package org.jcodec.common;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import org.jcodec.common.io.AutoPool;
import org.jcodec.common.io.AutoResource;
import org.jcodec.common.io.SeekableByteChannel;

public class AutoFileChannelWrapper implements SeekableByteChannel, AutoResource {
  private static final long THRESHOLD = 5000L;
  
  private FileChannel ch;
  
  private File file;
  
  private long savedPos;
  
  private long curTime;
  
  private long accessTime;
  
  public AutoFileChannelWrapper(File file) throws IOException {
    this.file = file;
    this.curTime = System.currentTimeMillis();
    AutoPool.getInstance().add(this);
    ensureOpen();
  }
  
  private void ensureOpen() throws IOException {
    this.accessTime = this.curTime;
    if (this.ch == null || !this.ch.isOpen()) {
      this.ch = new FileInputStream(this.file).getChannel();
      this.ch.position(this.savedPos);
    } 
  }
  
  public int read(ByteBuffer arg0) throws IOException {
    ensureOpen();
    int r = this.ch.read(arg0);
    this.savedPos = this.ch.position();
    return r;
  }
  
  public void close() throws IOException {
    if (this.ch != null && this.ch.isOpen()) {
      this.savedPos = this.ch.position();
      this.ch.close();
      this.ch = null;
    } 
  }
  
  public boolean isOpen() {
    return (this.ch != null && this.ch.isOpen());
  }
  
  public int write(ByteBuffer arg0) throws IOException {
    ensureOpen();
    int w = this.ch.write(arg0);
    this.savedPos = this.ch.position();
    return w;
  }
  
  public long position() throws IOException {
    ensureOpen();
    return this.ch.position();
  }
  
  public SeekableByteChannel setPosition(long newPosition) throws IOException {
    ensureOpen();
    this.ch.position(newPosition);
    this.savedPos = newPosition;
    return this;
  }
  
  public long size() throws IOException {
    ensureOpen();
    return this.ch.size();
  }
  
  public SeekableByteChannel truncate(long size) throws IOException {
    ensureOpen();
    this.ch.truncate(size);
    this.savedPos = this.ch.position();
    return this;
  }
  
  public void setCurTime(long curTime) {
    this.curTime = curTime;
    if (this.ch != null && this.ch.isOpen() && curTime - this.accessTime > 5000L)
      try {
        close();
      } catch (IOException e) {
        throw new RuntimeException(e);
      }  
  }
}