/*
Copyright (c) 2005 Health Market Science, Inc.

Licensed 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.healthmarketscience.jackcess.impl;

import java.io.Closeable;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.util.Arrays;

/**
 * Byte manipulation and display utilities
 * @author Tim McCune
 */
public final class ByteUtil {
  
  private static final String[] HEX_CHARS = new String[] {
      "0", "1", "2", "3", "4", "5", "6", "7",
      "8", "9", "A", "B", "C", "D", "E", "F"};

  private static final int NUM_BYTES_PER_BLOCK = 4;
  private static final int NUM_BYTES_PER_LINE = 24;
      
  private ByteUtil() {}

  /**
   * Put an integer into the given buffer at the given offset as a 3-byte
   * integer.
   * @param buffer buffer into which to insert the int
   * @param val Int to convert
   */    
  public static void put3ByteInt(ByteBuffer buffer, int val)
  {
    put3ByteInt(buffer, val, buffer.order());
  }
  
  /**
   * Put an integer into the given buffer at the given offset as a 3-byte
   * integer.
   * @param buffer buffer into which to insert the int
   * @param val Int to convert
   * @param order  the order to insert the bytes of the int
   */    
  public static void put3ByteInt(ByteBuffer buffer, int val, ByteOrder order)
  {
    int pos = buffer.position();
    put3ByteInt(buffer, val, pos, order);
    buffer.position(pos + 3);
  }
  
  /**
   * Put an integer into the given buffer at the given offset as a 3-byte
   * integer.
   * @param buffer buffer into which to insert the int
   * @param val Int to convert
   * @param offset offset at which to insert the int
   * @param order  the order to insert the bytes of the int
   */    
  public static void put3ByteInt(ByteBuffer buffer, int val, int offset,
                                 ByteOrder order) {

    int offInc = 1;
    if(order == ByteOrder.BIG_ENDIAN) {
      offInc = -1;
      offset += 2;
    }

    buffer.put(offset, (byte) (val & 0xFF));
    buffer.put(offset + (1 * offInc), (byte) ((val >>> 8) & 0xFF));
    buffer.put(offset + (2 * offInc), (byte) ((val >>> 16) & 0xFF));
  }

  /**
   * Read a 3 byte int from a buffer
   * @param buffer Buffer containing the bytes
   * @return The int
   */
  public static int get3ByteInt(ByteBuffer buffer) {
    return get3ByteInt(buffer, buffer.order());
  }

  /**
   * Read a 3 byte int from a buffer
   * @param buffer Buffer containing the bytes
   * @param order  the order of the bytes of the int
   * @return The int
   */
  public static int get3ByteInt(ByteBuffer buffer, ByteOrder order) {  
    int pos = buffer.position();
    int rtn = get3ByteInt(buffer, pos, order);
    buffer.position(pos + 3);
    return rtn;
  }

  /**
   * Read a 3 byte int from a buffer
   * @param buffer Buffer containing the bytes
   * @param offset Offset at which to start reading the int
   * @return The int
   */
  public static int get3ByteInt(ByteBuffer buffer, int offset) {
    return get3ByteInt(buffer, offset, buffer.order());
  }
  
  /**
   * Read a 3 byte int from a buffer
   * @param buffer Buffer containing the bytes
   * @param offset Offset at which to start reading the int
   * @param order  the order of the bytes of the int
   * @return The int
   */
  public static int get3ByteInt(ByteBuffer buffer, int offset,
                                ByteOrder order) {

    int offInc = 1;
    if(order == ByteOrder.BIG_ENDIAN) {
      offInc = -1;
      offset += 2;
    }
    
    int rtn = getUnsignedByte(buffer, offset);
    rtn += (getUnsignedByte(buffer, offset + (1 * offInc)) << 8);
    rtn += (getUnsignedByte(buffer, offset + (2 * offInc)) << 16);
    return rtn;
  }

  /**
   * Read an unsigned byte from a buffer
   * @param buffer Buffer containing the bytes
   * @return The unsigned byte as an int
   */
  public static int getUnsignedByte(ByteBuffer buffer) {
    int pos = buffer.position();
    int rtn = getUnsignedByte(buffer, pos);
    buffer.position(pos + 1);
    return rtn;
  }

