//-------------------------------------------------------------------------------
//Libraries
//-------------------------------------------------------------------------------
#include <WiFi.h>
#include <NTPClient.h>
#include <WiFiClientSecure.h>
#include <HTTPClient.h>
#include <base64.h>

//-------------------------------------------------------------------------------
//Global variables
//-------------------------------------------------------------------------------

//-------------------------------------------------------------------------------
// Debug mode? true = yes; false = no
//-------------------------------------------------------------------------------
const bool DEBUG = true;

//-------------------------------------------------------------------------------
// 1000 milliseconds = 1 second
// 60 seconds = 1 minute
// 60 minutes = 1 hour
// 1000 * 60 * 60 = 3_600_000

//-------------------------------------------------------------------------------
// delay time in milliseconds (1h)
//-------------------------------------------------------------------------------
const unsigned long DELAY = 3600000;

//-------------------------------------------------------------------------------
// delay time for debugging in milliseconds (1s)
//-------------------------------------------------------------------------------
const unsigned long DEBUG_DELAY = 1000;

//-------------------------------------------------------------------------------
// value indicating gpio pin
//-------------------------------------------------------------------------------
const int GPIO34 = 34;

//-------------------------------------------------------------------------------
// ADC value
//-------------------------------------------------------------------------------
int iLuxResistorResolution = 10;

float fLuxValue = 0.0;

//-------------------------------------------------------------------------------
// Wifi settings
//-------------------------------------------------------------------------------
const char* WIFI_SSID = "";  // Enter SSID here
const char* WIFI_PASSWORD = "";  //Enter Password here

int iElapsedConnectionTime = 0;

//-------------------------------------------------------------------------------
// Github settings
//-------------------------------------------------------------------------------
const char*  GITHUB_ADDRESS = "api.github.com";

const char* GITHUB_ROOT_CA = \
"-----BEGIN CERTIFICATE-----\n" \
"MIIDrzCCApegAwIBAgIQCDvgVpBCRrGhdWrJWZHHSjANBgkqhkiG9w0BAQUFADBh\n" \
"MQswCQYDVQQGEwJVUzEVMBMGA1UEChMMRGlnaUNlcnQgSW5jMRkwFwYDVQQLExB3\n" \
"d3cuZGlnaWNlcnQuY29tMSAwHgYDVQQDExdEaWdpQ2VydCBHbG9iYWwgUm9vdCBD\n" \
"QTAeFw0wNjExMTAwMDAwMDBaFw0zMTExMTAwMDAwMDBaMGExCzAJBgNVBAYTAlVT\n" \
"MRUwEwYDVQQKEwxEaWdpQ2VydCBJbmMxGTAXBgNVBAsTEHd3dy5kaWdpY2VydC5j\n" \
"b20xIDAeBgNVBAMTF0RpZ2lDZXJ0IEdsb2JhbCBSb290IENBMIIBIjANBgkqhkiG\n" \
"9w0BAQEFAAOCAQ8AMIIBCgKCAQEA4jvhEXLeqKTTo1eqUKKPC3eQyaKl7hLOllsB\n" \
"CSDMAZOnTjC3U/dDxGkAV53ijSLdhwZAAIEJzs4bg7/fzTtxRuLWZscFs3YnFo97\n" \
"nh6Vfe63SKMI2tavegw5BmV/Sl0fvBf4q77uKNd0f3p4mVmFaG5cIzJLv07A6Fpt\n" \
"43C/dxC//AH2hdmoRBBYMql1GNXRor5H4idq9Joz+EkIYIvUX7Q6hL+hqkpMfT7P\n" \
"T19sdl6gSzeRntwi5m3OFBqOasv+zbMUZBfHWymeMr/y7vrTC0LUq7dBMtoM1O/4\n" \
"gdW7jVg/tRvoSSiicNoxBN33shbyTApOB6jtSj1etX+jkMOvJwIDAQABo2MwYTAO\n" \
"BgNVHQ8BAf8EBAMCAYYwDwYDVR0TAQH/BAUwAwEB/zAdBgNVHQ4EFgQUA95QNVbR\n" \
"TLtm8KPiGxvDl7I90VUwHwYDVR0jBBgwFoAUA95QNVbRTLtm8KPiGxvDl7I90VUw\n" \
"DQYJKoZIhvcNAQEFBQADggEBAMucN6pIExIK+t1EnE9SsPTfrgT1eXkIoyQY/Esr\n" \
"hMAtudXH/vTBH1jLuG2cenTnmCmrEbXjcKChzUyImZOMkXDiqw8cvpOp/2PV5Adg\n" \
"06O/nVsJ8dWO41P0jmP6P6fbtGbfYmbW0W5BjfIttep3Sp+dWOIrWcBAI+0tKIJF\n" \
"PnlUkiaY4IBIqDfv8NZ5YBberOgOzW6sRBc4L0na4UU+Krk2U886UAb3LujEV0ls\n" \
"YSEY1QSteDwsOoBrp+uvFRTp2InBuThs4pFsiv9kuXclVzDAGySj4dzp30d8tbQk\n" \
"CAUw7C29C79Fv1C5qfPrmAESrciIxpg0X40KPMbp1ZWVbd4=\n" \
"-----END CERTIFICATE-----\n";

