/*
 * 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.thrift.transport;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Random;
import org.apache.thrift.TConfiguration;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * FileTransport implementation of the TTransport interface. Currently this is a straightforward
 * port of the cpp implementation
 *
 * <p>It may make better sense to provide a basic stream access on top of the framed file format The
 * FileTransport can then be a user of this framed file format with some additional logic for
 * chunking.
 */
public class TFileTransport extends TTransport {

  private static final Logger LOGGER = LoggerFactory.getLogger(TFileTransport.class.getName());

  public static class TruncableBufferedInputStream extends BufferedInputStream {
    public void trunc() {
      pos = count = 0;
    }

    public TruncableBufferedInputStream(InputStream in) {
      super(in);
    }

    public TruncableBufferedInputStream(InputStream in, int size) {
      super(in, size);
    }
  }

  public static class Event {
    private byte[] buf_;
    private int nread_;
    private int navailable_;

    /**
     * Initialize an event. Initially, it has no valid contents
     *
     * @param buf byte array buffer to store event
     */
    public Event(byte[] buf) {
      buf_ = buf;
      nread_ = navailable_ = 0;
    }

    public byte[] getBuf() {
      return buf_;
    }

    public int getSize() {
      return buf_.length;
    }

    public void setAvailable(int sz) {
      nread_ = 0;
      navailable_ = sz;
    }

    public int getRemaining() {
      return (navailable_ - nread_);
    }

    public int emit(byte[] buf, int offset, int ndesired) {
      if ((ndesired == 0) || (ndesired > getRemaining())) ndesired = getRemaining();

      if (ndesired <= 0) return (ndesired);

      System.arraycopy(buf_, nread_, buf, offset, ndesired);
      nread_ += ndesired;

      return (ndesired);
    }
  }

  public static class ChunkState {
    /** Chunk Size. Must be same across all implementations */
    public static final int DEFAULT_CHUNK_SIZE = 16 * 1024 * 1024;

    private int chunk_size_ = DEFAULT_CHUNK_SIZE;
    private long offset_ = 0;

    public ChunkState() {}

    public ChunkState(int chunk_size) {
      chunk_size_ = chunk_size;
    }

    public void skip(int size) {
      offset_ += size;
    }

    public void seek(long offset) {
      offset_ = offset;
    }

    public int getChunkSize() {
      return chunk_size_;
    }

    public int getChunkNum() {
      return ((int) (offset_ / chunk_size_));
    }

    public int getRemaining() {
      return (chunk_size_ - ((int) (offset_ % chunk_size_)));
    }

    public long getOffset() {
      return (offset_);
    }
  }

  public enum TailPolicy {
    NOWAIT(0, 0),
    WAIT_FOREVER(500, -1);

    /** Time in milliseconds to sleep before next read If 0, no sleep */
    public final int timeout_;

    /** Number of retries before giving up if 0, no retries if -1, retry forever */
    public final int retries_;

    /**
     * ctor for policy
     *
     * @param timeout sleep time for this particular policy
     * @param retries number of retries
     */
    TailPolicy(int timeout, int retries) {
      timeout_ = timeout;
      retries_ = retries;
    }
  }

  /** Current tailing policy */
  TailPolicy currentPolicy_ = TailPolicy.NOWAIT;

  /** Underlying file being read */
  protected TSeekableFile inputFile_ = null;

  /** Underlying outputStream */
  protected OutputStream outputStream_ = null;

  /** Event currently read in */
  Event currentEvent_ = null;

  /** InputStream currently being used for reading */
  InputStream inputStream_ = null;

  /** current Chunk state */
  ChunkState cs = null;

  /** is read only? */
  private boolean readOnly_ = false;

  /**
   * Get File Tailing Policy
   *
   * @return current read policy
   */
  public TailPolicy getTailPolicy() {
    return (currentPolicy_);
  }

