/*********************************************************************************
 *      Copyright:  (C) 2022 LingYun IoT System Studio
 *                  All rights reserved.
 *
 *       Filename:  packet.c
 *    Description:  This file is packet API functions
 *
 *        Version:  1.0.0(18/04/22)
 *         Author:  Guo Wenxue <guowenxue@gmail.com>
 *      ChangeLog:  1, Release initial version on "18/04/22 16:30:25"
 *
 ********************************************************************************/

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <time.h>
#include "packet.h"
#include "logger.h"
#include "ds18b20.h"

int get_devid(char *devid, int size, int sn)
{
    if( !devid || size<DEVID_LEN )
    {
        log_error("Invalid input arugments\n");
        return -1;
    }

    memset(devid, 0, size);
    snprintf(devid, size, "RPI#%04d", sn);
    return 0;
}

int get_time(struct tm *ptm)
{
    if( !ptm )
    {
        log_error("Invalid input arugments\n");
        return -1;
    }

    time_t now = time(NULL);
    localtime_r(&now, ptm);

    return 0;
}

int packet_segmented_pack(pack_info_t *pack_info, uint8_t *pack_buf, int size)
{
    char              strtime[TIME_LEN] = {'\0'};
    struct tm        *ptm;
    char             *buf = (char *)pack_buf;

    if( !pack_info || !buf || size<=0 )
    {
        log_error("Invalid input arguments\n");
        return -1;
    }

    ptm = &pack_info->sample_time;
    snprintf(strtime, sizeof(strtime), "%04d-%02d-%02d %02d:%02d:%02d",
            ptm->tm_year+1900, ptm->tm_mon+1, ptm->tm_mday,
            ptm->tm_hour, ptm->tm_min, ptm->tm_sec);

    memset(buf, 0, size);
    snprintf(buf, size, "%s|%s|%.3f", pack_info->devid, strtime, pack_info->temper);

    return strlen(buf);
}

int packet_json_pack(pack_info_t *pack_info, uint8_t *pack_buf, int size)
{
    char              strtime[TIME_LEN] = {'\0'};
    struct tm        *ptm;
    char             *buf = (char *)pack_buf;

    if( !pack_info || !buf || size<=0 )
    {
        log_error("Invalid input arguments\n");
        return -1;
    }

    ptm = &pack_info->sample_time;
    snprintf(strtime, sizeof(strtime), "%04d-%02d-%2d %02d:%02d:%02d",
            ptm->tm_year+1900, ptm->tm_mon+1, ptm->tm_mday,
            ptm->tm_hour, ptm->tm_min, ptm->tm_sec);

    memset(buf, 0, size);
    snprintf(buf, size, "{\"devid\":\"%s\", \"time\":\"%s\",\"temperature\":\"%.3f\"}",
            pack_info->devid, strtime, pack_info->temper);

    return strlen(buf);
}

/*
 * description: compute the CRC-ITU-T for the data buffer
 *   input args:
 *               $data  :  data pointer
 *               $length:  number of bytes in the buffer
 * return value: the 16-bits CRC value
 */

/*
 * The CRC-ITU-T, also known as CRC-16-ITU-T or CRC-16-V.41, uses the polynomial:
 *     0x1021:  x^16 + x^12 + x^5 + 1
 */
#define CRC16_ITU_T_POLY 0x1021   /* Define the CRC-ITU-T polynomial */
uint16_t crc_itu_t(const uint8_t *data, size_t length)
{
    uint16_t          crc = 0xFFFF;
    size_t            i, j;

    for (i=0; i<length; i++)
    {
        crc ^= ((uint16_t)data[i] << 8);

        for(j=0; j<8; j++)
        {
            if (crc & 0x8000)
            {
                crc = (crc << 1) ^ CRC16_ITU_T_POLY;
            }
            else
            {
                crc <<= 1;
            }
        }
    }

    return crc;
}

int ushort_to_bytes(uint16_t val, uint8_t *bytes)
{
    int              size  = sizeof (uint16_t);
    int              i = 0;

    if( !bytes )
        return 0;

    while (size)
    {
        *(bytes + --size) = (val >> ((8 * i++) & 0xFF));
    }

    return sizeof(uint16_t);
}

uint16_t bytes_to_ushort(uint8_t *bytes, int len)
{
    int            i = 0;
    uint16_t       val = 0;

    if( !bytes || len > sizeof(uint16_t) )
        return 0;

    for(i=0; i<len; i++)
    {
        val += bytes[i];

        if (i < len - 1)
            val = val << 8;
    }

    return val;
}

/* TLV(Tag Length Value) PDU(Protocal Data Unit) format:
 *
 * +-----------+-----------+------------+-------------+-------------+
 * | Header(2B)|  Tag(1B)  | Length(2B) |  Value(nB)  |  CRC16(2B)  |
 * +-----------+-----------+------------+-------------+-------------+
 *
 * Header(2B): 0xFE 0xFD
 *    Tag(1B): 0x01->temperature 0x02->Humidity 0x03->Noisy ...
 * Length(2B): Data value length, include Header+Tag+Length+Value+CRC16
 *  Value(nB): Data value
 *  CRC16(2B): CRC from Header to Value
 */

/*  description: package a TLV packet
 *   input args:
 *               $pack_info:  packet data contains devid, time and temperature
 *               $pack_buf :  packet output buffer
 *               $size     :  packet output buffer size
 * return value: <0: failure   >0: packet bytes
 */

int packet_tlv_pack(pack_info_t *pack_info, uint8_t *pack_buf, int size)
{
    struct tm          *ptm;
    int                 ofset = 0;
    uint16_t            len;
    uint16_t            crc;

    if( !pack_info || !pack_buf || size<TLV_FIXSIZE )

