#include <AccelStepper.h>

int targets [10];
int moveIndex = 0;
int targetIndex = 0;
int currentAngle = 0;
AccelStepper stepper(AccelStepper::DRIVER, 4, 3);

void setup() {
  stepper.setMaxSpeed(250);
  stepper.setAcceleration(20);

  TCCR1A = 0;
  TCCR1B = 0;
  TCCR1B |= (1 << CS10);
  TIMSK1 |= (1 << TOIE1);

  Serial.begin(9600);
  Serial.println(F("Enter an angle between 0 and 360 degrees."));
}

void zeroStepper() {
  long zero = stepper.currentPosition();
  zero = zero >= 360 ? zero - 360 : zero < 0 ? zero + 360 : zero;
  stepper.setCurrentPosition(zero);
}

void moveStepper(int angle) {
  if (angle == currentAngle) {
    return;
  }
  
  angle = angle > 360 ? 360 : angle < 0 ? 0 : angle;
  int target = angle;

  if (currentAngle > angle) {
    zeroStepper();
    if (currentAngle - angle > (360.0 - currentAngle) + angle) {
      target = stepper.currentPosition() > 0 ? target + 360 : target;
    }
  }
  else {
    zeroStepper();
    if (angle - currentAngle > (360.0 - angle) + currentAngle) {
      target = (360.0 - angle) * -1.0;
    }
  }

  currentAngle = angle;
  stepper.moveTo(target);
}

ISR(TIMER1_OVF_vect) {
  stepper.run();
}

void loop() {
  if (Serial.available()) {
    int angle = Serial.parseInt();
    while (Serial.available()) {
      Serial.read();
    }
    targets[targetIndex] = angle;
    targetIndex++;
  }

  if (!stepper.isRunning() && moveIndex < targetIndex) {
    moveStepper(targets[moveIndex]);
    if (moveIndex < 9) {
      moveIndex++;
    }
    else {
      targetIndex = 0;
      moveIndex = 0;
    }
  }
}