package org.apache.lucene.util;

/**
 * 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.
 */


/*
 * Some of this code came from the excellent Unicode
 * conversion examples from:
 *
 *   http://www.unicode.org/Public/PROGRAMS/CVTUTF
 *
 * Full Copyright for that code follows:
*/

/*
 * Copyright 2001-2004 Unicode, Inc.
 * 
 * Disclaimer
 * 
 * This source code is provided as is by Unicode, Inc. No claims are
 * made as to fitness for any particular purpose. No warranties of any
 * kind are expressed or implied. The recipient agrees to determine
 * applicability of information provided. If this file has been
 * purchased on magnetic or optical media from Unicode, Inc., the
 * sole remedy for any claim will be exchange of defective media
 * within 90 days of receipt.
 * 
 * Limitations on Rights to Redistribute This Code
 * 
 * Unicode, Inc. hereby grants the right to freely use the information
 * supplied in this file in the creation of products supporting the
 * Unicode Standard, and to make copies of this file in any form
 * for internal or external distribution as long as this notice
 * remains attached.
 */

/**
 * Class to encode java's UTF16 char[] into UTF8 byte[]
 * without always allocating a new byte[] as
 * String.getBytes("UTF-8") does.
 *
 * <p><b>WARNING</b>: This API is a new and experimental and
 * may suddenly change. </p>
 */

final public class UnicodeUtil {

  public static final int UNI_SUR_HIGH_START = 0xD800;
  public static final int UNI_SUR_HIGH_END = 0xDBFF;
  public static final int UNI_SUR_LOW_START = 0xDC00;
  public static final int UNI_SUR_LOW_END = 0xDFFF;
  public static final int UNI_REPLACEMENT_CHAR = 0xFFFD;

  private static final long UNI_MAX_BMP = 0x0000FFFF;

  private static final int HALF_BASE = 0x0010000;
  private static final long HALF_SHIFT = 10;
  private static final long HALF_MASK = 0x3FFL;

  public static final class UTF8Result {
    public byte[] result = new byte[10];
    public int length;

    public void setLength(int newLength) {
      if (result.length < newLength) {
        byte[] newArray = new byte[(int) (1.5*newLength)];
        System.arraycopy(result, 0, newArray, 0, length);
        result = newArray;
      }
      length = newLength;
    }
  }

  public static final class UTF16Result {
    public char[] result = new char[10];
    public int[] offsets = new int[10];
    public int length;

    public void setLength(int newLength) {
      if (result.length < newLength) {
        char[] newArray = new char[(int) (1.5*newLength)];
        System.arraycopy(result, 0, newArray, 0, length);
        result = newArray;
      }
      length = newLength;
    }

    public void copyText(UTF16Result other) {
      setLength(other.length);
      System.arraycopy(other.result, 0, result, 0, length);
    }
  }

  /** Encode characters from a char[] source, starting at
   *  offset and stopping when the character 0xffff is seen.
   *  Returns the number of bytes written to bytesOut. */
  public static void UTF16toUTF8(final char[] source, final int offset, UTF8Result result) {

    int upto = 0;
    int i = offset;
    byte[] out = result.result;

    while(true) {
      
      final int code = (int) source[i++];

      if (upto+4 > out.length) {
        byte[] newOut = new byte[2*out.length];
        assert newOut.length >= upto+4;
        System.arraycopy(out, 0, newOut, 0, upto);
        result.result = out = newOut;
      }
      if (code < 0x80)
        out[upto++] = (byte) code;
      else if (code < 0x800) {
        out[upto++] = (byte) (0xC0 | (code >> 6));
        out[upto++] = (byte)(0x80 | (code & 0x3F));
      } else if (code < 0xD800 || code > 0xDFFF) {
        if (code == 0xffff)
          // END
          break;
        out[upto++] = (byte)(0xE0 | (code >> 12));
        out[upto++] = (byte)(0x80 | ((code >> 6) & 0x3F));
        out[upto++] = (byte)(0x80 | (code & 0x3F));
      } else {
        // surrogate pair
        // confirm valid high surrogate
        if (code < 0xDC00 && source[i] != 0xffff) {
          int utf32 = (int) source[i];
          // confirm valid low surrogate and write pair
          if (utf32 >= 0xDC00 && utf32 <= 0xDFFF) { 
            utf32 = ((code - 0xD7C0) << 10) + (utf32 & 0x3FF);
            i++;
            out[upto++] = (byte)(0xF0 | (utf32 >> 18));
            out[upto++] = (byte)(0x80 | ((utf32 >> 12) & 0x3F));
            out[upto++] = (byte)(0x80 | ((utf32 >> 6) & 0x3F));
            out[upto++] = (byte)(0x80 | (utf32 & 0x3F));
            continue;
          }
        }
        // replace unpaired surrogate or out-of-order low surrogate
        // with substitution character
        out[upto++] = (byte) 0xEF;
        out[upto++] = (byte) 0xBF;
        out[upto++] = (byte) 0xBD;
      }
    }
    //assert matches(source, offset, i-offset-1, out, upto);
    result.length = upto;
  }

