// Copyright 2018-2019 Espressif Systems (Shanghai) PTE LTD
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include <stdint.h>
#include <reent.h>
#include <sys/time.h>

#include "esp_system.h"
#include "esp_timer.h"

static uint64_t s_boot_time;

static os_timer_t microsecond_overflow_timer;
static uint32_t microsecond_last_overflow_tick;
static uint32_t microsecond_overflow_count;

static bool microsecond_overflow_timer_start_flag = false;

static void microsecond_overflow_tick(void* arg)
{
    uint32_t m = system_get_time();

    if (m < microsecond_last_overflow_tick) {
        microsecond_overflow_count ++;
    }

    microsecond_last_overflow_tick = m;
}

/* Start a timer which period is 60s to check the overflow of microsecond. */
static void microsecond_overflow_set_check_timer(void)
{
    if (microsecond_overflow_timer_start_flag == false) {
        os_timer_disarm(&microsecond_overflow_timer);
        os_timer_setfn(&microsecond_overflow_timer, (os_timer_func_t*)microsecond_overflow_tick, 0);
        os_timer_arm(&microsecond_overflow_timer, 60 * 1000, 1);

        microsecond_overflow_timer_start_flag = true;
    }
}

static void set_boot_time(uint64_t time_us)
{
    s_boot_time = time_us;
}

static uint64_t get_boot_time()
{
    uint64_t result;

    result = s_boot_time;

    return result;
}

static uint64_t get_time_since_boot()
{
    uint32_t m = system_get_time();
    uint32_t c = microsecond_overflow_count + ((m < microsecond_last_overflow_tick) ? 1 : 0);

    uint64_t microseconds = c * (1LL << 32) + m;

    return microseconds;
}

int _gettimeofday_r(struct _reent* r, struct timeval* tv, void* tz)
{
    (void) tz;

    /* ToDo: This can be moved to system start up. */
    microsecond_overflow_set_check_timer();

    if (tv) {
        uint64_t microseconds = get_boot_time() + get_time_since_boot();
        tv->tv_sec = microseconds / 1000000;
        tv->tv_usec = microseconds % 1000000;
    }

    return 0;
}

int settimeofday(const struct timeval* tv, const struct timezone* tz)
{
    (void) tz;

    microsecond_overflow_set_check_timer();

    if (tv) {
        uint64_t now = ((uint64_t) tv->tv_sec) * 1000000LL + tv->tv_usec;
        uint64_t since_boot = get_time_since_boot();
        set_boot_time(now - since_boot);
    }

    return 0;
}