/*
 *
 * 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.
 *
 */
package org.apache.activemq.artemis.protocol.amqp.converter;

import java.nio.ByteBuffer;
import java.util.UUID;

import org.apache.activemq.artemis.protocol.amqp.exceptions.ActiveMQAMQPIllegalStateException;
import org.apache.qpid.proton.amqp.Binary;
import org.apache.qpid.proton.amqp.UnsignedLong;

/**
 * Helper class for identifying and converting message-id and correlation-id values between the
 * AMQP types and the Strings values used by JMS.
 * <p>
 * AMQP messages allow for 4 types of message-id/correlation-id: message-id-string,
 * message-id-binary, message-id-uuid, or message-id-ulong. In order to accept or return a
 * string representation of these for interoperability with other AMQP clients, the following
 * encoding can be used after removing or before adding the "ID:" prefix used for a JMSMessageID
 * value:<br>
 * <p>
 * {@literal "AMQP_BINARY:<hex representation of binary content>"}<br>
 * {@literal "AMQP_UUID:<string representation of uuid>"}<br>
 * {@literal "AMQP_ULONG:<string representation of ulong>"}<br>
 * {@literal "AMQP_STRING:<string>"}<br>
 * <p>
 * The AMQP_STRING encoding exists only for escaping message-id-string values that happen to
 * begin with one of the encoding prefixes (including AMQP_STRING itself). It MUST NOT be used
 * otherwise.
 * <p>
 * When provided a string for conversion which attempts to identify itself as an encoded binary,
 * uuid, or ulong but can't be converted into the indicated format, an exception will be thrown.
 */
public class AMQPMessageIdHelper {

   public static final AMQPMessageIdHelper INSTANCE = new AMQPMessageIdHelper();

   public static final String AMQP_STRING_PREFIX = "AMQP_STRING:";
   public static final String AMQP_UUID_PREFIX = "AMQP_UUID:";
   public static final String AMQP_ULONG_PREFIX = "AMQP_ULONG:";
   public static final String AMQP_BINARY_PREFIX = "AMQP_BINARY:";

   private static final int AMQP_UUID_PREFIX_LENGTH = AMQP_UUID_PREFIX.length();
   private static final int AMQP_ULONG_PREFIX_LENGTH = AMQP_ULONG_PREFIX.length();
   private static final int AMQP_STRING_PREFIX_LENGTH = AMQP_STRING_PREFIX.length();
   private static final int AMQP_BINARY_PREFIX_LENGTH = AMQP_BINARY_PREFIX.length();
   private static final char[] HEX_CHARS = "0123456789ABCDEF".toCharArray();

   /**
    * Takes the provided AMQP messageId style object, and convert it to a base string. Encodes
    * type information as a prefix where necessary to convey or escape the type of the provided
    * object.
    *
    * @param messageId
    *        the raw messageId object to process
    * @return the base string to be used in creating the actual id.
    */
   public String toBaseMessageIdString(Object messageId) {
      if (messageId == null) {
         return null;
      } else if (messageId instanceof String) {
         String stringId = (String) messageId;

         // If the given string has a type encoding prefix,
         // we need to escape it as an encoded string (even if
         // the existing encoding prefix was also for string)
         if (hasTypeEncodingPrefix(stringId)) {
            return AMQP_STRING_PREFIX + stringId;
         } else {
            return stringId;
         }
      } else if (messageId instanceof UUID) {
         return AMQP_UUID_PREFIX + messageId.toString();
      } else if (messageId instanceof UnsignedLong) {
         return AMQP_ULONG_PREFIX + messageId.toString();
      } else if (messageId instanceof Binary) {
         ByteBuffer dup = ((Binary) messageId).asByteBuffer();

         byte[] bytes = new byte[dup.remaining()];
         dup.get(bytes);

         String hex = convertBinaryToHexString(bytes);

         return AMQP_BINARY_PREFIX + hex;
      } else {
         throw new IllegalArgumentException("Unsupported type provided: " + messageId.getClass());
      }
   }

