/*
 * 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.flink.client.python;

import org.apache.flink.client.deployment.application.UnsuccessfulExecutionException;
import org.apache.flink.configuration.ConfigConstants;
import org.apache.flink.configuration.ConfigurationUtils;
import org.apache.flink.configuration.ReadableConfig;
import org.apache.flink.core.fs.Path;
import org.apache.flink.python.util.PythonDependencyUtils;
import org.apache.flink.util.CompressionUtils;
import org.apache.flink.util.ExceptionUtils;
import org.apache.flink.util.FileUtils;
import org.apache.flink.util.NetUtils;
import org.apache.flink.util.OperatingSystem;
import org.apache.flink.util.Preconditions;
import org.apache.flink.util.StringUtils;

import org.apache.flink.shaded.guava33.com.google.common.base.Strings;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import py4j.CallbackClient;
import py4j.Gateway;
import py4j.GatewayServer;

import java.io.File;
import java.io.IOException;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.nio.file.FileSystems;
import java.nio.file.FileVisitResult;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.nio.file.SimpleFileVisitor;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.UUID;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.stream.Collectors;

import static org.apache.flink.python.PythonOptions.PYTHON_ARCHIVES;
import static org.apache.flink.python.PythonOptions.PYTHON_CLIENT_EXECUTABLE;
import static org.apache.flink.python.PythonOptions.PYTHON_FILES;
import static org.apache.flink.python.PythonOptions.PYTHON_PATH;
import static org.apache.flink.python.util.PythonDependencyUtils.FILE_DELIMITER;

/** The util class help to prepare Python env and run the python process. */
final class PythonEnvUtils {
    private static final Logger LOG = LoggerFactory.getLogger(PythonEnvUtils.class);

    private static final String PYTHON_ARCHIVES_DIR = "python-archives";

    static final String PYFLINK_CLIENT_EXECUTABLE = "PYFLINK_CLIENT_EXECUTABLE";

    static final long CHECK_INTERVAL = 100;

    static final long TIMEOUT_MILLIS = 10000;

    public static int maxConcurrentPythonFunctionFactories = 10;

    static volatile Throwable capturedJavaException = null;

    /** Wraps Python exec environment. */
    static class PythonEnvironment {
        String tempDirectory;

        String archivesDirectory;

        String pythonExec = OperatingSystem.isWindows() ? "python.exe" : "python";

        String pythonPath;

        Map<String, String> systemEnv = new HashMap<>();
    }

    /**
     * Prepares PythonEnvironment to start python process.
     *
     * @param config The Python configurations.
     * @param entryPointScript The entry point script, optional.
     * @param tmpDir The temporary directory which files will be copied to.
     * @return PythonEnvironment the Python environment which will be executed in Python process.
     */
    static PythonEnvironment preparePythonEnvironment(
            ReadableConfig config, String entryPointScript, String tmpDir) throws IOException {
        PythonEnvironment env = new PythonEnvironment();

        // 1. set the path of python interpreter.
        String pythonExec =
                config.getOptional(PYTHON_CLIENT_EXECUTABLE)
                        .orElse(System.getenv(PYFLINK_CLIENT_EXECUTABLE));
        if (pythonExec != null) {
            env.pythonExec = pythonExec;
        }

        // 2. setup temporary local directory for the user files
        tmpDir = new File(tmpDir).getAbsolutePath();
        Path tmpDirPath = new Path(tmpDir);
        tmpDirPath.getFileSystem().mkdirs(tmpDirPath);
        env.tempDirectory = tmpDir;

        // 3. append the internal lib files to PYTHONPATH.
        if (System.getenv(ConfigConstants.ENV_FLINK_OPT_DIR) != null) {
            String pythonLibDir =
                    System.getenv(ConfigConstants.ENV_FLINK_OPT_DIR) + File.separator + "python";
            env.pythonPath =
                    getLibFiles(pythonLibDir).stream()
                            .map(p -> p.toFile().getAbsolutePath())
                            .collect(Collectors.joining(File.pathSeparator));
        }

        // 4. copy relevant python files to tmp dir and set them in PYTHONPATH.
        if (config.getOptional(PYTHON_FILES).isPresent()) {
            List<Path> pythonFiles =
                    Arrays.stream(config.get(PYTHON_FILES).split(FILE_DELIMITER))
                            .map(Path::new)
                            .collect(Collectors.toList());
            addToPythonPath(env, pythonFiles);
        }

        // 5. set the archives directory as the working directory, then user could access the
        // content of the archives via relative path
        if (config.getOptional(PYTHON_ARCHIVES).isPresent()
                && (config.getOptional(PYTHON_CLIENT_EXECUTABLE).isPresent()
                        || !StringUtils.isNullOrWhitespaceOnly(
                                System.getenv(PYFLINK_CLIENT_EXECUTABLE)))) {
            env.archivesDirectory = String.join(File.separator, tmpDir, PYTHON_ARCHIVES_DIR);

