/*
 * Copyright (C) 2015-2018 Alibaba Group Holding Limited
 */

#include "MQTTPacket.h"

#include <string.h>


/**
  * Determines the length of the MQTT publish packet that would be produced using the supplied parameters
  * @param qos the MQTT QoS of the publish (packetid is omitted for QoS 0)
  * @param topicName the topic name to be used in the publish
  * @param payloadlen the length of the payload to be sent
  * @return the length of buffer needed to contain the serialized version of the packet
  */
int MQTTSerialize_publishLength(int qos, MQTTString topicName, int payloadlen)
{
    int len = 0;

    len += 2 + MQTTstrlen(topicName) + payloadlen;
    if (qos > 0) {
        len += 2;    /* packetid */
    }
    return len;
}


/**
  * Serializes the supplied publish data into the supplied buffer, ready for sending
  * @param buf the buffer into which the packet will be serialized
  * @param buflen the length in bytes of the supplied buffer
  * @param dup integer - the MQTT dup flag
  * @param qos integer - the MQTT QoS value
  * @param retained integer - the MQTT retained flag
  * @param packetid integer - the MQTT packet identifier
  * @param topicName MQTTString - the MQTT topic in the publish
  * @param payload byte buffer - the MQTT publish payload
  * @param payloadlen integer - the length of the MQTT payload
  * @return the length of the serialized data.  <= 0 indicates error
  */
int MQTTSerialize_publish(unsigned char *buf, int buflen, unsigned char dup, int qos, unsigned char retained,
                          unsigned short packetid,
                          MQTTString topicName, unsigned char *payload, int payloadlen)
{
    unsigned char *ptr = buf;
    MQTTHeader header = {0};
    int rem_len = 0;
    int rc = 0;

    if (MQTTPacket_len(rem_len = MQTTSerialize_publishLength(qos, topicName, payloadlen)) > buflen) {
        rc = MQTTPACKET_BUFFER_TOO_SHORT;
        goto exit;
    }

    MQTT_HEADER_SET_TYPE(header.byte, PUBLISH);
    MQTT_HEADER_SET_DUP(header.byte, dup);
    MQTT_HEADER_SET_QOS(header.byte, qos);
    MQTT_HEADER_SET_RETAIN(header.byte, retained);
    writeChar(&ptr, header.byte); /* write header */

    ptr += MQTTPacket_encode(ptr, rem_len); /* write remaining length */;

    writeMQTTString(&ptr, topicName);

    if (qos > 0) {
        writeInt(&ptr, packetid);
    }

    memcpy(ptr, payload, payloadlen);
    ptr += payloadlen;

    rc = ptr - buf;

exit:
    return rc;
}



/**
  * Serializes the ack packet into the supplied buffer.
  * @param buf the buffer into which the packet will be serialized
  * @param buflen the length in bytes of the supplied buffer
  * @param type the MQTT packet type
  * @param dup the MQTT dup flag
  * @param packetid the MQTT packet identifier
  * @return serialized length, or error if 0
  */
int MQTTSerialize_ack(unsigned char *buf, int buflen, unsigned char packettype, unsigned char dup,
                      unsigned short packetid)
{
    MQTTHeader header = {0};
    int rc = 0;
    unsigned char *ptr = buf;

    if (buflen < 4) {
        rc = MQTTPACKET_BUFFER_TOO_SHORT;
        goto exit;
    }
    MQTT_HEADER_SET_TYPE(header.byte, packettype);
    MQTT_HEADER_SET_DUP(header.byte, dup);
    MQTT_HEADER_SET_QOS(header.byte, ((packettype == PUBREL) ? 1 : 0));
    writeChar(&ptr, header.byte); /* write header */

    ptr += MQTTPacket_encode(ptr, 2); /* write remaining length */
    writeInt(&ptr, packetid);
    rc = ptr - buf;
exit:
    return rc;
}


/**
  * Serializes a puback packet into the supplied buffer.
  * @param buf the buffer into which the packet will be serialized
  * @param buflen the length in bytes of the supplied buffer
  * @param packetid integer - the MQTT packet identifier
  * @return serialized length, or error if 0
  */
/*  int MQTTSerialize_puback(unsigned char* buf, int buflen, unsigned short packetid) */
/*  { */
/*   return MQTTSerialize_ack(buf, buflen, PUBACK, 0, packetid); */
/*  } */

#if WITH_MQTT_QOS2_PACKET
/**
  * Serializes a pubrel packet into the supplied buffer.
  * @param buf the buffer into which the packet will be serialized
  * @param buflen the length in bytes of the supplied buffer
  * @param dup integer - the MQTT dup flag
  * @param packetid integer - the MQTT packet identifier
  * @return serialized length, or error if 0
  */
int MQTTSerialize_pubrel(unsigned char *buf, int buflen, unsigned char dup, unsigned short packetid)
{
    return MQTTSerialize_ack(buf, buflen, PUBREL, dup, packetid);
}


/**
  * Serializes a pubrel packet into the supplied buffer.
  * @param buf the buffer into which the packet will be serialized
  * @param buflen the length in bytes of the supplied buffer
  * @param packetid integer - the MQTT packet identifier
  * @return serialized length, or error if 0
  */
int MQTTSerialize_pubcomp(unsigned char *buf, int buflen, unsigned short packetid)
{
    return MQTTSerialize_ack(buf, buflen, PUBCOMP, 0, packetid);
}
#endif  /* #if WITH_MQTT_QOS2_PACKET */