/* LwIP SNTP example

   This example code is in the Public Domain (or CC0 licensed, at your option.)

   Unless required by applicable law or agreed to in writing, this
   software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
   CONDITIONS OF ANY KIND, either express or implied.
*/
#include <string.h>
#include <time.h>
#include <sys/time.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/event_groups.h"
#include "esp_system.h"
#include "esp_event.h"
#include "esp_log.h"
#include "esp_attr.h"
#include "esp_sleep.h"
#include "nvs_flash.h"
#include "protocol_examples_common.h"
#include "esp_sntp.h"

static const char *TAG = "example";

#ifndef INET6_ADDRSTRLEN
#define INET6_ADDRSTRLEN 48
#endif

/* Variable holding number of times ESP32 restarted since first boot.
 * It is placed into RTC memory using RTC_DATA_ATTR and
 * maintains its value when ESP32 wakes from deep sleep.
 */
RTC_DATA_ATTR static int boot_count = 0;

static void obtain_time(void);
static void initialize_sntp(void);

#ifdef CONFIG_SNTP_TIME_SYNC_METHOD_CUSTOM
void sntp_sync_time(struct timeval *tv)
{
   settimeofday(tv, NULL);
   ESP_LOGI(TAG, "Time is synchronized from custom code");
   sntp_set_sync_status(SNTP_SYNC_STATUS_COMPLETED);
}
#endif

void time_sync_notification_cb(struct timeval *tv)
{
    ESP_LOGI(TAG, "Notification of a time synchronization event");
}

void app_main(void)
{
    ++boot_count;
    ESP_LOGI(TAG, "Boot count: %d", boot_count);

    time_t now;
    struct tm timeinfo;
    time(&now);
    localtime_r(&now, &timeinfo);
    // Is time set? If not, tm_year will be (1970 - 1900).
    if (timeinfo.tm_year < (2016 - 1900)) {
        ESP_LOGI(TAG, "Time is not set yet. Connecting to WiFi and getting time over NTP.");
        obtain_time();
        // update 'now' variable with current time
        time(&now);
    }
#ifdef CONFIG_SNTP_TIME_SYNC_METHOD_SMOOTH
    else {
        // add 500 ms error to the current system time.
        // Only to demonstrate a work of adjusting method!
        {
            ESP_LOGI(TAG, "Add a error for test adjtime");
            struct timeval tv_now;
            gettimeofday(&tv_now, NULL);
            int64_t cpu_time = (int64_t)tv_now.tv_sec * 1000000L + (int64_t)tv_now.tv_usec;
            int64_t error_time = cpu_time + 500 * 1000L;
            struct timeval tv_error = { .tv_sec = error_time / 1000000L, .tv_usec = error_time % 1000000L };
            settimeofday(&tv_error, NULL);
        }

        ESP_LOGI(TAG, "Time was set, now just adjusting it. Use SMOOTH SYNC method.");
        obtain_time();
        // update 'now' variable with current time
        time(&now);
    }
#endif

    char strftime_buf[64];

    // Set timezone to Eastern Standard Time and print local time
    setenv("TZ", "EST5EDT,M3.2.0/2,M11.1.0", 1);
    tzset();
    localtime_r(&now, &timeinfo);
    strftime(strftime_buf, sizeof(strftime_buf), "%c", &timeinfo);
    ESP_LOGI(TAG, "The current date/time in New York is: %s", strftime_buf);

    // Set timezone to China Standard Time
    setenv("TZ", "CST-8", 1);
    tzset();
    localtime_r(&now, &timeinfo);
    strftime(strftime_buf, sizeof(strftime_buf), "%c", &timeinfo);
    ESP_LOGI(TAG, "The current date/time in Shanghai is: %s", strftime_buf);

    if (sntp_get_sync_mode() == SNTP_SYNC_MODE_SMOOTH) {
        struct timeval outdelta;
        while (sntp_get_sync_status() == SNTP_SYNC_STATUS_IN_PROGRESS) {
            adjtime(NULL, &outdelta);
            ESP_LOGI(TAG, "Waiting for adjusting time ... outdelta = %jd sec: %li ms: %li us",
                        (intmax_t)outdelta.tv_sec,
                        outdelta.tv_usec/1000,
                        outdelta.tv_usec%1000);
            vTaskDelay(2000 / portTICK_PERIOD_MS);
        }
    }

    const int deep_sleep_sec = 10;
    ESP_LOGI(TAG, "Entering deep sleep for %d seconds", deep_sleep_sec);
    esp_deep_sleep(1000000LL * deep_sleep_sec);
}

static void obtain_time(void)
{
    ESP_ERROR_CHECK( nvs_flash_init() );
    ESP_ERROR_CHECK(esp_netif_init());
    ESP_ERROR_CHECK( esp_event_loop_create_default() );

