/*
 * 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.metric;

import java.net.ConnectException;
import java.net.SocketTimeoutException;
import java.nio.charset.Charset;
import java.util.Date;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.RejectedExecutionHandler;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.ThreadPoolExecutor.DiscardPolicy;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;

import com.alibaba.csp.sentinel.Constants;
import com.alibaba.csp.sentinel.concurrent.NamedThreadFactory;
import com.alibaba.csp.sentinel.config.SentinelConfig;
import com.alibaba.csp.sentinel.dashboard.datasource.entity.MetricEntity;
import com.alibaba.csp.sentinel.dashboard.discovery.AppInfo;
import com.alibaba.csp.sentinel.dashboard.discovery.AppManagement;
import com.alibaba.csp.sentinel.dashboard.discovery.MachineInfo;
import com.alibaba.csp.sentinel.node.metric.MetricNode;
import com.alibaba.csp.sentinel.util.StringUtil;

import com.alibaba.csp.sentinel.dashboard.repository.metric.MetricsRepository;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.concurrent.FutureCallback;
import org.apache.http.entity.ContentType;
import org.apache.http.impl.client.DefaultRedirectStrategy;
import org.apache.http.impl.nio.client.CloseableHttpAsyncClient;
import org.apache.http.impl.nio.client.HttpAsyncClients;
import org.apache.http.impl.nio.reactor.IOReactorConfig;
import org.apache.http.protocol.HTTP;
import org.apache.http.util.EntityUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

/**
 * Fetch metric of machines.
 *
 * @author leyou
 */
@Component
public class MetricFetcher {

	public static final String NO_METRICS = "No metrics";

	private static final int HTTP_OK = 200;

	private static final long MAX_LAST_FETCH_INTERVAL_MS = 1000 * 15;

	private static final long FETCH_INTERVAL_SECOND = 6;

	private static final Charset DEFAULT_CHARSET = Charset.forName(SentinelConfig.charset());

	private final static String METRIC_URL_PATH = "metric";

	private static Logger logger = LoggerFactory.getLogger(MetricFetcher.class);

	private final long intervalSecond = 1;

	private Map<String, AtomicLong> appLastFetchTime = new ConcurrentHashMap<>();

	@Autowired
	private MetricsRepository<MetricEntity> metricStore;

	@Autowired
	private AppManagement appManagement;

	private CloseableHttpAsyncClient httpclient;

	@SuppressWarnings("PMD.ThreadPoolCreationRule")
	private ScheduledExecutorService fetchScheduleService = Executors.newScheduledThreadPool(1,
			new NamedThreadFactory("sentinel-dashboard-metrics-fetch-task"));

	private ExecutorService fetchService;

	private ExecutorService fetchWorker;

	public MetricFetcher() {
		int cores = Runtime.getRuntime().availableProcessors() * 2;
		long keepAliveTime = 0;
		int queueSize = 2048;
		RejectedExecutionHandler handler = new DiscardPolicy();
		fetchService = new ThreadPoolExecutor(cores, cores, keepAliveTime, TimeUnit.MILLISECONDS,
				new ArrayBlockingQueue<>(queueSize), new NamedThreadFactory("sentinel-dashboard-metrics-fetchService"),
				handler);
		fetchWorker = new ThreadPoolExecutor(cores, cores, keepAliveTime, TimeUnit.MILLISECONDS,
				new ArrayBlockingQueue<>(queueSize), new NamedThreadFactory("sentinel-dashboard-metrics-fetchWorker"),
				handler);
		IOReactorConfig ioConfig = IOReactorConfig.custom().setConnectTimeout(3000).setSoTimeout(3000)
				.setIoThreadCount(Runtime.getRuntime().availableProcessors() * 2).build();

		httpclient = HttpAsyncClients.custom().setRedirectStrategy(new DefaultRedirectStrategy() {
			@Override
			protected boolean isRedirectable(final String method) {
				return false;
			}
		}).setMaxConnTotal(4000).setMaxConnPerRoute(1000).setDefaultIOReactorConfig(ioConfig).build();
		httpclient.start();
		start();
	}

	private void start() {
		fetchScheduleService.scheduleAtFixedRate(() -> {
			try {
				fetchAllApp();
			}
			catch (Exception e) {
				logger.info("fetchAllApp error:", e);
			}
		}, 10, intervalSecond, TimeUnit.SECONDS);
	}

	private void writeMetric(Map<String, MetricEntity> map) {
		if (map.isEmpty()) {
			return;
		}
		Date date = new Date();
		for (MetricEntity entity : map.values()) {
			entity.setGmtCreate(date);
			entity.setGmtModified(date);
		}
		metricStore.saveAll(map.values());
	}

