/**
*@file            ocpp_process.c
*@author          Parikshit Tyagi
*@co-author       
*@version         1.4
*@date            20 August 2019
*@brief           
*
*/

#include "ocpp_helper.h"

/**
 * This Frame is most crucial part for sending OCPP packet frame from CP to CMS, the CMS does not understand packet format apart from it
 * OCPP Payload --> [
 *                     <message Code>  <data type --> int>,
 *                     <message UUID>  <data type --> string>,
 *                     <action>        <data type --> string>,
 *                     <action data>   <data type --> JSON>
 *                  ]
*/

char *ocppFrameArray = "[%s,\"%s\",\"%s\",%s]";


//*****************************************UUID-Block-Start***********************************//
/**
 * This block generates UUID according to RFC 4122 using /dev/urandom of 36 length for OCPP message Packet
 * in order to identify each message processed by server
 */

/**
 * @brief   --> It get file descriptor of /dev/urandom or /dev/random in UNIX machine
 * @parmas  --> void
*/

static
int random_get_fd(void)
{
    int i, fd;
    struct timeval tv;

    gettimeofday(&tv, 0);
    fd = open("/dev/urandom", O_RDONLY);
    if(fd == -1)
        fd = open("/dev/random", O_RDONLY | O_NONBLOCK);
    if (fd >=0)
    {
        i = fcntl(fd, F_GETFD);
        if (i >= 0)
            fcntl(fd, F_SETFD, i | FD_CLOEXEC);
    }
    srand((getpid() << 16) ^ getuid() ^ tv.tv_sec ^ tv.tv_usec);
    /* Crank the random number generator a few times */
    gettimeofday(&tv, 0);
    for (i = (tv.tv_sec ^ tv.tv_usec) & 0x1F; i > 0; i--)
        rand();
    return fd;    

}

/**
 *  @brief   -->  Generate a stream of random nbytes into buf.
 *               Use /dev/urandom if possible, and if not,
 *               use glibc pseudo-random functions.
 *  @param  --> void *buf      : buffer pointer of no data type where random data generated from /dev/urandom is to be copied
 *              size_t nbytes  : size of the buffer or the no of bytes to be written 
*/

static
void random_get_bytes(void *buf, size_t nbytes)
{
    size_t i, n = nbytes;
    int fd = random_get_fd();
    int lose_counter = 0;
    unsigned char *cp = (unsigned char *)buf;

    if (fd >= 0)
    {
        while(n > 0)
        {
            ssize_t x = read(fd, cp, n);
            if(x <= 0)
            {
                if (lose_counter++ > 16)
                    break;
                continue;
            }
            n -= x;
            cp += x;
            lose_counter = 0;
        }
        close(fd);      
    }
    /*
	 * We do this all the time, but this is the only source of
	 * randomness if /dev/random/urandom is out to lunch.
	 */

    for (cp = buf, i = 0; i < nbytes; i++)
        *cp++ ^= (rand() >> 7) & 0xFF;

    return;
}

/**
 *  @brief   --> This function generates UUID of 16 octects according to RFC4122
 *  @param  --> uuid_t out : uuid_t type of GUID octets
 *               int *num   : this is static value taken for OR and AND operations in the function
*/

static
void __uuid_generate_random(uuid_t out, int *num)
{
    uuid_t buf;
    struct uuid uu;
    int i, n;

    if (!num || !*num)
        n = 1;
    else
        n = *num;

    for(i = 0; i < n; i++)
    {
        random_get_bytes(buf, sizeof(buf));
        uuid_unpack(buf, &uu);

        uu.clock_seq = (uu.clock_seq & 0x3FFF) | 0x8000;
        uu.time_hi_and_version = (uu.time_hi_and_version & 0x0FFF) | 0x4000;
        
