/*
    * Copyright 2012 The Netty Project
    *
    * The Netty Project 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.
   */
  package io.netty.util.internal;
  
  import java.io.IOException;
  
  import static io.netty.util.internal.ObjectUtil.*;
  
  /**
   * String utility class.
   */
  public final class StringUtil {
  
      public static final String NEWLINE = SystemPropertyUtil.get("line.separator", "\n");
      public static final char DOUBLE_QUOTE = '\"';
      public static final char COMMA = ',';
      public static final char LINE_FEED = '\n';
      public static final char CARRIAGE_RETURN = '\r';
      public static final String EMPTY_STRING = "";
      private static final String[] BYTE2HEX_PAD = new String[256];
      private static final String[] BYTE2HEX_NOPAD = new String[256];
  
      /**
       * 2 - Quote character at beginning and end.
       * 5 - Extra allowance for anticipated escape characters that may be added.
       */
      private static final int CSV_NUMBER_ESCAPE_CHARACTERS = 2 + 5;
      private static final char PACKAGE_SEPARATOR_CHAR = '.';
  
      static {
          // Generate the lookup table that converts a byte into a 2-digit hexadecimal integer.
          int i;
          for (i = 0; i < 10; i ++) {
              BYTE2HEX_PAD[i] = "0" + i;
              BYTE2HEX_NOPAD[i] = String.valueOf(i);
          }
          for (; i < 16; i ++) {
              char c = (char) ('a' + i - 10);
              BYTE2HEX_PAD[i] = "0" + c;
              BYTE2HEX_NOPAD[i] = String.valueOf(c);
          }
          for (; i < BYTE2HEX_PAD.length; i ++) {
              String str = Integer.toHexString(i);
              BYTE2HEX_PAD[i] = str;
              BYTE2HEX_NOPAD[i] = str;
          }
      }
  
      private StringUtil() {
          // Unused.
      }
  
      /**
       * Get the item after one char delim if the delim is found (else null).
       * This operation is a simplified and optimized
       * version of {@link String#split(String, int)}.
       */
      public static String substringAfter(String value, char delim) {
          int pos = value.indexOf(delim);
          if (pos >= 0) {
              return value.substring(pos + 1);
          }
          return null;
      }
  
      /**
       * Checks if two strings have the same suffix of specified length
       *
       * @param s            string
       * @param p            string
       * @param len length of the common suffix
       * @return true if both s and p are not null and both have the same suffix. Otherwise - false
       */
      public static boolean commonSuffixOfLength(String s, String p, int len) {
          return s != null && p != null && len >= 0 && s.regionMatches(s.length() - len, p, p.length() - len, len);
      }
  
      /**
       * Converts the specified byte value into a 2-digit hexadecimal integer.
       */
      public static String byteToHexStringPadded(int value) {
          return BYTE2HEX_PAD[value & 0xff];
      }
  
      /**
       * Converts the specified byte value into a 2-digit hexadecimal integer and appends it to the specified buffer.
      */
     public static <T extends Appendable> T byteToHexStringPadded(T buf, int value) {
         try {
             buf.append(byteToHexStringPadded(value));
         } catch (IOException e) {
             PlatformDependent.throwException(e);
         }
         return buf;
     }
 
     /**
      * Converts the specified byte array into a hexadecimal value.
      */
     public static String toHexStringPadded(byte[] src) {
         return toHexStringPadded(src, 0, src.length);
     }
 
     /**
      * Converts the specified byte array into a hexadecimal value.
      */
     public static String toHexStringPadded(byte[] src, int offset, int length) {
         return toHexStringPadded(new StringBuilder(length << 1), src, offset, length).toString();
     }
 
     /**
      * Converts the specified byte array into a hexadecimal value and appends it to the specified buffer.
      */
     public static <T extends Appendable> T toHexStringPadded(T dst, byte[] src) {
         return toHexStringPadded(dst, src, 0, src.length);
     }
 
     /**
      * Converts the specified byte array into a hexadecimal value and appends it to the specified buffer.
      */
     public static <T extends Appendable> T toHexStringPadded(T dst, byte[] src, int offset, int length) {
         final int end = offset + length;
         for (int i = offset; i < end; i ++) {
             byteToHexStringPadded(dst, src[i]);
         }
         return dst;
     }
 
     /**
      * Converts the specified byte value into a hexadecimal integer.
      */
     public static String byteToHexString(int value) {
         return BYTE2HEX_NOPAD[value & 0xff];
     }
 
     /**
      * Converts the specified byte value into a hexadecimal integer and appends it to the specified buffer.
      */
     public static <T extends Appendable> T byteToHexString(T buf, int value) {
         try {
             buf.append(byteToHexString(value));
         } catch (IOException e) {
             PlatformDependent.throwException(e);
         }
         return buf;
     }
 
