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package org.apache.lucene.analysis.icu.segmentation;

import com.ibm.icu.lang.UCharacter;
import com.ibm.icu.lang.UCharacterEnums.ECharacterCategory;
import com.ibm.icu.lang.UScript;
import com.ibm.icu.text.UTF16;

An iterator that locates ISO 15924 script boundaries in text. 

This is not the same as simply looking at the Unicode block, or even the 
Script property. Some characters are 'common' across multiple scripts, and
some 'inherit' the script value of text surrounding them.

This is similar to ICU (internal-only) UScriptRun, with the following
differences:

 
Doesn't attempt to match paired punctuation. For tokenization purposes, this
is not necessary. It's also quite expensive. 
 
Non-spacing marks inherit the script of their base character, following 
 recommendations from UTR #24.

@lucene.experimental
/**
 * An iterator that locates ISO 15924 script boundaries in text. 
 * <p>
 * This is not the same as simply looking at the Unicode block, or even the 
 * Script property. Some characters are 'common' across multiple scripts, and
 * some 'inherit' the script value of text surrounding them.
 * <p>
 * This is similar to ICU (internal-only) UScriptRun, with the following
 * differences:
 * <ul>
 *  <li>Doesn't attempt to match paired punctuation. For tokenization purposes, this
 * is not necessary. It's also quite expensive. 
 *  <li>Non-spacing marks inherit the script of their base character, following 
 *  recommendations from UTR #24.
 * </ul>
 * @lucene.experimental
 */
final class ScriptIterator {
  private char text[];
  private int start;
  private int limit;
  private int index;

  private int scriptStart;
  private int scriptLimit;
  private int scriptCode;
  
  private final boolean combineCJ;
  
  
Params:
combineCJ – if true: Han,Hiragana,Katakana will all return as UScript.JAPANESE/**
   * @param combineCJ if true: Han,Hiragana,Katakana will all return as {@link UScript#JAPANESE}
   */
  ScriptIterator(boolean combineCJ) {
    this.combineCJ = combineCJ;
  }

  
Get the start of this script run
Returns:
start position of script run/**
   * Get the start of this script run
   * 
   * @return start position of script run
   */
  int getScriptStart() {
    return scriptStart;
  }

  
Get the index of the first character after the end of this script run
Returns:
position of the first character after this script run/**
   * Get the index of the first character after the end of this script run
   * 
   * @return position of the first character after this script run
   */
  int getScriptLimit() {
    return scriptLimit;
  }

  
Get the UScript script code for this script run
Returns:
code for the script of the current run/**
   * Get the UScript script code for this script run
   * 
   * @return code for the script of the current run
   */
  int getScriptCode() {
    return scriptCode;
  }

  
Iterates to the next script run, returning true if one exists.
Returns:
true if there is another script run, false otherwise./**
   * Iterates to the next script run, returning true if one exists.
   * 
   * @return true if there is another script run, false otherwise.
   */
  boolean next() {
    if (scriptLimit >= limit)
      return false;

    scriptCode = UScript.COMMON;
    scriptStart = scriptLimit;

    while (index < limit) {
      final int ch = UTF16.charAt(text, start, limit, index - start);
      final int sc = getScript(ch);

      /*
       * From UTR #24: Implementations that determine the boundaries between
       * characters of given scripts should never break between a non-spacing
       * mark and its base character. Thus for boundary determinations and
       * similar sorts of processing, a non-spacing mark — whatever its script
       * value — should inherit the script value of its base character.
       */
      if (isSameScript(scriptCode, sc)
          || UCharacter.getType(ch) == ECharacterCategory.NON_SPACING_MARK) {
        index += UTF16.getCharCount(ch);

        /*
         * Inherited or Common becomes the script code of the surrounding text.
         */
        if (scriptCode <= UScript.INHERITED && sc > UScript.INHERITED) {
          scriptCode = sc;
        }

      } else {
        break;
      }
    }

    scriptLimit = index;
    return true;
  }

  
Determine if two scripts are compatible. /** Determine if two scripts are compatible. */
  private static boolean isSameScript(int scriptOne, int scriptTwo) {
    return scriptOne <= UScript.INHERITED || scriptTwo <= UScript.INHERITED
        || scriptOne == scriptTwo;
  }

  
Set a new region of text to be examined by this iterator
Params:
text – text buffer to examine
start – offset into buffer
length – maximum length to examine/**
   * Set a new region of text to be examined by this iterator
   * 
   * @param text text buffer to examine
   * @param start offset into buffer
   * @param length maximum length to examine
   */
  void setText(char text[], int start, int length) {
    this.text = text;
    this.start = start;
    this.index = start;
    this.limit = start + length;
    this.scriptStart = start;
    this.scriptLimit = start;
    this.scriptCode = UScript.INVALID_CODE;
  }

  
linear fast-path for basic latin case /** linear fast-path for basic latin case */
  private static final int basicLatin[] = new int[128];

  static {
    for (int i = 0; i < basicLatin.length; i++)
      basicLatin[i] = UScript.getScript(i);
  }

  
fast version of UScript.getScript(). Basic Latin is an array lookup /** fast version of UScript.getScript(). Basic Latin is an array lookup */
  private int getScript(int codepoint) {
    if (0 <= codepoint && codepoint < basicLatin.length) {
      return basicLatin[codepoint];
    } else {
      int script = UScript.getScript(codepoint);
      if (combineCJ) {
        if (script == UScript.HAN || script == UScript.HIRAGANA || script == UScript.KATAKANA) {
          return UScript.JAPANESE;
        } else if (codepoint >= 0xFF10 && codepoint <= 0xFF19) {
          // when using CJK dictionary breaking, don't let full width numbers go to it, otherwise
          // they are treated as punctuation. we currently have no cleaner way to fix this!
          return UScript.LATIN; 
        } else {
          return script;
        }
      } else {
        return script;
      }
    }
  }
}