/*

 * Copyright (c) 2010, 2014, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package jdk.nashorn.internal.codegen;

import java.io.BufferedInputStream;

import java.io.BufferedOutputStream;

import java.io.DataInputStream;

import java.io.DataOutputStream;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.InputStream;

import java.net.URL;

import java.nio.file.Files;

import java.nio.file.Path;

import java.security.AccessController;

import java.security.MessageDigest;

import java.security.PrivilegedAction;

import java.text.SimpleDateFormat;

import java.util.Base64;

import java.util.Date;

import java.util.Map;

import java.util.Timer;

import java.util.TimerTask;

import java.util.concurrent.TimeUnit;

import java.util.concurrent.atomic.AtomicBoolean;

import java.util.function.Function;

import java.util.function.IntFunction;

import java.util.function.Predicate;

import java.util.stream.Stream;

import jdk.nashorn.internal.codegen.types.Type;

import jdk.nashorn.internal.runtime.Context;

import jdk.nashorn.internal.runtime.RecompilableScriptFunctionData;

import jdk.nashorn.internal.runtime.Source;

import jdk.nashorn.internal.runtime.logging.DebugLogger;

import jdk.nashorn.internal.runtime.options.Options;

/**

 * Static utility that encapsulates persistence of type information for functions compiled with optimistic

 * typing. With this feature enabled, when a JavaScript function is recompiled because it gets deoptimized,

 * the type information for deoptimization is stored in a cache file. If the same function is compiled in a

 * subsequent JVM invocation, the type information is used for initial compilation, thus allowing the system

 * to skip a lot of intermediate recompilations and immediately emit a version of the code that has its

 * optimistic types at (or near) the steady state.

 * </p><p>

 * Normally, the type info persistence feature is disabled. When the {@code nashorn.typeInfo.maxFiles} system

 * property is specified with a value greater than 0, it is enabled and operates in an operating-system

 * specific per-user cache directory. You can override the directory by specifying it in the

 * {@code nashorn.typeInfo.cacheDir} directory. The maximum number of files is softly enforced by a task that

 * cleans up the directory periodically on a separate thread. It is run after some delay after a new file is

 * added to the cache. The default delay is 20 seconds, and can be set using the

 * {@code nashorn.typeInfo.cleanupDelaySeconds} system property. You can also specify the word

 * {@code unlimited} as the value for {@code nashorn.typeInfo.maxFiles} in which case the type info cache is

 * allowed to grow without limits.

 */

public final class OptimisticTypesPersistence {

    // Default is 0, for disabling the feature when not specified. A reasonable default when enabled is

    // dependent on the application; setting it to e.g. 20000 is probably good enough for most uses and will

    // usually cap the cache directory to about 80MB presuming a 4kB filesystem allocation unit. There is one

    // file per JavaScript function.

    private static final int DEFAULT_MAX_FILES = 0;

    // Constants for signifying that the cache should not be limited

    private static final int UNLIMITED_FILES = -1;

    // Maximum number of files that should be cached on disk. The maximum will be softly enforced.

    private static final int MAX_FILES = getMaxFiles();

    // Number of seconds to wait between adding a new file to the cache and running a cleanup process

    private static final int DEFAULT_CLEANUP_DELAY = 20;

    private static final int CLEANUP_DELAY = Math.max(0, Options.getIntProperty(

            "nashorn.typeInfo.cleanupDelaySeconds", DEFAULT_CLEANUP_DELAY));

    // The name of the default subdirectory within the system cache directory where we store type info.

    private static final String DEFAULT_CACHE_SUBDIR_NAME = "com.oracle.java.NashornTypeInfo";

    // The directory where we cache type info

    private static final File baseCacheDir = createBaseCacheDir();

    private static final File cacheDir = createCacheDir(baseCacheDir);

    // In-process locks to make sure we don't have a cross-thread race condition manipulating any file.

    private static final Object[] locks = cacheDir == null ? null : createLockArray();

    // Only report one read/write error every minute

    private static final long ERROR_REPORT_THRESHOLD = 60000L;

    private static volatile long lastReportedError;

    private static final AtomicBoolean scheduledCleanup;

    private static final Timer cleanupTimer;

    static {

        if (baseCacheDir == null || MAX_FILES == UNLIMITED_FILES) {

            scheduledCleanup = null;

            cleanupTimer = null;

        } else {

            scheduledCleanup = new AtomicBoolean();

            cleanupTimer = new Timer(true);

        }

    }

    /**

     * Retrieves an opaque descriptor for the persistence location for a given function. It should be passed

     * to {@link #load(Object)} and {@link #store(Object, Map)} methods.