  /**
   * Set file Tailing Policy
   *
   * @param policy New policy to set
   * @return Old policy
   */
  public TailPolicy setTailPolicy(TailPolicy policy) {
    TailPolicy old = currentPolicy_;
    currentPolicy_ = policy;
    return (old);
  }

  /**
   * Initialize read input stream
   *
   * @return input stream to read from file
   */
  private InputStream createInputStream() throws TTransportException {
    InputStream is;
    try {
      if (inputStream_ != null) {
        ((TruncableBufferedInputStream) inputStream_).trunc();
        is = inputStream_;
      } else {
        is = new TruncableBufferedInputStream(inputFile_.getInputStream());
      }
    } catch (IOException iox) {
      throw new TTransportException(iox.getMessage(), iox);
    }
    return (is);
  }

  /**
   * Read (potentially tailing) an input stream
   *
   * @param is InputStream to read from
   * @param buf Buffer to read into
   * @param off Offset in buffer to read into
   * @param len Number of bytes to read
   * @param tp policy to use if we hit EOF
   * @return number of bytes read
   */
  private int tailRead(InputStream is, byte[] buf, int off, int len, TailPolicy tp)
      throws TTransportException {
    int orig_len = len;
    try {
      int retries = 0;
      while (len > 0) {
        int cnt = is.read(buf, off, len);
        if (cnt > 0) {
          off += cnt;
          len -= cnt;
          retries = 0;
          cs.skip(cnt); // remember that we read so many bytes
        } else if (cnt == -1) {
          // EOF
          retries++;

          if ((tp.retries_ != -1) && tp.retries_ < retries) return (orig_len - len);

          if (tp.timeout_ > 0) {
            try {
              Thread.sleep(tp.timeout_);
            } catch (InterruptedException e) {
            }
          }
        } else {
          // either non-zero or -1 is what the contract says!
          throw new TTransportException("Unexpected return from InputStream.read = " + cnt);
        }
      }
    } catch (IOException iox) {
      throw new TTransportException(iox.getMessage(), iox);
    }

    return (orig_len - len);
  }

  /**
   * Event is corrupted. Do recovery
   *
   * @return true if recovery could be performed and we can read more data false is returned only
   *     when nothing more can be read
   */
  private boolean performRecovery() throws TTransportException {
    int numChunks = getNumChunks();
    int curChunk = cs.getChunkNum();

    if (curChunk >= (numChunks - 1)) {
      return false;
    }
    seekToChunk(curChunk + 1);
    return true;
  }

  /**
   * Read event from underlying file
   *
   * @return true if event could be read, false otherwise (on EOF)
   */
  private boolean readEvent() throws TTransportException {
    byte[] ebytes = new byte[4];
    int esize;
    int nread;
    int nrequested;

    retry:
    do {
      // corner case. read to end of chunk
      nrequested = cs.getRemaining();
      if (nrequested < 4) {
        nread = tailRead(inputStream_, ebytes, 0, nrequested, currentPolicy_);
        if (nread != nrequested) {
          return (false);
        }
      }

      // assuming serialized on little endian machine
      nread = tailRead(inputStream_, ebytes, 0, 4, currentPolicy_);
      if (nread != 4) {
        return (false);
      }

      esize = 0;
      for (int i = 3; i >= 0; i--) {
        int val = (0x000000ff & (int) ebytes[i]);
        esize |= (val << (i * 8));
      }

      // check if event is corrupted and do recovery as required
      if (esize > cs.getRemaining()) {
        throw new TTransportException("FileTransport error: bad event size");
        /*
                  if(performRecovery()) {
                  esize=0;
                  } else {
                  return false;
                  }
        */
      }
    } while (esize == 0);

    // reset existing event or get a larger one
    if (currentEvent_.getSize() < esize) currentEvent_ = new Event(new byte[esize]);

    // populate the event
    byte[] buf = currentEvent_.getBuf();
    nread = tailRead(inputStream_, buf, 0, esize, currentPolicy_);
    if (nread != esize) {
      return (false);
    }
    currentEvent_.setAvailable(esize);
    return (true);
  }