  /**
   * Read an unsigned byte from a buffer
   * @param buffer Buffer containing the bytes
   * @param offset Offset at which to read the byte
   * @return The unsigned byte as an int
   */
  public static int getUnsignedByte(ByteBuffer buffer, int offset) {  
    return asUnsignedByte(buffer.get(offset));
  }
  
  /**
   * Read an unsigned short from a buffer
   * @param buffer Buffer containing the short
   * @return The unsigned short as an int
   */
  public static int getUnsignedShort(ByteBuffer buffer) {
    int pos = buffer.position();
    int rtn = getUnsignedShort(buffer, pos);
    buffer.position(pos + 2);
    return rtn;
  }

  /**
   * Read an unsigned short from a buffer
   * @param buffer Buffer containing the short
   * @param offset Offset at which to read the short
   * @return The unsigned short as an int
   */
  public static int getUnsignedShort(ByteBuffer buffer, int offset) {  
    return asUnsignedShort(buffer.getShort(offset));
  }

  
  /**
   * @param buffer Buffer containing the bytes
   * @param order  the order of the bytes of the int
   * @return an int from the current position in the given buffer, read using
   *         the given ByteOrder
   */
  public static int getInt(ByteBuffer buffer, ByteOrder order) {
    int offset = buffer.position();
    int rtn = getInt(buffer, offset, order);
    buffer.position(offset + 4);
    return rtn;
  }
  
  /**
   * @param buffer Buffer containing the bytes
   * @param offset Offset at which to start reading the int
   * @param order  the order of the bytes of the int
   * @return an int from the given position in the given buffer, read using
   *         the given ByteOrder
   */
  public static int getInt(ByteBuffer buffer, int offset, ByteOrder order) {
    ByteOrder origOrder = buffer.order();
    try {
      return buffer.order(order).getInt(offset);
    } finally {
      buffer.order(origOrder);
    }
  }
  
  /**
   * Writes an int at the current position in the given buffer, using the
   * given ByteOrder
   * @param buffer buffer into which to insert the int
   * @param val Int to insert
   * @param order the order to insert the bytes of the int
   */
  public static void putInt(ByteBuffer buffer, int val, ByteOrder order) {
    int offset = buffer.position();
    putInt(buffer, val, offset, order);
    buffer.position(offset + 4);
  }
  
  /**
   * Writes an int at the given position in the given buffer, using the
   * given ByteOrder
   * @param buffer buffer into which to insert the int
   * @param val Int to insert
   * @param offset offset at which to insert the int
   * @param order the order to insert the bytes of the int
   */
  public static void putInt(ByteBuffer buffer, int val, int offset,
                            ByteOrder order)
  {
    ByteOrder origOrder = buffer.order();
    try {
      buffer.order(order).putInt(offset, val);
    } finally {
      buffer.order(origOrder);
    }
  }

  /**
   * Read an unsigned variable length int from a buffer
   * @param buffer Buffer containing the variable length int
   * @return The unsigned int
   */
  public static int getUnsignedVarInt(ByteBuffer buffer, int numBytes) {
    int pos = buffer.position();
    int rtn = getUnsignedVarInt(buffer, pos, numBytes);
    buffer.position(pos + numBytes);
    return rtn;
  }

  /**
   * Read an unsigned variable length int from a buffer
   * @param buffer Buffer containing the variable length int
   * @param offset Offset at which to read the value
   * @return The unsigned int
   */
  public static int getUnsignedVarInt(ByteBuffer buffer, int offset, 
                                      int numBytes) {  
    switch(numBytes) {
    case 1:
      return getUnsignedByte(buffer, offset);
    case 2:
      return getUnsignedShort(buffer, offset);
    case 3:
      return get3ByteInt(buffer, offset);
    case 4:
      return buffer.getInt(offset);
    default:
      throw new IllegalArgumentException("Invalid num bytes " + numBytes);
    }
  }

  /**
   * Reads an array of bytes from the given buffer
   * @param buffer Buffer containing the desired bytes
   * @param len length of the desired bytes
   * @return a new buffer with the given number of bytes from the current
   *         position in the given buffer
   */
  public static byte[] getBytes(ByteBuffer buffer, int len)
  {
      byte[] bytes = new byte[len];
      buffer.get(bytes);    
      return bytes;
  }