  /** Encode characters from a char[] source, starting at
   *  offset for length chars.  Returns the number of bytes
   *  written to bytesOut. */
  public static void UTF16toUTF8(final char[] source, final int offset, final int length, UTF8Result result) {

    int upto = 0;
    int i = offset;
    final int end = offset + length;
    byte[] out = result.result;

    while(i < end) {
      
      final int code = (int) source[i++];

      if (upto+4 > out.length) {
        byte[] newOut = new byte[2*out.length];
        assert newOut.length >= upto+4;
        System.arraycopy(out, 0, newOut, 0, upto);
        result.result = out = newOut;
      }
      if (code < 0x80)
        out[upto++] = (byte) code;
      else if (code < 0x800) {
        out[upto++] = (byte) (0xC0 | (code >> 6));
        out[upto++] = (byte)(0x80 | (code & 0x3F));
      } else if (code < 0xD800 || code > 0xDFFF) {
        out[upto++] = (byte)(0xE0 | (code >> 12));
        out[upto++] = (byte)(0x80 | ((code >> 6) & 0x3F));
        out[upto++] = (byte)(0x80 | (code & 0x3F));
      } else {
        // surrogate pair
        // confirm valid high surrogate
        if (code < 0xDC00 && i < end && source[i] != 0xffff) {
          int utf32 = (int) source[i];
          // confirm valid low surrogate and write pair
          if (utf32 >= 0xDC00 && utf32 <= 0xDFFF) { 
            utf32 = ((code - 0xD7C0) << 10) + (utf32 & 0x3FF);
            i++;
            out[upto++] = (byte)(0xF0 | (utf32 >> 18));
            out[upto++] = (byte)(0x80 | ((utf32 >> 12) & 0x3F));
            out[upto++] = (byte)(0x80 | ((utf32 >> 6) & 0x3F));
            out[upto++] = (byte)(0x80 | (utf32 & 0x3F));
            continue;
          }
        }
        // replace unpaired surrogate or out-of-order low surrogate
        // with substitution character
        out[upto++] = (byte) 0xEF;
        out[upto++] = (byte) 0xBF;
        out[upto++] = (byte) 0xBD;
      }
    }
    //assert matches(source, offset, length, out, upto);
    result.length = upto;
  }

  /** Encode characters from this String, starting at offset
   *  for length characters.  Returns the number of bytes
   *  written to bytesOut. */
  public static void UTF16toUTF8(final String s, final int offset, final int length, UTF8Result result) {
    final int end = offset + length;

    byte[] out = result.result;

    int upto = 0;
    for(int i=offset;i<end;i++) {
      final int code = (int) s.charAt(i);

      if (upto+4 > out.length) {
        byte[] newOut = new byte[2*out.length];
        assert newOut.length >= upto+4;
        System.arraycopy(out, 0, newOut, 0, upto);
        result.result = out = newOut;
      }
      if (code < 0x80)
        out[upto++] = (byte) code;
      else if (code < 0x800) {
        out[upto++] = (byte) (0xC0 | (code >> 6));
        out[upto++] = (byte)(0x80 | (code & 0x3F));
      } else if (code < 0xD800 || code > 0xDFFF) {
        out[upto++] = (byte)(0xE0 | (code >> 12));
        out[upto++] = (byte)(0x80 | ((code >> 6) & 0x3F));
        out[upto++] = (byte)(0x80 | (code & 0x3F));
      } else {
        // surrogate pair
        // confirm valid high surrogate
        if (code < 0xDC00 && (i < end-1)) {
          int utf32 = (int) s.charAt(i+1);
          // confirm valid low surrogate and write pair
          if (utf32 >= 0xDC00 && utf32 <= 0xDFFF) { 
            utf32 = ((code - 0xD7C0) << 10) + (utf32 & 0x3FF);
            i++;
            out[upto++] = (byte)(0xF0 | (utf32 >> 18));
            out[upto++] = (byte)(0x80 | ((utf32 >> 12) & 0x3F));
            out[upto++] = (byte)(0x80 | ((utf32 >> 6) & 0x3F));
            out[upto++] = (byte)(0x80 | (utf32 & 0x3F));
            continue;
          }
        }
        // replace unpaired surrogate or out-of-order low surrogate
        // with substitution character
        out[upto++] = (byte) 0xEF;
        out[upto++] = (byte) 0xBF;
        out[upto++] = (byte) 0xBD;
      }
    }
    //assert matches(s, offset, length, out, upto);
    result.length = upto;
  }

  /** Convert UTF8 bytes into UTF16 characters.  If offset
   *  is non-zero, conversion starts at that starting point
   *  in utf8, re-using the results from the previous call
   *  up until offset. */
  public static void UTF8toUTF16(final byte[] utf8, final int offset, final int length, final UTF16Result result) {

    final int end = offset + length;
    char[] out = result.result;
    if (result.offsets.length <= end) {
      int[] newOffsets = new int[2*end];
      System.arraycopy(result.offsets, 0, newOffsets, 0, result.offsets.length);
      result.offsets  = newOffsets;
    }
    final int[] offsets = result.offsets;