        uuid_pack(&uu, out);
        out += sizeof(uuid_t);
    }
}


/**
 *  @brief   --> This function unpacks/parse the GUID generated by sending uuid_t to UUID struct mentioned in RFC4122
 *  @param  --> const uuid_t in : Used for sending GUID of uuid_t type
 *               struct uuid *uu : uuid structure passed for parsing the values from GUID octet to readable UUID struct
*/

static
void uuid_unpack(const uuid_t in, struct uuid *uu)
{
    const uint8_t   *ptr = in;
    uint32_t        tmp;

    tmp = *ptr++;
    tmp = (tmp << 8) | *ptr++;
    tmp = (tmp << 8) | *ptr++;
    tmp = (tmp << 8) | *ptr++;
    uu->time_low = tmp;
    
    tmp = *ptr++;
    tmp = (tmp << 8) | *ptr++;
    uu->time_mid = tmp;

    tmp = *ptr++;
    tmp = (tmp << 8) | *ptr++;
    uu->time_hi_and_version = tmp;

    tmp = *ptr++;
    tmp = (tmp << 8) | *ptr++;
    uu->clock_seq = tmp;

    memcpy(uu->node, ptr, 6);
}


/**
 *  @brief   --> This packet packs the struct uuid into GUID octets
 *  @param  --> const struct uuid **uu : uuid structure passed for generating GUID
 *               uuid_t ptr             : GUID pointer to be passed
*/

static
void uuid_pack(const struct uuid *uu, uuid_t ptr)
{
    uint32_t   tmp;
    unsigned char   *out = ptr;

    tmp = uu->time_low;
    out[3] = (unsigned char)tmp;
    tmp >>= 8;
    out[2] = (unsigned char)tmp;
    tmp >>= 8;
    out[1] = (unsigned char)tmp;
    tmp >>= 8;
    out[0] = (unsigned char)tmp;

    tmp = uu->time_mid;
    out[5] = (unsigned char)tmp;
    tmp >>= 8;
    out[4] = (unsigned char)tmp;

    tmp = uu->time_hi_and_version;
	out[7] = (unsigned char) tmp;
	tmp >>= 8;
	out[6] = (unsigned char) tmp;

	tmp = uu->clock_seq;
	out[9] = (unsigned char) tmp;
	tmp >>= 8;
	out[8] = (unsigned char) tmp;

	memcpy(out+10, uu->node, 6);

}


/**
 *  @brief   --> to parse GUID generated into readable UUID of 36 bit lower format
 *  @param  --> const uuid_t uu : uuid_t type data to be passed once it has 16 Octets generated
 *               char *out       : char pointer to be passed which will point to the UUID generated
*/

static   
void uuid_unparse_lower(const uuid_t uu, char *out)
{
    uuid_unparse_x(uu, out, fmt_lower);
}


/**
 *  @brief   --> this is sub functionality of above function which first unpack the GUID octect and then prints into lower format
 *  @param  --> const uuid_t uu : uuid_t type data to be passed once it has 16 Octets generated
 *               char *out       : char pointer to be passed which will point to the UUID generated
 *               const char *fmt : lower character format defined in ocpp_helper.h file
*/

static
void uuid_unparse_x(const uuid_t uu, char *out, const char *fmt)
{
    struct uuid uuid;

    uuid_unpack(uu, &uuid);
    sprintf(out, fmt,
    uuid.time_low, uuid.time_mid, uuid.time_hi_and_version,
    uuid.clock_seq >> 8, uuid.clock_seq & 0xFF,
    uuid.node[0], uuid.node[1], uuid.node[2],
    uuid.node[3], uuid.node[4], uuid.node[5]);
}

//*******************************************************UUID Block Ends************************//


//******************************************Read-Config.json*****************************//

