#include <ArduinoJson.h>

WiFiClient wifiClient;

void SetTimeZone(unsigned long currentUtcEpochTime)
{
  const char* timeZoneServer = "api.timezonedb.com";
  String timeZoneUrl = "/v2/get-time-zone?key=XXXXXXXXX&format=json&by=zone&zone=Europe/Berlin";

  const unsigned long HTTP_TIMEOUT = 10000;                 // max respone time from server
  const size_t MAX_CONTENT_SIZE = 2048;                     // max size of the HTTP response

  const unsigned long START_YEAR_2036 = 2082754800;

  //check if time is valid (> 1.1.1970) and before 1.1.2036 (NTP Bug of 7.2.2036)
  if ((currentUtcEpochTime > (24*3600)) && (currentUtcEpochTime < START_YEAR_2036))
  {
    timeZoneUrl += "&time=";
    timeZoneUrl += String(currentUtcEpochTime);
  }

  if (!wifiClient.connect(timeZoneServer, 80)) {
    Serial.println("*Wortuhr: Could not connect to time zone server");
    wifiClient.stop();
    return;
  }
  
  wifiClient.print("GET ");
  wifiClient.print(timeZoneUrl);
  wifiClient.println(" HTTP/1.0");
  wifiClient.print("Host: ");
  wifiClient.println(timeZoneServer);
  wifiClient.println("Connection: close");
  wifiClient.println();

  // Skip HTTP headers so that we are at the beginning of the response's body
  // HTTP headers end with an empty line
  char endOfHeaders[] = "\r\n\r\n";

  wifiClient.setTimeout(HTTP_TIMEOUT);
  bool ok = wifiClient.find(endOfHeaders);

  if (!ok) {
    Serial.println("*Wortuhr: No response or invalid response from Timezone server!");
    wifiClient.stop();
    return;
  }

  //Parse JSON response
  const size_t bufferSize = JSON_OBJECT_SIZE(13) + 260;
  DynamicJsonBuffer jsonBuffer(bufferSize);

  //const char* json = "{\"status\":\"OK\",\"message\":\"\",\"countryCode\":\"DE\",\"countryName\":\"Germany\",\"zoneName\":\"Europe/Berlin\",\"abbreviation\":\"CEST\",\"gmtOffset\":7200,\"dst\":\"1\",\"dstStart\":1521939600,\"dstEnd\":1540688399,\"nextAbbreviation\":\"CET\",\"timestamp\":1526505696,\"formatted\":\"2018-05-16 21:21:36\"}";

  JsonObject& root = jsonBuffer.parseObject(wifiClient);

  const char* status = root["status"]; // "OK"
  //const char* message = root["message"]; // ""
  //const char* countryCode = root["countryCode"]; // "DE"
  //const char* countryName = root["countryName"]; // "Germany"
  //const char* zoneName = root["zoneName"]; // "Europe/Berlin"
  //const char* abbreviation = root["abbreviation"]; // "CEST"
  long gmtOffset = root["gmtOffset"]; // 7200
  //const char* dst = root["dst"]; // "1"
  //long dstStart = root["dstStart"]; // 1521939600
  long dstEnd = root["dstEnd"]; // 1540688399
  //const char* nextAbbreviation = root["nextAbbreviation"]; // "CET"
  //long timestamp = root["timestamp"]; // 1526505696
  //const char* formatted = root["formatted"]; // "2018-05-16 21:21:36"

  if (String(status) == "OK")
  {
    currentTimeZone = gmtOffset;
    if (dstEnd > 0) timeZoneValidUntil = dstEnd;
    timeClient.setTimeOffset(currentTimeZone);
    doTimeRepaint = true; //do a repaint immediately
    Serial.println("*Wortuhr: Saved time zone: " + String(currentTimeZone) + "s (valid until epoch time: " + String(timeZoneValidUntil) + ")");
  }
  else
  {
    Serial.println("*Wortuhr: Timezone json invalid! (Status: '" + String(status) + "'");
  }
  wifiClient.stop();

}