/**
 * Logback: the reliable, generic, fast and flexible logging framework.
 * Copyright (C) 1999-2015, QOS.ch. All rights reserved.
 *
 * This program and the accompanying materials are dual-licensed under
 * either the terms of the Eclipse Public License v1.0 as published by
 * the Eclipse Foundation
 *
 *   or (per the licensee's choosing)
 *
 * under the terms of the GNU Lesser General Public License version 2.1
 * as published by the Free Software Foundation.
 */
package ch.qos.logback.core;

import static ch.qos.logback.core.CoreConstants.CODES_URL;
import static ch.qos.logback.core.CoreConstants.MORE_INFO_PREFIX;

import java.io.File;
import java.io.IOException;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;
import java.util.Map;
import java.util.Map.Entry;

import ch.qos.logback.core.recovery.ResilientFileOutputStream;
import ch.qos.logback.core.util.ContextUtil;
import ch.qos.logback.core.util.FileSize;
import ch.qos.logback.core.util.FileUtil;

/**
 * FileAppender appends log events to a file.
 * 
 * For more information about this appender, please refer to the online manual
 * at http://logback.qos.ch/manual/appenders.html#FileAppender
 * 
 * @author Ceki Gülcü
 */
public class FileAppender<E> extends OutputStreamAppender<E> {

    public static final long DEFAULT_BUFFER_SIZE = 8192;

    static protected String COLLISION_WITH_EARLIER_APPENDER_URL = CODES_URL + "#earlier_fa_collision";

    /**
     * Append to or truncate the file? The default value for this variable is
     * <code>true</code>, meaning that by default a <code>FileAppender</code> will
     * append to an existing file and not truncate it.
     */
    protected boolean append = true;

    /**
     * The name of the active log file.
     */
    protected String fileName = null;

    private boolean prudent = false;

    private FileSize bufferSize = new FileSize(DEFAULT_BUFFER_SIZE);

    /**
     * The <b>File</b> property takes a string value which should be the name of the
     * file to append to.
     */
    public void setFile(String file) {
        if (file == null) {
            fileName = file;
        } else {
            // Trim spaces from both ends. The users probably does not want
            // trailing spaces in file names.
            fileName = file.trim();
        }
    }

    /**
     * Returns the value of the <b>Append</b> property.
     */
    public boolean isAppend() {
        return append;
    }

    /**
     * This method is used by derived classes to obtain the raw file property.
     * Regular users should not be calling this method.
     * 
     * @return the value of the file property
     */
    final public String rawFileProperty() {
        return fileName;
    }

    /**
     * Returns the value of the <b>File</b> property.
     * 
     * <p>
     * This method may be overridden by derived classes.
     * 
     */
    public String getFile() {
        return fileName;
    }

    /**
     * If the value of <b>File</b> is not <code>null</code>, then {@link #openFile}
     * is called with the values of <b>File</b> and <b>Append</b> properties.
     */
    public void start() {
        int errors = 0;
        if (getFile() != null) {
            addInfo("File property is set to [" + fileName + "]");

            if (prudent) {
                if (!isAppend()) {
                    setAppend(true);
                    addWarn("Setting \"Append\" property to true on account of \"Prudent\" mode");
                }
            }

            if (checkForFileCollisionInPreviousFileAppenders()) {
                addError("Collisions detected with FileAppender/RollingAppender instances defined earlier. Aborting.");
                addError(MORE_INFO_PREFIX + COLLISION_WITH_EARLIER_APPENDER_URL);
                errors++;
            } else {
                // file should be opened only if collision free
                try {
                    openFile(getFile());
                } catch (java.io.IOException e) {
                    errors++;
                    addError("openFile(" + fileName + "," + append + ") call failed.", e);
                }
            }
        } else {
            errors++;
            addError("\"File\" property not set for appender named [" + name + "].");
        }
        if (errors == 0) {
            super.start();
        }
    }

    @Override
    public void stop() {
        if(!isStarted())
            return;

        super.stop();

