/*
 * Copyright 2022 the original author or authors.
 *
 * 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 gradlebuild.cleanup.services;

import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.nio.file.Files;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Arrays;
import java.util.List;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import java.util.function.BiConsumer;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.stream.Collectors;
import java.util.stream.Stream;

import static java.util.regex.Pattern.quote;

/**
 * NOTICE: this class is invoked via java command line, so we must NOT DEPEND ON ANY 3RD-PARTY LIBRARIES except JDK 11.
 *
 * Usage: java build-logic/cleanup/src/main/java/gradlebuild/cleanup/services/KillLeakingJavaProcesses.java
 */
public class KillLeakingJavaProcesses {
    enum ExecutionMode {
        /**
         * Run at the beginning of each build. Kill potentially leaked processes in previous builds.
         * Only kill local Gradle processes (classpath in checkout directory).
         * Not clean up global Gradle processes (i.e. classpath in ~/.gradle/...).
         */
        KILL_LEAKED_PROCESSES_FROM_PREVIOUS_BUILDS,
        /**
         * Run at the end of each build. Kill potentially leaked processes in the current build.
         * Only kill local Gradle processes (classpath in checkout directory).
         * Not clean up global Gradle processes (i.e. classpath in ~/.gradle/...).
         * Because the step is not guaranteed to run (e.g. build timeout), we need `KILL_LEAKED_PROCESSES_FROM_PREVIOUS_BUILDS` mode.
         */
        KILL_PROCESSES_STARTED_BY_GRADLE,
        /**
         * Run when we want to retry the build. Kill all Gradle processes, regardless of they're global or local.
         */
        KILL_ALL_GRADLE_PROCESSES
    }

    private static final Pattern UNIX_PID_PATTERN = Pattern.compile("([0-9]+)");
    private static final Pattern WINDOWS_PID_PATTERN = Pattern.compile("([0-9]+)\\s*$");
    private static final String MY_PID = String.valueOf(ProcessHandle.current().pid());
    private static final String JAVA_EXECUTABLE_PATTERN_STR = "java(?:\\.exe)?";
    private static final String GRADLE_MAIN_CLASS_PATTERN_STR = "(org\\.gradle\\.[a-zA-Z]+)";
    private static final String PLAY_SERVER_PATTERN_STR = "(play\\.core\\.server\\.NettyServer)";
    private static final String JAVA_PROCESS_STACK_TRACES_MONITOR_PATTERN_STR = "(JavaProcessStackTracesMonitor\\.java)";
    private static ExecutionMode executionMode;

    static String generateAllGradleProcessPattern() {
        return "(?i)[/\\\\]" + JAVA_EXECUTABLE_PATTERN_STR + ".+("
            + GRADLE_MAIN_CLASS_PATTERN_STR + "|"
            + PLAY_SERVER_PATTERN_STR + "|"
            + JAVA_PROCESS_STACK_TRACES_MONITOR_PATTERN_STR
            + ").*";
    }

    static String generateLeakingProcessKillPattern(String rootProjectDir) {
        String kotlinCompilerDaemonPattern = "(?:" + quote("-Dkotlin.environment.keepalive") + ".+org\\.jetbrains\\.kotlin\\.daemon\\.KotlinCompileDaemon)";
        String quotedRootProjectDir = quote(rootProjectDir);
        String perfTestClasspathPattern = "(?:-cp.+\\\\build\\\\tmp\\\\performance-test-files.+?" + GRADLE_MAIN_CLASS_PATTERN_STR + ")";
        String buildDirClasspathPattern = "(?:-(classpath|cp) \"?" + quotedRootProjectDir + ".+?" + GRADLE_MAIN_CLASS_PATTERN_STR + ")";
        String playServerPattern = "(?:-classpath.+" + quotedRootProjectDir + ".+?" + PLAY_SERVER_PATTERN_STR + ")";
        return "(?i)[/\\\\]" + "(" + JAVA_EXECUTABLE_PATTERN_STR + ".+?" + "(?:"
            + perfTestClasspathPattern + "|"
            + buildDirClasspathPattern + "|"
            + playServerPattern + "|"
            + kotlinCompilerDaemonPattern + "|"
            + JAVA_PROCESS_STACK_TRACES_MONITOR_PATTERN_STR + ").+)";
    }

    public static void main(String[] args) {
        initExecutionMode(args);

        File rootProjectDir = new File(System.getProperty("user.dir"));

        cleanPsOutputAndThreaddumpFilesFromPreviousRun(rootProjectDir);

        List<String> psOutput = ps(rootProjectDir);

        writePsOutputToFile(rootProjectDir, psOutput);

        if (executionMode == ExecutionMode.KILL_ALL_GRADLE_PROCESSES) {
            Pattern commandLineArgsPattern = Pattern.compile(generateAllGradleProcessPattern());
            forEachJavaProcess(psOutput, commandLineArgsPattern, (pid, line) -> {
                System.out.println("Killing Gradle process with PID " + pid + ": " + line);
                pkill(pid);
            });
        } else {
            forEachLeakingJavaProcess(rootProjectDir, (pid, line) -> {
                System.out.println("A process wasn't shutdown properly in a previous Gradle run. Killing process with PID " + pid + ": " + line);
                pkill(pid);
            });
        }
    }

