/* Copyright (c) 2011-2015, The Linux Foundation. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 *       copyright notice, this list of conditions and the following
 *       disclaimer in the documentation and/or other materials provided
 *       with the distribution.
 *     * Neither the name of The Linux Foundatoin, nor the names of its
 *       contributors may be used to endorse or promote products derived
 *       from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
 * IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
#include <log_util.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <pthread.h>
#include <timepps.h>
#include <linux/types.h>
#include <stdbool.h>
#include "loc_cfg.h"
#include <inttypes.h>
#include <time.h>
#include <math.h>

#define BILLION_NSEC  (1E9)

typedef struct timespec pps_sync_time;

//DRsync kernel timestamp
static struct timespec drsyncKernelTs = {0,0};
//DRsync userspace timestamp
static struct timespec drsyncUserTs = {0,0};

static struct timespec prevDrsyncKernelTs = {0,0};

//flag to stop fetching timestamp
static int isActive = 0;
static pps_handle handle;

static pthread_mutex_t ts_lock;
static int skipPPSPulseCnt = 0;
static int gnssOutageInSec = 1;
static loc_param_s_type gps_conf_param_table[] =
{
    {"IGNORE_PPS_PULSE_COUNT", &skipPPSPulseCnt, NULL, 'n'},
    {"GNSS_OUTAGE_DURATION", &gnssOutageInSec, NULL, 'n'}
};

typedef enum {
    KERNEL_REPORTED_CLOCK_BOOTTIME = 0,
    KERNEL_REPORTED_CLOCK_REALTIME,
    KERNEL_REPORTED_CLOCK_UNKNOWN = 0xfe,
    KERNEL_REPORTED_CLOCK_MAX = 0xff
} kernel_reported_time_e;

  /*  checks the PPS source and opens it */
int check_device(char *path, pps_handle *handle)
{
     int ret;

     /* Try to find the source by using the supplied "path" name */
     ret = open(path, O_RDONLY);
     if (ret < 0)
     {
         LOC_LOGV("%s:%d unable to open device %s", __func__, __LINE__, path);
         return ret;
     }

     /* Open the PPS source */
     ret = pps_create(ret, handle);
     if (ret < 0)
     {
         LOC_LOGV( "%s:%d cannot create a PPS source from device %s", __func__, __LINE__, path);
         return -1;
     }
     return 0;
}


/* calculate the time difference between two given times in argument -
** returns the result in timeDifference parametter*/
static inline void calculate_time_difference(pps_sync_time time1,
                            pps_sync_time time2, pps_sync_time* timeDifference)
{
    if (time2.tv_nsec < time1.tv_nsec) {
        timeDifference->tv_sec = time2.tv_sec - 1 - time1.tv_sec;
        timeDifference->tv_nsec = BILLION_NSEC + time2.tv_nsec - time1.tv_nsec;
    } else {
        timeDifference->tv_sec = time2.tv_sec - time1.tv_sec;
        timeDifference->tv_nsec = time2.tv_nsec - time1.tv_nsec;
    }
}

/*add two timespec values and return the result in third resultTime parameter*/
static inline void pps_sync_time_add(pps_sync_time time1,
                            pps_sync_time time2, pps_sync_time* resultTime)
{
    if (time2.tv_nsec + time1.tv_nsec >= BILLION_NSEC) {
        resultTime->tv_sec = time2.tv_sec + time1.tv_sec + 1;
        resultTime->tv_nsec = time2.tv_nsec + time1.tv_nsec - BILLION_NSEC;
    } else {
        resultTime->tv_sec = time2.tv_sec + time1.tv_sec;
        resultTime->tv_nsec = time2.tv_nsec + time1.tv_nsec;
    }
}

#define MAX_REALTIME_OFFSET_DELTA_DIFFERENCE  10
#define MAX_PPS_KERNEL_TO_USERSPACE_LATENCY   100    /*in milli-second*/

static inline double convertTimeToMilliSec(pps_sync_time timeToConvert)
{
   return ((double)(timeToConvert.tv_sec * 1000) + (double)(timeToConvert.tv_nsec * 0.000001));
}

/*returnValue: 1 = offsetTime OK, 0 = offsetTime NOT OK*/
static inline bool isTimeOffsetOk(pps_sync_time offsetTime)
{
    double offsetInMillis = convertTimeToMilliSec(offsetTime);
    return (fabs(offsetInMillis) <= MAX_REALTIME_OFFSET_DELTA_DIFFERENCE)? true: false;
}

/*check whether kernel PPS timestamp is a CLOCK_BOOTTIME or CLOCK_REALTIME*/
static kernel_reported_time_e get_reported_time_type(pps_sync_time userBootTs,
                                                    pps_sync_time userRealTs,
                                                    pps_sync_time kernelTs)
{
    double userRealMs, userBootMs, kernelTsMs;
    kernel_reported_time_e reportedTime = KERNEL_REPORTED_CLOCK_UNKNOWN;

    userRealMs = convertTimeToMilliSec(userRealTs);
    userBootMs = convertTimeToMilliSec(userBootTs);
    kernelTsMs = convertTimeToMilliSec(kernelTs);

    if(fabs(userBootMs - kernelTsMs) <= MAX_PPS_KERNEL_TO_USERSPACE_LATENCY) {
        reportedTime = KERNEL_REPORTED_CLOCK_BOOTTIME;
    } else if (fabs(userRealMs - kernelTsMs) <= MAX_PPS_KERNEL_TO_USERSPACE_LATENCY) {
        reportedTime = KERNEL_REPORTED_CLOCK_REALTIME;
    } else {
        reportedTime = KERNEL_REPORTED_CLOCK_UNKNOWN;
    }