/**
 *  @brief   --> to read the JSON configuration file defined and return JSON format data
 *  @param  --> const char *filepath : filepath of the json configuration file
*/

cJSON 
*readConfigFile(const char *filepath)
{
    printf("Config File Path -> %s\n", filepath);
    char *source = NULL;
    cJSON *config_json = NULL;
    FILE *fp = fopen(filepath, "r");                      //reading file in read mode
    if(fp != NULL){
        if(fseek(fp, 0L, SEEK_END) == 0){
            long bufsize = ftell(fp);
            if (bufsize == -1){
                fprintf(stderr,"Error during initialization of buffer\n");
            }
            source = malloc(sizeof(char)*(bufsize));
            if (fseek(fp, 0L, SEEK_SET) != 0)
            {
                fprintf(stderr,"Error while backtracing the file\n");
            }
            size_t newLen = fread(source, sizeof(char), bufsize, fp);
            if (ferror(fp) != 0){
                fprintf(stderr,"Error reading file");
            }
            else{
                source[newLen++] = '\0';
            }
        }
        fclose(fp);
    }
    printf("Buffer -> \n%s\n", source);
    config_json = cJSON_Parse(source);
    if(config_json == NULL){
        const char *error_ptr = cJSON_GetErrorPtr();
        if (error_ptr != NULL)
        {
            fprintf(stderr, "Error before: %s\n", error_ptr);
        }
    }
    free(source);
    return config_json;
}

//**********************************************************************************//



//*****************************************************OCPP-Packet-Formation*********************//

/**
 *  @brief   --> to make a structure frame for consolidated and neccessary data required for sending OCPPFrame.
 *               it returns ocpp_frame struct once parsed
 *  @param  --> char *messagecode : According to OCPP, messageCode is the code for RPC call/response/error
 *               char *actiontocms : The action that is needed to be taken by CMS, requested by CP
 *               cJSON *jsonpacket : The JSON packet to be send according to the action schema defined in OCPP1.6J schemas
*/

ocpp_frame 
*formOCPPFrame(char *messagecode, char *actiontocms, cJSON *jsonpacket)
{
    printf("Inside formOCPP packet\n");
    uuid_t binuuid;
    int num = 1;
    char *uuid = malloc(37);     //UUID of 36 length hence allocation 37 for 36 + '\0' 
    if (uuid == NULL)
    {
        fprintf(stderr, "Failed to provide memory for UUID\n");
    }
    ocpp_frame *frame = NULL;
    frame = (ocpp_frame *)malloc(sizeof(ocpp_frame));  //allocating memory for ocppframe
    if (frame == NULL)
    {
        fprintf(stderr, "Unable to allocate memory to ocpp frame\n");
    }
    memset(frame, 0, sizeof(frame));                  //initializing frame with zero
    frame->messageCode = (char *)malloc(sizeof(messagecode) +1);     //allocating memory for messageCode of ocpp frame
    if(frame->messageCode == NULL)
    {
        printf("Unable to locate memory for messagecode");
    }
    memset(frame->messageCode, 0, strlen(messagecode) +1);     //initializing frame with zero
    __uuid_generate_random(binuuid, &num);                    //calling function to generate GUID
    uuid_unparse_lower(binuuid, uuid);                        //Parsing GUID in 36 bits char uuid lower format
    frame->messageID = (char *)malloc(strlen(uuid) +1);      //allocating memory equivalent to UUID + '\0'
    if (frame->messageID == NULL)
    {
        printf("Not able to assign message ID\n");
    }
    memset(frame->messageID, 0, strlen(uuid) +1);             //initializing frame with zero
    frame->action = (char *)malloc(strlen(actiontocms) +1);   //allocating memory equivalent to actiontocms
    if (frame->action == NULL)
    {
        printf("Unable to allocate memory of action frame\n");
    }
    memset(frame->action, 0, strlen(actiontocms) +1);       
    strncpy(frame->messageCode, messagecode, strlen(messagecode));     //copying messagecode in ocpp frame
    strncpy(frame->messageID, uuid, strlen(uuid));                     //copying messageID in ocpp frame
    strncpy(frame->action, actiontocms, strlen(actiontocms));         //copying action in ocpp frame
    frame->jsonPacket = jsonpacket;                               //frame->jsonPacket frame pointing towards jsonpacket passed through argument
    free(uuid);                                                  //freeing memory allocated for uuid
    return frame;
}