  /**
   * Reads an array of bytes from the given buffer at the given offset
   * @param buffer Buffer containing the desired bytes
   * @param offset Offset at which to read the bytes
   * @param len length of the desired bytes
   * @return a new buffer with the given number of bytes from the given
   *         position in the given buffer
   */
  public static byte[] getBytes(ByteBuffer buffer, int offset, int len)
  {
    int origPos = buffer.position();
    try {
      buffer.position(offset);
      return getBytes(buffer, len);
    } finally {
      buffer.position(origPos);
    }
  }

  /**
   * Concatenates and returns the given byte arrays.
   */
  public static byte[] concat(byte[] b1, byte[] b2) {
    byte[] out = new byte[b1.length + b2.length];
    System.arraycopy(b1, 0, out, 0, b1.length);
    System.arraycopy(b2, 0, out, b1.length, b2.length);
    return out;
  }
  
  /**
   * Sets all bits in the given remaining byte range to 0.
   */
  public static void clearRemaining(ByteBuffer buffer)
  {
    if(!buffer.hasRemaining()) {
      return;
    }
    int pos = buffer.position();
    clearRange(buffer, pos, pos + buffer.remaining());
  }

  /**
   * Sets all bits in the given byte range to 0.
   */
  public static void clearRange(ByteBuffer buffer, int start,
                                int end)
  {
    putRange(buffer, start, end, (byte)0x00);
  }

  /**
   * Sets all bits in the given byte range to 1.
   */
  public static void fillRange(ByteBuffer buffer, int start,
                               int end)
  {
    putRange(buffer, start, end, (byte)0xff);
  }
  
  /**
   * Sets all bytes in the given byte range to the given byte value.
   */
  public static void putRange(ByteBuffer buffer, int start,
                              int end, byte b)
  {
    for(int i = start; i < end; ++i) {
      buffer.put(i, b);
    }
  }

  /**
   * Matches a pattern of bytes against the given buffer starting at the given
   * offset.
   */
  public static boolean matchesRange(ByteBuffer buffer, int start,
                                     byte[] pattern)
  {
    for(int i = 0; i < pattern.length; ++i) {
      if(pattern[i] != buffer.get(start + i)) {
        return false;
      }
    }
    return true;
  }

  /**
   * Searches for a pattern of bytes in the given buffer starting at the
   * given offset.
   * @return the offset of the pattern if a match is found, -1 otherwise
   */
  public static int findRange(ByteBuffer buffer, int start, byte[] pattern)
  {
    byte firstByte = pattern[0];
    int limit = buffer.limit() - pattern.length;
    for(int i = start; i < limit; ++i) {
      if((firstByte == buffer.get(i)) && matchesRange(buffer, i, pattern)) {
        return i;
      }
    }
    return -1;
  }
  
  /**
   * Convert a byte buffer to a hexadecimal string for display
   * @param buffer Buffer to display, starting at offset 0
   * @param size Number of bytes to read from the buffer
   * @return The display String
   */
  public static String toHexString(ByteBuffer buffer, int size) {
    return toHexString(buffer, 0, size);
  }
  
  /**
   * Convert a byte array to a hexadecimal string for display
   * @param array byte array to display, starting at offset 0
   * @return The display String
   */
  public static String toHexString(byte[] array) {
    return toHexString(ByteBuffer.wrap(array), 0, array.length);
  }
  
  /**
   * Convert a byte buffer to a hexadecimal string for display
   * @param buffer Buffer to display, starting at offset 0
   * @param offset Offset at which to start reading the buffer
   * @param size Number of bytes to read from the buffer
   * @return The display String
   */
  public static String toHexString(ByteBuffer buffer, int offset, int size) {
    return toHexString(buffer, offset, size, true);
  }    

  /**
   * Convert a byte buffer to a hexadecimal string for display
   * @param buffer Buffer to display, starting at offset 0
   * @param offset Offset at which to start reading the buffer
   * @param size Number of bytes to read from the buffer
   * @param formatted flag indicating if formatting is required
   * @return The display String
   */
  public static String toHexString(ByteBuffer buffer,
                                   int offset, int size, boolean formatted) {
    
    int bufLen = size * 2;
    if(formatted) {
      bufLen += size + 
        (7 * ((size + NUM_BYTES_PER_LINE - 1) / NUM_BYTES_PER_LINE));
    }
    StringBuilder rtn = new StringBuilder(bufLen);
    int position = buffer.position();
    buffer.position(offset);
    size = Math.min(size, buffer.remaining());

    for (int i = 0; i < size; i++) {
      byte b = buffer.get();
      byte h = (byte) (b & 0xF0);
      h = (byte) (h >>> 4);
      h = (byte) (h & 0x0F);
      rtn.append(HEX_CHARS[h]);
      h = (byte) (b & 0x0F);
      rtn.append(HEX_CHARS[h]);

      int next = (i + 1);
      if(formatted && (next < size))
      {
        if((next % NUM_BYTES_PER_LINE) == 0) {

          rtn.append("\n");