	/**
	 * Traverse each APP, and then pull the metric of all machines for that APP.
	 */
	private void fetchAllApp() {
		List<String> apps = appManagement.getAppNames();
		if (apps == null) {
			return;
		}
		for (final String app : apps) {
			fetchService.submit(() -> {
				try {
					doFetchAppMetric(app);
				}
				catch (Exception e) {
					logger.error("fetchAppMetric error", e);
				}
			});
		}
	}

	/**
	 * fetch metric between [startTime, endTime], both side inclusive
	 */
	private void fetchOnce(String app, long startTime, long endTime, int maxWaitSeconds) {
		if (maxWaitSeconds <= 0) {
			throw new IllegalArgumentException("maxWaitSeconds must > 0, but " + maxWaitSeconds);
		}
		AppInfo appInfo = appManagement.getDetailApp(app);
		// auto remove for app
		if (appInfo.isDead()) {
			logger.info("Dead app removed: {}", app);
			appManagement.removeApp(app);
			return;
		}
		Set<MachineInfo> machines = appInfo.getMachines();
		logger.debug("enter fetchOnce(" + app + "), machines.size()=" + machines.size() + ", time intervalMs ["
				+ startTime + ", " + endTime + "]");
		if (machines.isEmpty()) {
			return;
		}
		final String msg = "fetch";
		AtomicLong unhealthy = new AtomicLong();
		final AtomicLong success = new AtomicLong();
		final AtomicLong fail = new AtomicLong();

		long start = System.currentTimeMillis();
		/** app_resource_timeSecond -> metric */
		final Map<String, MetricEntity> metricMap = new ConcurrentHashMap<>(16);
		final CountDownLatch latch = new CountDownLatch(machines.size());
		for (final MachineInfo machine : machines) {
			// auto remove
			if (machine.isDead()) {
				latch.countDown();
				appManagement.getDetailApp(app).removeMachine(machine.getIp(), machine.getPort());
				logger.info("Dead machine removed: {}:{} of {}", machine.getIp(), machine.getPort(), app);
				continue;
			}
			if (!machine.isHealthy()) {
				latch.countDown();
				unhealthy.incrementAndGet();
				continue;
			}
			final String url = "http://" + machine.getIp() + ":" + machine.getPort() + "/" + METRIC_URL_PATH
					+ "?startTime=" + startTime + "&endTime=" + endTime + "&refetch=" + false;
			final HttpGet httpGet = new HttpGet(url);
			httpGet.setHeader(HTTP.CONN_DIRECTIVE, HTTP.CONN_CLOSE);
			httpclient.execute(httpGet, new FutureCallback<HttpResponse>() {
				@Override
				public void completed(final HttpResponse response) {
					try {
						handleResponse(response, machine, metricMap);
						success.incrementAndGet();
					}
					catch (Exception e) {
						logger.error(msg + " metric " + url + " error:", e);
					}
					finally {
						latch.countDown();
					}
				}

				@Override
				public void failed(final Exception ex) {
					latch.countDown();
					fail.incrementAndGet();
					httpGet.abort();
					if (ex instanceof SocketTimeoutException) {
						logger.error("Failed to fetch metric from <{}>: socket timeout", url);
					}
					else if (ex instanceof ConnectException) {
						logger.error("Failed to fetch metric from <{}> (ConnectionException: {})", url,
								ex.getMessage());
					}
					else {
						logger.error(msg + " metric " + url + " error", ex);
					}
				}

				@Override
				public void cancelled() {
					latch.countDown();
					fail.incrementAndGet();
					httpGet.abort();
				}
			});
		}
		try {
			latch.await(maxWaitSeconds, TimeUnit.SECONDS);
		}
		catch (Exception e) {
			logger.info(msg + " metric, wait http client error:", e);
		}
		long cost = System.currentTimeMillis() - start;
		// logger.info("finished " + msg + " metric for " + app + ", time intervalMs [" +
		// startTime + ", " + endTime
		// + "], total machines=" + machines.size() + ", dead=" + dead + ", fetch
		// success="
		// + success + ", fetch fail=" + fail + ", time cost=" + cost + " ms");
		writeMetric(metricMap);
	}