/**
 *  @brief   --> to make ocpp payload and it to CMS and if the payload is sent successfully then return 0
 *  @param  --> wsclient *c        : websocket client, from which the payload will be sent
 *               ocpp_frame *packet : the ocpp packet frame that is to be sent
*/

//For success this message sends 0 otherwise -1
int sendFrameToCMS(wsclient *c,ocpp_frame *packet){
    int responseLength = 0;
    //using snprintf printing values of OCPPFrame in ocppMessagePayload taking reference of ocppFrameArray
    snprintf(ocppMessagePayload ,MESSAGE_LEN, ocppFrameArray, packet->messageCode, packet->messageID, packet->action,cJSON_Print(packet->jsonPacket));
    responseLength = libwsclient_send(c, ocppMessagePayload);        //calling function which accepts wsClient and char *payload 
    if(responseLength > 0){
        memset(ocppMessagePayload, 0, sizeof(ocppMessagePayload));   //reinitializing the ocppMessagePayload for other messages
        return 0;
    }
    else
    {
        return -1;
    }
    
}


/**
 *  @brief   --> This function sends the sub-string of the packet received and used for parsing it
 *  @param  --> char *source : source string pointer
 *               char *target : target string that is to be changed
 *               int from     : index value of source string from where values are to be parsed
 *               int to       : index value till the value needs to be parsed
*/

static 
int  getSubString(char *source, char *target,int from, int to)
{
        int length=0;
        int i=0,j=0;
        //get length
        while(source[i++]!='\0')
                length++;
        if(from<0 || from>length){
                printf("Invalid \'from\' index\n");
                return 1;
        }
        if(to>length){
                printf("Invalid \'to\' index\n");
                return 1;
        }
        for(i=from,j=0;i<=to;i++,j++){
                target[j]=source[i];
        }
        //assign NULL at the end of string
        target[j]='\0';
        return 0;
}


/**
 *  @brief   --> This function parses messages that come from CMS to CP into ocppFrame
 *  @param  --> char *payload : The response payload that comes from server to client
*/

ocpp_frame 
    *parseOCPPFrame(char *payload)
{   
    int count = 0;
    ocpp_frame *frame = NULL;
    frame = (ocpp_frame *)malloc(sizeof(ocpp_frame));     //allocating memory for ocppFrame
    if (frame == NULL)
    {
        fprintf(stderr, "Unable to allocate memory to ocpp frame\n");
    }
    memset(frame, 0, sizeof(frame));          //initializing ocppFrame with zero
    char *jsonStr = NULL;
    char *str = NULL;
    str = (char *)malloc(strlen(payload)+1);     //allocating memory for the payload from response to remove '[]' from the payload
    if(str == NULL){
        fprintf(stderr, "Unable to allocate memory to string");
    }
    getSubString(payload, str, 1, strlen(payload)-2);  //function called to parse response and leaving both exterme end indexes 
    char delim[] = ",";                              //assigning delimiter to seperate the values
    char *ptr = strtok(str, delim);                  //strtok function used from string.h library for segregating values
    while(ptr != NULL)
    {
        //switch condition to address each messages seperately
        switch (count++)
        {
        //case for parsing messageCode and saving into ocppFrame->messageCode
        case 0:
            frame->messageCode = (char *)malloc(strlen(ptr)+1);
            if(frame->messageCode == NULL)
            {
                fprintf(stderr,"Unable to locate memory for messagecode");
            }
            memset(frame->messageCode, 0, strlen(ptr));
            strncpy(frame->messageCode, ptr, strlen(ptr)+1);
            break;
        
