#include <Arduino.h>
#include <U8g2lib.h>
#include <Wire.h>

U8G2_SSD1306_128X64_NONAME_F_SW_I2C u8g2(U8G2_R0, /* clock=*/ SCL, /* data=*/ SDA, /* reset=*/ U8X8_PIN_NONE);   // All Boards without Reset of the Display

#define FIRST_ROW_Y 16
#define FIRST_ROW_X 16
#define BOX_H 38

//Hardware pin definitions
const int UVOUT = A0; //Output from the sensor
const int REF_3V3 = A1; //3.3V power on the Arduino board
const int VBATT = A2; //Battery voltage

float maxUV = 0; //Max UV index read


void setup()
{ 
  pinMode(UVOUT, INPUT);
  pinMode(REF_3V3, INPUT);
  pinMode(VBATT, INPUT);
 
  u8g2.begin();

}

void loop()
{
  u8g2.firstPage();
  do {
    int uvLevel = averageAnalogRead(UVOUT);
    int refLevel = averageAnalogRead(REF_3V3);

    //Use the 3.3V power pin as a reference to get a very accurate output value from sensor
    float outputVoltage = 3.3 / refLevel * uvLevel;

    float uvIntensity = mapfloat(outputVoltage, 0.99, 2.6, 0.0, 15.0); //Convert the voltage to a UV intensity level

    readBattery();
    if (maxUV < uvIntensity) {
        maxUV = uvIntensity;
      }
    u8g2.drawFrame(0,FIRST_ROW_Y+1,128,BOX_H);
    u8g2.setFont(u8g2_font_logisoso18_tf);

    //Instant UV
    u8g2.setCursor(10,40);
    u8g2.print(uvIntensity);
    //UV Max
    u8g2.setCursor(70,40);
    u8g2.print(maxUV);

    u8g2.setFont(u8g2_font_u8glib_4_tf);
    u8g2.setCursor(10,52); u8g2.print(F("INSTANT"));
    u8g2.setCursor(75,52); u8g2.print(F("MAXIMUM"));

    showUVCategory();
    u8g2.setCursor(88,64); u8g2.print(F("F.Marzocca"));
    
   } while ( u8g2.nextPage() );
  delay(200);
}

// Reads maxUV and prints the UV category
void showUVCategory() {
  char strCat[12];

  byte categ = (byte)(maxUV+0.5);  //round up
  if ((categ >= 0) && (categ < 3)) {
    strcpy(strCat, "LOW"); 
  } else if ((categ >= 3) && (categ < 6)) {
    strcpy(strCat, "MODERATE");
  } else if ((categ >= 6) && (categ < 8)) {
    strcpy(strCat, "HIGH !");
  } else if ((categ >= 8) && (categ < 10)) {
     strcpy(strCat, "VERY HIGH!");
  } else if (categ >= 11) {
    strcpy(strCat, "EXTREME!");
  }
  
   u8g2.setCursor(0,64);
   u8g2.print(strCat);
  
}

//Takes an average of readings on a given pin
//Returns the average
int averageAnalogRead(int pinToRead)
{
  byte numberOfReadings = 16;
  unsigned int runningValue = 0; 

  for(int x = 0 ; x < numberOfReadings ; x++)
    runningValue += analogRead(pinToRead);
  runningValue /= numberOfReadings;

  return(runningValue);  
}

//The Arduino Map function but for floats
//From: http://forum.arduino.cc/index.php?topic=3922.0
float mapfloat(float x, float in_min, float in_max, float out_min, float out_max)
{
  return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
}

void readBattery() {
   long battery = readBattVcc(); 
   long VccMin = 2300; //Battery minimum voltage read on Vcc
   byte batteryBar; //Battery progress bar
   int barStep = 140; //step for battery progress bar (235)

   batteryBar = (battery - VccMin)/barStep;
   
       //battery icon
    u8g2.setFont(u8g2_font_open_iconic_embedded_2x_t);
    u8g2.drawGlyph(1, FIRST_ROW_Y, 73 );
    
    // battery status cursor
    u8g2.setFont(u8g2_font_open_iconic_play_1x_t);
    for (byte i=1; i<=batteryBar; i++) {
       u8g2.drawGlyph( 128-9*i,FIRST_ROW_Y-4,75);
    }
    
    // battery voltage
    u8g2.setFont(u8g2_font_freedoomr10_tu);
    u8g2.setCursor(25, FIRST_ROW_Y);
    u8g2.print(float(battery)/1000, 3);
 
}


long readBattVcc()
{
    int sum=0;
    int sample_count=0;
    long voltage= 0;
    #define NUM_SAMPLES 10
    // take a number of analog samples and add them up
    while (sample_count < NUM_SAMPLES) {
        sum += analogRead(VBATT);
        sample_count++;
        delay(2);
    }
        // calculate the voltage
    // use 5000 for a 5.0V ADC reference voltage
    // 5020V is the calibrated reference voltage (in millivolts) for my project
    voltage = ((long)sum / (long)NUM_SAMPLES * 5020) / 1024.0;
    return voltage; //Vbattery in millivolts
}