WiFiClientSecure* client;

unsigned long ulGitHubCommitCounter = 0;

String sGithubToken = "";

String sGitHubUser = "";
String sGitHubRepo = "";

//-------------------------------------------------------------------------------
//Data
//-------------------------------------------------------------------------------
String sData = "";

//-------------------------------------------------------------------------------
//Time
//-------------------------------------------------------------------------------
// Define NTP Client to get time
WiFiUDP ntpUDP;
NTPClient timeClient(ntpUDP);

//-------------------------------------------------------------------------------
//Initialization
//-------------------------------------------------------------------------------
void setup()
{
  // Set baud rate to 115200
  Serial.begin(115200);
  delay(100);

  //connect to your local wi-fi network
  WiFi.begin(WIFI_SSID, WIFI_PASSWORD);

  //connect to wi-fi network
  connectToWiFi();

  // Initialize a NTPClient to get time
  timeClient.begin();
  // Set offset time in seconds to adjust for your timezone, for example:
  // GMT +1 = 3600
  // GMT +8 = 28800
  // GMT -1 = -3600
  // GMT 0 = 0
  timeClient.setTimeOffset(3600);
}

//-------------------------------------------------------------------------------
//Main loop
//-------------------------------------------------------------------------------
void loop()
{
  //connect to wi-fi network
  connectToWiFi();

  // store actual time
  String sTime = getTimestamp();
  
  // Store value of gpio34 adc1_ch6
  int iADC1_6_Value = analogRead(GPIO34);
  fLuxValue = calculateLuxValue(iADC1_6_Value);

  // Build data string
  sData = "Value: " + String(fLuxValue) + " lux\nTime: " + sTime;
  Serial.println(sData);

  // send value with timestamp to github repo
  sendPUTRequest(fLuxValue, sTime);
  
  // sleep for value ulDelayTime (default: 1 hour) to save energy
  // avoiding busy wait
  delay(DELAY);
}

//-------------------------------------------------------------------------------
//Functions
//-------------------------------------------------------------------------------

//-------------------------------------------------------------------------------
// Connects to wifi
void connectToWiFi()
{
  //check wi-fi is connected to wi-fi network
  if (WiFi.status() != WL_CONNECTED)
  {
    Serial.println("WiFi disconnected..");
    Serial.println("Trying to reconnect..");
    
    while (WiFi.status() != WL_CONNECTED)
    {
      delay(1000);
      iElapsedConnectionTime++;
      Serial.println("Elapsed connection time: " + iElapsedConnectionTime);
    }
    iElapsedConnectionTime = 0;
    Serial.println("WiFi connected..!");
    Serial.print("Got IP: ");  Serial.println(WiFi.localIP());  
  }
}

//-------------------------------------------------------------------------------
// Gets realtime from WiFi device via udp (specified at beginning)
String getTimestamp()
{
  while(!timeClient.update()) {
    timeClient.forceUpdate();
  }
  
  return timeClient.getFormattedTime();
}

//-------------------------------------------------------------------------------
// Get percentage of ADC value and multiplicate it with one percent of 10 lux
float calculateLuxValue(int iADC)
{
  float fADC1Percent = ((float)4095) / 100;
  float fADCPercent = ((float)iADC) / fADC1Percent;
  float fLux1Percent = ((float)iLuxResistorResolution) / 100;
  
  return fADCPercent * fLux1Percent;
}

//-------------------------------------------------------------------------------
void sendPUTRequest(float fLuxValue, String sTimestamp)
{
  HTTPClient https;

  String sContent = "{\"timestamp\":\"" + sTimestamp + "\",\"value\":\"" + String(fLuxValue) + "\"}";

  String sEncodedFile = base64::encode(sContent);
  
  String sRequestBody = "{\"message\": \"Sensor data " + String(ulGitHubCommitCounter) + "\",\"content\" :\"" + sEncodedFile + "\"}";

  int iContentLength = sRequestBody.length();

  client = new WiFiClientSecure;
  
  client->setCACert(GITHUB_ROOT_CA);

  if (https.begin(*client, "https://api.github.com/repos/" + sGitHubUser + "/" + sGitHubRepo + "/contents/Measurement" + String(ulGitHubCommitCounter) + ".json"))
  {
    https.addHeader("Host", "api.github.com");
    https.addHeader("Content-Type", "application/json");
    https.addHeader("Authorization", ("Bearer " + sGithubToken));
    https.addHeader("Content-Length", String(iContentLength));
    
    // start connection and send HTTP header
    int httpCode = https.PUT(sRequestBody);
      
    // httpCode will be negative on error
    if (httpCode > 0)
    {
      Serial.println("PUT code: " + String(httpCode));
      
      if (httpCode == HTTP_CODE_OK || httpCode == HTTP_CODE_MOVED_PERMANENTLY)
      {
        String payload = https.getString();
        Serial.println(payload);
      }
    }
    else
    {
      Serial.println("PUT failed, error: " + https.errorToString(httpCode).c_str());
    }
      https.end();
  }
  else
  {
    Serial.println("Unable to connect to server");
  }
  ulGitHubCommitCounter++;
}