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/*
 * Copyright (c) 1998-2018 John Caron and University Corporation for Atmospheric Research/Unidata
 * See LICENSE for license information.
 */

package ucar.nc2.iosp;

import javax.annotation.Nullable;
import thredds.inventory.MFile;
import thredds.inventory.MFiles;
import ucar.ma2.Array;
import ucar.ma2.InvalidRangeException;
import ucar.ma2.Section;
import ucar.ma2.StructureDataIterator;
import ucar.nc2.Group;
import ucar.nc2.NetcdfFile;
import ucar.nc2.NetcdfFiles;
import ucar.nc2.ParsedSectionSpec;
import ucar.nc2.Structure;
import ucar.nc2.util.CancelTask;
import ucar.unidata.io.RandomAccessFile;
import ucar.unidata.util.Format;
import java.io.File;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.channels.WritableByteChannel;
import java.util.Formatter;

/**
 * Abstract base class for IOSP implementations that provides default implementations
 * of readToByteChannel(...) and readSection(...).
 * 
 * Implementations should make sure to handle the RandomAccessFile properly by
 * doing one of the following:
 * 

 * Write your own open(...) and close() methods that keep track of the
 * RandomAccessFile, be sure to close the RandomAccessFile in your close()
 * method.
 * Write your own open(...) and close() methods that call the open(...)
 * and close() methods defined here, use the "raf" variable also defined
 * here.
 * Don't write an open(...) or close() method, so that those defined
 * here are used.
 * 
 */
public abstract class AbstractIOServiceProvider implements IOServiceProvider {
  /**
   * Subclasses that use AbstractIOServiceProvider.open(...) or .close()
   * should use this (instead of their own private variable).
   */
  protected ucar.unidata.io.RandomAccessFile raf;
  protected String location;
  protected int rafOrder = RandomAccessFile.BIG_ENDIAN;

  // In general, ncfile doesnt exist until after open is called.
  // That argues for open() changing to a builder.
  protected NetcdfFile ncfile;

  @Override
  public void open(RandomAccessFile raf, NetcdfFile ncfile, CancelTask cancelTask) throws IOException {
    this.raf = raf;
    this.location = (raf != null) ? raf.getLocation() : null;
    this.ncfile = ncfile;
  }

  // TODO: Is there an alternative to making this method public? Maybe in 6?
  public void setNetcdfFile(NetcdfFile ncfile) {
    this.ncfile = ncfile;
  }

  @Override
  public boolean isBuilder() {
    return false;
  }

  @Override
  public void build(RandomAccessFile raf, Group.Builder rootGroup, CancelTask cancelTask) throws IOException {
    throw new UnsupportedOperationException(
        String.format("Class %s does not implement build() method", this.getClass().getName()));
  }

  @Override
  public void buildFinish(NetcdfFile ncfile) {
    // No op
  }

  @Override
  public void close() throws java.io.IOException {
    if (raf != null)
      raf.close();
    raf = null;
  }

  // release any resources like file handles
  public void release() throws IOException {
    if (raf != null)
      raf.close();
    raf = null;
  }

  // reacquire any resources like file handles
  public void reacquire() throws IOException {
    raf = NetcdfFiles.getRaf(location, -1);
    raf.order(rafOrder);
  }

  // default implementation, reads into an Array, then writes to WritableByteChannel
  // subclasses should override if possible
  // LOOK DataOutputStream uses big-endian
  @Override
  public long readToByteChannel(ucar.nc2.Variable v2, Section section, WritableByteChannel channel)
      throws java.io.IOException, ucar.ma2.InvalidRangeException {

    Array data = readData(v2, section);
    return IospHelper.copyToByteChannel(data, channel);
  }

  @Override
  public long readToOutputStream(ucar.nc2.Variable v2, Section section, OutputStream out)
      throws java.io.IOException, ucar.ma2.InvalidRangeException {

    Array data = readData(v2, section);
    return IospHelper.copyToOutputStream(data, out);
  }

  @Override
  public long streamToByteChannel(ucar.nc2.Variable v2, Section section, WritableByteChannel channel)
      throws java.io.IOException, ucar.ma2.InvalidRangeException {

    Array data = readData(v2, section);
    return IospHelper.copyToByteChannel(data, channel);
  }

  @Override
  public ucar.ma2.Array readSection(ParsedSectionSpec cer) throws IOException, InvalidRangeException {
    return IospHelper.readSection(cer); // IOSPs can optimize by overriding
  }

  @Override
  public StructureDataIterator getStructureIterator(Structure s, int bufferSize) throws java.io.IOException {
    return null;
  }

  @Override
  @Nullable
  public Object sendIospMessage(@Nullable Object message) {
    if (message == NetcdfFile.IOSP_MESSAGE_RANDOM_ACCESS_FILE) {
      return raf;
    }
    return null;
  }

  @Override
  public boolean syncExtend() throws IOException {
    return false;
  }

  /**
   * Returns the time that the underlying file(s) were last modified. If they've changed since they were stored in the
   * cache, they will be closed and reopened with {@link ucar.nc2.util.cache.FileFactory}.
   *
   * @return a {@code long} value representing the time the file(s) were last modified or {@code 0L} if the
   *         last-modified time couldn't be determined for any reason.
   */
  public long getLastModified() {
    if (location != null) {
      MFile file = MFiles.create(location);
      return file.getLastModified();
    } else {
      return 0;
    }
  }

  @Override
  public String toStringDebug(Object o) {
    return "";
  }

  @Override
  public String getDetailInfo() {
    if (raf == null)
      return "";
    try {
      Formatter fout = new Formatter();
      double size = raf.length() / (1000.0 * 1000.0);
      fout.format(" raf = %s%n", raf.getLocation());
      fout.format(" size= %d (%s Mb)%n%n", raf.length(), Format.dfrac(size, 3));
      return fout.toString();

    } catch (IOException e) {
      return e.getMessage();
    }
  }

  @Override
  public String getFileTypeVersion() {
    return "N/A";
  }

}