        } else {
          
          rtn.append(" ");

          if ((next % NUM_BYTES_PER_BLOCK) == 0) {
            rtn.append(" ");
          }
        }
      }
    }

    buffer.position(position);
    return rtn.toString();
  }

  /**
   * Convert the given number of bytes from the given database page to a
   * hexidecimal string for display.
   */
  public static String toHexString(DatabaseImpl db, int pageNumber, int size)
    throws IOException
  {
    ByteBuffer buffer = db.getPageChannel().createPageBuffer();
    db.getPageChannel().readPage(buffer, pageNumber);
    return toHexString(buffer, size);
  }

  /**
   * Writes a sequence of hexidecimal values into the given buffer, where
   * every two characters represent one byte value.
   */
  public static void writeHexString(ByteBuffer buffer,
                                    String hexStr)
    throws IOException
  {
    char[] hexChars = hexStr.toCharArray();
    if((hexChars.length % 2) != 0) {
      throw new IOException("Hex string length must be even");
    }
    for(int i = 0; i < hexChars.length; i += 2) {
      String tmpStr = new String(hexChars, i, 2);
      buffer.put((byte)Integer.parseInt(tmpStr, 16));
    }
  }

  /**
   * Writes a chunk of data to a file in pretty printed hexidecimal.
   */
  public static void toHexFile(
      String fileName,
      ByteBuffer buffer, 
      int offset, int size)
    throws IOException
  {
    PrintWriter writer = new PrintWriter(
        new FileWriter(fileName));
    try {
      writer.println(toHexString(buffer, offset, size));
    } finally {
      writer.close();
    }
  }

  /**
   * @return the byte value converted to an unsigned int value
   */
  public static int asUnsignedByte(byte b) { 
    return b & 0xFF;
  }
  
  /**
   * @return the short value converted to an unsigned int value
   */
  public static int asUnsignedShort(short s) { 
    return s & 0xFFFF;
  }

  /**
   * Swaps the 8 bytes (changes endianness) of the bytes at the given offset.
   *
   * @param bytes buffer containing bytes to swap
   * @param offset offset of the first byte of the bytes to swap
   */
  public static void swap8Bytes(byte[] bytes, int offset)
  {
    swapBytesAt(bytes, offset + 0, offset + 7);
    swapBytesAt(bytes, offset + 1, offset + 6);
    swapBytesAt(bytes, offset + 2, offset + 5);
    swapBytesAt(bytes, offset + 3, offset + 4);
  }

  /**
   * Swaps the 4 bytes (changes endianness) of the bytes at the given offset.
   *
   * @param bytes buffer containing bytes to swap
   * @param offset offset of the first byte of the bytes to swap
   */
  public static void swap4Bytes(byte[] bytes, int offset)
  {
    swapBytesAt(bytes, offset + 0, offset + 3);
    swapBytesAt(bytes, offset + 1, offset + 2);
  }

  /**
   * Swaps the 2 bytes (changes endianness) of the bytes at the given offset.
   *
   * @param bytes buffer containing bytes to swap
   * @param offset offset of the first byte of the bytes to swap
   */
  public static void swap2Bytes(byte[] bytes, int offset)
  {
    swapBytesAt(bytes, offset + 0, offset + 1);
  }

  /**
   * Swaps the bytes at the given positions.
   */
  private static void swapBytesAt(byte[] bytes, int p1, int p2)
  {
    byte b = bytes[p1];
    bytes[p1] = bytes[p2];
    bytes[p2] = b;
  }

  /**
   * Moves the position of the given buffer the given count from the current
   * position.
   * @return the new buffer position
   */
  public static int forward(ByteBuffer buffer, int count)
  {
    int newPos = buffer.position() + count;
    buffer.position(newPos);
    return newPos;
  }

