#include <Wire.h>
#include "Adafruit_SGP30.h"

#define TCAADDR 0x70
Adafruit_SGP30 sgp;



extern "C" {
#include "utility/twi.h"  // from Wire library, so we can do bus scanning
}

void tcaselect(uint8_t i) {
  if (i > 7) return;

  Wire.beginTransmission(TCAADDR);
  Wire.write(1 << i);
  Wire.endTransmission();
}


/* return absolute humidity [mg/m^3] with approximation formula
* @param temperature [°C]
* @param humidity [%RH]
*/
uint32_t getAbsoluteHumidity(float temperature, float humidity) {
    // approximation formula from Sensirion SGP30 Driver Integration chapter 3.15
    const float absoluteHumidity = 216.7f * ((humidity / 100.0f) * 6.112f * exp((17.62f * temperature) / (243.12f + temperature)) / (273.15f + temperature)); // [g/m^3]
    const uint32_t absoluteHumidityScaled = static_cast<uint32_t>(1000.0f * absoluteHumidity); // [mg/m^3]
    return absoluteHumidityScaled;
}

void setup() {
    while (!Serial);
    delay(1000);
    Wire.begin();

  Serial.begin(115200);
  Serial.println("SGP30 test");

  tcaselect(0); //Select sensor... using 0 and 1 at the moment

  if (! sgp.begin()){
    Serial.println("Sensor not found :(");
    while (1);
  }
}

int counter = 0;


void loop() {

  // If you have a temperature / humidity sensor, you can set the absolute humidity to enable the humditiy compensation for the air quality signals
  //float temperature = 22.1; // [°C]
  //float humidity = 45.2; // [%RH]
  //sgp.setHumidity(getAbsoluteHumidity(temperature, humidity));

  if (! sgp.IAQmeasure()) {
    Serial.println("Measurement failed");
    return;
  }
  tcaselect(0); //seems to be ignoring this and reading second one no matter what

    uint16_t TVOC_base, eCO2_base;
    if (! sgp.getIAQBaseline(&eCO2_base, &TVOC_base)) {
      Serial.println("Failed to get baseline readings");
      return;
    }

  Serial.print("Sens 0 TVOC "); Serial.print(sgp.TVOC); Serial.print(" ppb \t");
  Serial.print("eCO2 "); Serial.print(sgp.eCO2); Serial.println(" ppm");
  delay(500);

  tcaselect(1);

    if (! sgp.getIAQBaseline(&eCO2_base, &TVOC_base)) {
      Serial.println("Failed to get baseline readings");
      return;
    }

  Serial.print("Sens 1 TVOC "); Serial.print(sgp.TVOC); Serial.print(" ppb \t");
  Serial.print("eCO2 "); Serial.print(sgp.eCO2); Serial.println(" ppm");
  delay(500);

  counter++;
  if (counter == 30) {
    counter = 0;

//    uint16_t TVOC_base, eCO2_base;
    if (! sgp.getIAQBaseline(&eCO2_base, &TVOC_base)) {
      Serial.println("Failed to get baseline readings");
      return;
    }
    Serial.print("****Baseline values: eCO2: 0x"); Serial.print(eCO2_base, HEX);
    Serial.print(" & TVOC: 0x"); Serial.println(TVOC_base, HEX);
  }
}