  /**
   * open if both input/output open unless readonly
   *
   * @return true
   */
  public boolean isOpen() {
    return ((inputStream_ != null) && (readOnly_ || (outputStream_ != null)));
  }

  /**
   * Diverging from the cpp model and sticking to the TSocket model Files are not opened in ctor -
   * but in explicit open call
   */
  public void open() throws TTransportException {
    if (isOpen()) throw new TTransportException(TTransportException.ALREADY_OPEN);

    try {
      inputStream_ = createInputStream();
      cs = new ChunkState();
      currentEvent_ = new Event(new byte[256]);

      if (!readOnly_) outputStream_ = new BufferedOutputStream(inputFile_.getOutputStream());
    } catch (IOException iox) {
      throw new TTransportException(TTransportException.NOT_OPEN, iox);
    }
  }

  /** Closes the transport. */
  public void close() {
    if (inputFile_ != null) {
      try {
        inputFile_.close();
      } catch (IOException iox) {
        LOGGER.warn("WARNING: Error closing input file: " + iox.getMessage());
      }
      inputFile_ = null;
    }
    if (outputStream_ != null) {
      try {
        outputStream_.close();
      } catch (IOException iox) {
        LOGGER.warn("WARNING: Error closing output stream: " + iox.getMessage());
      }
      outputStream_ = null;
    }
  }

  /**
   * File Transport ctor
   *
   * @param path File path to read and write from
   * @param readOnly Whether this is a read-only transport
   * @throws IOException if there is an error accessing the file.
   */
  public TFileTransport(final String path, boolean readOnly) throws IOException {
    inputFile_ = new TStandardFile(path);
    readOnly_ = readOnly;
  }

  /**
   * File Transport ctor
   *
   * @param inputFile open TSeekableFile to read/write from
   * @param readOnly Whether this is a read-only transport
   */
  public TFileTransport(TSeekableFile inputFile, boolean readOnly) {
    inputFile_ = inputFile;
    readOnly_ = readOnly;
  }

  /**
   * Cloned from TTransport.java:readAll(). Only difference is throwing an EOF exception where one
   * is detected.
   */
  public int readAll(byte[] buf, int off, int len) throws TTransportException {
    int got = 0;
    int ret = 0;
    while (got < len) {
      ret = read(buf, off + got, len - got);
      if (ret < 0) {
        throw new TTransportException("Error in reading from file");
      }
      if (ret == 0) {
        throw new TTransportException(TTransportException.END_OF_FILE, "End of File reached");
      }
      got += ret;
    }
    return got;
  }

  /**
   * Reads up to len bytes into buffer buf, starting at offset off.
   *
   * @param buf Array to read into
   * @param off Index to start reading at
   * @param len Maximum number of bytes to read
   * @return The number of bytes actually read
   * @throws TTransportException if there was an error reading data
   */
  public int read(byte[] buf, int off, int len) throws TTransportException {
    if (!isOpen())
      throw new TTransportException(TTransportException.NOT_OPEN, "Must open before reading");

    if (currentEvent_.getRemaining() == 0 && !readEvent()) {
      return 0;
    }

    return currentEvent_.emit(buf, off, len);
  }

  public int getNumChunks() throws TTransportException {
    if (!isOpen())
      throw new TTransportException(TTransportException.NOT_OPEN, "Must open before getNumChunks");
    try {
      long len = inputFile_.length();
      if (len == 0) return 0;
      else return (((int) (len / cs.getChunkSize())) + 1);

    } catch (IOException iox) {
      throw new TTransportException(iox.getMessage(), iox);
    }
  }

  public int getCurChunk() throws TTransportException {
    if (!isOpen())
      throw new TTransportException(TTransportException.NOT_OPEN, "Must open before getCurChunk");
    return (cs.getChunkNum());
  }

  public void seekToChunk(int chunk) throws TTransportException {
    if (!isOpen())
      throw new TTransportException(TTransportException.NOT_OPEN, "Must open before seeking");

    int numChunks = getNumChunks();

