/*
    * ====================================================================
    * 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.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  
  package org.apache.hc.core5.util;
  
  import java.util.BitSet;
  
  import org.apache.hc.core5.annotation.Contract;
  import org.apache.hc.core5.annotation.ThreadingBehavior;
  
  /**
   * Tokenizer that can be used as a foundation for more complex parsing routines.
   * Methods of this class are designed to produce near zero intermediate garbage
   * and make no intermediate copies of input data.
   * <p>
   * This class is immutable and thread safe.
   *
   * @since 5.1
   */
  @Contract(threading = ThreadingBehavior.IMMUTABLE)
  public class Tokenizer {
  
      public static class Cursor {
  
          private final int lowerBound;
          private final int upperBound;
          private int pos;
  
          public Cursor(final int lowerBound, final int upperBound) {
              super();
              Args.notNegative(lowerBound, "lowerBound");
              Args.check(lowerBound <= upperBound, "lowerBound cannot be greater than upperBound");
              this.lowerBound = lowerBound;
              this.upperBound = upperBound;
              this.pos = lowerBound;
          }
  
          public int getLowerBound() {
              return this.lowerBound;
          }
  
          public int getUpperBound() {
              return this.upperBound;
          }
  
          public int getPos() {
              return this.pos;
          }
  
          public void updatePos(final int pos) {
              Args.check(pos >= this.lowerBound, "pos: %s < lowerBound: %s", pos, this.lowerBound);
              Args.check(pos <= this.upperBound, "pos: %s > upperBound: %s", pos, this.upperBound);
              this.pos = pos;
          }
  
          public boolean atEnd() {
              return this.pos >= this.upperBound;
          }
  
          @Override
          public String toString() {
              final StringBuilder buffer = new StringBuilder();
              buffer.append('[');
              buffer.append(this.lowerBound);
              buffer.append('>');
              buffer.append(this.pos);
              buffer.append('>');
              buffer.append(this.upperBound);
              buffer.append(']');
              return buffer.toString();
          }
  
      }
  
      public static BitSet INIT_BITSET(final int ... b) {
         final BitSet bitset = new BitSet();
         for (final int aB : b) {
             bitset.set(aB);
         }
         return bitset;
     }
 
     /** Double quote */
     public static final char DQUOTE = '\"';
 
     /** Backward slash / escape character */
     public static final char ESCAPE = '\\';
 
     public static final int CR = 13; // <US-ASCII CR, carriage return (13)>
     public static final int LF = 10; // <US-ASCII LF, linefeed (10)>
     public static final int SP = 32; // <US-ASCII SP, space (32)>
     public static final int HT = 9;  // <US-ASCII HT, horizontal-tab (9)>
 
     public static boolean isWhitespace(final char ch) {
         return ch == SP || ch == HT || ch == CR || ch == LF;
     }
 
     public static final Tokenizer INSTANCE = new Tokenizer();
 
     /**
      * Extracts from the sequence of chars a token terminated with any of the given delimiters
      * or a whitespace characters.
      *
      * @param buf buffer with the sequence of chars to be parsed
      * @param cursor defines the bounds and current position of the buffer
      * @param delimiters set of delimiting characters. Can be {@code null} if the token
      *  is not delimited by any character.
      */
     public String parseContent(final CharSequence buf, final Cursor cursor, final BitSet delimiters) {
         Args.notNull(buf, "Char sequence");
         Args.notNull(cursor, "Parser cursor");
         final StringBuilder dst = new StringBuilder();
         copyContent(buf, cursor, delimiters, dst);
         return dst.toString();
     }
 
     /**
      * Extracts from the sequence of chars a token terminated with any of the given delimiters
      * discarding semantically insignificant whitespace characters.
      *
      * @param buf buffer with the sequence of chars to be parsed
      * @param cursor defines the bounds and current position of the buffer
      * @param delimiters set of delimiting characters. Can be {@code null} if the token
      *  is not delimited by any character.
      */
     public String parseToken(final CharSequence buf, final Cursor cursor, final BitSet delimiters) {
         Args.notNull(buf, "Char sequence");
         Args.notNull(cursor, "Parser cursor");
         final StringBuilder dst = new StringBuilder();
         boolean whitespace = false;
         while (!cursor.atEnd()) {
             final char current = buf.charAt(cursor.getPos());
             if (delimiters != null && delimiters.get(current)) {
                 break;
             } else if (isWhitespace(current)) {
                 skipWhiteSpace(buf, cursor);
                 whitespace = true;
             } else {
                 if (whitespace && dst.length() > 0) {
                     dst.append(' ');
                 }
                 copyContent(buf, cursor, delimiters, dst);
                 whitespace = false;
             }
         }
         return dst.toString();
     }
 
