/*
 * 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.activemq.artemis.core.paging.impl;

import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;
import java.util.concurrent.atomic.AtomicInteger;

import org.apache.activemq.artemis.api.core.ActiveMQBuffer;
import org.apache.activemq.artemis.api.core.ActiveMQBuffers;
import org.apache.activemq.artemis.api.core.SimpleString;
import org.apache.activemq.artemis.core.io.SequentialFile;
import org.apache.activemq.artemis.core.io.SequentialFileFactory;
import org.apache.activemq.artemis.core.paging.PagedMessage;
import org.apache.activemq.artemis.core.paging.cursor.LivePageCache;
import org.apache.activemq.artemis.core.paging.cursor.PageSubscriptionCounter;
import org.apache.activemq.artemis.core.persistence.StorageManager;
import org.apache.activemq.artemis.core.server.ActiveMQMessageBundle;
import org.apache.activemq.artemis.core.server.ActiveMQServerLogger;
import org.apache.activemq.artemis.core.server.LargeServerMessage;
import org.apache.activemq.artemis.utils.ConcurrentHashSet;
import org.apache.activemq.artemis.utils.DataConstants;

public final class Page implements Comparable<Page> {

   // Constants -----------------------------------------------------
   private static final boolean isTrace = ActiveMQServerLogger.LOGGER.isTraceEnabled();
   private static final boolean isDebug = ActiveMQServerLogger.LOGGER.isDebugEnabled();

   public static final int SIZE_RECORD = DataConstants.SIZE_BYTE + DataConstants.SIZE_INT + DataConstants.SIZE_BYTE;

   private static final byte START_BYTE = (byte) '{';

   private static final byte END_BYTE = (byte) '}';

   // Attributes ----------------------------------------------------

   private final int pageId;

   private boolean suspiciousRecords = false;

   private final AtomicInteger numberOfMessages = new AtomicInteger(0);

   private final SequentialFile file;

   private final SequentialFileFactory fileFactory;

   /**
    * The page cache that will be filled with data as we write more data
    */
   private volatile LivePageCache pageCache;

   private final AtomicInteger size = new AtomicInteger(0);

   private final StorageManager storageManager;

   private final SimpleString storeName;

   /**
    * A list of subscriptions containing pending counters (with non tx adds) on this page
    */
   private Set<PageSubscriptionCounter> pendingCounters;

   public Page(final SimpleString storeName,
               final StorageManager storageManager,
               final SequentialFileFactory factory,
               final SequentialFile file,
               final int pageId) throws Exception {
      this.pageId = pageId;
      this.file = file;
      fileFactory = factory;
      this.storageManager = storageManager;
      this.storeName = storeName;
   }

   public int getPageId() {
      return pageId;
   }

   public void setLiveCache(LivePageCache pageCache) {
      this.pageCache = pageCache;
   }

   public synchronized List<PagedMessage> read(StorageManager storage) throws Exception {
      if (isDebug) {
         ActiveMQServerLogger.LOGGER.debug("reading page " + this.pageId + " on address = " + storeName);
      }

      if (!file.isOpen()) {
         throw ActiveMQMessageBundle.BUNDLE.invalidPageIO();
      }

      ArrayList<PagedMessage> messages = new ArrayList<PagedMessage>();

      size.set((int) file.size());
      // Using direct buffer, as described on https://jira.jboss.org/browse/HORNETQ-467
      ByteBuffer directBuffer = storage.allocateDirectBuffer((int) file.size());
      ActiveMQBuffer fileBuffer = null;
      try {

         file.position(0);
         file.read(directBuffer);

         directBuffer.rewind();

         fileBuffer = ActiveMQBuffers.wrappedBuffer(directBuffer);
         fileBuffer.writerIndex(fileBuffer.capacity());

         while (fileBuffer.readable()) {
            final int position = fileBuffer.readerIndex();

            byte byteRead = fileBuffer.readByte();

            if (byteRead == Page.START_BYTE) {
               if (fileBuffer.readerIndex() + DataConstants.SIZE_INT < fileBuffer.capacity()) {
                  int messageSize = fileBuffer.readInt();
                  int oldPos = fileBuffer.readerIndex();
                  if (fileBuffer.readerIndex() + messageSize < fileBuffer.capacity() && fileBuffer.getByte(oldPos + messageSize) == Page.END_BYTE) {
                     PagedMessage msg = new PagedMessageImpl();
                     msg.decode(fileBuffer);
                     byte b = fileBuffer.readByte();
                     if (b != Page.END_BYTE) {
                        // Sanity Check: This would only happen if there is a bug on decode or any internal code, as
                        // this
                        // constraint was already checked
                        throw new IllegalStateException("Internal error, it wasn't possible to locate END_BYTE " + b);
                     }
                     msg.initMessage(storage);
                     if (isTrace) {
                        ActiveMQServerLogger.LOGGER.trace("Reading message " + msg + " on pageId=" + this.pageId + " for address=" + storeName);
                     }
                     messages.add(msg);
                  }
                  else {
                     markFileAsSuspect(file.getFileName(), position, messages.size());
                     break;
                  }
               }
            }
            else {
               markFileAsSuspect(file.getFileName(), position, messages.size());
               break;
            }
         }
      }
      finally {
         if (fileBuffer != null) {
            fileBuffer.byteBuf().unwrap().release();
         }
         storage.freeDirectBuffer(directBuffer);
      }

      numberOfMessages.set(messages.size());

      return messages;
   }

   public synchronized void write(final PagedMessage message) throws Exception {
      if (!file.isOpen()) {

         return;
      }

      ByteBuffer buffer = fileFactory.newBuffer(message.getEncodeSize() + Page.SIZE_RECORD);