     /**
      * Converts the specified byte array into a hexadecimal value.
      */
     public static String toHexString(byte[] src) {
         return toHexString(src, 0, src.length);
     }
 
     /**
      * Converts the specified byte array into a hexadecimal value.
      */
     public static String toHexString(byte[] src, int offset, int length) {
         return toHexString(new StringBuilder(length << 1), src, offset, length).toString();
     }
 
     /**
      * Converts the specified byte array into a hexadecimal value and appends it to the specified buffer.
      */
     public static <T extends Appendable> T toHexString(T dst, byte[] src) {
         return toHexString(dst, src, 0, src.length);
     }
 
     /**
      * Converts the specified byte array into a hexadecimal value and appends it to the specified buffer.
      */
     public static <T extends Appendable> T toHexString(T dst, byte[] src, int offset, int length) {
         assert length >= 0;
         if (length == 0) {
             return dst;
         }
 
         final int end = offset + length;
         final int endMinusOne = end - 1;
         int i;
 
         // Skip preceding zeroes.
         for (i = offset; i < endMinusOne; i ++) {
             if (src[i] != 0) {
                 break;
             }
         }
 
         byteToHexString(dst, src[i ++]);
         int remaining = end - i;
         toHexStringPadded(dst, src, i, remaining);
 
         return dst;
     }
 
     /**
      * Helper to decode half of a hexadecimal number from a string.
      * @param c The ASCII character of the hexadecimal number to decode.
      * Must be in the range {@code [0-9a-fA-F]}.
      * @return The hexadecimal value represented in the ASCII character
      * given, or {@code -1} if the character is invalid.
      */
     public static int decodeHexNibble(final char c) {
         // Character.digit() is not used here, as it addresses a larger
         // set of characters (both ASCII and full-width latin letters).
         if (c >= '0' && c <= '9') {
             return c - '0';
         }
         if (c >= 'A' && c <= 'F') {
             return c - 'A' + 0xA;
         }
         if (c >= 'a' && c <= 'f') {
             return c - 'a' + 0xA;
         }
         return -1;
     }
 
     /**
      * Decode a 2-digit hex byte from within a string.
      */
     public static byte decodeHexByte(CharSequence s, int pos) {
         int hi = decodeHexNibble(s.charAt(pos));
         int lo = decodeHexNibble(s.charAt(pos + 1));
         if (hi == -1 || lo == -1) {
             throw new IllegalArgumentException(String.format(
                     "invalid hex byte '%s' at index %d of '%s'", s.subSequence(pos, pos + 2), pos, s));
         }
         return (byte) ((hi << 4) + lo);
     }
 
     /**
      * Decodes part of a string with <a href="http://en.wikipedia.org/wiki/Hex_dump">hex dump</a>
      *
      * @param hexDump a {@link CharSequence} which contains the hex dump
      * @param fromIndex start of hex dump in {@code hexDump}
      * @param length hex string length
      */
     public static byte[] decodeHexDump(CharSequence hexDump, int fromIndex, int length) {
         if (length < 0 || (length & 1) != 0) {
             throw new IllegalArgumentException("length: " + length);
         }
         if (length == 0) {
             return EmptyArrays.EMPTY_BYTES;
         }
         byte[] bytes = new byte[length >>> 1];
         for (int i = 0; i < length; i += 2) {
             bytes[i >>> 1] = decodeHexByte(hexDump, fromIndex + i);
         }
         return bytes;
     }
 
     /**
      * Decodes a <a href="http://en.wikipedia.org/wiki/Hex_dump">hex dump</a>
      */
     public static byte[] decodeHexDump(CharSequence hexDump) {
         return decodeHexDump(hexDump, 0, hexDump.length());
     }
 
     /**
      * The shortcut to {@link #simpleClassName(Class) simpleClassName(o.getClass())}.
      */
     public static String simpleClassName(Object o) {
         if (o == null) {
             return "null_object";
         } else {
             return simpleClassName(o.getClass());
         }
     }
 
     /**
      * Generates a simplified name from a {@link Class}.  Similar to {@link Class#getSimpleName()}, but it works fine
      * with anonymous classes.
      */
     public static String simpleClassName(Class<?> clazz) {
         String className = ObjectUtil.checkNotNull(clazz, "clazz").getName();
         final int lastDotIdx = className.lastIndexOf(PACKAGE_SEPARATOR_CHAR);
         if (lastDotIdx > -1) {
             return className.substring(lastDotIdx + 1);
         }
         return className;
     }
 
