/*
 * 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.logging.log4j.core.appender;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.Serializable;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;
import java.nio.file.FileSystems;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.attribute.FileOwnerAttributeView;
import java.nio.file.attribute.FileTime;
import java.nio.file.attribute.PosixFileAttributeView;
import java.nio.file.attribute.PosixFilePermission;
import java.nio.file.attribute.PosixFilePermissions;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;

import org.apache.logging.log4j.core.Layout;
import org.apache.logging.log4j.core.LoggerContext;
import org.apache.logging.log4j.core.config.Configuration;
import org.apache.logging.log4j.core.util.Constants;
import org.apache.logging.log4j.core.util.FileUtils;
import org.apache.logging.log4j.util.StackLocatorUtil;


/**
 * Manages actual File I/O for File Appenders.
 */
public class FileManager extends OutputStreamManager {

    private static final FileManagerFactory FACTORY = new FileManagerFactory();

    private final boolean isAppend;
    private final boolean createOnDemand;
    private final boolean isLocking;
    private final String advertiseURI;
    private final int bufferSize;
    private final Set<PosixFilePermission> filePermissions;
    private final String fileOwner;
    private final String fileGroup;
    private final boolean attributeViewEnabled;

    /**
     * @since 2.9
     */
    protected FileManager(final LoggerContext loggerContext, final String fileName, final OutputStream os, final boolean append, final boolean locking,
            final boolean createOnDemand, final String advertiseURI, final Layout<? extends Serializable> layout,
            final String filePermissions, final String fileOwner, final String fileGroup, final boolean writeHeader,
            final ByteBuffer buffer) {
        super(loggerContext, os, fileName, createOnDemand, layout, writeHeader, buffer);
        this.isAppend = append;
        this.createOnDemand = createOnDemand;
        this.isLocking = locking;
        this.advertiseURI = advertiseURI;
        this.bufferSize = buffer.capacity();

        final Set<String> views = FileSystems.getDefault().supportedFileAttributeViews();
        if (views.contains("posix")) {
            this.filePermissions = filePermissions != null ? PosixFilePermissions.fromString(filePermissions) : null;
            this.fileGroup = fileGroup;
        } else {
            this.filePermissions = null;
            this.fileGroup = null;
            if (filePermissions != null) {
                LOGGER.warn("Posix file attribute permissions defined but it is not supported by this files system.");
            }
            if (fileGroup != null) {
                LOGGER.warn("Posix file attribute group defined but it is not supported by this files system.");
            }
        }

        if (views.contains("owner")) {
            this.fileOwner = fileOwner;
        } else {
            this.fileOwner = null;
            if (fileOwner != null) {
                LOGGER.warn("Owner file attribute defined but it is not supported by this files system.");
            }
        }

        // Supported and defined
        this.attributeViewEnabled = this.filePermissions != null || this.fileOwner != null || this.fileGroup != null;
    }

    /**
     * Returns the FileManager.
     * @param fileName The name of the file to manage.
     * @param append true if the file should be appended to, false if it should be overwritten.
     * @param locking true if the file should be locked while writing, false otherwise.
     * @param bufferedIo true if the contents should be buffered as they are written.
     * @param createOnDemand true if you want to lazy-create the file (a.k.a. on-demand.)
     * @param advertiseUri the URI to use when advertising the file
     * @param layout The layout
     * @param bufferSize buffer size for buffered IO
     * @param filePermissions File permissions
     * @param fileOwner File owner
     * @param fileGroup File group
     * @param configuration The configuration.
     * @return A FileManager for the File.
     */
    public static FileManager getFileManager(final String fileName, final boolean append, boolean locking,
            final boolean bufferedIo, final boolean createOnDemand, final String advertiseUri,
            final Layout<? extends Serializable> layout,
            final int bufferSize, final String filePermissions, final String fileOwner, final String fileGroup,
            final Configuration configuration) {

        if (locking && bufferedIo) {
            locking = false;
        }
        return narrow(FileManager.class, getManager(fileName, new FactoryData(append, locking, bufferedIo, bufferSize,
                createOnDemand, advertiseUri, layout, filePermissions, fileOwner, fileGroup, configuration), FACTORY));
    }