    /**
     * NTP server address could be aquired via DHCP,
     * see following menuconfig options:
     * 'LWIP_DHCP_GET_NTP_SRV' - enable STNP over DHCP
     * 'LWIP_SNTP_DEBUG' - enable debugging messages
     *
     * NOTE: This call should be made BEFORE esp aquires IP address from DHCP,
     * otherwise NTP option would be rejected by default.
     */
#if LWIP_DHCP_GET_NTP_SRV
    esp_sntp_servermode_dhcp(1);      // accept NTP offers from DHCP server, if any
#endif

    /* This helper function configures Wi-Fi or Ethernet, as selected in menuconfig.
     * Read "Establishing Wi-Fi or Ethernet Connection" section in
     * examples/protocols/README.md for more information about this function.
     */
    ESP_ERROR_CHECK(example_connect());

    initialize_sntp();

    // wait for time to be set
    time_t now = 0;
    struct tm timeinfo = { 0 };
    int retry = 0;
    const int retry_count = 15;
    while (sntp_get_sync_status() == SNTP_SYNC_STATUS_RESET && ++retry < retry_count) {
        ESP_LOGI(TAG, "Waiting for system time to be set... (%d/%d)", retry, retry_count);
        vTaskDelay(2000 / portTICK_PERIOD_MS);
    }
    time(&now);
    localtime_r(&now, &timeinfo);

    ESP_ERROR_CHECK( example_disconnect() );
}

static void initialize_sntp(void)
{
    ESP_LOGI(TAG, "Initializing SNTP");
    esp_sntp_setoperatingmode(ESP_SNTP_OPMODE_POLL);

/*
 * If 'NTP over DHCP' is enabled, we set dynamic pool address
 * as a 'secondary' server. It will act as a fallback server in case that address
 * provided via NTP over DHCP is not accessible
 */
#if LWIP_DHCP_GET_NTP_SRV && SNTP_MAX_SERVERS > 1
    esp_sntp_setservername(1, "pool.ntp.org");

#if LWIP_IPV6 && SNTP_MAX_SERVERS > 2          // statically assigned IPv6 address is also possible
    ip_addr_t ip6;
    if (ipaddr_aton("2a01:3f7::1", &ip6)) {    // ipv6 ntp source "ntp.netnod.se"
        esp_sntp_setserver(2, &ip6);
    }
#endif  /* LWIP_IPV6 */

#else   /* LWIP_DHCP_GET_NTP_SRV && (SNTP_MAX_SERVERS > 1) */
    // otherwise, use DNS address from a pool
    esp_sntp_setservername(0, CONFIG_SNTP_TIME_SERVER);

    esp_sntp_setservername(1, "pool.ntp.org");     // set the secondary NTP server (will be used only if SNTP_MAX_SERVERS > 1)
#endif

    sntp_set_time_sync_notification_cb(time_sync_notification_cb);
#ifdef CONFIG_SNTP_TIME_SYNC_METHOD_SMOOTH
    sntp_set_sync_mode(SNTP_SYNC_MODE_SMOOTH);
#endif
    esp_sntp_init();

    ESP_LOGI(TAG, "List of configured NTP servers:");

    for (uint8_t i = 0; i < SNTP_MAX_SERVERS; ++i){
        if (esp_sntp_getservername(i)){
            ESP_LOGI(TAG, "server %d: %s", i, esp_sntp_getservername(i));
        } else {
            // we have either IPv4 or IPv6 address, let's print it
            char buff[INET6_ADDRSTRLEN];
            ip_addr_t const *ip = esp_sntp_getserver(i);
            if (ipaddr_ntoa_r(ip, buff, INET6_ADDRSTRLEN) != NULL)
                ESP_LOGI(TAG, "server %d: %s", i, buff);
        }
    }
}