     /**
      * Escapes the specified value, if necessary according to
      * <a href="https://tools.ietf.org/html/rfc4180#section-2">RFC-4180</a>.
      *
      * @param value The value which will be escaped according to
      *              <a href="https://tools.ietf.org/html/rfc4180#section-2">RFC-4180</a>
      * @return {@link CharSequence} the escaped value if necessary, or the value unchanged
      */
     public static CharSequence escapeCsv(CharSequence value) {
         int length = checkNotNull(value, "value").length();
         if (length == 0) {
             return value;
         }
         int last = length - 1;
         boolean quoted = isDoubleQuote(value.charAt(0)) && isDoubleQuote(value.charAt(last)) && length != 1;
         boolean foundSpecialCharacter = false;
         boolean escapedDoubleQuote = false;
         StringBuilder escaped = new StringBuilder(length + CSV_NUMBER_ESCAPE_CHARACTERS).append(DOUBLE_QUOTE);
         for (int i = 0; i < length; i++) {
             char current = value.charAt(i);
             switch (current) {
                 case DOUBLE_QUOTE:
                     if (i == 0 || i == last) {
                         if (!quoted) {
                             escaped.append(DOUBLE_QUOTE);
                         } else {
                             continue;
                         }
                     } else {
                         boolean isNextCharDoubleQuote = isDoubleQuote(value.charAt(i + 1));
                         if (!isDoubleQuote(value.charAt(i - 1)) &&
                                 (!isNextCharDoubleQuote || i + 1 == last)) {
                             escaped.append(DOUBLE_QUOTE);
                             escapedDoubleQuote = true;
                         }
                         break;
                     }
                 case LINE_FEED:
                 case CARRIAGE_RETURN:
                 case COMMA:
                     foundSpecialCharacter = true;
             }
             escaped.append(current);
         }
         return escapedDoubleQuote || foundSpecialCharacter && !quoted ?
                 escaped.append(DOUBLE_QUOTE) : value;
     }
 
     /**
      * Unescapes the specified escaped CSV field, if necessary according to
      * <a href="https://tools.ietf.org/html/rfc4180#section-2">RFC-4180</a>.
      *
      * @param value The escaped CSV field which will be unescaped according to
      *              <a href="https://tools.ietf.org/html/rfc4180#section-2">RFC-4180</a>
      * @return {@link CharSequence} the unescaped value if necessary, or the value unchanged
      */
     public static CharSequence unescapeCsv(CharSequence value) {
         int length = checkNotNull(value, "value").length();
         if (length == 0) {
             return value;
         }
         int last = length - 1;
         boolean quoted = isDoubleQuote(value.charAt(0)) && isDoubleQuote(value.charAt(last)) && length != 1;
         if (!quoted) {
             validateCsvFormat(value);
             return value;
         }
         StringBuilder unescaped = InternalThreadLocalMap.get().stringBuilder();
         for (int i = 1; i < last; i++) {
             char current = value.charAt(i);
             if (current == DOUBLE_QUOTE) {
                 if (isDoubleQuote(value.charAt(i + 1)) && (i + 1) != last) {
                     // Followed by a double-quote but not the last character
                     // Just skip the next double-quote
                     i++;
                 } else {
                     // Not followed by a double-quote or the following double-quote is the last character
                     throw newInvalidEscapedCsvFieldException(value, i);
                 }
             }
             unescaped.append(current);
         }
         return unescaped.toString();
     }
 
     /**
      * Validate if {@code value} is a valid csv field without double-quotes.
      *
      * @throws IllegalArgumentException if {@code value} needs to be encoded with double-quotes.
      */
     private static void validateCsvFormat(CharSequence value) {
         int length = value.length();
         for (int i = 0; i < length; i++) {
             switch (value.charAt(i)) {
                 case DOUBLE_QUOTE:
                 case LINE_FEED:
                 case CARRIAGE_RETURN:
                 case COMMA:
                     // If value contains any special character, it should be enclosed with double-quotes
                     throw newInvalidEscapedCsvFieldException(value, i);
                 default:
             }
         }
     }
 
     private static IllegalArgumentException newInvalidEscapedCsvFieldException(CharSequence value, int index) {
         return new IllegalArgumentException("invalid escaped CSV field: " + value + " index: " + index);
     }
 
     /**
      * Get the length of a string, {@code null} input is considered {@code 0} length.
      */
     public static int length(String s) {
         return s == null ? 0 : s.length();
     }
 
     /**
      * Determine if a string is {@code null} or {@link String#isEmpty()} returns {@code true}.
      */
     public static boolean isNullOrEmpty(String s) {
         return s == null || s.isEmpty();
     }
 
     /**
      * Determine if {@code c} lies within the range of values defined for
      * <a href="http://unicode.org/glossary/#surrogate_code_point">Surrogate Code Point</a>.
      * @param c the character to check.
      * @return {@code true} if {@code c} lies within the range of values defined for
      * <a href="http://unicode.org/glossary/#surrogate_code_point">Surrogate Code Point</a>. {@code false} otherwise.
      */
     public static boolean isSurrogate(char c) {
         return c >= '\uD800' && c <= '\uDFFF';
     }
 
     private static boolean isDoubleQuote(char c) {
         return c == DOUBLE_QUOTE;
     }
 }