    @Override
    protected OutputStream createOutputStream() throws IOException {
        final String filename = getFileName();
        LOGGER.debug("Now writing to {} at {}", filename, new Date());
        final File file = new File(filename);
        final FileOutputStream fos = new FileOutputStream(file, isAppend);
        if (file.exists() && file.length() == 0) {
            try {
                FileTime now = FileTime.fromMillis(System.currentTimeMillis());
                Files.setAttribute(file.toPath(), "creationTime", now);
            } catch (Exception ex) {
                LOGGER.warn("Unable to set current file tiem for {}", filename);
            }
            writeHeader(fos);
        }
        defineAttributeView(Paths.get(filename));
        return fos;
    }

    protected void defineAttributeView(final Path path) {
        if (attributeViewEnabled) {
            try {
                // FileOutputStream may not create new file on all jvm
                path.toFile().createNewFile();

                FileUtils.defineFilePosixAttributeView(path, filePermissions, fileOwner, fileGroup);
            } catch (final Exception e) {
                LOGGER.error("Could not define attribute view on path \"{}\" got {}", path, e.getMessage(), e);
            }
        }
    }

    @Override
    protected synchronized void write(final byte[] bytes, final int offset, final int length,
            final boolean immediateFlush) {
        if (isLocking) {
            try {
                @SuppressWarnings("resource")
                final FileChannel channel = ((FileOutputStream) getOutputStream()).getChannel();
                /*
                 * Lock the whole file. This could be optimized to only lock from the current file position. Note that
                 * locking may be advisory on some systems and mandatory on others, so locking just from the current
                 * position would allow reading on systems where locking is mandatory. Also, Java 6 will throw an
                 * exception if the region of the file is already locked by another FileChannel in the same JVM.
                 * Hopefully, that will be avoided since every file should have a single file manager - unless two
                 * different files strings are configured that somehow map to the same file.
                 */
                try (final FileLock lock = channel.lock(0, Long.MAX_VALUE, false)) {
                    super.write(bytes, offset, length, immediateFlush);
                }
            } catch (final IOException ex) {
                throw new AppenderLoggingException("Unable to obtain lock on " + getName(), ex);
            }
        } else {
            super.write(bytes, offset, length, immediateFlush);
        }
    }

    /**
     * Overrides {@link OutputStreamManager#writeToDestination(byte[], int, int)} to add support for file locking.
     *
     * @param bytes the array containing data
     * @param offset from where to write
     * @param length how many bytes to write
     * @since 2.8
     */
    @Override
    protected synchronized void writeToDestination(final byte[] bytes, final int offset, final int length) {
        if (isLocking) {
            try {
                @SuppressWarnings("resource")
                final FileChannel channel = ((FileOutputStream) getOutputStream()).getChannel();
                /*
                 * Lock the whole file. This could be optimized to only lock from the current file position. Note that
                 * locking may be advisory on some systems and mandatory on others, so locking just from the current
                 * position would allow reading on systems where locking is mandatory. Also, Java 6 will throw an
                 * exception if the region of the file is already locked by another FileChannel in the same JVM.
                 * Hopefully, that will be avoided since every file should have a single file manager - unless two
                 * different files strings are configured that somehow map to the same file.
                 */
                try (final FileLock lock = channel.lock(0, Long.MAX_VALUE, false)) {
                    super.writeToDestination(bytes, offset, length);
                }
            } catch (final IOException ex) {
                throw new AppenderLoggingException("Unable to obtain lock on " + getName(), ex);
            }
        } else {
            super.writeToDestination(bytes, offset, length);
        }
    }

    /**
     * Returns the name of the File being managed.
     * @return The name of the File being managed.
     */
    public String getFileName() {
        return getName();
    }
    /**
     * Returns the append status.
     * @return true if the file will be appended to, false if it is overwritten.
     */
    public boolean isAppend() {
        return isAppend;
    }

    /**
     * Returns the lazy-create.
     * @return true if the file will be lazy-created.
     */
    public boolean isCreateOnDemand() {
        return createOnDemand;
    }

    /**
     * Returns the lock status.
     * @return true if the file will be locked when writing, false otherwise.
     */
    public boolean isLocking() {
        return isLocking;
    }

    /**
     * Returns the buffer size to use if the appender was configured with BufferedIO=true, otherwise returns a negative
     * number.
     * @return the buffer size, or a negative number if the output stream is not buffered
     */
    public int getBufferSize() {
        return bufferSize;
    }

