time zone support

clock.cpp

@@ -1,14 +1,20 @@
 #include "clock.h"
 
 #include <ESP8266WiFi.h>
+#include <ESP8266HTTPClient.h>
+#include <WiFiClient.h>
 #include <DS1307RTC.h>
+#include <jsonlib.h>
+#include <stdlib.h>
 
 Clock::Clock(ClockSettings const& settings):
     m_settings(settings),
     m_last_NTP_check(0),
     m_NTP_waiting_for_response(false),
     m_UDP(),
-    m_NTP_ip()
+    m_NTP_ip(),
+    m_TZ_offset(0),
+    m_next_TZ_check(0)
 {
     setSyncProvider(RTC.get);
     m_UDP.begin(NTP_PORT);
@@ -17,6 +23,7 @@ Clock::Clock(ClockSettings const& settings):
 void Clock::internet_update()
 {
     ntp_update();
+    tz_update();
 }
 
 void Clock::ntp_update()
@@ -87,3 +94,71 @@ void Clock::ntp_checkResponse()
     Serial.print("Time: ");
     Serial.println(UNIX_time);
 }
+
+void Clock::tz_update()
+{
+    //it's no use to do anything before we have the right UTC time
+    if(timeStatus() != timeSet)
+        return;
+
+    //rate limiting
+    if(now() <= m_next_TZ_check)
+        return;
+
+    Serial.println("Updating timezones");
+
+    WiFiClient client;
+    HTTPClient http;
+
+    String url = "http://api.timezonedb.com/v2.1/get-time-zone?key=";
+    url += m_settings.api_key();
+    url += "&format=json&by=zone&zone=";
+    url += m_settings.time_zone();
+
+    Serial.print("Connecting to \"");
+    Serial.print(url);
+    Serial.println("\"");
+
+    if(!http.begin(client, url))
+    {
+        Serial.println("Cannot connect");
+        m_next_TZ_check = now() + TZ_RETRY_COOLDOWN;
+    }
+    else
+    {
+        int response = http.GET();
+        if(response <= 0)
+        {
+            Serial.print("Error: ");
+            Serial.println(http.errorToString(response));
+            m_next_TZ_check = now() + TZ_RETRY_COOLDOWN;
+        }
+        else if(response == HTTP_CODE_OK || response == HTTP_CODE_MOVED_PERMANENTLY)
+        {
+            String payload = http.getString();
+
+            int offset = jsonExtract(payload, "gmtOffset").toInt();
+            String end = jsonExtract(payload, "zoneEnd");
+
+            time_t const zoneEnd = atoll(end.c_str());
+
+            Serial.print("offset: ");
+            Serial.println(offset);
+            Serial.print("Zone end: ");
+            Serial.println(zoneEnd);
+
+            m_TZ_offset = offset;
+
+            time_t const time = now();
+            if(time >= zoneEnd)
+                m_next_TZ_check = time + TZ_RETRY_COOLDOWN;
+            else if(zoneEnd - time > TZ_RETRY_COOLDOWN)
+                m_next_TZ_check = zoneEnd - TZ_RETRY_COOLDOWN;
+            else
+                m_next_TZ_check = zoneEnd;
+
+            Serial.print("next check: ");
+            Serial.println(m_next_TZ_check);
+        }
+    }
+}

clock.h

@@ -7,6 +7,7 @@
 
 unsigned int const NTP_BUFFER_SIZE = 48;
 unsigned int const NTP_PORT = 123;
+unsigned int const TZ_RETRY_COOLDOWN = 60;
 
 class Clock
 {
@@ -20,6 +21,8 @@ class Clock
         void ntp_ask();
         void ntp_checkResponse();
 
+        void tz_update();
+
     protected:
         ClockSettings const& m_settings;
 
@@ -29,6 +32,9 @@ class Clock
         WiFiUDP   m_UDP;
         IPAddress m_NTP_ip;
         uint8_t   m_NTP_buffer[NTP_BUFFER_SIZE];
+
+        int       m_TZ_offset;
+        time_t    m_next_TZ_check;
 };
 
 #endif //CLOCK_H

clock_settings.cpp

@@ -5,13 +5,17 @@
 #include <limits.h>
 
 ClockSettings::ClockSettings():
-    m_server(nullptr)
+    m_server(nullptr),
+    m_api_key(nullptr),
+    m_time_zone(nullptr)
 {
 }
 
 ClockSettings::~ClockSettings()
 {
     delete[] m_server;
+    delete[] m_api_key;
+    delete[] m_time_zone;
 }
 
 void ClockSettings::add_info(char const* key, char const* val)
@@ -41,6 +45,20 @@ void ClockSettings::add_info(char const* key, char const* val)
             m_cooldown *= 60;
         }
     }
+    else if(string_equals(key, "key"))
+    {
+        if(m_api_key != nullptr)
+            delete[] m_api_key;
+
+        m_api_key = val;
+    }
+    else if(string_equals(key, "zone"))
+    {
+        if(m_time_zone != nullptr)
+            delete[] m_time_zone;
+
+        m_time_zone = val;
+    }
     else
         delete[] val;
 

clock_settings.h

@@ -11,10 +11,14 @@ class ClockSettings
 
         inline char const*const server() const {return m_server;}
         inline unsigned int cooldown() const {return m_cooldown;}
+        inline char const*const api_key() const {return m_api_key;}
+        inline char const*const time_zone() const {return m_time_zone;}
 
     protected:
         char const* m_server;
         unsigned int m_cooldown;
+        char const* m_api_key;
+        char const* m_time_zone;
 };
 
 #endif //CLOCK_SETTINGS_H

readme.md

@@ -14,6 +14,8 @@ The time is kept using a real-time clock, coupled with an NTP connection to avoi
 TODO
 
 ##Software installation
+Pre-requisite: a [TimeZone database](https://timezonedb.com) API key is needed to convert from UTC to the local timezone
+
 1. Install the [Arduino IDE](https://www.arduino.cc/en/Main/Software)
 2. Install the [ESP8266 arduino extension](https://github.com/esp8266/Arduino)
     1. add `https://arduino.esp8266.com/stable/package_esp8266com_index.json` to the "Additional Boards Manager URLs" field in the IDE's preferences

settings.ini

@@ -13,10 +13,16 @@
 ssid=WIFI_SSID
 password=WIFI_PASSWORD
 
-; Configuration of the NTP connection.
+; Configuration of the clock (NTP & time zones)
 ; Since the RTC module is here to do most of the time keeping,
 ; the NTP requests can be quite far in between
+; The timezone information is provided by https://timezonedb.com
+; which provides an easy API instead of the weirdly-formatted IANA database
 [clock]
 server=pool.ntp.org
 ; time between NTP requests, in minutes
 cooldown=15
+; https://timezonedb.com API key
+key=API_KEY
+; timezone name (see https://en.wikipedia.org/wiki/List_of_tz_database_time_zones)
+zone=Europe/Paris