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

#include "MQTTPacket.h"

#include <string.h>

/**
  * Determines the length of the MQTT connect packet that would be produced using the supplied connect options.
  * @param options the options to be used to build the connect packet
  * @return the length of buffer needed to contain the serialized version of the packet
  */
int MQTTSerialize_connectLength(MQTTPacket_connectData *options)
{
    int len = 0;


    if (options->MQTTVersion == 3) {
        len = 12;    /* variable depending on MQTT or MQIsdp */
    } else if (options->MQTTVersion == 4) {
        len = 10;
    }

    len += MQTTstrlen(options->clientID) + 2;
    if (options->willFlag) {
        len += MQTTstrlen(options->will.topicName) + 2 + MQTTstrlen(options->will.message) + 2;
    }
    if (options->username.cstring || options->username.lenstring.data) {
        len += MQTTstrlen(options->username) + 2;
    }
    if (options->password.cstring || options->password.lenstring.data) {
        len += MQTTstrlen(options->password) + 2;
    }

    return len;
}


/**
  * Serializes the connect options into the buffer.
  * @param buf the buffer into which the packet will be serialized
  * @param len the length in bytes of the supplied buffer
  * @param options the options to be used to build the connect packet
  * @return serialized length, or error if 0
  */
int MQTTSerialize_connect(unsigned char *buf, int buflen, MQTTPacket_connectData *options)
{
    unsigned char *ptr = buf;
    MQTTHeader header = {0};
    MQTTConnectFlags flags = {0};
    int len = 0;
    int rc = -1;

    if (MQTTPacket_len(len = MQTTSerialize_connectLength(options)) > buflen) {
        rc = MQTTPACKET_BUFFER_TOO_SHORT;
        goto exit;
    }

    header.byte = 0;
    MQTT_HEADER_SET_TYPE(header.byte, CONNECT);

    writeChar(&ptr, header.byte); /* write header */

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

    if (options->MQTTVersion == 4) {
        writeCString(&ptr, "MQTT");
        writeChar(&ptr, (char) 4);
    } else {
        writeCString(&ptr, "MQIsdp");
        writeChar(&ptr, (char) 3);
    }

    flags.all = 0;
    flags.all |= (options->cleansession) ? MQTT_CONN_FLAG_CLEAN_SESSION : 0;
    flags.all |= (options->willFlag) ? MQTT_CONN_FLAG_WILL_FLAG : 0;
    if (flags.all & MQTT_CONN_FLAG_WILL_FLAG) {
        flags.all |= ((options->will.qos & 0x03) << 3);
        flags.all |= (options->will.retained) ? MQTT_CONN_FLAG_WILL_RETAIN : 0;
    }

    if (options->username.cstring || options->username.lenstring.data) {
        flags.all |= MQTT_CONN_FLAG_USER_NAME;
    }
    if (options->password.cstring || options->password.lenstring.data) {
        flags.all |= MQTT_CONN_FLAG_PASSWORD;
    }

    writeChar(&ptr, flags.all);
    writeInt(&ptr, options->keepAliveInterval);
    writeMQTTString(&ptr, options->clientID);
    if (options->willFlag) {
        writeMQTTString(&ptr, options->will.topicName);
        writeMQTTString(&ptr, options->will.message);
    }
    if (flags.all & MQTT_CONN_FLAG_USER_NAME) {
        writeMQTTString(&ptr, options->username);
    }
    if (flags.all & MQTT_CONN_FLAG_PASSWORD) {
        writeMQTTString(&ptr, options->password);
    }

    rc = ptr - buf;

exit:
    return rc;
}


/**
  * Deserializes the supplied (wire) buffer into connack data - return code
  * @param sessionPresent the session present flag returned (only for MQTT 3.1.1)
  * @param connack_rc returned integer value of the connack return code
  * @param buf the raw buffer data, of the correct length determined by the remaining length field
  * @param len the length in bytes of the data in the supplied buffer
  * @return error code.  1 is success, 0 is failure
  */
int MQTTDeserialize_connack(unsigned char *sessionPresent, unsigned char *connack_rc, unsigned char *buf, int buflen)
{
    MQTTHeader header = {0};
    unsigned char *curdata = buf;
    unsigned char *enddata = NULL;
    int rc = 0;
    int mylen;
    MQTTConnackFlags flags = {0};

    header.byte = readChar(&curdata);
    if (MQTT_HEADER_GET_TYPE(header.byte) != CONNACK) {
        goto exit;
    }

    curdata += (rc = MQTTPacket_decodeBuf(curdata, &mylen)); /* read remaining length */
    enddata = curdata + mylen;
    if (enddata - curdata < 2) {
        goto exit;
    }

    flags.all = readChar(&curdata);
    *sessionPresent = flags.bits.sessionpresent;
    *connack_rc = readChar(&curdata);

    rc = 1;
exit:
    return rc;
}


/**
  * Serializes a 0-length packet into the supplied buffer, ready for writing to a socket
  * @param buf the buffer into which the packet will be serialized
  * @param buflen the length in bytes of the supplied buffer, to avoid overruns
  * @param packettype the message type
  * @return serialized length, or error if 0
  */
int MQTTSerialize_zero(unsigned char *buf, int buflen, unsigned char packettype)
{
    MQTTHeader header = {0};
    int rc = -1;
    unsigned char *ptr = buf;

    if (buflen < 2) {
        rc = MQTTPACKET_BUFFER_TOO_SHORT;
        goto exit;
    }
    header.byte = 0;
    MQTT_HEADER_SET_TYPE(header.byte, packettype);
    writeChar(&ptr, header.byte); /* write header */

    ptr += MQTTPacket_encode(ptr, 0); /* write remaining length */
    rc = ptr - buf;
exit:
    return rc;
}


/**
  * Serializes a disconnect packet into the supplied buffer, ready for writing to a socket
  * @param buf the buffer into which the packet will be serialized
  * @param buflen the length in bytes of the supplied buffer, to avoid overruns
  * @return serialized length, or error if 0
  */
int MQTTSerialize_disconnect(unsigned char *buf, int buflen)
{
    return MQTTSerialize_zero(buf, buflen, DISCONNECT);
}


/**
  * Serializes a disconnect packet into the supplied buffer, ready for writing to a socket
  * @param buf the buffer into which the packet will be serialized
  * @param buflen the length in bytes of the supplied buffer, to avoid overruns
  * @return serialized length, or error if 0
  */
int MQTTSerialize_pingreq(unsigned char *buf, int buflen)
{
    return MQTTSerialize_zero(buf, buflen, PINGREQ);
}