        Map<String, String> map = ContextUtil.getFilenameCollisionMap(context);
        if (map == null || getName() == null)
            return;

        map.remove(getName());
    }

    protected boolean checkForFileCollisionInPreviousFileAppenders() {
        boolean collisionsDetected = false;
        if (fileName == null) {
            return false;
        }
        @SuppressWarnings("unchecked")
        Map<String, String> previousFilesMap = (Map<String, String>) context
                .getObject(CoreConstants.FA_FILENAME_COLLISION_MAP);
        if (previousFilesMap == null) {
            return collisionsDetected;
        }
        for (Entry<String, String> entry : previousFilesMap.entrySet()) {
            if (fileName.equals(entry.getValue())) {
                addErrorForCollision("File", entry.getValue(), entry.getKey());
                collisionsDetected = true;
            }
        }
        if (name != null) {
            previousFilesMap.put(getName(), fileName);
        }
        return collisionsDetected;
    }

    protected void addErrorForCollision(String optionName, String optionValue, String appenderName) {
        addError("'" + optionName + "' option has the same value \"" + optionValue + "\" as that given for appender ["
                + appenderName + "] defined earlier.");
    }

    /**
     * <p>
     * Sets and <i>opens</i> the file where the log output will go. The specified
     * file must be writable.
     * 
     * <p>
     * If there was already an opened file, then the previous file is closed first.
     * 
     * <p>
     * <b>Do not use this method directly. To configure a FileAppender or one of its
     * subclasses, set its properties one by one and then call start().</b>
     * 
     * @param file_name The path to the log file.
     */
    public void openFile(String file_name) throws IOException {
        streamWriteLock.lock();
        try {
            File file = new File(file_name);
            boolean result = FileUtil.createMissingParentDirectories(file);
            if (!result) {
                addError("Failed to create parent directories for [" + file.getAbsolutePath() + "]");
            }

            ResilientFileOutputStream resilientFos = new ResilientFileOutputStream(file, append, bufferSize.getSize());
            resilientFos.setContext(context);
            setOutputStream(resilientFos);
        } finally {
            streamWriteLock.unlock();
        }
    }

    /**
     * @see #setPrudent(boolean)
     * 
     * @return true if in prudent mode
     */
    public boolean isPrudent() {
        return prudent;
    }

    /**
     * When prudent is set to true, file appenders from multiple JVMs can safely
     * write to the same file.
     * 
     * @param prudent
     */
    public void setPrudent(boolean prudent) {
        this.prudent = prudent;
    }

    public void setAppend(boolean append) {
        this.append = append;
    }

    public void setBufferSize(FileSize bufferSize) {
        addInfo("Setting bufferSize to [" + bufferSize.toString() + "]");
        this.bufferSize = bufferSize;
    }

    @Override
    protected void writeOut(E event) throws IOException {
        if (prudent) {
            safeWriteOut(event);
        } else {
            super.writeOut(event);
        }
    }

    private void safeWriteOut(E event) {
        byte[] byteArray = this.encoder.encode(event);
        if (byteArray == null || byteArray.length == 0)
            return;

        streamWriteLock.lock();
        try {
           safeWriteBytes(byteArray);
        } finally {
            streamWriteLock.unlock();
        }
    }

    private void safeWriteBytes(byte[] byteArray) {
        ResilientFileOutputStream resilientFOS = (ResilientFileOutputStream) getOutputStream();
        FileChannel fileChannel = resilientFOS.getChannel();
        if (fileChannel == null) {
            return;
        }

        // Clear any current interrupt (see LOGBACK-875)
        boolean interrupted = Thread.interrupted();

        FileLock fileLock = null;
        try {
            fileLock = fileChannel.lock();
            long position = fileChannel.position();
            long size = fileChannel.size();
            if (size != position) {
                fileChannel.position(size);
            }
            writeByteArrayToOutputStreamWithPossibleFlush(byteArray);
        } catch (IOException e) {
            // Mainly to catch FileLockInterruptionExceptions (see LOGBACK-875)
            resilientFOS.postIOFailure(e);
        } finally {
            releaseFileLock(fileLock);

            // Re-interrupt if we started in an interrupted state (see LOGBACK-875)
            if (interrupted) {
                Thread.currentThread().interrupt();
            }
        }
    }

    private void releaseFileLock(FileLock fileLock) {
        if (fileLock != null && fileLock.isValid()) {
            try {
                fileLock.release();
            } catch (IOException e) {
                addError("failed to release lock", e);
            }
        }
    }
}