    /**
     * Returns posix file permissions if defined and the OS supports posix file attribute,
     * null otherwise.
     * @return File posix permissions
     * @see PosixFileAttributeView
     */
    public Set<PosixFilePermission> getFilePermissions() {
        return filePermissions;
    }

    /**
     * Returns file owner if defined and the OS supports owner file attribute view,
     * null otherwise.
     * @return File owner
     * @see FileOwnerAttributeView
     */
    public String getFileOwner() {
        return fileOwner;
    }

    /**
     * Returns file group if defined and the OS supports posix/group file attribute view,
     * null otherwise.
     * @return File group
     * @see PosixFileAttributeView
     */
    public String getFileGroup() {
        return fileGroup;
    }

    /**
     * Returns true if file attribute view enabled for this file manager.
     *
     * @return True if posix or owner supported and defined false otherwise.
     */
    public boolean isAttributeViewEnabled() {
        return attributeViewEnabled;
    }

    /**
     * FileManager's content format is specified by: <code>Key: "fileURI" Value: provided "advertiseURI" param</code>.
     *
     * @return Map of content format keys supporting FileManager
     */
    @Override
    public Map<String, String> getContentFormat() {
        final Map<String, String> result = new HashMap<>(super.getContentFormat());
        result.put("fileURI", advertiseURI);
        return result;
    }

    /**
     * Factory Data.
     */
    private static class FactoryData extends ConfigurationFactoryData {
        private final boolean append;
        private final boolean locking;
        private final boolean bufferedIo;
        private final int bufferSize;
        private final boolean createOnDemand;
        private final String advertiseURI;
        private final Layout<? extends Serializable> layout;
        private final String filePermissions;
        private final String fileOwner;
        private final String fileGroup;

        /**
         * Constructor.
         * @param append Append status.
         * @param locking Locking status.
         * @param bufferedIo Buffering flag.
         * @param bufferSize Buffer size.
         * @param createOnDemand if you want to lazy-create the file (a.k.a. on-demand.)
         * @param advertiseURI the URI to use when advertising the file
         * @param layout The layout
         * @param filePermissions File permissions
         * @param fileOwner File owner
         * @param fileGroup File group
         * @param configuration the configuration
         */
        public FactoryData(final boolean append, final boolean locking, final boolean bufferedIo, final int bufferSize,
                final boolean createOnDemand, final String advertiseURI, final Layout<? extends Serializable> layout,
                final String filePermissions, final String fileOwner, final String fileGroup,
                final Configuration configuration) {
            super(configuration);
            this.append = append;
            this.locking = locking;
            this.bufferedIo = bufferedIo;
            this.bufferSize = bufferSize;
            this.createOnDemand = createOnDemand;
            this.advertiseURI = advertiseURI;
            this.layout = layout;
            this.filePermissions = filePermissions;
            this.fileOwner = fileOwner;
            this.fileGroup = fileGroup;
        }
    }

    /**
     * Factory to create a FileManager.
     */
    private static class FileManagerFactory implements ManagerFactory<FileManager, FactoryData> {

        /**
         * Creates a FileManager.
         * @param name The name of the File.
         * @param data The FactoryData
         * @return The FileManager for the File.
         */
        @Override
        public FileManager createManager(final String name, final FactoryData data) {
            final File file = new File(name);
            try {
                FileUtils.makeParentDirs(file);
                final int actualSize = data.bufferedIo ? data.bufferSize : Constants.ENCODER_BYTE_BUFFER_SIZE;
                final ByteBuffer byteBuffer = ByteBuffer.wrap(new byte[actualSize]);
                final FileOutputStream fos = data.createOnDemand ? null : new FileOutputStream(file, data.append);
                final boolean writeHeader = file.exists() && file.length() == 0;
                final FileManager fm = new FileManager(data.getLoggerContext(), name, fos, data.append, data.locking,
                        data.createOnDemand, data.advertiseURI, data.layout,
                        data.filePermissions, data.fileOwner, data.fileGroup, writeHeader, byteBuffer);
                if (fos != null && fm.attributeViewEnabled) {
                    fm.defineAttributeView(file.toPath());
                }
                return fm;
            } catch (final IOException ex) {
                LOGGER.error("FileManager (" + name + ") " + ex, ex);
            }
            return null;
        }
    }

}