      ActiveMQBuffer wrap = ActiveMQBuffers.wrappedBuffer(buffer);
      wrap.clear();

      wrap.writeByte(Page.START_BYTE);
      wrap.writeInt(0);
      int startIndex = wrap.writerIndex();
      message.encode(wrap);
      int endIndex = wrap.writerIndex();
      wrap.setInt(1, endIndex - startIndex); // The encoded length
      wrap.writeByte(Page.END_BYTE);

      buffer.rewind();

      file.writeDirect(buffer, false);

      if (pageCache != null) {
         pageCache.addLiveMessage(message);
      }

      numberOfMessages.incrementAndGet();
      size.addAndGet(buffer.limit());

      storageManager.pageWrite(message, pageId);
   }

   public void sync() throws Exception {
      file.sync();
   }

   public void open() throws Exception {
      if (!file.isOpen()) {
         file.open();
      }
      size.set((int) file.size());
      file.position(0);
   }

   public synchronized void close() throws Exception {
      if (storageManager != null) {
         storageManager.pageClosed(storeName, pageId);
      }
      if (pageCache != null) {
         pageCache.close();
         // leave it to the soft cache to decide when to release it now
         pageCache = null;
      }
      file.close();

      Set<PageSubscriptionCounter> counters = getPendingCounters();
      if (counters != null) {
         for (PageSubscriptionCounter counter : counters) {
            counter.cleanupNonTXCounters(this.getPageId());
         }
      }
   }

   public boolean isLive() {
      return pageCache != null;
   }

   public boolean delete(final PagedMessage[] messages) throws Exception {
      if (storageManager != null) {
         storageManager.pageDeleted(storeName, pageId);
      }

      if (isDebug) {
         ActiveMQServerLogger.LOGGER.debug("Deleting pageId=" + pageId + " on store " + storeName);
      }

      if (messages != null) {
         for (PagedMessage msg : messages) {
            if (msg.getMessage().isLargeMessage()) {
               LargeServerMessage lmsg = (LargeServerMessage) msg.getMessage();

               // Remember, cannot call delete directly here
               // Because the large-message may be linked to another message
               // or it may still being delivered even though it has been acked already
               lmsg.decrementDelayDeletionCount();
            }
         }
      }

      try {
         if (suspiciousRecords) {
            ActiveMQServerLogger.LOGGER.pageInvalid(file.getFileName(), file.getFileName());
            file.renameTo(file.getFileName() + ".invalidPage");
         }
         else {
            file.delete();
         }

         return true;
      }
      catch (Exception e) {
         ActiveMQServerLogger.LOGGER.pageDeleteError(e);
         return false;
      }
   }

   public int getNumberOfMessages() {
      return numberOfMessages.intValue();
   }

   public int getSize() {
      return size.intValue();
   }

   @Override
   public String toString() {
      return "Page::pageID=" + this.pageId + ", file=" + this.file;
   }

   public int compareTo(Page otherPage) {
      return otherPage.getPageId() - this.pageId;
   }

   @Override
   protected void finalize() {
      try {
         if (file != null && file.isOpen()) {
            file.close();
         }
      }
      catch (Exception e) {
         ActiveMQServerLogger.LOGGER.pageFinaliseError(e);
      }
   }

   @Override
   public int hashCode() {
      final int prime = 31;
      int result = 1;
      result = prime * result + pageId;
      return result;
   }

   @Override
   public boolean equals(Object obj) {
      if (this == obj)
         return true;
      if (obj == null)
         return false;
      if (getClass() != obj.getClass())
         return false;
      Page other = (Page) obj;
      if (pageId != other.pageId)
         return false;
      return true;
   }

   /**
    * @param position
    * @param msgNumber
    */
   private void markFileAsSuspect(final String fileName, final int position, final int msgNumber) {
      ActiveMQServerLogger.LOGGER.pageSuspectFile(fileName, position, msgNumber);
      suspiciousRecords = true;
   }

   public SequentialFile getFile() {
      return file;
   }

   /**
    * This will indicate a page that will need to be called on cleanup when the page has been closed and confirmed
    *
    * @param pageSubscriptionCounter
    */
   public void addPendingCounter(PageSubscriptionCounter pageSubscriptionCounter) {
      Set<PageSubscriptionCounter> counter = getOrCreatePendingCounters();
      pendingCounters.add(pageSubscriptionCounter);
   }

   private synchronized Set<PageSubscriptionCounter> getPendingCounters() {
      return pendingCounters;
   }

   private synchronized Set<PageSubscriptionCounter> getOrCreatePendingCounters() {
      if (pendingCounters == null) {
         pendingCounters = new ConcurrentHashSet<PageSubscriptionCounter>();
      }

      return pendingCounters;
   }
}
