/*
 * SPDX-License-Identifier: Apache-2.0
 *
 * The OpenSearch Contributors require contributions made to
 * this file be licensed under the Apache-2.0 license or a
 * compatible open source license.
 */

/*
 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch 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.
 */

/*
 * Modifications Copyright OpenSearch Contributors. See
 * GitHub history for details.
 */

package org.opensearch.monitor.os;

import static org.hamcrest.CoreMatchers.not;
import static org.hamcrest.CoreMatchers.nullValue;
import static org.hamcrest.Matchers.allOf;
import static org.hamcrest.Matchers.anyOf;
import static org.hamcrest.Matchers.both;
import static org.hamcrest.Matchers.equalTo;
import static org.hamcrest.Matchers.greaterThan;
import static org.hamcrest.Matchers.greaterThanOrEqualTo;
import static org.hamcrest.Matchers.is;
import static org.hamcrest.Matchers.lessThanOrEqualTo;
import static org.hamcrest.Matchers.notNullValue;
import static org.junit.Assume.assumeThat;

import java.io.IOException;
import java.math.BigInteger;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Locale;
import java.util.stream.Collectors;

import org.apache.logging.log4j.Logger;
import org.apache.lucene.util.Constants;
import org.opensearch.test.OpenSearchTestCase;

import static org.mockito.ArgumentMatchers.anyString;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.never;
import static org.mockito.Mockito.reset;
import static org.mockito.Mockito.times;
import static org.mockito.Mockito.verify;

public class OsProbeTests extends OpenSearchTestCase {

    public void testOsInfo() throws IOException {
        final int allocatedProcessors = randomIntBetween(1, Runtime.getRuntime().availableProcessors());
        final long refreshInterval = randomBoolean() ? -1 : randomNonNegativeLong();
        final String prettyName;
        if (Constants.LINUX) {
            prettyName = randomFrom("Fedora 28 (Workstation Edition)", "Linux", null);
        } else {
            prettyName = Constants.OS_NAME;
        }
        final OsProbe osProbe = new OsProbe() {

            @Override
            List<String> readOsRelease() throws IOException {
                assert Constants.LINUX : Constants.OS_NAME;
                if (prettyName != null) {
                    final String quote = randomFrom("\"", "'", "");
                    final String space = randomFrom(" ", "");
                    final String prettyNameLine = String.format(Locale.ROOT, "PRETTY_NAME=%s%s%s%s", quote, prettyName, quote, space);
                    return Arrays.asList("NAME=" + randomAlphaOfLength(16), prettyNameLine);
                } else {
                    return Collections.singletonList("NAME=" + randomAlphaOfLength(16));
                }
            }

        };
        final OsInfo info = osProbe.osInfo(refreshInterval, allocatedProcessors);
        assertNotNull(info);
        assertThat(info.getRefreshInterval(), equalTo(refreshInterval));
        assertThat(info.getName(), equalTo(Constants.OS_NAME));
        if (Constants.LINUX) {
            if (prettyName != null) {
                assertThat(info.getPrettyName(), equalTo(prettyName));
            } else {
                assertThat(info.getPrettyName(), equalTo(Constants.OS_NAME));
            }
        }
        assertThat(info.getArch(), equalTo(Constants.OS_ARCH));
        assertThat(info.getVersion(), equalTo(Constants.OS_VERSION));
        assertThat(info.getAllocatedProcessors(), equalTo(allocatedProcessors));
        assertThat(info.getAvailableProcessors(), equalTo(Runtime.getRuntime().availableProcessors()));
    }