     * @param source the source where the function comes from

     * @param functionId the unique ID number of the function within the source

     * @param paramTypes the types of the function parameters (as persistence is per parameter type

     * specialization).

     * @return an opaque descriptor for the persistence location. Can be null if persistence is disabled.

     */

    public static Object getLocationDescriptor(final Source source, final int functionId, final Type[] paramTypes) {

        if(cacheDir == null) {

            return null;

        }

        final StringBuilder b = new StringBuilder(48);

        // Base64-encode the digest of the source, and append the function id.

        b.append(source.getDigest()).append('-').append(functionId);

        // Finally, if this is a parameter-type specialized version of the function, add the parameter types

        // to the file name.

        if(paramTypes != null && paramTypes.length > 0) {

            b.append('-');

            for(final Type t: paramTypes) {

                b.append(Type.getShortSignatureDescriptor(t));

            }

        }

        return new LocationDescriptor(new File(cacheDir, b.toString()));

    }

    private static final class LocationDescriptor {

        private final File file;

        LocationDescriptor(final File file) {

            this.file = file;

        }

    }

    /**

     * Stores the map of optimistic types for a given function.

     * @param locationDescriptor the opaque persistence location descriptor, retrieved by calling

     * {@link #getLocationDescriptor(Source, int, Type[])}.

     * @param optimisticTypes the map of optimistic types.

     */

    @SuppressWarnings("resource")

    public static void store(final Object locationDescriptor, final Map<Integer, Type> optimisticTypes) {

        if(locationDescriptor == null || optimisticTypes.isEmpty()) {

            return;

        }

        final File file = ((LocationDescriptor)locationDescriptor).file;

        AccessController.doPrivileged(new PrivilegedAction<Void>() {

            @Override

            public Void run() {

                synchronized(getFileLock(file)) {

                    if (!file.exists()) {

                        // If the file already exists, we aren't increasing the number of cached files, so

                        // don't schedule cleanup.

                        scheduleCleanup();

                    }

                    try (final FileOutputStream out = new FileOutputStream(file)) {

                        out.getChannel().lock(); // lock exclusive

                        final DataOutputStream dout = new DataOutputStream(new BufferedOutputStream(out));

                        Type.writeTypeMap(optimisticTypes, dout);

                        dout.flush();

                    } catch(final Exception e) {

                        reportError("write", file, e);

                    }

                }

                return null;

            }

        });

    }

    /**

     * Loads the map of optimistic types for a given function.

     * @param locationDescriptor the opaque persistence location descriptor, retrieved by calling

     * {@link #getLocationDescriptor(Source, int, Type[])}.

     * @return the map of optimistic types, or null if persisted type information could not be retrieved.

     */

    @SuppressWarnings("resource")

    public static Map<Integer, Type> load(final Object locationDescriptor) {

        if (locationDescriptor == null) {

            return null;

        }

        final File file = ((LocationDescriptor)locationDescriptor).file;

        return AccessController.doPrivileged(new PrivilegedAction<Map<Integer, Type>>() {

            @Override

            public Map<Integer, Type> run() {

                try {

                    if(!file.isFile()) {

                        return null;

                    }

                    synchronized(getFileLock(file)) {

                        try (final FileInputStream in = new FileInputStream(file)) {

                            in.getChannel().lock(0, Long.MAX_VALUE, true); // lock shared

                            final DataInputStream din = new DataInputStream(new BufferedInputStream(in));

                            return Type.readTypeMap(din);

                        }

                    }

                } catch (final Exception e) {

                    reportError("read", file, e);

                    return null;

                }

            }

        });

    }

    private static void reportError(final String msg, final File file, final Exception e) {

        final long now = System.currentTimeMillis();

        if(now - lastReportedError > ERROR_REPORT_THRESHOLD) {

            getLogger().warning(String.format("Failed to %s %s", msg, file), e);

            lastReportedError = now;

        }

    }

    private static File createBaseCacheDir() {

        if(MAX_FILES == 0 || Options.getBooleanProperty("nashorn.typeInfo.disabled")) {

            return null;

        }

        try {

            return createBaseCacheDirPrivileged();

        } catch(final Exception e) {

            getLogger().warning("Failed to create cache dir", e);

            return null;