    // If incremental decoding fell in the middle of a
    // single unicode character, rollback to its start:
    int upto = offset;
    while(offsets[upto] == -1)
      upto--;

    int outUpto = offsets[upto];

    // Pre-allocate for worst case 1-for-1
    if (outUpto+length >= out.length) {
      char[] newOut = new char[2*(outUpto+length)];
      System.arraycopy(out, 0, newOut, 0, outUpto);
      result.result = out = newOut;
    }

    while (upto < end) {

      final int b = utf8[upto]&0xff;
      final int ch;

      offsets[upto++] = outUpto;

      if (b < 0xc0) {
        assert b < 0x80;
        ch = b;
      } else if (b < 0xe0) {
        ch = ((b&0x1f)<<6) + (utf8[upto]&0x3f);
        offsets[upto++] = -1;
      } else if (b < 0xf0) {
        ch = ((b&0xf)<<12) + ((utf8[upto]&0x3f)<<6) + (utf8[upto+1]&0x3f);
        offsets[upto++] = -1;
        offsets[upto++] = -1;
      } else {
        assert b < 0xf8;
        ch = ((b&0x7)<<18) + ((utf8[upto]&0x3f)<<12) + ((utf8[upto+1]&0x3f)<<6) + (utf8[upto+2]&0x3f);
        offsets[upto++] = -1;
        offsets[upto++] = -1;
        offsets[upto++] = -1;
      }

      if (ch <= UNI_MAX_BMP) {
        // target is a character <= 0xFFFF
        out[outUpto++] = (char) ch;
      } else {
        // target is a character in range 0xFFFF - 0x10FFFF
        final int chHalf = ch - HALF_BASE;
        out[outUpto++] = (char) ((chHalf >> HALF_SHIFT) + UNI_SUR_HIGH_START);
        out[outUpto++] = (char) ((chHalf & HALF_MASK) + UNI_SUR_LOW_START);
      }
    }

    offsets[upto] = outUpto;
    result.length = outUpto;
  }

  // Only called from assert
  /*
  private static boolean matches(char[] source, int offset, int length, byte[] result, int upto) {
    try {
      String s1 = new String(source, offset, length);
      String s2 = new String(result, 0, upto, "UTF-8");
      if (!s1.equals(s2)) {
        //System.out.println("DIFF: s1 len=" + s1.length());
        //for(int i=0;i<s1.length();i++)
        //  System.out.println("    " + i + ": " + (int) s1.charAt(i));
        //System.out.println("s2 len=" + s2.length());
        //for(int i=0;i<s2.length();i++)
        //  System.out.println("    " + i + ": " + (int) s2.charAt(i));

        // If the input string was invalid, then the
        // difference is OK
        if (!validUTF16String(s1))
          return true;

        return false;
      }
      return s1.equals(s2);
    } catch (UnsupportedEncodingException uee) {
      return false;
    }
  }

  // Only called from assert
  private static boolean matches(String source, int offset, int length, byte[] result, int upto) {
    try {
      String s1 = source.substring(offset, offset+length);
      String s2 = new String(result, 0, upto, "UTF-8");
      if (!s1.equals(s2)) {
        // Allow a difference if s1 is not valid UTF-16

        //System.out.println("DIFF: s1 len=" + s1.length());
        //for(int i=0;i<s1.length();i++)
        //  System.out.println("    " + i + ": " + (int) s1.charAt(i));
        //System.out.println("  s2 len=" + s2.length());
        //for(int i=0;i<s2.length();i++)
        //  System.out.println("    " + i + ": " + (int) s2.charAt(i));

        // If the input string was invalid, then the
        // difference is OK
        if (!validUTF16String(s1))
          return true;

        return false;
      }
      return s1.equals(s2);
    } catch (UnsupportedEncodingException uee) {
      return false;
    }
  }

  public static final boolean validUTF16String(String s) {
    final int size = s.length();
    for(int i=0;i<size;i++) {
      char ch = s.charAt(i);
      if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_HIGH_END) {
        if (i < size-1) {
          i++;
          char nextCH = s.charAt(i);
          if (nextCH >= UNI_SUR_LOW_START && nextCH <= UNI_SUR_LOW_END) {
            // Valid surrogate pair
          } else
            // Unmatched high surrogate
            return false;
        } else
          // Unmatched high surrogate
          return false;
      } else if (ch >= UNI_SUR_LOW_START && ch <= UNI_SUR_LOW_END)
        // Unmatched low surrogate
        return false;
    }

    return true;
  }

  public static final boolean validUTF16String(char[] s, int size) {
    for(int i=0;i<size;i++) {
      char ch = s[i];
      if (ch >= UNI_SUR_HIGH_START && ch <= UNI_SUR_HIGH_END) {
        if (i < size-1) {
          i++;
          char nextCH = s[i];
          if (nextCH >= UNI_SUR_LOW_START && nextCH <= UNI_SUR_LOW_END) {
            // Valid surrogate pair
          } else
            return false;
        } else
          return false;
      } else if (ch >= UNI_SUR_LOW_START && ch <= UNI_SUR_LOW_END)
        // Unmatched low surrogate
        return false;
    }

    return true;
  }
  */
}