    // file is empty, seeking to chunk is pointless
    if (numChunks == 0) {
      return;
    }

    // negative indicates reverse seek (from the end)
    if (chunk < 0) {
      chunk += numChunks;
    }

    // too large a value for reverse seek, just seek to beginning
    if (chunk < 0) {
      chunk = 0;
    }

    long eofOffset = 0;
    boolean seekToEnd = (chunk >= numChunks);
    if (seekToEnd) {
      chunk = chunk - 1;
      try {
        eofOffset = inputFile_.length();
      } catch (IOException iox) {
        throw new TTransportException(iox.getMessage(), iox);
      }
    }

    if (chunk * cs.getChunkSize() != cs.getOffset()) {
      try {
        inputFile_.seek((long) chunk * cs.getChunkSize());
      } catch (IOException iox) {
        throw new TTransportException("Seek to chunk " + chunk + " " + iox.getMessage(), iox);
      }

      cs.seek((long) chunk * cs.getChunkSize());
      currentEvent_.setAvailable(0);
      inputStream_ = createInputStream();
    }

    if (seekToEnd) {
      // waiting forever here - otherwise we can hit EOF and end up
      // having consumed partial data from the data stream.
      TailPolicy old = setTailPolicy(TailPolicy.WAIT_FOREVER);
      while (cs.getOffset() < eofOffset) {
        readEvent();
      }
      currentEvent_.setAvailable(0);
      setTailPolicy(old);
    }
  }

  public void seekToEnd() throws TTransportException {
    if (!isOpen())
      throw new TTransportException(TTransportException.NOT_OPEN, "Must open before seeking");
    seekToChunk(getNumChunks());
  }

  /**
   * Writes up to len bytes from the buffer.
   *
   * @param buf The output data buffer
   * @param off The offset to start writing from
   * @param len The number of bytes to write
   * @throws TTransportException if there was an error writing data
   */
  public void write(byte[] buf, int off, int len) throws TTransportException {
    throw new TTransportException("Not Supported");
  }

  /**
   * Flush any pending data out of a transport buffer.
   *
   * @throws TTransportException if there was an error writing out data.
   */
  public void flush() throws TTransportException {
    throw new TTransportException("Not Supported");
  }

  @Override
  public TConfiguration getConfiguration() {
    return null;
  }

  @Override
  public void updateKnownMessageSize(long size) throws TTransportException {}

  @Override
  public void checkReadBytesAvailable(long numBytes) throws TTransportException {}

  /** test program */
  public static void main(String[] args) throws Exception {

    int num_chunks = 10;

    if ((args.length < 1)
        || args[0].equals("--help")
        || args[0].equals("-h")
        || args[0].equals("-?")) {
      printUsage();
    }

    if (args.length > 1) {
      try {
        num_chunks = Integer.parseInt(args[1]);
      } catch (Exception e) {
        LOGGER.error("Cannot parse " + args[1]);
        printUsage();
      }
    }

    TFileTransport t = new TFileTransport(args[0], true);
    t.open();
    LOGGER.info("NumChunks=" + t.getNumChunks());

    Random r = new Random();
    for (int j = 0; j < num_chunks; j++) {
      byte[] buf = new byte[4096];
      int cnum = r.nextInt(t.getNumChunks() - 1);
      LOGGER.info("Reading chunk " + cnum);
      t.seekToChunk(cnum);
      for (int i = 0; i < 4096; i++) {
        t.read(buf, 0, 4096);
      }
    }
  }

  private static void printUsage() {
    LOGGER.error("Usage: TFileTransport <filename> [num_chunks]");
    LOGGER.error("       (Opens and reads num_chunks chunks from file randomly)");
    System.exit(1);
  }
}