    LOC_LOGV("[%s] Detected PPS timestamp type (0:Boot, 1:Real, 0xfe:Unknown):0x%x",
              __func__, reportedTime);

    return reportedTime;
}

/*compute_real_to_boot_time - converts the kernel real time stamp to boot time reference*/
static int compute_real_to_boot_time(pps_info ppsFetchTime)
{
    int retVal = 0;
    /*Offset between REAL_TIME to BOOT_TIME*/
    static pps_sync_time time_offset = {0, 0};
    pps_sync_time  drSyncUserRealTs, drSyncUserBootTs;
    pps_sync_time  deltaRealToBootTime = {0, 0};
    pps_sync_time  deltaOffsetTime = {0, 0};
    kernel_reported_time_e  ppsTimeType;

    retVal = clock_gettime(CLOCK_BOOTTIME,&drSyncUserBootTs);
    if (retVal != 0) {
        LOC_LOGE("[%s]Error Reading CLOCK_BOOTTIME", __func__);
        retVal = -1;
        goto exit0;
    }
    retVal = clock_gettime(CLOCK_REALTIME,&drSyncUserRealTs);
    if (retVal != 0){
        LOC_LOGE("[%s]Error Reading CLOCK_REALTIME", __func__);
        retVal = -1;
        goto exit0;
    }

    ppsTimeType = get_reported_time_type(drSyncUserBootTs, drSyncUserRealTs, ppsFetchTime);

    if (KERNEL_REPORTED_CLOCK_BOOTTIME == ppsTimeType) {

        /*Store PPS kernel time*/
        drsyncKernelTs.tv_sec = ppsFetchTime.tv_sec;
        drsyncKernelTs.tv_nsec = ppsFetchTime.tv_nsec;
        /*Store User PPS fetch time*/
        drsyncUserTs.tv_sec = drSyncUserBootTs.tv_sec;
        drsyncUserTs.tv_nsec = drSyncUserBootTs.tv_nsec;

        LOC_LOGV("[compute_real_to_boot] PPS TimeType CLOCK_BOOTTIME -- report as is");
        retVal = 0;
    } else if (KERNEL_REPORTED_CLOCK_REALTIME == ppsTimeType) {

        /* Calculate time difference between REALTIME to BOOT_TIME*/
        calculate_time_difference(drSyncUserRealTs, drSyncUserBootTs, &deltaRealToBootTime);

        /* Calculate the time difference between stored offset and computed one now*/
        calculate_time_difference(time_offset, deltaRealToBootTime, &deltaOffsetTime);

        if ((0 == time_offset.tv_sec && 0 == time_offset.tv_nsec) ||
            (isTimeOffsetOk(deltaOffsetTime))) {
            /* if Time Offset does not change beyond threshold then
            ** convert to boot time*/
            drsyncUserTs.tv_sec = drSyncUserBootTs.tv_sec;
            drsyncUserTs.tv_nsec = drSyncUserBootTs.tv_nsec;
            pps_sync_time_add(ppsFetchTime, deltaRealToBootTime, &drsyncKernelTs);
            retVal = 0;
        } else {
            /*The offset is too high, jump detected in realTime tick, either
            ** wall clock changed by user of NTP, skip PPS, re-sync @ next tick
            */
            LOC_LOGE("[%s] Jump detected in CLOCK_REALTIME - Offset %ld:%ld", __func__,
                    deltaOffsetTime.tv_sec, deltaOffsetTime.tv_nsec);
            retVal = -1;
        }
        time_offset.tv_sec = deltaRealToBootTime.tv_sec;
        time_offset.tv_nsec = deltaRealToBootTime.tv_nsec;

        LOC_LOGV("[compute_real_to_boot] KernelRealTs %ld:%ld ComputedTs %ld:%ld RealTs %ld:%ld BootTs %ld:%ld Offset %ld:%ld retVal %d ",
                ppsFetchTime.tv_sec, ppsFetchTime.tv_nsec,
                drsyncKernelTs.tv_sec, drsyncKernelTs.tv_nsec, drSyncUserRealTs.tv_sec,
                drSyncUserRealTs.tv_nsec, drsyncUserTs.tv_sec, drsyncUserTs.tv_nsec,
                time_offset.tv_sec, time_offset.tv_nsec, retVal);
    } else {
        LOC_LOGV("[compute_real_to_boot] PPS TimeType Unknown -- KernelTs %ld:%ld userRealTs %ld:%ld userBootTs %ld:%ld",
                ppsFetchTime.tv_sec, ppsFetchTime.tv_nsec,
                drSyncUserRealTs.tv_sec, drSyncUserRealTs.tv_nsec,
                drsyncUserTs.tv_sec, drsyncUserTs.tv_nsec);
        retVal = -1;
    }

exit0:
    return retVal;