    {
        log_error("Invalid input arguments\n");
        return -1;
    }

    /*+----------------------+
     *|    TLV Header(2B)    |
     *+----------------------+*/
    ofset += ushort_to_bytes(TLV_HEADER, pack_buf);

    /*+----------------------+
     *|      TLV Tag(1B)     |
     *+----------------------+*/
    pack_buf[ofset++] = TAG_TEMPERATURE;

    /* Skip data length here, we will calculate it later */
    ofset += 2;

    /*+----------------------+
     *|  payload data value  |
     *+----------------------+*/

    /* 6 bytes sample time */
    ptm = &pack_info->sample_time;
    pack_buf[ofset++] = (uint8_t)(ptm->tm_year+1900-2000);
    pack_buf[ofset++] = (uint8_t)(ptm->tm_mon+1);
    pack_buf[ofset++] = (uint8_t)(ptm->tm_mday);
    pack_buf[ofset++] = (uint8_t)(ptm->tm_hour);
    pack_buf[ofset++] = (uint8_t)(ptm->tm_min);
    pack_buf[ofset++] = (uint8_t)(ptm->tm_sec);

    /* 8 bytes device SN */
    strncpy((char *)(pack_buf+ofset), pack_info->devid, DEVID_LEN);
    ofset += DEVID_LEN;

    /* 2 bytes temperature value */
    pack_buf[ofset++] = (int)pack_info->temper;  /* integer part */
    pack_buf[ofset++] = (((int)(pack_info->temper*100))%100); /* fractional part */

    /*+----------------------+
     *|    TLV Length(2B)    |
     *+----------------------+*/
    len = ofset + 2; /* include CRC */
    ushort_to_bytes(len, pack_buf+3);

    /*+----------------------+
     *|      TLV CRC(2B)     |
     *+----------------------+*/
    crc = crc_itu_t(pack_buf, ofset); /* from Header to payload data */
    ofset += ushort_to_bytes(crc, pack_buf+ofset);

    return ofset;
}

/*  description: package a TLV packet.
 *   input args:
 *               $pack_info:  packet data contains devid, time and temperature
 *               $pack_buf :  packet output buffer
 *               $size     :  packet output buffer size
 * return value: <0: failure  0: not integrated  >0: processed packet len
 */

int parser_tlv_pack(pack_info_t *pack_info, uint8_t *pack_buf, int size)
{
    int                 ofset = 0;
    uint16_t            crc;
    uint16_t            payload_len;

    uint16_t            pack_head;
    uint8_t             pack_tag;
    uint16_t            pack_len;
    uint16_t            pack_crc;

    if( !pack_info || !pack_buf )
    {
        log_error("Invalid input arguments\n");
        return -1;
    }

    if( size < TLV_FIXSIZE )
    {
        log_warn("TLV packet bytes less than min. size\n");
        return 0;
    }

    /*+----------------------+
     *|    TLV Header(2B)    |
     *+----------------------+*/
    pack_head = bytes_to_ushort(pack_buf, 2);
    ofset += 2;

    if( TLV_HEADER != pack_head)
        return -2;

    /*+----------------------+
     *|      TLV Tag(1B)     |
     *+----------------------+*/
    pack_tag = pack_buf[ofset];
    ofset ++;

    /*+----------------------+
     *|    TLV Length(2B)    |
     *+----------------------+*/
    pack_len = bytes_to_ushort(pack_buf+ofset, 2);
    ofset += 2;

    log_debug("header: 0x%02x tag: 0x%02x len: 0x%02x\n", pack_head, pack_tag, pack_len);

    /* Packet length is from Header to CRC16(include) */
    if( pack_len > size )
    {
        log_warn("TLV packet bytes less than length\n");
        return 0;
    }

    /*+----------------------+
     *|      TLV CRC(2B)     |
     *+----------------------+*/

    /* packet CRC */
    pack_crc = bytes_to_ushort(pack_buf+pack_len-2, 2);

    /* calculate CRC  */
    payload_len = pack_len - TLV_FIXSIZE;
    crc = crc_itu_t(pack_buf, ofset+payload_len); /* from Header to payload data */

    if( crc != pack_crc)
    {
        log_error("calculate CRC[0x%04x] != packet CRC[0x%04x]\n", crc, pack_crc);
        return -3;
    }

    /*+----------------------+
     *|  payload data value  |
     *+----------------------+*/

    pack_info->tag = pack_tag;

    if( pack_tag == TAG_TEMPERATURE )
    {
        /* 6 bytes sample time */
        pack_info->sample_time.tm_year = pack_buf[ofset++] + 2000 - 1900;
        pack_info->sample_time.tm_mon = pack_buf[ofset++] - 1;
        pack_info->sample_time.tm_mday = pack_buf[ofset++] ;
        pack_info->sample_time.tm_hour = pack_buf[ofset++];
        pack_info->sample_time.tm_min = pack_buf[ofset++];
        pack_info->sample_time.tm_sec = pack_buf[ofset++];

        /* 8 bytes device SN */
        strncpy(pack_info->devid, (char *)(pack_buf+ofset), DEVID_LEN);
        ofset += DEVID_LEN;

        /* 2 bytes temperature value */
        pack_info->temper = (float)pack_buf[ofset] + (float)pack_buf[ofset+1]/100.0f;
    }

    return pack_len;
}