#define PIN_SENSOR A0

#define LED_RED 11 
#define LED_GREEN 10
#define LED_BLUE 9

#define WAIT  100
unsigned int ticks = 0;  
unsigned int batteryCapacity = 50000; // could be just local variable in loop().
unsigned int batteryLevel = 0;

//***************************************************

void setup() {
  // put your setup code here, to run once:

     // Initialize serial monitor:
     Serial.begin(9600);

    // Specify pin functions:
     pinMode(LED_RED, OUTPUT);
     pinMode(LED_GREEN, OUTPUT);
     pinMode(LED_BLUE, OUTPUT);

}

//***************************************************

void RGB_color(int red, int green, int blue) {

     // PWM output on digital pins (accepts integer values in interval [0, 255]):
     analogWrite(LED_RED, red);
     analogWrite(LED_GREEN, green);
     analogWrite(LED_BLUE, blue);

}

//***************************************************

double getBatteryPercentage() {

     // Calculate battery charge percentage:
     double percentage;
     percentage = ((double)batteryLevel / (double)batteryCapacity)*100;
     return percentage;
}

//***************************************************

void ShowBatteryPercentage() {

    // Battery percentage is sent to serial monitor and 
    // corresponding LED color is determined and lit:

     double PercentFull;
     int level;

     PercentFull = getBatteryPercentage();


     // Serial Monitor output:

     // Show time elapsed:
     Serial.print(ticks);
     Serial.print(" ms.    Charge at  ");

    // Show percent charge:
    Serial.print(PercentFull); // no new line here.
    Serial.println("%"); // prints "%" and creates a new line.

   
     // Determine LED color, based on battery charge:
     // (red: [0, 25), yellow: [25, 50), cyan: [50, 75), white [75,100), green: 100.]

     level = int(PercentFull / 25.0);
     
     switch (level) {
         case 0: RGB_color(125, 0, 0); break; // red
         case 1: RGB_color(125, 80, 0); break; // yellow
         case 2: RGB_color(0, 125, 125); break; // cyan
         case 3: RGB_color(125, 125, 125); break; // white
     }

} 

//***************************************************

void loop () {
 // put your main code here, to run repeatedly:

     int sensorValue = 0;

     sensorValue = analogRead(PIN_SENSOR);
     batteryLevel += sensorValue;
     ticks += WAIT;

     // Test if it is time to stop charging:
     if(batteryLevel >= batteryCapacity) {
          Serial.print(ticks);
          Serial.print(" ms.    ");
          Serial.println("FULLY CHARGED");
          batteryLevel = batteryCapacity; // prevent battery level to exceed battery capacity.
          ticks = 0;
          RGB_color(0, 125, 0); // LED is green, when battery is fully charged.
          delay(30000); // wait 30 seconds.
     }
     else {
          ShowBatteryPercentage();
     }

     delay(WAIT);
}