  /**
   * Returns a copy of the given array of the given length.
   */
  public static byte[] copyOf(byte[] arr, int newLength)
  {
    return copyOf(arr, 0, newLength, 0);
  }

  /**
   * Returns a copy of the given array of the given length starting at the
   * given position.
   */
  public static byte[] copyOf(byte[] arr, int offset, int newLength)
  {
    return copyOf(arr, offset, newLength, 0);
  }

  /**
   * Returns a copy of the given array of the given length starting at the
   * given position.
   */
  public static byte[] copyOf(byte[] arr, int offset, int newLength, 
                              int dstOffset)
  {
    byte[] newArr = new byte[newLength];
    int srcLen = arr.length - offset;
    int dstLen = newLength - dstOffset;
    System.arraycopy(arr, offset, newArr, dstOffset, Math.min(srcLen, dstLen));
    return newArr;
  }

  /**
   * Copies the given InputStream to the given OutputStream.
   */
  public static void copy(InputStream in, OutputStream out) throws IOException {
    byte[] buf = new byte[8 * 1024];
    int read = 0;
    while((read = in.read(buf)) > -1) {
      out.write(buf, 0, read);
    }
  }

  /**
   * Closes the given Closeable if non-null, swallows any IOExceptions.
   */
  public static void closeQuietly(Closeable c) {
    if(c != null) {
      try {
        c.close();
      } catch(IOException ignored) {}
    }
  }

  /**
   * Utility byte stream similar to ByteArrayOutputStream but with extended
   * accessibility to the bytes.
   */
  public static class ByteStream extends OutputStream
  {
    private byte[] _bytes;
    private int _length;
    private int _lastLength;


    public ByteStream() {
      this(32);
    }

    public ByteStream(int capacity) {
      _bytes = new byte[capacity];
    }

    public int getLength() {
      return _length;
    }

    public byte[] getBytes() {
      return _bytes;
    }

    protected void ensureNewCapacity(int numBytes) {
      int newLength = _length + numBytes;
      if(newLength > _bytes.length) {
        byte[] temp = new byte[newLength * 2];
        System.arraycopy(_bytes, 0, temp, 0, _length);
        _bytes = temp;
      }
    }

    @Override
    public void write(int b) {
      ensureNewCapacity(1);
      _bytes[_length++] = (byte)b;
    }

    @Override
    public void write(byte[] b) {
      write(b, 0, b.length);
    }

    @Override
    public void write(byte[] b, int offset, int length) {
      ensureNewCapacity(length);
      System.arraycopy(b, offset, _bytes, _length, length);
      _length += length;
    }

    public byte get(int offset) {
      return _bytes[offset];
    }

    public void set(int offset, byte b) {
      _bytes[offset] = b;
    }

    public void writeFill(int length, byte b) {
      ensureNewCapacity(length);
      int oldLength = _length;
      _length += length;
      Arrays.fill(_bytes, oldLength, _length, b);
    }

    public void skip(int n) {
      ensureNewCapacity(n);
      _length += n;
    }

    public void writeTo(ByteStream out) {
      out.write(_bytes, 0, _length);
    }

    public byte[] toByteArray() {

      byte[] result = null;
      if(_length == _bytes.length) {
        result = _bytes;
        _bytes = null;
      } else {
        result = copyOf(_bytes, _length);
        if(_lastLength == _length) {
          // if we get the same result length bytes twice in a row, clear the
          // _bytes so that the next _bytes will be _lastLength
          _bytes = null;
        }
      }

      // save result length so we can potentially get the right length of the
      // next byte[] in reset()
      _lastLength = _length;

      return result;
    }

    public void reset() {
      _length = 0;
      if(_bytes == null) {
        _bytes = new byte[_lastLength];
      }
    }

    public void trimTrailing(byte minTrimCode, byte maxTrimCode)
    {
      int minTrim = ByteUtil.asUnsignedByte(minTrimCode);
      int maxTrim = ByteUtil.asUnsignedByte(maxTrimCode);

      int idx = _length - 1;
      while(idx >= 0) {
        int val = asUnsignedByte(get(idx));
        if((val >= minTrim) && (val <= maxTrim)) {
          --idx;
        } else {
          break;
        }
      }

      _length = idx + 1;
    }
  }

}