#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <RTClib.h>

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64 
#define buttonPin 2
const int speakerPin = A3;

Adafruit_SSD1306 oled(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);
RTC_DS1307 rtc;

String displayTime;
DateTime timerStart;
int mode = 0;
int hour, minute, second;
int timerHour, timerMinute, timerSecond, pauseSecond;
int alarmHour, alarmMinute;
bool timerToggle = false;
bool buttonPressed = false;

void setup() {
  Serial.begin(9600);
  //Set pinmodes for button and speaker, attach interupt to button
  pinMode(buttonPin, INPUT_PULLUP);
  pinMode(speakerPin, OUTPUT);
  attachInterrupt(0, buttonPress, FALLING);
  //Check OLED connection
  if (!oled.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("SSD1306 allocation failed"));
    while (true);
  }

  delay(1000);    
  //Setuo OLED display     
  oled.clearDisplay();
  oled.setTextSize(1);         
  oled.setTextColor(WHITE);     
  oled.setCursor(0, 10);        
  //Check RTC connection
  if (! rtc.begin()) {
    Serial.println("Couldn't find RTC");
    Serial.flush();
    while (true);
  }
  //Setup clock, timer
  rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
  timerStart = rtc.now();
  timerHour, timerMinute, timerSecond, pauseSecond, alarmHour, alarmMinute = 0;
  //Print System instructions to serial
  Serial.println("----Serial Open----\n");
  Serial.println("System Options : ");
  Serial.println("    Mode 1: Clock");
  Serial.println("    Mode 2: Timer");
  Serial.println("    Mode 3: Alarm");
  Serial.println("\nSystem Instructions : ");
  Serial.println("    -- Hold Button for >1s to change mode");
}

void loop() {

  //Check if button interrupt has executed (buttonPressed == true)
  if (buttonPressed) {
    int count = 0;
    bool buttonState = 0;

    Serial.println("(Start Press)");
    //While button is pressed, increase count/read button input
    while (!buttonState){
      count += 1;
      buttonState = digitalRead(buttonPin);
      delay(20);
    }
    //Calculate duration of press, change mode if > 1s
    float duration = count*20.00/1000;
    Serial.print("(End press. Press time: ");
    Serial.print(duration);
    Serial.println(" s)\n");
    if (duration >= 1){
      timerToggle = false;
      changeMode();
    }
    //Pause timer if mode is Timer (1) and press is  < 1s
    else if (duration < 1 && mode == 1) {
      pauseTimer();
      if (timerToggle) { Serial.println(">> Timer Start"); }
      else { Serial.println(">> Timer Pause"); }
    }
    //Set alarm minute if mode is Alarm (2) and press is  < 1s
    else if (duration < 1 && mode == 2) {
      alarmMinute +=1;
      if (alarmMinute == 60) { alarmMinute = 0; }
    }
    //Set alarm hour if mode is Alarm (3) and press is  < 1s
    else if (duration < 1 && mode == 3) {
      alarmHour +=1;
      if (alarmHour == 24) { alarmHour = 0; }
    }
    //Attempt to halt the flow of time if mode if Clock (1) and press is < 1s
    else { Serial.println(">> Cannot stop time... :( ");}
   
    delay(200);
    //Turn interrupts back on
    interrupts();
    buttonPressed = false;
  }

  //Display time on OLED depending on mode
  displayTime = getTime(mode);
  oledDisplayCenter(displayTime);
  //Activate alarm if set alarm time equals real time
  if (hour == alarmHour && minute == alarmMinute){
    soundAlarm();
  }

}

//Function to display text in centre of OLED
void oledDisplayCenter(String text) {
  int16_t x1;
  int16_t y1;
  uint16_t width;
  uint16_t height;

  //Print text to OLED
  oled.getTextBounds(text, 0, 0, &x1, &y1, &width, &height);
  oled.clearDisplay(); 
  oled.setCursor((SCREEN_WIDTH - width) / 2, (SCREEN_HEIGHT - height) / 2);
  oled.println(text); 
  oled.display();