            // extract archives to archives directory
            config.getOptional(PYTHON_ARCHIVES)
                    .ifPresent(
                            pyArchives -> {
                                for (String archive : pyArchives.split(FILE_DELIMITER)) {
                                    final Path archivePath;
                                    final String targetDirName;
                                    final String originalFileName;
                                    if (archive.contains(PythonDependencyUtils.PARAM_DELIMITER)) {
                                        String[] filePathAndTargetDir =
                                                archive.split(
                                                        PythonDependencyUtils.PARAM_DELIMITER, 2);
                                        archivePath = new Path(filePathAndTargetDir[0]);
                                        targetDirName = filePathAndTargetDir[1];
                                        originalFileName = archivePath.getName();
                                    } else {
                                        archivePath = new Path(archive);
                                        originalFileName = archivePath.getName();
                                        targetDirName = originalFileName;
                                    }

                                    Path localArchivePath = archivePath;
                                    try {
                                        if (archivePath.getFileSystem().isDistributedFS()) {
                                            localArchivePath =
                                                    new Path(
                                                            env.tempDirectory,
                                                            String.join(
                                                                    File.separator,
                                                                    UUID.randomUUID().toString(),
                                                                    originalFileName));
                                            FileUtils.copy(archivePath, localArchivePath, false);
                                        }
                                    } catch (IOException e) {
                                        String msg =
                                                String.format(
                                                        "Error occurred when copying %s to %s.",
                                                        archivePath, localArchivePath);
                                        throw new RuntimeException(msg, e);
                                    }

                                    try {
                                        CompressionUtils.extractFile(
                                                localArchivePath.getPath(),
                                                String.join(
                                                        File.separator,
                                                        env.archivesDirectory,
                                                        targetDirName),
                                                originalFileName);
                                    } catch (IOException e) {
                                        throw new RuntimeException(
                                                "Extract archives to archives directory failed.",
                                                e);
                                    }
                                }
                            });
        }

        // 4. append configured python.pythonpath to the PYTHONPATH.
        if (config.getOptional(PYTHON_PATH).isPresent()) {
            env.pythonPath =
                    String.join(
                            File.pathSeparator,
                            config.getOptional(PYTHON_PATH).get(),
                            env.pythonPath);
        }

        if (entryPointScript != null) {
            addToPythonPath(env, Collections.singletonList(new Path(entryPointScript)));
        }
        return env;
    }

    /**
     * Creates symbolLink in working directory for pyflink lib.
     *
     * @param libPath the pyflink lib file path.
     * @param symbolicLinkPath the symbolic link to pyflink lib.
     */
    private static void createSymbolicLink(
            java.nio.file.Path libPath, java.nio.file.Path symbolicLinkPath) throws IOException {
        try {
            Files.createSymbolicLink(symbolicLinkPath, libPath);
        } catch (IOException e) {
            LOG.warn(
                    "Create symbol link from {} to {} failed and copy instead.",
                    symbolicLinkPath,
                    libPath,
                    e);
            Files.copy(libPath, symbolicLinkPath);
        }
    }

    /**
     * Gets pyflink dependent libs in specified directory.
     *
     * @param libDir The lib directory
     */
    private static List<java.nio.file.Path> getLibFiles(String libDir) {
        final List<java.nio.file.Path> libFiles = new ArrayList<>();
        SimpleFileVisitor<java.nio.file.Path> finder =
                new SimpleFileVisitor<java.nio.file.Path>() {
                    @Override
                    public FileVisitResult visitFile(
                            java.nio.file.Path file, BasicFileAttributes attrs) throws IOException {
                        // only include zip file
                        if (file.toString().endsWith(".zip")) {
                            libFiles.add(file);
                        }
                        return FileVisitResult.CONTINUE;
                    }
                };
        try {
            Files.walkFileTree(FileSystems.getDefault().getPath(libDir), finder);
        } catch (Throwable t) {
            // ignore, this may occur when executing `flink run` using the PyFlink Python package.
        }
        return libFiles;
    }

    private static void addToPythonPath(PythonEnvironment env, List<Path> pythonFiles)
            throws IOException {
        List<String> pythonPathList = new ArrayList<>();
        Path tmpDirPath = new Path(env.tempDirectory);