    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/66629")
    public void testOsStats() {
        final OsProbe osProbe = new OsProbe();
        OsStats stats = osProbe.osStats();
        assertNotNull(stats);
        assertThat(stats.getTimestamp(), greaterThan(0L));
        assertThat(
            stats.getCpu().getPercent(),
            anyOf(equalTo((short) -1), is(both(greaterThanOrEqualTo((short) 0)).and(lessThanOrEqualTo((short) 100))))
        );
        double[] loadAverage = stats.getCpu().getLoadAverage();
        if (loadAverage != null) {
            assertThat(loadAverage.length, equalTo(3));
        }
        if (Constants.WINDOWS) {
            // load average is unavailable on Windows
            assertNull(loadAverage);
        } else if (Constants.LINUX) {
            // we should be able to get the load average
            assertNotNull(loadAverage);
            assertThat(loadAverage[0], greaterThanOrEqualTo((double) 0));
            assertThat(loadAverage[1], greaterThanOrEqualTo((double) 0));
            assertThat(loadAverage[2], greaterThanOrEqualTo((double) 0));
        } else if (Constants.MAC_OS_X) {
            // one minute load average is available, but 10-minute and 15-minute load averages are not
            assertNotNull(loadAverage);
            assertThat(loadAverage[0], greaterThanOrEqualTo((double) 0));
            assertThat(loadAverage[1], equalTo((double) -1));
            assertThat(loadAverage[2], equalTo((double) -1));
        } else {
            // unknown system, but the best case is that we have the one-minute load average
            if (loadAverage != null) {
                assertThat(loadAverage[0], anyOf(equalTo((double) -1), greaterThanOrEqualTo((double) 0)));
                assertThat(loadAverage[1], equalTo((double) -1));
                assertThat(loadAverage[2], equalTo((double) -1));
            }
        }

        assertNotNull(stats.getMem());
        assertThat(stats.getMem().getTotal().getBytes(), greaterThan(0L));
        assertThat(stats.getMem().getFree().getBytes(), greaterThan(0L));
        assertThat(stats.getMem().getFreePercent(), allOf(greaterThanOrEqualTo((short) 0), lessThanOrEqualTo((short) 100)));
        assertThat(stats.getMem().getUsed().getBytes(), greaterThan(0L));
        assertThat(stats.getMem().getUsedPercent(), allOf(greaterThanOrEqualTo((short) 0), lessThanOrEqualTo((short) 100)));

        assertNotNull(stats.getSwap());
        assertNotNull(stats.getSwap().getTotal());

        long total = stats.getSwap().getTotal().getBytes();
        if (total > 0) {
            assertThat(stats.getSwap().getTotal().getBytes(), greaterThan(0L));
            assertThat(stats.getSwap().getFree().getBytes(), greaterThan(0L));
            assertThat(stats.getSwap().getUsed().getBytes(), greaterThanOrEqualTo(0L));
        } else {
            // On platforms with no swap
            assertThat(stats.getSwap().getTotal().getBytes(), equalTo(0L));
            assertThat(stats.getSwap().getFree().getBytes(), equalTo(0L));
            assertThat(stats.getSwap().getUsed().getBytes(), equalTo(0L));
        }

        if (Constants.LINUX) {
            if (stats.getCgroup() != null) {
                assertThat(stats.getCgroup().getCpuAcctControlGroup(), notNullValue());
                assertThat(stats.getCgroup().getCpuAcctUsageNanos(), greaterThan(0L));
                assertThat(stats.getCgroup().getCpuCfsQuotaMicros(), anyOf(equalTo(-1L), greaterThanOrEqualTo(0L)));
                assertThat(stats.getCgroup().getCpuCfsPeriodMicros(), greaterThanOrEqualTo(0L));
                assertThat(stats.getCgroup().getCpuStat().getNumberOfElapsedPeriods(), greaterThanOrEqualTo(0L));
                assertThat(stats.getCgroup().getCpuStat().getNumberOfTimesThrottled(), greaterThanOrEqualTo(0L));
                assertThat(stats.getCgroup().getCpuStat().getTimeThrottledNanos(), greaterThanOrEqualTo(0L));
                // These could be null if transported from a node running an older version, but shouldn't be null on the current node
                assertThat(stats.getCgroup().getMemoryControlGroup(), notNullValue());
                assertThat(stats.getCgroup().getMemoryLimitInBytes(), notNullValue());
                assertThat(new BigInteger(stats.getCgroup().getMemoryLimitInBytes()), greaterThan(BigInteger.ZERO));
                assertThat(stats.getCgroup().getMemoryUsageInBytes(), notNullValue());
                assertThat(new BigInteger(stats.getCgroup().getMemoryUsageInBytes()), greaterThan(BigInteger.ZERO));
            }
        } else {
            assertNull(stats.getCgroup());
        }
    }

    public void testGetSystemLoadAverage() {
        assumeTrue("test runs on Linux only", Constants.LINUX);

        final OsProbe probe = new OsProbe() {
            @Override
            String readProcLoadavg() {
                return "1.51 1.69 1.99 3/417 23251";
            }
        };

        final double[] systemLoadAverage = probe.getSystemLoadAverage();

        assertNotNull(systemLoadAverage);
        assertThat(systemLoadAverage.length, equalTo(3));

