        }
    }
}
