/*
 * 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 com.alibaba.dubbo.container.page.pages;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.Enumeration;
import java.util.List;

import com.alibaba.dubbo.common.URL;
import com.alibaba.dubbo.container.page.Menu;
import com.alibaba.dubbo.container.page.Page;
import com.alibaba.dubbo.container.page.PageHandler;
import org.apache.log4j.Appender;
import org.apache.log4j.FileAppender;
import org.apache.log4j.Level;
import org.apache.log4j.LogManager;

/**
 * LogPageHandler
 */
@Menu(name = "Log", desc = "Show system log.", order = Integer.MAX_VALUE - 11000)
public class LogPageHandler implements PageHandler {

    private static final int SHOW_LOG_LENGTH = 30000;

    private File file;

    @SuppressWarnings("unchecked")
    public LogPageHandler() {
        try {
            org.apache.log4j.Logger logger = LogManager.getRootLogger();
            if (logger != null) {
                Enumeration<Appender> appenders = logger.getAllAppenders();
                if (appenders != null) {
                    while (appenders.hasMoreElements()) {
                        Appender appender = appenders.nextElement();
                        if (appender instanceof FileAppender) {
                            FileAppender fileAppender = (FileAppender) appender;
                            String filename = fileAppender.getFile();
                            file = new File(filename);
                            break;
                        }
                    }
                }
            }
        } catch (Throwable t) {
        }
    }

    @Override
    public Page handle(URL url) {
        long size = 0;
        String content = "";
        String modified = "Not exist";
        if (file != null && file.exists()) {
            try {
                FileInputStream fis = new FileInputStream(file);
                FileChannel channel = fis.getChannel();
                size = channel.size();
                ByteBuffer bb;
                if (size <= SHOW_LOG_LENGTH) {
                    bb = ByteBuffer.allocate((int) size);
                    channel.read(bb, 0);
                } else {
                    int pos = (int) (size - SHOW_LOG_LENGTH);
                    bb = ByteBuffer.allocate(SHOW_LOG_LENGTH);
                    channel.read(bb, pos);
                }
                bb.flip();
                content = new String(bb.array())
                        .replace("<", "&lt;")
                        .replace(">", "&gt;")
                        .replace("\n", "<br/><br/>");
                modified = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date(file.lastModified()));
            } catch (IOException e) {
            }
        }
        Level level = LogManager.getRootLogger().getLevel();
        List<List<String>> rows = new ArrayList<>();
        List<String> row = new ArrayList<>();
        row.add(content);
        rows.add(row);
        return new Page(
                "Log",
                "Log",
                new String[] {(file == null ? "" : file.getName()) + ", " + size + " bytes, " + modified + ", " + level
                },
                rows);
    }
}