}


/* fetches the timestamp from the PPS source */
int read_pps(pps_handle *handle)
{
    struct timespec timeout;
    pps_info infobuf;
    int ret;
    static  bool isFirstPulseReceived = false;
    static unsigned int skipPulseCnt = 0;
    // 3sec timeout
    timeout.tv_sec = 3;
    timeout.tv_nsec = 0;

    ret = pps_fetch(*handle, PPS_TSFMT_TSPEC, &infobuf, &timeout);

    if (ret < 0 && ret !=-EINTR)
    {
        LOC_LOGV("%s:%d pps_fetch() error %d", __func__, __LINE__, ret);
        return -1;
    }
    if (!isFirstPulseReceived && (skipPPSPulseCnt > 0)) {
        skipPulseCnt = skipPPSPulseCnt;
        isFirstPulseReceived = true;
        LOC_LOGV("%s:%d first pps pulse received %ld (sec) %ld (nsec)",
                  __func__, __LINE__, infobuf.tv_sec, infobuf.tv_nsec)
    }else if (isFirstPulseReceived && (skipPPSPulseCnt > 0) &&
              ((infobuf.tv_sec - prevDrsyncKernelTs.tv_sec) > gnssOutageInSec)) {
        LOC_LOGV("%s:%d long RF outage detected, ignore next %d PPS Pulses",
                  __func__, __LINE__, skipPPSPulseCnt)
        skipPulseCnt = skipPPSPulseCnt;
    }
    prevDrsyncKernelTs.tv_sec = infobuf.tv_sec;
    prevDrsyncKernelTs.tv_nsec = infobuf.tv_nsec;
    /* check if this dr sync pulse need to be ignored or not*/
    if (skipPulseCnt > 0) {
        LOC_LOGV("%s:%d skip pps count %d, ignoring this pps pulse %ld (sec)  %ld (nsec)",
                  __func__,__LINE__, skipPulseCnt, infobuf.tv_sec, infobuf.tv_nsec);
        skipPulseCnt--;
        return 0;
    }
    /* update dr syncpulse time*/

    pthread_mutex_lock(&ts_lock);

    ret = compute_real_to_boot_time(infobuf);

    pthread_mutex_unlock(&ts_lock);

    return 0;
}

#ifdef __cplusplus
extern "C" {
#endif
/* infinitely calls read_pps() */
void *thread_handle(void *input)
{
    int ret;
    if(input != NULL)
    {
        LOC_LOGV("%s:%d Thread Input is present", __func__, __LINE__);
    }
    while(isActive)
    {
        ret = read_pps(&handle);

        if (ret == -1 && errno != ETIMEDOUT )
        {
            LOC_LOGV("%s:%d Could not fetch PPS source", __func__, __LINE__);
        }
    }
    return NULL;
}

/*  opens the device and fetches from PPS source */
int initPPS(char *devname)
{
    int ret,pid;
    pthread_t thread;
    isActive = 1;

    ret = check_device(devname, &handle);
    if (ret < 0)
    {
        LOC_LOGV("%s:%d Could not find PPS source", __func__, __LINE__);
        return 0;
    }
    UTIL_READ_CONF(LOC_PATH_GPS_CONF, gps_conf_param_table);
    pthread_mutex_init(&ts_lock,NULL);

    pid = pthread_create(&thread,NULL,&thread_handle,NULL);
    if(pid != 0)
    {
        LOC_LOGV("%s:%d Could not create thread in InitPPS", __func__, __LINE__);
        return 0;
    }
    return 1;
}

/* stops fetching and closes the device */
void deInitPPS()
{
    pthread_mutex_lock(&ts_lock);
    isActive = 0;
    pthread_mutex_unlock(&ts_lock);

    pthread_mutex_destroy(&ts_lock);
    pps_destroy(handle);
}

/* retrieves DRsync kernel timestamp,DRsync userspace timestamp
   and updates current timestamp */
/* Returns:
 *     1. @Param out DRsync kernel timestamp
 *     2. @Param out DRsync userspace timestamp
 *     3. @Param out current timestamp
 */
int getPPS(struct timespec *fineKernelTs ,struct timespec *currentTs,
           struct timespec *fineUserTs)
{
    int ret;

    pthread_mutex_lock(&ts_lock);
    fineKernelTs->tv_sec = drsyncKernelTs.tv_sec;
    fineKernelTs->tv_nsec = drsyncKernelTs.tv_nsec;

    fineUserTs->tv_sec = drsyncUserTs.tv_sec;
    fineUserTs->tv_nsec = drsyncUserTs.tv_nsec;

    ret = clock_gettime(CLOCK_BOOTTIME,currentTs);
    pthread_mutex_unlock(&ts_lock);
    if(ret != 0)
    {
       LOC_LOGV("%s:%d clock_gettime() error",__func__,__LINE__);
       return 0;
    }
    return 1;
}

#ifdef __cplusplus
}
#endif