        // avoid silliness with representing doubles
        assertThat(systemLoadAverage[0], equalTo(Double.parseDouble("1.51")));
        assertThat(systemLoadAverage[1], equalTo(Double.parseDouble("1.69")));
        assertThat(systemLoadAverage[2], equalTo(Double.parseDouble("1.99")));
    }

    public void testCgroupProbe() {
        assumeTrue("test runs on Linux only", Constants.LINUX);

        final boolean areCgroupStatsAvailable = randomBoolean();
        final String hierarchy = randomAlphaOfLength(16);

        final OsProbe probe = buildStubOsProbe(areCgroupStatsAvailable, hierarchy);

        final OsStats.Cgroup cgroup = probe.osStats().getCgroup();

        if (areCgroupStatsAvailable) {
            assertNotNull(cgroup);
            assertThat(cgroup.getCpuAcctControlGroup(), equalTo("/" + hierarchy));
            assertThat(cgroup.getCpuAcctUsageNanos(), equalTo(364869866063112L));
            assertThat(cgroup.getCpuControlGroup(), equalTo("/" + hierarchy));
            assertThat(cgroup.getCpuCfsPeriodMicros(), equalTo(100000L));
            assertThat(cgroup.getCpuCfsQuotaMicros(), equalTo(50000L));
            assertThat(cgroup.getCpuStat().getNumberOfElapsedPeriods(), equalTo(17992L));
            assertThat(cgroup.getCpuStat().getNumberOfTimesThrottled(), equalTo(1311L));
            assertThat(cgroup.getCpuStat().getTimeThrottledNanos(), equalTo(139298645489L));
            assertThat(cgroup.getMemoryLimitInBytes(), equalTo("18446744073709551615"));
            assertThat(cgroup.getMemoryUsageInBytes(), equalTo("4796416"));
        } else {
            assertNull(cgroup);
        }
    }

    public void testCgroupProbeWithMissingCpuAcct() {
        assumeTrue("test runs on Linux only", Constants.LINUX);

        final String hierarchy = randomAlphaOfLength(16);

        // This cgroup data is missing a line about cpuacct
        List<String> procSelfCgroupLines = getProcSelfGroupLines(hierarchy).stream()
            .map(line -> line.replaceFirst(",cpuacct", ""))
            .collect(Collectors.toList());

        final OsProbe probe = buildStubOsProbe(true, hierarchy, procSelfCgroupLines);

        final OsStats.Cgroup cgroup = probe.osStats().getCgroup();

        assertNull(cgroup);
    }

    public void testCgroupProbeWithMissingCpu() {
        assumeTrue("test runs on Linux only", Constants.LINUX);

        final String hierarchy = randomAlphaOfLength(16);

        // This cgroup data is missing a line about cpu
        List<String> procSelfCgroupLines = getProcSelfGroupLines(hierarchy).stream()
            .map(line -> line.replaceFirst(":cpu,", ":"))
            .collect(Collectors.toList());

        final OsProbe probe = buildStubOsProbe(true, hierarchy, procSelfCgroupLines);

        final OsStats.Cgroup cgroup = probe.osStats().getCgroup();

        assertNull(cgroup);
    }

    public void testCgroupProbeWithMissingMemory() {
        assumeTrue("test runs on Linux only", Constants.LINUX);

        final String hierarchy = randomAlphaOfLength(16);

