/*
 * Copyright (c) 2013, 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.
 *
 * 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.testlibrary;

import java.io.IOException;
import java.nio.file.DirectoryNotEmptyException;
import java.nio.file.FileVisitResult;
import java.nio.file.Files;
import java.nio.file.NoSuchFileException;
import java.nio.file.Path;
import java.nio.file.SimpleFileVisitor;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.TimeUnit;


/**
 * Common library for various test file utility functions.
 */
public final class FileUtils {

    private static final boolean isWindows =
                            System.getProperty("os.name").startsWith("Windows");
    private static final int RETRY_DELETE_MILLIS = isWindows ? 500 : 0;
    private static final int MAX_RETRY_DELETE_TIMES = isWindows ? 15 : 0;

    /**
     * Deletes a file, retrying if necessary.
     *
     * @param path  the file to delete
     *
     * @throws NoSuchFileException
     *         if the file does not exist (optional specific exception)
     * @throws DirectoryNotEmptyException
     *         if the file is a directory and could not otherwise be deleted
     *         because the directory is not empty (optional specific exception)
     * @throws IOException
     *         if an I/O error occurs
     */
    public static void deleteFileWithRetry(Path path)
        throws IOException
    {
        try {
            deleteFileWithRetry0(path);
        } catch (InterruptedException x) {
            throw new IOException("Interrupted while deleting.", x);
        }
    }

    /**
     * Deletes a file, retrying if necessary.
     * No exception thrown if file doesn't exist.
     *
     * @param path  the file to delete
     *
     * @throws NoSuchFileException
     *         if the file does not exist (optional specific exception)
     * @throws DirectoryNotEmptyException
     *         if the file is a directory and could not otherwise be deleted
     *         because the directory is not empty (optional specific exception)
     * @throws IOException
     *         if an I/O error occurs
     */
    public static void deleteFileIfExistsWithRetry(Path path)
        throws IOException
    {
        try {
            if(Files.exists(path))
                deleteFileWithRetry0(path);
        } catch (InterruptedException x) {
            throw new IOException("Interrupted while deleting.", x);
        }
    }

    private static void deleteFileWithRetry0(Path path)
        throws IOException, InterruptedException
    {
        int times = 0;
        IOException ioe = null;
        while (true) {
            try {
                Files.delete(path);
                while (Files.exists(path)) {
                    times++;
                    if (times > MAX_RETRY_DELETE_TIMES)
                        throw new IOException("File still exists after " + times + " waits.");
                    Thread.sleep(RETRY_DELETE_MILLIS);
                }
                break;
            } catch (NoSuchFileException | DirectoryNotEmptyException x) {
                throw x;
            } catch (IOException x) {
                // Backoff/retry in case another process is accessing the file
                times++;
                if (ioe == null)
                    ioe = x;
                else
                    ioe.addSuppressed(x);

                if (times > MAX_RETRY_DELETE_TIMES)
                    throw ioe;
                Thread.sleep(RETRY_DELETE_MILLIS);
            }
        }
    }

    /**
     * Deletes a directory and its subdirectories, retrying if necessary.
     *
     * @param dir  the directory to delete
     *
     * @throws  IOException
     *          If an I/O error occurs. Any such exceptions are caught
     *          internally. If only one is caught, then it is re-thrown.
     *          If more than one exception is caught, then the second and
     *          following exceptions are added as suppressed exceptions of the
     *          first one caught, which is then re-thrown.
     */
    public static void deleteFileTreeWithRetry(Path dir)
         throws IOException
    {
        IOException ioe = null;
        final List<IOException> excs = deleteFileTreeUnchecked(dir);
        if (!excs.isEmpty()) {
            ioe = excs.remove(0);
            for (IOException x : excs)
                ioe.addSuppressed(x);
        }
        if (ioe != null)
            throw ioe;
    }

    public static List<IOException> deleteFileTreeUnchecked(Path dir) {
        final List<IOException> excs = new ArrayList<>();
        try {
            java.nio.file.Files.walkFileTree(dir, new SimpleFileVisitor<Path>() {
                @Override
                public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) {
                    try {
                        deleteFileWithRetry0(file);
                    } catch (IOException x) {
                        excs.add(x);
                    } catch (InterruptedException x) {
                        excs.add(new IOException("Interrupted while deleting.", x));
                        return FileVisitResult.TERMINATE;
                    }
                    return FileVisitResult.CONTINUE;
                }
                @Override
                public FileVisitResult postVisitDirectory(Path dir, IOException exc) {
                    try {
                        deleteFileWithRetry0(dir);
                    } catch (IOException x) {
                        excs.add(x);
                    } catch (InterruptedException x) {
                        excs.add(new IOException("Interrupted while deleting.", x));
                        return FileVisitResult.TERMINATE;
                    }
                    return FileVisitResult.CONTINUE;
                }
                @Override
                public FileVisitResult visitFileFailed(Path file, IOException exc) {
                    excs.add(exc);
                    return FileVisitResult.CONTINUE;
                }
            });
        } catch (IOException x) {
            excs.add(x);
        }
        return excs;
    }

    /**
     * Checks whether all file systems are accessible. This is performed
     * by checking free disk space on all mounted file systems via a
     * separate, spawned process. File systems are considered to be
     * accessible if this process completes successfully before a given
     * fixed duration has elapsed.
     *
     * @implNote On Unix this executes the {@code df} command in a separate
     * process and on Windows always returns {@code true}.
     */
    public static boolean areFileSystemsAccessible() throws IOException {
        boolean areFileSystemsAccessible = true;
        if (!isWindows) {
            // try to check whether 'df' hangs
            System.out.println("\n--- df output ---");
            System.out.flush();
            Process proc = new ProcessBuilder("df").inheritIO().start();
            try {
                proc.waitFor(90, TimeUnit.SECONDS);
            } catch (InterruptedException ignored) {
            }
            try {
                int exitValue = proc.exitValue();
                if (exitValue != 0) {
                    System.err.printf("df process exited with %d != 0%n",
                        exitValue);
                    areFileSystemsAccessible = false;
                }
            } catch (IllegalThreadStateException ignored) {
                System.err.println("df command apparently hung");
                areFileSystemsAccessible = false;
            }
        }
        return areFileSystemsAccessible;
    }
}
