#include <U8g2lib.h>
U8G2_SSD1306_128X64_NONAME_F_HW_I2C u8g2(U8G2_R0, /* reset=*/U8X8_PIN_NONE);
//U8G2_SH1106_128X64_NONAME_F_HW_I2C u8g2(U8G2_R0, /* reset=*/U8X8_PIN_NONE);

#include <Wire.h>  // must be included here so that Arduino library object file references work
#include <RtcDS3231.h>
RtcDS3231<TwoWire> Rtc(Wire);
RtcDateTime now;

volatile bool interrupt_2 = false;
volatile unsigned long bounce_2 = 0;
volatile unsigned long lpress_2 = 0;

volatile bool interrupt_3 = false;
volatile unsigned long bounce_3 = 0;
volatile unsigned long lpress_3 = 0;

void buttons_interrupt_handler_2() {

  interrupt_2 = true;
  bounce_2 = millis();
  lpress_2 = millis();
}

void buttons_interrupt_handler_3() {

  interrupt_3 = true;
  bounce_3 = millis();
  lpress_3 = millis();
}

void setup() {
  Serial.begin(9600);

  pinMode(2, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(2), buttons_interrupt_handler_2, FALLING);
  pinMode(3, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(3), buttons_interrupt_handler_3, FALLING);

  Rtc.Begin();

  //RtcDateTime compiled = RtcDateTime(__DATE__, __TIME__);
  //Rtc.SetDateTime(compiled + 0*60*60 + 8);

  //Rtc.SetDateTime(RtcDateTime(2018, 1, 17, 7, 53, 00));


  rtc_set();

}

void loop() {

  static bool init = true;

  if (init) {
    init = false;
    u8g2.initDisplay();
    u8g2.setContrast(30);
    u8g2.setFlipMode(0);
    u8g2.setPowerSave(0);
  }

  now = Rtc.GetDateTime();
  bool rtclock_err = !Rtc.IsDateTimeValid();

  static char date[11], time[9];
  snprintf(date, 11, "%02u-%02u-%04u", now.Month(), now.Day(), now.Year());
  snprintf(time, 9, "%02u:%02u:%02u", now.Hour(), now.Minute(), now.Second());
  u8g2.clearBuffer();
  u8g2.drawRFrame(0, 0, 128, 64, 5);
  u8g2.setFont(u8g2_font_t0_22b_mf);
  u8g2.drawStr(9, 18, date);
  u8g2.drawStr(20, 38, time);
  if (!rtclock_err) u8g2.drawStr(53, 58, "OK");
  else u8g2.drawStr(26, 58, "rtc err");
  u8g2.sendBuffer();
  delay(300);
}

int pin2int() {

  int impulse = 0;
  static bool longpress = false;

  noInterrupts();

  if (digitalRead(2)) lpress_2 = millis();
  else bounce_2 = millis();

  if (interrupt_2) {
    if (millis() - bounce_2 > 20) {
      interrupt_2 = false;
      impulse = !longpress; //impulse shortpress
      longpress = false;
    }
  }

  if (!longpress) {
    if (millis() - lpress_2 > 750) {
      longpress = true;
      lpress_2 = millis();
      impulse = 2; //impulse longpress(once)

    }
  }

  if (longpress) {
    if (millis() - lpress_2 > 500) {
      lpress_2 = millis();
      impulse = 3; //impulse longpress(repeat)
    }
  }

  interrupts();

  return impulse;
}

int pin3int() {

  int impulse = 0;
  static bool longpress = false;

  noInterrupts();

  if (digitalRead(3)) lpress_3 = millis();
  else bounce_3 = millis();

  if (interrupt_3) {
    if (millis() - bounce_3 > 20) {
      interrupt_3 = false;
      impulse = !longpress; //impulse shortpress
      longpress = false;
    }
  }

  if (!longpress) {
    if (millis() - lpress_3 > 750) {
      longpress = true;
      lpress_3 = millis();
      impulse = 2; //impulse longpress(once)
    }
  }

