/*
 *
 * 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.qpid.jms.provider.amqp.message;

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

import org.apache.qpid.jms.exceptions.IdConversionException;
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>
 *
 * {@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:";
    public static final String AMQP_NO_PREFIX = "AMQP_NO_PREFIX:";
    public static final String JMS_ID_PREFIX = "ID:";

    private static final String AMQP_PREFIX = "AMQP_";
    private static final int JMS_ID_PREFIX_LENGTH = JMS_ID_PREFIX.length();
    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 int AMQP_NO_PREFIX_LENGTH = AMQP_NO_PREFIX.length();
    private static final char[] HEX_CHARS = "0123456789ABCDEF".toCharArray();

    /**
     * Checks whether the given string begins with "ID:" prefix used to denote a JMSMessageID
     *
     * @param string the string to check
     * @return true if and only id the string begins with "ID:"
     */
    public boolean hasMessageIdPrefix(String string) {
        if (string == null) {
            return false;
        }

        return string.startsWith(JMS_ID_PREFIX);
    }

    public String toMessageIdString(Object idObject) {
        if (idObject instanceof String) {
            final String stringId = (String) idObject;

            boolean hasMessageIdPrefix = hasMessageIdPrefix(stringId);
            if (!hasMessageIdPrefix) {
                // For JMSMessageID, has no "ID:" prefix, we need to record
                // that for later use as a JMSCorrelationID.
                return JMS_ID_PREFIX + AMQP_NO_PREFIX + stringId;
            } else if (hasTypeEncodingPrefix(stringId, JMS_ID_PREFIX_LENGTH)) {
                // We are for a JMSMessageID value, but have 'ID:' followed by
                // one of the encoding prefixes. Need to escape the entire string
                // to preserve for later re-use as a JMSCorrelationID.
                return JMS_ID_PREFIX + AMQP_STRING_PREFIX + stringId;
            } else {
                // It has "ID:" prefix and doesn't have encoding prefix, use it as-is.
                return stringId;
            }
        } else {
            // Not a string, convert it
            return convertToIdString(idObject);
        }
    }

    public String toCorrelationIdString(Object idObject) {

        if (idObject instanceof String) {
            final String stringId = (String) idObject;

            boolean hasMessageIdPrefix = hasMessageIdPrefix(stringId);
            if (!hasMessageIdPrefix) {
                // For JMSCorrelationID, has no "ID:" prefix, use it as-is.
                return stringId;
            } else if (hasTypeEncodingPrefix(stringId, JMS_ID_PREFIX_LENGTH)) {
                // We are for a JMSCorrelationID value, but have 'ID:' followed by
                // one of the encoding prefixes. Need to escape the entire string
                // to preserve for later re-use as a JMSCorrelationID.
                return JMS_ID_PREFIX + AMQP_STRING_PREFIX + stringId;
            } else {
                // It has "ID:" prefix and doesn't have encoding prefix, use it as-is.
                return stringId;
            }
        } else {
            // Not a string, convert it
            return convertToIdString(idObject);
        }
    }

    /**
     * Takes the provided non-String AMQP message-id/correlation-id object, and
     * convert it it to a String usable as either a JMSMessageID or JMSCorrelationID
     * value, encoding the type information as a prefix to convey for later use
     * in reversing the process if used to set JMSCorrelationID on a message.
     *
     * @param idObject the object to process
     * @return string to be used for the actual JMS ID.
     */
    private String convertToIdString(Object idObject) {
        if (idObject == null) {
            return null;
        }

        if (idObject instanceof UUID) {
            return JMS_ID_PREFIX + AMQP_UUID_PREFIX + idObject.toString();
        } else if (idObject instanceof UnsignedLong) {
            return JMS_ID_PREFIX + AMQP_ULONG_PREFIX + idObject.toString();
        } else if (idObject instanceof Binary) {
            ByteBuffer dup = ((Binary) idObject).asByteBuffer();

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

            String hex = convertBinaryToHexString(bytes);

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

    private boolean hasTypeEncodingPrefix(String stringId, int offset) {
        if(!stringId.startsWith(AMQP_PREFIX, offset)){
            return false;
        }

        return hasAmqpBinaryPrefix(stringId, offset) ||
                    hasAmqpUuidPrefix(stringId, offset) ||
                        hasAmqpUlongPrefix(stringId, offset) ||
                            hasAmqpStringPrefix(stringId, offset) ||
                                 hasAmqpNoPrefix(stringId, offset);
    }

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

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

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

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

    private boolean hasAmqpNoPrefix(String stringId, int offset) {
        return stringId.startsWith(AMQP_NO_PREFIX, offset);
    }

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

        if(!AmqpMessageIdHelper.INSTANCE.hasMessageIdPrefix(origId)) {
            // We have a string without any "ID:" prefix, it is an
            // application-specific String, use it as-is.
            return origId;
        }

        try {
            if (hasAmqpNoPrefix(origId, JMS_ID_PREFIX_LENGTH)) {
                // Prefix telling us there was originally no "ID:" prefix,
                // strip it and return the remainder
                return origId.substring(JMS_ID_PREFIX_LENGTH + AMQP_NO_PREFIX_LENGTH);
            } else if (hasAmqpUuidPrefix(origId, JMS_ID_PREFIX_LENGTH)) {
                String uuidString = origId.substring(JMS_ID_PREFIX_LENGTH + AMQP_UUID_PREFIX_LENGTH);
                return UUID.fromString(uuidString);
            } else if (hasAmqpUlongPrefix(origId, JMS_ID_PREFIX_LENGTH)) {
                String ulongString = origId.substring(JMS_ID_PREFIX_LENGTH + AMQP_ULONG_PREFIX_LENGTH);
                return UnsignedLong.valueOf(ulongString);
            } else if (hasAmqpStringPrefix(origId, JMS_ID_PREFIX_LENGTH)) {
                return origId.substring(JMS_ID_PREFIX_LENGTH + AMQP_STRING_PREFIX_LENGTH);
            } else if (hasAmqpBinaryPrefix(origId, JMS_ID_PREFIX_LENGTH)) {
                String hexString = origId.substring(JMS_ID_PREFIX_LENGTH + AMQP_BINARY_PREFIX_LENGTH);
                byte[] bytes = convertHexStringToBinary(hexString);
                return new Binary(bytes);
            } else {
                // We have a string without any encoding prefix needing processed,
                // so transmit it as-is, including the "ID:"
                return origId;
            }
        } catch (IllegalArgumentException e) {
            throw new IdConversionException("Unable to convert ID value", e);
        }
    }

    /**
     * Convert the provided hex-string into a binary representation where each byte represents
     * two characters of the hex string.
     *
     * The hex characters may be upper or lower case.
     *
     * @param hexString string to convert
     * @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;
    }

    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);
    }

    /**
     * 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.
     *
     * The returned hex characters are upper-case.
     *
     * @param bytes binary to convert
     * @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();
    }
}
