/*
 * Copyright 1999-2018 Alibaba Group Holding 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 com.alibaba.csp.sentinel.dashboard.repository.metric;

import com.alibaba.csp.sentinel.dashboard.datasource.entity.MetricEntity;
import com.alibaba.csp.sentinel.util.StringUtil;
import com.alibaba.csp.sentinel.util.TimeUtil;
import org.springframework.stereotype.Component;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.util.stream.Collectors;

/**
 * Caches metrics data in a period of time in memory.
 *
 * @author Carpenter Lee
 * @author Eric Zhao
 */
@Component
public class InMemoryMetricsRepository implements MetricsRepository<MetricEntity> {

	private static final long MAX_METRIC_LIVE_TIME_MS = 1000 * 60 * 5;

	/**
	 * {@code app -> resource -> timestamp -> metric}
	 */
	private Map<String, Map<String, LinkedHashMap<Long, MetricEntity>>> allMetrics = new ConcurrentHashMap<>();

	private final ReentrantReadWriteLock readWriteLock = new ReentrantReadWriteLock();

	@Override
	public void save(MetricEntity entity) {
		if (entity == null || StringUtil.isBlank(entity.getApp())) {
			return;
		}
		readWriteLock.writeLock().lock();
		try {
			allMetrics.computeIfAbsent(entity.getApp(), e -> new HashMap<>(16))
					.computeIfAbsent(entity.getResource(), e -> new LinkedHashMap<Long, MetricEntity>() {
						@Override
						protected boolean removeEldestEntry(Entry<Long, MetricEntity> eldest) {
							// Metric older than {@link #MAX_METRIC_LIVE_TIME_MS} will be
							// removed.
							return eldest.getKey() < TimeUtil.currentTimeMillis() - MAX_METRIC_LIVE_TIME_MS;
						}
					}).put(entity.getTimestamp().getTime(), entity);
		}
		finally {
			readWriteLock.writeLock().unlock();
		}

	}

	@Override
	public void saveAll(Iterable<MetricEntity> metrics) {
		if (metrics == null) {
			return;
		}
		readWriteLock.writeLock().lock();
		try {
			metrics.forEach(this::save);
		}
		finally {
			readWriteLock.writeLock().unlock();
		}
	}

	@Override
	public List<MetricEntity> queryByAppAndResourceBetween(String app, String resource, long startTime, long endTime) {
		List<MetricEntity> results = new ArrayList<>();
		if (StringUtil.isBlank(app)) {
			return results;
		}
		Map<String, LinkedHashMap<Long, MetricEntity>> resourceMap = allMetrics.get(app);
		if (resourceMap == null) {
			return results;
		}
		LinkedHashMap<Long, MetricEntity> metricsMap = resourceMap.get(resource);
		if (metricsMap == null) {
			return results;
		}
		readWriteLock.readLock().lock();
		try {
			for (Entry<Long, MetricEntity> entry : metricsMap.entrySet()) {
				if (entry.getKey() >= startTime && entry.getKey() <= endTime) {
					results.add(entry.getValue());
				}
			}
			return results;
		}
		finally {
			readWriteLock.readLock().unlock();
		}
	}

	@Override
	public List<String> listResourcesOfApp(String app) {
		List<String> results = new ArrayList<>();
		if (StringUtil.isBlank(app)) {
			return results;
		}
		// resource -> timestamp -> metric
		Map<String, LinkedHashMap<Long, MetricEntity>> resourceMap = allMetrics.get(app);
		if (resourceMap == null) {
			return results;
		}
		final long minTimeMs = System.currentTimeMillis() - 1000 * 60;
		Map<String, MetricEntity> resourceCount = new ConcurrentHashMap<>(32);

		readWriteLock.readLock().lock();
		try {
			for (Entry<String, LinkedHashMap<Long, MetricEntity>> resourceMetrics : resourceMap.entrySet()) {
				for (Entry<Long, MetricEntity> metrics : resourceMetrics.getValue().entrySet()) {
					if (metrics.getKey() < minTimeMs) {
						continue;
					}
					MetricEntity newEntity = metrics.getValue();
					if (resourceCount.containsKey(resourceMetrics.getKey())) {
						MetricEntity oldEntity = resourceCount.get(resourceMetrics.getKey());
						oldEntity.addPassQps(newEntity.getPassQps());
						oldEntity.addRtAndSuccessQps(newEntity.getRt(), newEntity.getSuccessQps());
						oldEntity.addBlockQps(newEntity.getBlockQps());
						oldEntity.addExceptionQps(newEntity.getExceptionQps());
						oldEntity.addCount(1);
					}
					else {
						resourceCount.put(resourceMetrics.getKey(), MetricEntity.copyOf(newEntity));
					}
				}
			}
			// Order by last minute b_qps DESC.
			return resourceCount.entrySet().stream().sorted((o1, o2) -> {
				MetricEntity e1 = o1.getValue();
				MetricEntity e2 = o2.getValue();
				int t = e2.getBlockQps().compareTo(e1.getBlockQps());
				if (t != 0) {
					return t;
				}
				return e2.getPassQps().compareTo(e1.getPassQps());
			}).map(Entry::getKey).collect(Collectors.toList());
		}
		finally {
			readWriteLock.readLock().unlock();
		}
	}

}