        for (Path pythonFile : pythonFiles) {
            String sourceFileName = pythonFile.getName();
            // add random UUID parent directory to avoid name conflict.
            Path targetPath =
                    new Path(
                            tmpDirPath,
                            String.join(
                                    File.separator, UUID.randomUUID().toString(), sourceFileName));
            if (!pythonFile.getFileSystem().isDistributedFS()) {
                // if the path is local file, try to create symbolic link.
                new File(targetPath.getParent().toString()).mkdir();
                createSymbolicLink(
                        Paths.get(new File(pythonFile.getPath()).getAbsolutePath()),
                        Paths.get(targetPath.toString()));
            } else {
                try {
                    FileUtils.copy(pythonFile, targetPath, true);
                } catch (Exception e) {
                    LOG.error(
                            "Error occurred when copying {} to {}, skipping...",
                            pythonFile,
                            targetPath,
                            e);
                    continue;
                }
            }
            if (Files.isRegularFile(Paths.get(targetPath.toString()).toRealPath())
                    && sourceFileName.endsWith(".py")) {
                // add the parent directory of .py file itself to PYTHONPATH
                pythonPathList.add(targetPath.getParent().toString());
            } else if (Files.isRegularFile(Paths.get(targetPath.toString()).toRealPath())
                    && sourceFileName.endsWith(".zip")) {
                // expand the zip file and add the root directory to PYTHONPATH
                // as not all zip files are importable
                Path targetDirectory =
                        new Path(
                                targetPath.getParent(),
                                sourceFileName.substring(0, sourceFileName.lastIndexOf(".")));
                FileUtils.expandDirectory(targetPath, targetDirectory);
                pythonPathList.add(targetDirectory.toString());
            } else {
                pythonPathList.add(targetPath.toString());
            }
        }

        if (env.pythonPath != null && !env.pythonPath.isEmpty()) {
            pythonPathList.add(env.pythonPath);
        }
        env.pythonPath = String.join(File.pathSeparator, pythonPathList);
    }

    /**
     * Starts python process.
     *
     * @param pythonEnv the python Environment which will be in a process.
     * @param commands the commands that python process will execute.
     * @return the process represent the python process.
     * @throws IOException Thrown if an error occurred when python process start.
     */
    static Process startPythonProcess(
            PythonEnvironment pythonEnv, List<String> commands, boolean redirectToPipe)
            throws IOException {
        ProcessBuilder pythonProcessBuilder = new ProcessBuilder();
        Map<String, String> env = pythonProcessBuilder.environment();
        if (pythonEnv.pythonPath != null) {
            String defaultPythonPath = env.get("PYTHONPATH");
            if (Strings.isNullOrEmpty(defaultPythonPath)) {
                env.put("PYTHONPATH", pythonEnv.pythonPath);
            } else {
                env.put(
                        "PYTHONPATH",
                        String.join(File.pathSeparator, pythonEnv.pythonPath, defaultPythonPath));
            }
        }
        if (pythonEnv.archivesDirectory != null) {
            pythonProcessBuilder.directory(new File(pythonEnv.archivesDirectory));
        }
        pythonEnv.systemEnv.forEach(env::put);
        commands.add(0, pythonEnv.pythonExec);
        pythonProcessBuilder.command(commands);
        // redirect the stderr to stdout
        pythonProcessBuilder.redirectErrorStream(true);
        if (redirectToPipe) {
            pythonProcessBuilder.redirectOutput(ProcessBuilder.Redirect.PIPE);
        } else {
            // set the child process the output same as the parent process.
            pythonProcessBuilder.redirectOutput(ProcessBuilder.Redirect.INHERIT);
        }
        LOG.info(
                "Starting Python process with environment variables: {{}}, command: {}",
                ConfigurationUtils.hideSensitiveValues(env).entrySet().stream()
                        .map(e -> e.getKey() + "=" + e.getValue())
                        .collect(Collectors.joining(", ")),
                String.join(" ", commands));
        Process process = pythonProcessBuilder.start();
        if (!process.isAlive()) {
            throw new RuntimeException("Failed to start Python process. ");
        }

        return process;
    }

    /**
     * Creates a GatewayServer run in a daemon thread.
     *
     * @return The created GatewayServer
     */
    static GatewayServer startGatewayServer() throws ExecutionException, InterruptedException {
        CompletableFuture<GatewayServer> gatewayServerFuture = new CompletableFuture<>();
        Thread thread =
                new Thread(
                        () -> {
                            try (NetUtils.Port port = NetUtils.getAvailablePort()) {
                                int freePort = port.getPort();
                                GatewayServer server =
                                        new GatewayServer.GatewayServerBuilder()
                                                .gateway(
                                                        new Gateway(
                                                                new ConcurrentHashMap<
                                                                        String, Object>(),
                                                                new CallbackClient(freePort)))
                                                .javaPort(0)
                                                .build();
                                resetCallbackClientExecutorService(server);
                                gatewayServerFuture.complete(server);
                                server.start(true);
                            } catch (Throwable e) {
                                gatewayServerFuture.completeExceptionally(e);
                            }
                        });
        thread.setName("py4j-gateway");
        thread.setDaemon(true);
        thread.start();
        thread.join();
        return gatewayServerFuture.get();
    }