        }

    }

    private static File createBaseCacheDirPrivileged() {

        return AccessController.doPrivileged(new PrivilegedAction<File>() {

            @Override

            public File run() {

                final String explicitDir = System.getProperty("nashorn.typeInfo.cacheDir");

                final File dir;

                if(explicitDir != null) {

                    dir = new File(explicitDir);

                } else {

                    // When no directory is explicitly specified, get an operating system specific cache

                    // directory, and create "com.oracle.java.NashornTypeInfo" in it.

                    final File systemCacheDir = getSystemCacheDir();

                    dir = new File(systemCacheDir, DEFAULT_CACHE_SUBDIR_NAME);

                    if (isSymbolicLink(dir)) {

                        return null;

                    }

                }

                return dir;

            }

        });

    }

    private static File createCacheDir(final File baseDir) {

        if (baseDir == null) {

            return null;

        }

        try {

            return createCacheDirPrivileged(baseDir);

        } catch(final Exception e) {

            getLogger().warning("Failed to create cache dir", e);

            return null;

        }

    }

    private static File createCacheDirPrivileged(final File baseDir) {

        return AccessController.doPrivileged(new PrivilegedAction<File>() {

            @Override

            public File run() {

                final String versionDirName;

                try {

                    versionDirName = getVersionDirName();

                } catch(final Exception e) {

                    getLogger().warning("Failed to calculate version dir name", e);

                    return null;

                }

                final File versionDir = new File(baseDir, versionDirName);

                if (isSymbolicLink(versionDir)) {

                    return null;

                }

                versionDir.mkdirs();

                if (versionDir.isDirectory()) {

                    getLogger().info("Optimistic type persistence directory is " + versionDir);

                    return versionDir;

                }

                getLogger().warning("Could not create optimistic type persistence directory " + versionDir);

                return null;

            }

        });

    }

    /**

     * Returns an operating system specific root directory for cache files.

     * @return an operating system specific root directory for cache files.

     */

    private static File getSystemCacheDir() {

        final String os = System.getProperty("os.name", "generic");

        if("Mac OS X".equals(os)) {

            // Mac OS X stores caches in ~/Library/Caches

            return new File(new File(System.getProperty("user.home"), "Library"), "Caches");

        } else if(os.startsWith("Windows")) {

            // On Windows, temp directory is the best approximation of a cache directory, as its contents

            // persist across reboots and various cleanup utilities know about it. java.io.tmpdir normally

            // points to a user-specific temp directory, %HOME%\LocalSettings\Temp.

            return new File(System.getProperty("java.io.tmpdir"));

        } else {

            // In other cases we're presumably dealing with a UNIX flavor (Linux, Solaris, etc.); "~/.cache"

            return new File(System.getProperty("user.home"), ".cache");

        }

    }

    /**

     * In order to ensure that changes in Nashorn code don't cause corruption in the data, we'll create a

     * per-code-version directory. Normally, this will create the SHA-1 digest of the nashorn.jar. In case the classpath

     * for nashorn is local directory (e.g. during development), this will create the string "dev-" followed by the

     * timestamp of the most recent .class file.

     * @return

     */

    private static String getVersionDirName() throws Exception {

        final URL url = OptimisticTypesPersistence.class.getResource("");

        final String protocol = url.getProtocol();

        if (protocol.equals("jar")) {

            // Normal deployment: nashorn.jar

            final String jarUrlFile = url.getFile();

            final String filePath = jarUrlFile.substring(0, jarUrlFile.indexOf('!'));

            final URL file = new URL(filePath);

            try (final InputStream in = file.openStream()) {

                final byte[] buf = new byte[128*1024];

                final MessageDigest digest = MessageDigest.getInstance("SHA-1");

                for(;;) {

                    final int l = in.read(buf);

                    if(l == -1) {

                        return Base64.getUrlEncoder().withoutPadding().encodeToString(digest.digest());

                    }

                    digest.update(buf, 0, l);

                }

            }

        } else if(protocol.equals("file")) {

            // Development

            final String fileStr = url.getFile();

            final String className = OptimisticTypesPersistence.class.getName();

            final int packageNameLen = className.lastIndexOf('.');

            final String dirStr = fileStr.substring(0, fileStr.length() - packageNameLen - 1);

            final File dir = new File(dirStr);

            return "dev-" + new SimpleDateFormat("yyyyMMdd-HHmmss").format(new Date(getLastModifiedClassFile(

                    dir, 0L)));

        } else {

            throw new AssertionError();

        }

    }

    private static long getLastModifiedClassFile(final File dir, final long max) {

        long currentMax = max;

        for(final File f: dir.listFiles()) {

            if(f.getName().endsWith(".class")) {

                final long lastModified = f.lastModified();

                if (lastModified > currentMax) {

                    currentMax = lastModified;

                }

            } else if (f.isDirectory()) {

                final long lastModified = getLastModifiedClassFile(f, currentMax);

                if (lastModified > currentMax) {

                    currentMax = lastModified;

                }

            }

        }

        return currentMax;

    }

    /**

     * Returns true if the specified file is a symbolic link, and also logs a warning if it is.

