package org.davidmoten.text.utils;
   
   import java.util.Arrays;
   
   final class StringBuilder2 implements CharSequence {
   
       private char[] chars;
       private int length;
   
      StringBuilder2(String s) {
          this(s.toCharArray(), s.length());
      }
  
      StringBuilder2() {
          this(new char[16], 0);
      }
  
      private StringBuilder2(char[] chars, int length) {
          this.chars = chars;
          this.length = length;
      }
  
      char[] internalArray() {
          return chars;
      }
  
      @Override
      public int length() {
          return length;
      }
  
      @Override
      public char charAt(int index) {
          return chars[index];
      }
  
      @Override
      public CharSequence subSequence(int start, int end) {
          char[] chars2 = new char[end - start];
          System.arraycopy(chars, start, chars2, 0, end - start);
          return new StringBuilder2(chars2, chars2.length);
      }
  
      public void append(StringBuilder2 s) {
          int len = s.length();
          checkSize(len);
          System.arraycopy(s.chars, 0, chars, length, len);
          length += len;
      }
  
      private void checkSize(int len) {
          if (length + len > chars.length) {
              chars = Arrays.copyOf(chars, newSize(len));
          }
      }
  
      private int newSize(int len) {
          int newSize = chars.length * 2;
          if (newSize < length + len) {
              newSize = length + len;
          }
          return newSize;
      }
  
      public void setLength(int length) {
          this.length = length;
      }
  
      public void append(char ch) {
          checkSize(1);
          chars[length] = ch;
          length++;
      }
  
      public void delete(int start, int end) {
          System.arraycopy(chars, end, chars, start, length - end);
          length -= end - start;
      }
  
      public String substring(int start, int end) {
          return new String(chars, start, end - start);
      }
  
      @Override
      public String toString() {
          return new String(chars, 0, length);
      }
  
      /**
       * Trims right space from this and returns {@code this}.
       * 
       * @return this
       */
      StringBuilder2 rightTrim() {
          int i = length();
          while (i > 0) {
              if (!Character.isWhitespace(charAt(i - 1))) {
                  break;
              }
             i--;
         }
         length = i;
         return this;
     }
 
 }