    /**
     * Reset a daemon thread to the callback client thread pool so that the callback server can be
     * terminated when gate way server is shutting down. We need to shut down the none-daemon thread
     * firstly, then set a new thread created in a daemon thread to the ExecutorService.
     *
     * @param gatewayServer the gateway which creates the callback server.
     */
    private static void resetCallbackClientExecutorService(GatewayServer gatewayServer)
            throws NoSuchFieldException,
                    IllegalAccessException,
                    NoSuchMethodException,
                    InvocationTargetException {
        CallbackClient callbackClient = (CallbackClient) gatewayServer.getCallbackClient();
        // The Java API of py4j does not provide approach to set "daemonize_connections" parameter.
        // Use reflect to daemonize the connection thread.
        Field executor = CallbackClient.class.getDeclaredField("executor");
        executor.setAccessible(true);
        ((ScheduledExecutorService) executor.get(callbackClient)).shutdown();
        executor.set(callbackClient, Executors.newScheduledThreadPool(1, Thread::new));
        Method setupCleaner = CallbackClient.class.getDeclaredMethod("setupCleaner");
        setupCleaner.setAccessible(true);
        setupCleaner.invoke(callbackClient);
    }

    /**
     * Reset the callback client of gatewayServer with the given callbackListeningAddress and
     * callbackListeningPort after the callback server started.
     *
     * @param callbackServerListeningAddress the listening address of the callback server.
     * @param callbackServerListeningPort the listening port of the callback server.
     */
    public static void resetCallbackClient(
            GatewayServer gatewayServer,
            String callbackServerListeningAddress,
            int callbackServerListeningPort)
            throws UnknownHostException,
                    InvocationTargetException,
                    NoSuchMethodException,
                    IllegalAccessException,
                    NoSuchFieldException {

        gatewayServer.resetCallbackClient(
                InetAddress.getByName(callbackServerListeningAddress), callbackServerListeningPort);
        resetCallbackClientExecutorService(gatewayServer);
    }

    /**
     * Py4J both supports Java to Python RPC and Python to Java RPC. The GatewayServer object is the
     * entry point of Java to Python RPC. Since the Py4j Python client will only be launched only
     * once, the GatewayServer object needs to be reused.
     */
    private static GatewayServer gatewayServer = null;

    static GatewayServer getGatewayServer() {
        return gatewayServer;
    }

    static void setGatewayServer(GatewayServer gatewayServer) {
        Preconditions.checkArgument(gatewayServer == null || PythonEnvUtils.gatewayServer == null);
        PythonEnvUtils.gatewayServer = gatewayServer;
    }

    static Process launchPy4jPythonClient(
            GatewayServer gatewayServer,
            ReadableConfig config,
            List<String> commands,
            String entryPointScript,
            String tmpDir,
            boolean redirectToPipe)
            throws IOException {
        PythonEnvironment pythonEnv =
                PythonEnvUtils.preparePythonEnvironment(config, entryPointScript, tmpDir);
        // set env variable PYFLINK_GATEWAY_PORT for connecting of python gateway in python process.
        pythonEnv.systemEnv.put(
                "PYFLINK_GATEWAY_PORT", String.valueOf(gatewayServer.getListeningPort()));
        // start the python process.
        return PythonEnvUtils.startPythonProcess(pythonEnv, commands, redirectToPipe);
    }

    public static void setPythonException(Throwable pythonException) {
        if (ExceptionUtils.findThrowable(pythonException, UnsuccessfulExecutionException.class)
                .isPresent()) {
            capturedJavaException = pythonException;
        }
    }

    public static void shutdownPythonProcess(Process pythonProcess, long timeoutMillis) {
        pythonProcess.destroy();
        try {
            pythonProcess.waitFor(timeoutMillis, TimeUnit.MILLISECONDS);
        } catch (InterruptedException e) {
            throw new RuntimeException(
                    "Interrupt while waiting for the python process to stop.", e);
        }
        if (pythonProcess.isAlive()) {
            pythonProcess.destroyForcibly();
        }
    }

    /** The shutdown hook used to destroy the Python process. */
    public static class PythonProcessShutdownHook extends Thread {

        private final Process process;
        private final GatewayServer gatewayServer;
        private final String tmpDir;

        public PythonProcessShutdownHook(
                Process process, GatewayServer gatewayServer, String tmpDir) {
            this.process = process;
            this.gatewayServer = gatewayServer;
            this.tmpDir = tmpDir;
        }

        @Override
        public void run() {
            if (tmpDir != null) {
                FileUtils.deleteDirectoryQuietly(new File(tmpDir));
            }

            try {
                shutdownPythonProcess(process, TIMEOUT_MILLIS);
            } finally {
                gatewayServer.shutdown();
            }
        }
    }
}
