// -------- PIN SETUP --------
#define BUTTON_PIN D8     // button input (INPUT_PULLDOWN)
#define LED_PIN D2        // yellow LED


// -------- TIMING CONFIG --------
const unsigned long debounceDelay = 50;
const unsigned long longPressTime = 1000;
const unsigned long doublePressGap = 400;


// -------- SYSTEM STATE --------
int totalAmount = 0;
int goal = 100;

bool milestone25 = false;
bool milestone50 = false;
bool milestone75 = false;
bool milestone100 = false;


// -------- BUTTON STATE --------
bool buttonState = LOW;
bool lastButtonReading = LOW;

unsigned long lastDebounceTime = 0;
unsigned long pressStartTime = 0;
unsigned long lastReleaseTime = 0;

int pressCount = 0;


// -------- SETUP --------
void setup() {
  Serial.begin(115200);

  pinMode(BUTTON_PIN, INPUT_PULLDOWN);
  pinMode(LED_PIN, OUTPUT);

  digitalWrite(LED_PIN, LOW);
}


// -------- LOOP --------
void loop() {

  int reading = digitalRead(BUTTON_PIN);

  // -------- DEBOUNCE --------
  if (reading != lastButtonReading) {
    lastDebounceTime = millis();
  }

  if ((millis() - lastDebounceTime) > debounceDelay) {

    if (reading != buttonState) {
      buttonState = reading;

      // -------- BUTTON PRESSED --------
      if (buttonState == HIGH) {
        pressStartTime = millis();
      }

      // -------- BUTTON RELEASED --------
      else {
        unsigned long pressDuration = millis() - pressStartTime;

        // -------- LONG PRESS --------
        if (pressDuration >= longPressTime) {
          handleLongPress();
          pressCount = 0;
        } 
        else {
          pressCount++;
          lastReleaseTime = millis();
        }
      }
    }
  }

  // -------- SINGLE / DOUBLE --------
  if (pressCount > 0 && (millis() - lastReleaseTime) > doublePressGap) {

    if (pressCount == 1) {
      handleSinglePress();
    }
    else if (pressCount == 2) {
      handleDoublePress();
    }

    pressCount = 0;
  }

  lastButtonReading = reading;
}


// -------- ACTIONS --------

// Single press → ₹1
void handleSinglePress() {
  addAmount(1);
  blinkLED(1);
}

// Double press → ₹2
void handleDoublePress() {
  addAmount(2);
  blinkLED(2);
}

// Long press → ₹5
void handleLongPress() {
  addAmount(5);

  // long glow
  digitalWrite(LED_PIN, HIGH);
  delay(400);
  digitalWrite(LED_PIN, LOW);
}


// -------- CORE LOGIC --------

void addAmount(int value) {

  totalAmount += value;

  int percentage = (totalAmount * 100) / goal;

  Serial.print("Added: ");
  Serial.print(value);
  Serial.print(" | Total: ");
  Serial.print(totalAmount);
  Serial.print(" | ");
  Serial.print(percentage);
  Serial.println("%");

  // -------- CHECK GOAL WITH REMAINDER --------
  if (totalAmount >= goal) {

    int overflow = totalAmount - goal; // calculate leftover

    Serial.println("Milestone: Goal reached!");

    // celebration pattern
    for (int i = 0; i < 3; i++) {
      digitalWrite(LED_PIN, HIGH);
      delay(150);
      digitalWrite(LED_PIN, LOW);
      delay(150);
    }

    delay(500);

    // -------- RESET WITH CARRY FORWARD --------
    totalAmount = overflow;

    milestone25 = false;
    milestone50 = false;
    milestone75 = false;
    milestone100 = false;

    Serial.print("System Reset → Carry Forward: ");
    Serial.println(totalAmount);

    return; // stop further milestone checks
  }

  // -------- NORMAL MILESTONE CHECK --------
  checkMilestones(percentage);
}


// -------- LED HELPER --------

void blinkLED(int times) {
  for (int i = 0; i < times; i++) {
    digitalWrite(LED_PIN, HIGH);
    delay(120);
    digitalWrite(LED_PIN, LOW);
    delay(120);
  }
}


// -------- MILESTONE LOGIC --------

void checkMilestones(int percentage) {

  if (!milestone25 && percentage >= 25) {
    milestone25 = true;
    Serial.println("Milestone: 25% reached");
  }

  if (!milestone50 && percentage >= 50) {
    milestone50 = true;
    Serial.println("Milestone: 50% reached");
  }

  if (!milestone75 && percentage >= 75) {
    milestone75 = true;
    Serial.println("Milestone: 75% reached");
  }
}