  if (longpress) {
    if (millis() - lpress_3 > 500) {
      lpress_3 = millis();
      impulse = 3; //impulse longpress(repeat)
    }
  }

  interrupts();

  return impulse;
}

void rtc_set() {

  RtcDateTime now = Rtc.GetDateTime();

  u8g2.initDisplay();
  u8g2.setContrast(30);
  u8g2.setFlipMode(0);
  u8g2.setPowerSave(0);

  int Mon = now.Month();
  int Day = now.Day();
  int Yrs = now.Year();
  int Hrs = now.Hour();
  int Min = now.Minute();
  int Sec = now.Second();

  int cases = 8;
  bool init = true;
  unsigned long refresh = millis();
  unsigned long timeout = millis() + 10000;

  while (millis() < timeout) {

    int m = pin3int();
    int p = pin2int();

    if (!m & !p & !init) {
      if (millis() - refresh < 500)continue;
      refresh = millis();
      goto display;
    }

    if (!init) timeout = millis() + 99999;

    init = false;

    if (m >= 2) cases --;
    if (p >= 2) cases ++;

    if (cases < 1) cases = 8;
    if (cases > 8) cases = 1;

    switch (cases) {
      case 1:
        if (m == 1) Mon --;
        if (p == 1) Mon ++;
        break;
      case 2:
        if (m == 1) Day --;
        if (p == 1) Day ++;
        break;
      case 3:
        if (m == 1) Yrs --;
        if (p == 1) Yrs ++;
        break;
      case 4:
        if (m == 1) Hrs --;
        if (p == 1) Hrs ++;
        break;
      case 5:
        if (m == 1) Min --;
        if (p == 1) Min ++;
        break;
      case 6:
        if (m == 1) Sec --;
        if (p == 1) Sec ++;
        break;
      case 7:
        if (m == 1 | p == 1) {
          Rtc.SetDateTime(RtcDateTime(Yrs, Mon, Day, Hrs, Min, Sec));
          return;
        }
        break;
      case 8:
        if (m == 1 | p == 1) return;
        break;
    }

    if (Yrs < 2000)Yrs = 2099;
    if (Yrs > 2099)Yrs = 2000;
    if (Mon < 1)Mon = 12;
    if (Mon > 12)Mon = 1;
    if (Day < 1)Day = 31;
    if (Day > 31)Day = 1;
    if (Hrs < 0)Hrs = 23;
    if (Hrs > 23)Hrs = 0;
    if (Min < 0)Min = 59;
    if (Min > 59)Min = 0;
    if (Sec < 0)Sec = 59;
    if (Sec > 59)Sec = 0;

    static char date[11], time[9];
    snprintf(date, 11, "%02u-%02u-%04u", Mon, Day, Yrs);
    snprintf(time, 9, "%02u:%02u:%02u", Hrs, Min, Sec);

display:
    u8g2.clearBuffer();
    u8g2.drawRFrame(0, 0, 128, 64, 5);
    u8g2.setFont(u8g2_font_t0_22b_mf);
    u8g2.drawStr(9, 18, date);
    u8g2.drawStr(20, 38, time);
    u8g2.drawStr(8, 58, "SET   EXIT");

    switch (cases) {
      case 1:
        u8g2.drawFrame(8, 3, 24, 17);
        break;
      case 2:
        u8g2.drawFrame(41, 3, 24, 17);
        break;
      case 3:
        u8g2.drawFrame(74, 3, 46, 17);
        break;
      case 4:
        u8g2.drawFrame(19, 23, 24, 17);
        break;
      case 5:
        u8g2.drawFrame(52, 23, 24, 17);
        break;
      case 6:
        u8g2.drawFrame(85, 23, 24, 17);
        break;
      case 7:
        u8g2.drawFrame(7, 43, 36, 17);
        break;
      case 8:
        u8g2.drawFrame(73, 43, 47, 17);
        break;
    }
    u8g2.sendBuffer();
  }
}