     /**
      * Extracts from the sequence of chars a value which can be enclosed in quote marks and
      * terminated with any of the given delimiters discarding semantically insignificant
      * whitespace characters.
      *
      * @param buf buffer with the sequence of chars to be parsed
      * @param cursor defines the bounds and current position of the buffer
      * @param delimiters set of delimiting characters. Can be {@code null} if the value
      *  is not delimited by any character.
      */
     public String parseValue(final CharSequence buf, final Cursor cursor, final BitSet delimiters) {
         Args.notNull(buf, "Char sequence");
         Args.notNull(cursor, "Parser cursor");
         final StringBuilder dst = new StringBuilder();
         boolean whitespace = false;
         while (!cursor.atEnd()) {
             final char current = buf.charAt(cursor.getPos());
             if (delimiters != null && delimiters.get(current)) {
                 break;
             } else if (isWhitespace(current)) {
                 skipWhiteSpace(buf, cursor);
                 whitespace = true;
             } else if (current == DQUOTE) {
                 if (whitespace && dst.length() > 0) {
                     dst.append(' ');
                 }
                 copyQuotedContent(buf, cursor, dst);
                 whitespace = false;
             } else {
                 if (whitespace && dst.length() > 0) {
                     dst.append(' ');
                 }
                 copyUnquotedContent(buf, cursor, delimiters, dst);
                 whitespace = false;
             }
         }
         return dst.toString();
     }
 
     /**
      * Skips semantically insignificant whitespace characters and moves the cursor to the closest
      * non-whitespace character.
      *
      * @param buf buffer with the sequence of chars to be parsed
      * @param cursor defines the bounds and current position of the buffer
      */
     public void skipWhiteSpace(final CharSequence buf, final Cursor cursor) {
         Args.notNull(buf, "Char sequence");
         Args.notNull(cursor, "Parser cursor");
         int pos = cursor.getPos();
         final int indexFrom = cursor.getPos();
         final int indexTo = cursor.getUpperBound();
         for (int i = indexFrom; i < indexTo; i++) {
             final char current = buf.charAt(i);
             if (!isWhitespace(current)) {
                 break;
             }
             pos++;
         }
         cursor.updatePos(pos);
     }
 
     /**
      * Transfers content into the destination buffer until a whitespace character or any of
      * the given delimiters is encountered.
      *
      * @param buf buffer with the sequence of chars to be parsed
      * @param cursor defines the bounds and current position of the buffer
      * @param delimiters set of delimiting characters. Can be {@code null} if the value
      *  is delimited by a whitespace only.
      * @param dst destination buffer
      */
     public void copyContent(final CharSequence buf, final Cursor cursor, final BitSet delimiters,
                             final StringBuilder dst) {
         Args.notNull(buf, "Char sequence");
         Args.notNull(cursor, "Parser cursor");
         Args.notNull(dst, "String builder");
         int pos = cursor.getPos();
         final int indexFrom = cursor.getPos();
         final int indexTo = cursor.getUpperBound();
         for (int i = indexFrom; i < indexTo; i++) {
             final char current = buf.charAt(i);
             if ((delimiters != null && delimiters.get(current)) || isWhitespace(current)) {
                 break;
             }
             pos++;
             dst.append(current);
         }
         cursor.updatePos(pos);
     }
 
     /**
      * Transfers content into the destination buffer until a whitespace character,  a quote,
      * or any of the given delimiters is encountered.
      *
      * @param buf buffer with the sequence of chars to be parsed
      * @param cursor defines the bounds and current position of the buffer
      * @param delimiters set of delimiting characters. Can be {@code null} if the value
      *  is delimited by a whitespace or a quote only.
      * @param dst destination buffer
      */
     public void copyUnquotedContent(final CharSequence buf, final Cursor cursor,
             final BitSet delimiters, final StringBuilder dst) {
         Args.notNull(buf, "Char sequence");
         Args.notNull(cursor, "Parser cursor");
         Args.notNull(dst, "String builder");
         int pos = cursor.getPos();
         final int indexFrom = cursor.getPos();
         final int indexTo = cursor.getUpperBound();
         for (int i = indexFrom; i < indexTo; i++) {
             final char current = buf.charAt(i);
             if ((delimiters != null && delimiters.get(current))
                     || isWhitespace(current) || current == DQUOTE) {
                 break;
             }
             pos++;
             dst.append(current);
         }
         cursor.updatePos(pos);
     }
 
     /**
      * Transfers content enclosed with quote marks into the destination buffer.
      *
      * @param buf buffer with the sequence of chars to be parsed
      * @param cursor defines the bounds and current position of the buffer
      * @param dst destination buffer
      */
     public void copyQuotedContent(final CharSequence buf, final Cursor cursor,
             final StringBuilder dst) {
         Args.notNull(buf, "Char sequence");
         Args.notNull(cursor, "Parser cursor");
         Args.notNull(dst, "String builder");
         if (cursor.atEnd()) {
             return;
         }
         int pos = cursor.getPos();
         int indexFrom = cursor.getPos();
         final int indexTo = cursor.getUpperBound();
         char current = buf.charAt(pos);
         if (current != DQUOTE) {
             return;
         }
         pos++;
         indexFrom++;
         boolean escaped = false;
         for (int i = indexFrom; i < indexTo; i++, pos++) {
             current = buf.charAt(i);
             if (escaped) {
                 if (current != DQUOTE && current != ESCAPE) {
                     dst.append(ESCAPE);
                 }
                 dst.append(current);
                 escaped = false;
             } else {
                 if (current == DQUOTE) {
                     pos++;
                     break;
                 }
                 if (current == ESCAPE) {
                     escaped = true;
                 } else if (current != CR && current != LF) {
                     dst.append(current);
                 }
             }
         }
         cursor.updatePos(pos);
     }
 
 }