     * @param file the file

     * @return true if file is a symbolic link, false otherwise.

     */

    private static boolean isSymbolicLink(final File file) {

        if (Files.isSymbolicLink(file.toPath())) {

            getLogger().warning("Directory " + file + " is a symlink");

            return true;

        }

        return false;

    }

    private static Object[] createLockArray() {

        final Object[] lockArray = new Object[Runtime.getRuntime().availableProcessors() * 2];

        for (int i = 0; i < lockArray.length; ++i) {

            lockArray[i] = new Object();

        }

        return lockArray;

    }

    private static Object getFileLock(final File file) {

        return locks[(file.hashCode() & Integer.MAX_VALUE) % locks.length];

    }

    private static DebugLogger getLogger() {

        try {

            return Context.getContext().getLogger(RecompilableScriptFunctionData.class);

        } catch (final Exception e) {

            e.printStackTrace();

            return DebugLogger.DISABLED_LOGGER;

        }

    }

    private static void scheduleCleanup() {

        if (MAX_FILES != UNLIMITED_FILES && scheduledCleanup.compareAndSet(false, true)) {

            cleanupTimer.schedule(new TimerTask() {

                @Override

                public void run() {

                    scheduledCleanup.set(false);

                    try {

                        doCleanup();

                    } catch (final IOException e) {

                        // Ignore it. While this is unfortunate, we don't have good facility for reporting

                        // this, as we're running in a thread that has no access to Context, so we can't grab

                        // a DebugLogger.

                    }

                }

            }, TimeUnit.SECONDS.toMillis(CLEANUP_DELAY));

        }

    }

    private static void doCleanup() throws IOException {

        final Path[] files = getAllRegularFilesInLastModifiedOrder();

        final int nFiles = files.length;

        final int filesToDelete = Math.max(0, nFiles - MAX_FILES);

        int filesDeleted = 0;

        for (int i = 0; i < nFiles && filesDeleted < filesToDelete; ++i) {

            try {

                Files.deleteIfExists(files[i]);

                // Even if it didn't exist, we increment filesDeleted; it existed a moment earlier; something

                // else deleted it for us; that's okay with us.

                filesDeleted++;

            } catch (final Exception e) {

                // does not increase filesDeleted

            }

            files[i] = null; // gc eligible

    }

    private static Path[] getAllRegularFilesInLastModifiedOrder() throws IOException {

        try (final Stream<Path> filesStream = Files.walk(baseCacheDir.toPath())) {

            // TODO: rewrite below once we can use JDK8 syntactic constructs

            return filesStream

            .filter(new Predicate<Path>() {

                @Override

                public boolean test(final Path path) {

                    return !Files.isDirectory(path);

            })

            .map(new Function<Path, PathAndTime>() {

                @Override

                public PathAndTime apply(final Path path) {

                    return new PathAndTime(path);

                }

            })

            .sorted()

            .map(new Function<PathAndTime, Path>() {

                @Override

                public Path apply(final PathAndTime pathAndTime) {

                    return pathAndTime.path;

                }

            })

            .toArray(new IntFunction<Path[]>() { // Replace with Path::new

                @Override

                public Path[] apply(final int length) {

                    return new Path[length];

                }

            });

        }

    }

    private static class PathAndTime implements Comparable<PathAndTime> {

        private final Path path;

        private final long time;

        PathAndTime(final Path path) {

            this.path = path;

            this.time = getTime(path);

        }

        @Override

        public int compareTo(final PathAndTime other) {

            return Long.compare(time, other.time);

        }

        private static long getTime(final Path path) {

            try {

                return Files.getLastModifiedTime(path).toMillis();

            } catch (final IOException e) {

                // All files for which we can't retrieve the last modified date will be considered oldest.

                return -1L;

            }

        }

    }

    private static int getMaxFiles() {

        final String str = Options.getStringProperty("nashorn.typeInfo.maxFiles", null);