    private static void initExecutionMode(String[] args) {
        if (args.length != 1) {
            throw new IllegalArgumentException("Requires 1 param: " + Stream.of(ExecutionMode.values()).map(ExecutionMode::toString).collect(Collectors.joining("/")));
        }
        executionMode = ExecutionMode.valueOf(args[0]);
        if (executionMode == ExecutionMode.KILL_PROCESSES_STARTED_BY_GRADLE && !Boolean.parseBoolean(System.getenv("GRADLE_RUNNER_FINISHED"))) {
            // https://github.com/gradle/gradle-private/issues/3991
            System.out.println("Gradle runner not finished correctly (the build may be canceled). Fall back to KILL_ALL_GRADLE_PROCESSES.");
            executionMode = ExecutionMode.KILL_ALL_GRADLE_PROCESSES;
        }
    }

    private static void writePsOutputToFile(File rootProjectDir, List<String> psOutput) {
        String timestamp = LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyyy-MM-dd-HH-mm-ss"));
        File psOutFile = new File(rootProjectDir, timestamp + ".psoutput");

        try {
            Files.write(psOutFile.toPath(), psOutput);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    private static void cleanPsOutputAndThreaddumpFilesFromPreviousRun(File rootProjectDir) {
        if (executionMode == ExecutionMode.KILL_LEAKED_PROCESSES_FROM_PREVIOUS_BUILDS) {
            File[] psOutputs = rootProjectDir.listFiles((__, name) -> name.endsWith(".psoutput") || name.endsWith(".threaddump"));
            if (psOutputs != null) {
                Stream.of(psOutputs).forEach(File::delete);
            }
        }
    }

    static void pkill(String pid) {
        ExecResult execResult = run(isWindows() ? new String[]{"taskkill.exe", "/F", "/T", "/PID", pid} : new String[]{"kill", "-9", pid});
        if (execResult.code != 0) {
            System.out.println("Failed to kill daemon process " + pid + ". Maybe already killed?\nStdout:\n" + execResult.stdout + "\nStderr:\n" + execResult.stderr);
        }
    }

    static void forEachLeakingJavaProcess(File rootProjectDir, BiConsumer<String, String> action) {
        Pattern commandLineArgsPattern = Pattern.compile(generateLeakingProcessKillPattern(rootProjectDir.getPath()));
        forEachJavaProcess(ps(rootProjectDir), commandLineArgsPattern, action);
    }

    private static void forEachJavaProcess(List<String> psOutput, Pattern commandLineArgsPattern, BiConsumer<String, String> action) {
        Pattern pidPattern = isWindows() ? WINDOWS_PID_PATTERN : UNIX_PID_PATTERN;

        psOutput.forEach(line -> {
            Matcher commandLineArgsMatcher = commandLineArgsPattern.matcher(line);
            Matcher pidMatcher = pidPattern.matcher(line);
            if (commandLineArgsMatcher.find() && pidMatcher.find()) {
                String pid = pidMatcher.group(1);
                if (!MY_PID.equals(pid)) {
                    action.accept(pid, line);
                }
            }
        });
    }

    private static List<String> ps(File rootProjectDir) {
        return run(determinePsCommand()).assertZeroExit().stdout.lines().collect(Collectors.toList());
    }

    private static String[] determinePsCommand() {
        if (isWindows()) {
            return new String[]{"wmic", "process", "get", "processid,commandline"};
        } else if (isMacOS()) {
            return new String[]{"ps", "x", "-o", "pid,command"};
        } else {
            return new String[]{"ps", "x", "-o", "pid,cmd"};
        }
    }

    private static boolean isWindows() {
        return System.getProperty("os.name").toLowerCase().contains("windows");
    }

    private static boolean isMacOS() {
        return System.getProperty("os.name").toLowerCase().contains("mac");
    }

    private static class ExecResult {
        private final String[] args;
        private final int code;
        private final String stdout;
        private final String stderr;

        public ExecResult(String[] args, int code, String stdout, String stderr) {
            this.args = args;
            this.code = code;
            this.stdout = stdout;
            this.stderr = stderr;
        }

        @Override
        public String toString() {
            return "ExecResult{" + "code=" + code + "\n stdout='" + stdout + '\'' + "\n stderr='" + stderr + '\'' + '}';
        }

        ExecResult assertZeroExit() {
            if (code != 0) {
                throw new AssertionError(String.format("%s return:\n%s\n%s\n", Arrays.toString(args), stdout, stderr));
            }
            return this;
        }
    }

    private static ExecResult run(String... args) {
        try {
            Process process = new ProcessBuilder().command(args).start();
            CountDownLatch latch = new CountDownLatch(2);
            ByteArrayOutputStream stdout = connectStream(process.getInputStream(), latch);
            ByteArrayOutputStream stderr = connectStream(process.getErrorStream(), latch);

            process.waitFor(1, TimeUnit.MINUTES);
            latch.await(1, TimeUnit.MINUTES);
            return new ExecResult(args, process.exitValue(), stdout.toString(), stderr.toString());
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    private static ByteArrayOutputStream connectStream(InputStream forkedProcessOutput, CountDownLatch latch) {
        ByteArrayOutputStream os = new ByteArrayOutputStream();
        PrintStream ps = new PrintStream(os, true);
        new Thread(() -> {
            try {
                BufferedReader reader = new BufferedReader(new InputStreamReader(forkedProcessOutput));
                String line;
                while ((line = reader.readLine()) != null) {
                    ps.println(line);
                }
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                latch.countDown();
            }
        }).start();
        return os;
    }
}