}

//Function to register interrupt button press
void buttonPress(){
  buttonPressed = true;
  delay(20);
  //Stops interrupts to prevent interference during hold
  noInterrupts();
}

//Function to calculate and return time/timer output as String
String getTime(int mode){

  DateTime now = rtc.now();
  String time;

  //Change output depending on mode setting. 0 = Clock, 1 = Timer,
  //  2 = Set Alarm Minute, 3 = Set Alarm Hour
  switch (mode) {
    case 0:
      hour = now.hour();
      minute = now.minute();
      second = now.second();

      time = "";
      time += hour;
      time += ':';
      time += minute;
      time += ':';
      time += second;
      break;
      
    case 1:
      //Calculate seconds passed since timer started (timerToggle = true)
      if (timerToggle){
        timerSecond = now.second()-timerStart.second()+pauseSecond;
        //Add to minutes at 60 seconds, reset seconds
        if (timerSecond < 0) { timerSecond += 60; }
        if (timerSecond > 59) {
          timerStart = rtc.now(); 
          pauseSecond = 0;
          timerMinute += 1; 
        }
        //Add to hours at 60 minutes, reset minutes
        if (timerMinute < 0) { timerMinute += 60; }
        if (timerMinute > 59) {
          timerMinute = 0;
          timerHour += 1;
        }
      }
      //Create string from timer values
      time = "";
      time += timerHour;
      time += ':';
      time += timerMinute;
      time += ':';
      time += timerSecond; 
      break;

    case 2:
      //Create string from alarm values
      time = "";
      time += alarmHour;
      time += ':';
      time += alarmMinute;
      break;
    case 3:
      time = "";
      time += alarmHour;
      time += ':';
      time += alarmMinute;
      break;
  }

  return time;
}

//Function to iterate through modes then prints action to serial and OLED
void changeMode() {
  mode += 1;
  if (mode > 3) { mode = 0; }
  delay(50);
  if ( mode == 0 ){
    oledDisplayCenter("Alarm Set!");
    Serial.println("\nAlarm Set!");
    Serial.println("\nAlarm Instructions : ");
    Serial.println("    -- Hold Button for >1s for Timer");
    oledDisplayCenter("Mode Changed: Clock");
    Serial.println("Mode Changed: Clock");
  }
  if ( mode == 1 ){
    resetTimer();
    Serial.println("\nTimer Instructions : ");
    Serial.println("    -- Hold Button for >1s to Set Alarm");
    Serial.println("    -- Short press to start/stop timer\n");
    oledDisplayCenter("Mode Changed: Timer");
    Serial.println("Mode Changed: Timer");
  }
  if ( mode == 2 ){
    Serial.println("\nAlarm Instructions : ");
    Serial.println("    -- Hold Button for >1s to set hour");
    Serial.println("    -- Short press to set minute\n");
    oledDisplayCenter("Mode Changed: Set Alarm Minute");
    Serial.println("Mode Changed: Set Alarm Minute");
  }
  if ( mode == 3 ){
    Serial.println("\nAlarm Instructions : ");
    Serial.println("    -- Hold Button for >1s to see Clock");
    Serial.println("    -- Short press to set minute\n");
    oledDisplayCenter("Mode Changed: Set Alarm Hour");
    Serial.println("Mode Changed: Set Alarm Hour");
  }
  delay(100);
}

//Function to pause timer
void pauseTimer() {
  if (timerToggle) { 
    pauseSecond = timerSecond;
    timerToggle = false; 
  }
  else { timerToggle = true; }
  timerStart = rtc.now();
}

//Function to reset timer
void resetTimer() {
  timerHour = 0;
  timerMinute = 0;
  timerSecond = 0;
  pauseSecond = 0;
}

//Function to activate the buzzer for alarm
void soundAlarm() {

  for (int i = 0; i < 10; i++) {
    tone(speakerPin, 300, 100);
    delay(100);
    tone(speakerPin, 800, 100);
     delay(100);
    tone(speakerPin, 1300, 100);
     delay(100);
  }
}