	private void doFetchAppMetric(final String app) {
		long now = System.currentTimeMillis();
		long lastFetchMs = now - MAX_LAST_FETCH_INTERVAL_MS;
		if (appLastFetchTime.containsKey(app)) {
			lastFetchMs = Math.max(lastFetchMs, appLastFetchTime.get(app).get() + 1000);
		}
		// trim milliseconds
		lastFetchMs = lastFetchMs / 1000 * 1000;
		long endTime = lastFetchMs + FETCH_INTERVAL_SECOND * 1000;
		if (endTime > now - 1000 * 2) {
			// to near
			return;
		}
		// update last_fetch in advance.
		appLastFetchTime.computeIfAbsent(app, a -> new AtomicLong()).set(endTime);
		final long finalLastFetchMs = lastFetchMs;
		final long finalEndTime = endTime;
		try {
			// do real fetch async
			fetchWorker.submit(() -> {
				try {
					fetchOnce(app, finalLastFetchMs, finalEndTime, 5);
				}
				catch (Exception e) {
					logger.info("fetchOnce(" + app + ") error", e);
				}
			});
		}
		catch (Exception e) {
			logger.info("submit fetchOnce(" + app + ") fail, intervalMs [" + lastFetchMs + ", " + endTime + "]", e);
		}
	}

	private void handleResponse(final HttpResponse response, MachineInfo machine, Map<String, MetricEntity> metricMap)
			throws Exception {
		int code = response.getStatusLine().getStatusCode();
		if (code != HTTP_OK) {
			return;
		}
		Charset charset = null;
		try {
			String contentTypeStr = response.getFirstHeader("Content-type").getValue();
			if (StringUtil.isNotEmpty(contentTypeStr)) {
				ContentType contentType = ContentType.parse(contentTypeStr);
				charset = contentType.getCharset();
			}
		}
		catch (Exception ignore) {
		}
		String body = EntityUtils.toString(response.getEntity(), charset != null ? charset : DEFAULT_CHARSET);
		if (StringUtil.isEmpty(body) || body.startsWith(NO_METRICS)) {
			// logger.info(machine.getApp() + ":" + machine.getIp() + ":" +
			// machine.getPort() + ", bodyStr is empty");
			return;
		}
		String[] lines = body.split("\n");
		// logger.info(machine.getApp() + ":" + machine.getIp() + ":" + machine.getPort()
		// +
		// ", bodyStr.length()=" + body.length() + ", lines=" + lines.length);
		handleBody(lines, machine, metricMap);
	}

	private void handleBody(String[] lines, MachineInfo machine, Map<String, MetricEntity> map) {
		// logger.info("handleBody() lines=" + lines.length + ", machine=" + machine);
		if (lines.length < 1) {
			return;
		}

		for (String line : lines) {
			try {
				MetricNode node = MetricNode.fromThinString(line);
				if (shouldFilterOut(node.getResource())) {
					continue;
				}
				/*
				 * aggregation metrics by app_resource_timeSecond, ignore ip and port.
				 */
				String key = buildMetricKey(machine.getApp(), node.getResource(), node.getTimestamp());
				MetricEntity entity = map.get(key);
				if (entity != null) {
					entity.addPassQps(node.getPassQps());
					entity.addBlockQps(node.getBlockQps());
					entity.addRtAndSuccessQps(node.getRt(), node.getSuccessQps());
					entity.addExceptionQps(node.getExceptionQps());
					entity.addCount(1);
				}
				else {
					entity = new MetricEntity();
					entity.setApp(machine.getApp());
					entity.setTimestamp(new Date(node.getTimestamp()));
					entity.setPassQps(node.getPassQps());
					entity.setBlockQps(node.getBlockQps());
					entity.setRtAndSuccessQps(node.getRt(), node.getSuccessQps());
					entity.setExceptionQps(node.getExceptionQps());
					entity.setCount(1);
					entity.setResource(node.getResource());
					map.put(key, entity);
				}
			}
			catch (Exception e) {
				logger.warn("handleBody line exception, machine: {}, line: {}", machine.toLogString(), line);
			}
		}
	}

	private String buildMetricKey(String app, String resource, long timestamp) {
		return app + "__" + resource + "__" + (timestamp / 1000);
	}

	private boolean shouldFilterOut(String resource) {
		return RES_EXCLUSION_SET.contains(resource);
	}

	private static final Set<String> RES_EXCLUSION_SET = new HashSet<String>() {
		{
			add(Constants.TOTAL_IN_RESOURCE_NAME);
			add(Constants.SYSTEM_LOAD_RESOURCE_NAME);
			add(Constants.CPU_USAGE_RESOURCE_NAME);
		}
	};

}
