#include <SoftwareSerial.h>
#include <MP3Player_KT403A.h>

//MP3 Player
SoftwareSerial mp3(2, 3);

//HC-SR04
int Trig = A0;
int Echo = A1;
int duration;
float distance;

//LED
const int LED1 = A2;
const int LED2 = A3;
const int LED3 = A4;
const int LED4 = A5;

void setup() {
  //setup MP3 Player
  mp3.begin(9600);
  Serial.begin(9600);
  while (!Serial);
  delay(100);
  SelectPlayerDevice(0x02);
  SetVolume(0x1E);

  //setup Ultrasonic Sensor(HC-SR04)
  pinMode(Trig, OUTPUT);
  pinMode(Echo, INPUT);

  //LED
  pinMode(LED1, OUTPUT);
  pinMode(LED2, OUTPUT);
  pinMode(LED3, OUTPUT);
  pinMode(LED4, OUTPUT);
}

void loop() {
  //measure Distance
  digitalWrite(Trig, LOW);
  delayMicroseconds(1);
  digitalWrite(Trig, HIGH);
  delayMicroseconds(11);
  digitalWrite(Trig, LOW);
  duration = pulseIn(Echo, HIGH);
  if (duration > 0) {
    distance = duration / 2;
    distance = distance * 340 * 100 / 1000000;
    Serial.print(duration);
    Serial.print(" us ");
    Serial.print(distance);
    Serial.println(" cm");
  } else {
    distance = 400;
  }

  //detect Apologize
  if (distance < 60) {
    SpecifyMusicPlay(1);
    for (int i = 0; i < 100; i++) {
      setLED(true);
      delay(random(10, 50));
      setLED(false);
      delay(random(10, 50));
    }
  }
}

void setLED(boolean state) {
  digitalWrite(LED1, state);
  digitalWrite(LED2, state);
  digitalWrite(LED3, state);
  digitalWrite(LED4, state);
}