        //case for parsing messageID and saving into ocppFrame->messageID
        case 1:
            goto Cleanup;
            Cleanup: ;
            char *uuid = malloc(37);
            getSubString(ptr, uuid, 1, strlen(ptr)-2); //used to remove '""' commas from the message
            frame->messageID = (char *)malloc(strlen(ptr)+1);
            if (frame->messageID == NULL)
            {
                fprintf(stderr,"Not able to assign message ID\n");
            }
            memset(frame->messageID, 0, strlen(ptr)+1);
            //strncpy(frame->messageID, ptr, strlen(ptr) +1);
            strncpy(frame->messageID, uuid, strlen(uuid) +1);
            free(uuid);
            break;

        //once all the cases are addressed, this default case used in parsing the complete JSON packet since strtok will break json into different words
        default:
            if(jsonStr == NULL)
            {
                //For the firsttime allocating memory usign malloc for the first word
                jsonStr = (char *)malloc(strlen(ptr)+1);
                if(jsonStr == NULL)
                {
                    fprintf(stderr, "Error in allocating memory to jsonString\n");
                }
                strcpy(jsonStr, ptr);
            }
            else
            {
               //Reallocating memory according to the proceeding string coming 
               jsonStr = realloc(jsonStr, strlen(jsonStr)+strlen(ptr)+1);
               if(jsonStr == NULL)
               {
                   fprintf(stderr, "Error in re-allocating memory to jsonString\n");
               }
               strcat(jsonStr, ",");    
               strcat(jsonStr, ptr); 
            }
            break;
        }
        ptr = strtok(NULL, delim);
    }
    //assigning JSON packet in the frame
    frame->jsonPacket = cJSON_Parse(jsonStr);
    //Freeing memory
    free(str);
    free(jsonStr);

    return frame;
}


//****************************************************OCPP-Frame-ends***********************//


//****************************************************OCPP-Json-Packet**********************//

/**
 * Boot Notification Specific functions
 * 
 */


/**
 *  @brief   --> To make bootNotification JSON packet mentioned in OCPP1.6J and then returning it
 *  @param  --> cJSON *config : configuration required for bootNotification JSON packet, since most of them are static in 
 *               nature and are part of config.json
*/

cJSON *bootNotificationRequest(cJSON *config){
    cJSON *developmentPacket = NULL;
    cJSON *chargePointProfile = NULL;
    developmentPacket = cJSON_GetObjectItem(config, "development");
    if(developmentPacket == NULL)
    {
        const char *error_ptr = cJSON_GetErrorPtr();
        if (error_ptr != NULL)
        {
            fprintf(stderr, "Error before: %s\n", error_ptr);    
        } 
    }
    chargePointProfile = cJSON_GetObjectItem(developmentPacket, "chargePointProfile");
    if(chargePointProfile == NULL)
    {
        const char *error_ptr = cJSON_GetErrorPtr();
        if (error_ptr != NULL)
        {
            fprintf(stderr, "Error before: %s\n", error_ptr);     
        }
    }
    return chargePointProfile;
}


/**
 *  @brief   --> to change the time of client such that it can synchronize with CMS clock, this is part of BootNotification response,
 *               once CP is accepted in CMS
 *  @param  --> char *isoTime : This is the iso time format string that is sent by CMS to CP
*/

int changeTimeOfMachine(char *isoTime)
{
    printf("Inside change time code\n");
    struct tm tm;
    struct timeval set_tv;
    memset(&tm, 0, sizeof(struct tm));
    memset(&set_tv, 0, sizeof(struct timeval));
    strptime(isoTime, "%Y-%m-%dT%H:%M:%S", &tm);            //strptime coneverts the time string into tm struct and all the time values can be accessed from here
    time_t rawtime = mktime(&tm);           //This function returns rawtime or timestamp 
    if(rawtime == -1)
    {
        fprintf(stderr, "The mktime() function failed\n");
        return -1;
    }
    set_tv.tv_sec = rawtime;       //assigning raw time to set_tv.tv_sec
    set_tv.tv_usec = 0;

    printf("Time changed successfully\n");
    return 0; 
}