   /**
    * Takes the provided base id string and return the appropriate amqp messageId style object.
    * Converts the type based on any relevant encoding information found as a prefix.
    *
    * @param baseId
    *        the object to be converted to an AMQP MessageId value.
    * @return the AMQP messageId style object
    * @throws ActiveMQAMQPIllegalStateException
    *         if the provided baseId String indicates an encoded type but can't be converted to
    *         that type.
    */
   public Object toIdObject(String baseId) throws ActiveMQAMQPIllegalStateException {
      if (baseId == null) {
         return null;
      }

      try {
         if (hasAmqpUuidPrefix(baseId)) {
            String uuidString = strip(baseId, AMQP_UUID_PREFIX_LENGTH);
            return UUID.fromString(uuidString);
         } else if (hasAmqpUlongPrefix(baseId)) {
            String longString = strip(baseId, AMQP_ULONG_PREFIX_LENGTH);
            return UnsignedLong.valueOf(longString);
         } else if (hasAmqpStringPrefix(baseId)) {
            return strip(baseId, AMQP_STRING_PREFIX_LENGTH);
         } else if (hasAmqpBinaryPrefix(baseId)) {
            String hexString = strip(baseId, AMQP_BINARY_PREFIX_LENGTH);
            byte[] bytes = convertHexStringToBinary(hexString);
            return new Binary(bytes);
         } else {
            // We have a string without any type prefix, transmit it as-is.
            return baseId;
         }
      } catch (IllegalArgumentException e) {
         throw new ActiveMQAMQPIllegalStateException("Unable to convert ID value");
      }
   }

   /**
    * Convert the provided hex-string into a binary representation where each byte represents
    * two characters of the hex string.
    * <p>
    * The hex characters may be upper or lower case.
    *
    * @param hexString
    *        string to convert to a binary value.
    * @return a byte array containing the binary representation
    * @throws IllegalArgumentException
    *         if the provided String is a non-even length or contains non-hex characters
    */
   public byte[] convertHexStringToBinary(String hexString) throws IllegalArgumentException {
      int length = hexString.length();

      // As each byte needs two characters in the hex encoding, the string must be an even
      // length.
      if (length % 2 != 0) {
         throw new IllegalArgumentException("The provided hex String must be an even length, but was of length " + length + ": " + hexString);
      }

      byte[] binary = new byte[length / 2];

      for (int i = 0; i < length; i += 2) {
         char highBitsChar = hexString.charAt(i);
         char lowBitsChar = hexString.charAt(i + 1);

         int highBits = hexCharToInt(highBitsChar, hexString) << 4;
         int lowBits = hexCharToInt(lowBitsChar, hexString);

         binary[i / 2] = (byte) (highBits + lowBits);
      }

      return binary;
   }

   /**
    * Convert the provided binary into a hex-string representation where each character
    * represents 4 bits of the provided binary, i.e each byte requires two characters.
    * <p>
    * The returned hex characters are upper-case.
    *
    * @param bytes
    *        the binary value to convert to a hex String instance.
    * @return a String containing a hex representation of the bytes
    */
   public String convertBinaryToHexString(byte[] bytes) {
      // Each byte is represented as 2 chars
      StringBuilder builder = new StringBuilder(bytes.length * 2);

      for (byte b : bytes) {
         // The byte will be expanded to int before shifting, replicating the
         // sign bit, so mask everything beyond the first 4 bits afterwards
         int highBitsInt = (b >> 4) & 0xF;
         // We only want the first 4 bits
         int lowBitsInt = b & 0xF;

         builder.append(HEX_CHARS[highBitsInt]);
         builder.append(HEX_CHARS[lowBitsInt]);
      }

      return builder.toString();
   }

   // ----- Internal implementation ------------------------------------------//

   private boolean hasTypeEncodingPrefix(String stringId) {
      return hasAmqpBinaryPrefix(stringId) || hasAmqpUuidPrefix(stringId) || hasAmqpUlongPrefix(stringId) || hasAmqpStringPrefix(stringId);
   }

   private boolean hasAmqpStringPrefix(String stringId) {
      return stringId.startsWith(AMQP_STRING_PREFIX);
   }

   private boolean hasAmqpUlongPrefix(String stringId) {
      return stringId.startsWith(AMQP_ULONG_PREFIX);
   }

   private boolean hasAmqpUuidPrefix(String stringId) {
      return stringId.startsWith(AMQP_UUID_PREFIX);
   }

   private boolean hasAmqpBinaryPrefix(String stringId) {
      return stringId.startsWith(AMQP_BINARY_PREFIX);
   }

   private String strip(String id, int numChars) {
      return id.substring(numChars);
   }

   private int hexCharToInt(char ch, String orig) throws IllegalArgumentException {
      if (ch >= '0' && ch <= '9') {
         // subtract '0' to get difference in position as an int
         return ch - '0';
      } else if (ch >= 'A' && ch <= 'F') {
         // subtract 'A' to get difference in position as an int
         // and then add 10 for the offset of 'A'
         return ch - 'A' + 10;
      } else if (ch >= 'a' && ch <= 'f') {
         // subtract 'a' to get difference in position as an int
         // and then add 10 for the offset of 'a'
         return ch - 'a' + 10;
      }

      throw new IllegalArgumentException("The provided hex string contains non-hex character '" + ch + "': " + orig);
   }
}