        // This cgroup data is missing a line about memory
        List<String> procSelfCgroupLines = getProcSelfGroupLines(hierarchy).stream()
            .filter(line -> !line.contains(":memory:"))
            .collect(Collectors.toList());

        final OsProbe probe = buildStubOsProbe(true, hierarchy, procSelfCgroupLines);

        final OsStats.Cgroup cgroup = probe.osStats().getCgroup();

        assertNull(cgroup);
    }

    public void testLogWarnCpuMessageOnlyOnes() {
        final Logger logger = mock(Logger.class);

        final OsProbe noCpuStatsOsProbe = new OsProbe(logger) {
            @Override
            List<String> readSysFsCgroupCpuAcctCpuStat(String controlGroup) throws IOException {
                return Collections.singletonList("nr_periods 1");
            }
        };

        assumeThat("CGroups are available", noCpuStatsOsProbe.areCgroupStatsAvailable(), is(true));
        OsStats osStats = noCpuStatsOsProbe.osStats();

        // Depending on CGroups v1/v2, the cgroup stats may not be available
        assumeThat("CGroup is available", osStats.getCgroup(), is(not(nullValue())));

        // no nr_throttled and throttled_time
        verify(logger, times(2)).warn(anyString());
        reset(logger);
        noCpuStatsOsProbe.osStats();
        verify(logger, never()).warn(anyString());
    }

    private static List<String> getProcSelfGroupLines(String hierarchy) {
        return Arrays.asList(
            "10:freezer:/",
            "9:net_cls,net_prio:/",
            "8:pids:/",
            "7:blkio:/",
            "6:memory:/" + hierarchy,
            "5:devices:/user.slice",
            "4:hugetlb:/",
            "3:perf_event:/",
            "2:cpu,cpuacct,cpuset:/" + hierarchy,
            "1:name=systemd:/user.slice/user-1000.slice/session-2359.scope",
            "0::/cgroup2"
        );
    }

    private static OsProbe buildStubOsProbe(final boolean areCgroupStatsAvailable, final String hierarchy) {
        List<String> procSelfCgroupLines = getProcSelfGroupLines(hierarchy);

        return buildStubOsProbe(areCgroupStatsAvailable, hierarchy, procSelfCgroupLines);
    }

    /**
     * Builds a test instance of OsProbe. Methods that ordinarily read from the filesystem are overridden to return values based upon
     * the arguments to this method.
     *
     * @param areCgroupStatsAvailable whether or not cgroup data is available. Normally OsProbe establishes this for itself.
     * @param hierarchy a mock value used to generate a cgroup hierarchy.
     * @param procSelfCgroupLines the lines that will be used as the content of <code>/proc/self/cgroup</code>
     * @return a test instance
     */
    private static OsProbe buildStubOsProbe(
        final boolean areCgroupStatsAvailable,
        final String hierarchy,
        List<String> procSelfCgroupLines
    ) {
        return new OsProbe() {
            @Override
            List<String> readProcSelfCgroup() {
                return procSelfCgroupLines;
            }

            @Override
            String readSysFsCgroupCpuAcctCpuAcctUsage(String controlGroup) {
                assertThat(controlGroup, equalTo("/" + hierarchy));
                return "364869866063112";
            }

            @Override
            String readSysFsCgroupCpuAcctCpuCfsPeriod(String controlGroup) {
                assertThat(controlGroup, equalTo("/" + hierarchy));
                return "100000";
            }

            @Override
            String readSysFsCgroupCpuAcctCpuAcctCfsQuota(String controlGroup) {
                assertThat(controlGroup, equalTo("/" + hierarchy));
                return "50000";
            }

            @Override
            List<String> readSysFsCgroupCpuAcctCpuStat(String controlGroup) {
                return Arrays.asList("nr_periods 17992", "nr_throttled 1311", "throttled_time 139298645489");
            }

            @Override
            String readSysFsCgroupMemoryLimitInBytes(String controlGroup) {
                assertThat(controlGroup, equalTo("/" + hierarchy));
                // This is the highest value that can be stored in an unsigned 64 bit number, hence too big for long
                return "18446744073709551615";
            }

            @Override
            String readSysFsCgroupMemoryUsageInBytes(String controlGroup) {
                assertThat(controlGroup, equalTo("/" + hierarchy));
                return "4796416";
            }

            @Override
            boolean areCgroupStatsAvailable() {
                return areCgroupStatsAvailable;
            }
        };
    }

}