// arduino-relay-oled-control.ino
// This code controls a relay and an OLED display with a single push button.
// It features two modes of operation:
// 1. A short press keeps the relay on continuously until the button is released.
// 2. A long press (held for > 1 second) triggers a series of four 1-second pulses,
//    and then keeps the relay on until the button is released. During this time,
//    a stopwatch is shown on the OLED display. When the button is released,
//    the final stopwatch value remains on the display.

// --- Library Includes ---
// Required libraries for the SSD1306 OLED display.
// You must install these from the Arduino Library Manager.
#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

// --- Pin Definitions ---
// Change these constants to match your hardware setup.
const int RELAY_PIN = 7;     // The digital pin connected to the relay signal wire.
const int BUTTON_PIN = 2;    // The digital pin connected to the push button.

// OLED display settings. The SSD1306 is an I2C device.
#define OLED_RESET 4
#define SCREEN_WIDTH 128     // OLED display width, in pixels
#define SCREEN_HEIGHT 64     // OLED display height, in pixels
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

// --- State Variables ---
// These variables track the current state of the button, relay, and display.
int lastButtonState = HIGH;   // The previous state of the button.
long lastDebounceTime = 0;    // The last time the button state was changed.
long debounceDelay = 50;      // Debounce time in milliseconds.
bool buttonState = HIGH;      // The current state of the button.
bool isPulsing = false;       // A flag to check if the pulsing mode is active.
unsigned long lastPulseTime = 0;  // The last time a pulse started.
int pulseCount = 0;           // The number of pulses completed.
unsigned long lastPressTime = 0;  // The last time the button was pressed down.
const int longPressThreshold = 1000; // Threshold for a long press in milliseconds.
bool longPressTriggered = false; // Flag to ensure the long press action only triggers once.
unsigned long stopwatchStartTime = 0; // Time when the long press started for the stopwatch.

// --- Functions ---
void setup() {
  // Initialize the pins.
  pinMode(RELAY_PIN, OUTPUT);
  pinMode(BUTTON_PIN, INPUT_PULLUP); // Use internal pull-up resistor.

  // Start with the relay off.
  digitalWrite(RELAY_PIN, HIGH); // Many relay modules are 'active low', so HIGH turns it off.
  Serial.begin(9600); // For debugging purposes.
  Serial.println("Arduino Relay and OLED Control Initialized.");

  // Initialize the OLED display.
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { // Address 0x3C for 128x64 display
    Serial.println(F("SSD1306 allocation failed"));
    for (;;); // Don't proceed, loop forever
  }
  display.display(); // Show the initial Adafruit splash screen.
  delay(2000);
  display.clearDisplay(); // Clear the buffer.
}

void loop() {
  // Read the state of the button.
  int reading = digitalRead(BUTTON_PIN);

  // --- Button Debouncing Logic ---
  // Debouncing prevents false button presses due to mechanical jitter.
  if (reading != lastButtonState) {
    lastDebounceTime = millis();
  }

  if ((millis() - lastDebounceTime) > debounceDelay) {
    // If the button state has been stable for longer than the debounce delay.
    if (reading != buttonState) {
      buttonState = reading;

      // --- Button Press & Release Detection ---
      if (buttonState == LOW) { // The button is pressed (LOW due to INPUT_PULLUP).
        Serial.println("Button pressed.");
        lastPressTime = millis();
        longPressTriggered = false; // Reset the long press flag.
        isPulsing = false;
        pulseCount = 0;
        display.clearDisplay(); // Clear the display on a new press.
      } else { // The button is released (HIGH).
        Serial.println("Button released.");
        // The relay is turned off on release.
        digitalWrite(RELAY_PIN, HIGH);

        // This is the core logic for the button release.
        if (!longPressTriggered) {
          // This is a short press, relay on until release.
          Serial.println("Short press detected. Relay is on until release.");
          digitalWrite(RELAY_PIN, LOW); // Turn the relay on.
          delay(100); // Brief delay for short pulse effect
          digitalWrite(RELAY_PIN, HIGH); // Turn off after a very short time
          display.clearDisplay();
          display.display();
        } else {
          // This is a long press release, keep the final time on the display.
          unsigned long finalSeconds = (millis() - stopwatchStartTime) / 1000;
          
          display.clearDisplay();
          display.setTextSize(2); // Set text size to 2
          display.setTextColor(SSD1306_WHITE); // Set text color to white
          display.setCursor(0, 0);
          display.println("Brew Time:");
          display.setTextSize(4);
          display.setCursor(40, 30);
          display.print(finalSeconds);
          display.display();
        }
      }
    }
  }

  // --- Long Press Detection & Action ---
  if (buttonState == LOW && (millis() - lastPressTime) >= longPressThreshold) {
    if (!longPressTriggered) {
      Serial.println("Long press detected. Starting 4 pulses.");
      isPulsing = true;
      pulseCount = 0;
      lastPulseTime = millis();
      longPressTriggered = true; // Set the flag to true so this only triggers once.
      stopwatchStartTime = millis(); // Start the stopwatch.
    }
  }

  // --- Pulsing Mode (Long press) ---
  if (isPulsing) {
    // A simple non-blocking timer for a 1-second pulse.
    if (millis() - lastPulseTime >= 1000) { // 1000 milliseconds = 1 second
      if (pulseCount < 4) {
        // Toggle the relay state to create a pulse.
        digitalWrite(RELAY_PIN, !digitalRead(RELAY_PIN)); 
        Serial.print("Pulse #");
        Serial.print(pulseCount + 1);
        Serial.println(" - ON/OFF");
        lastPulseTime = millis();
        // Increment the pulse count on the falling edge of the pulse.
        if (digitalRead(RELAY_PIN) == HIGH) {
          pulseCount++;
        }
      } else {
        // All four pulses are done, but the button is still being pressed.
        isPulsing = false;
      }
    }
  }

  // --- Sustained 'ON' after Pulsing and Stopwatch Display (Long press) ---
  // If a long press was triggered and the button is still held down, show stopwatch.
  if (longPressTriggered && buttonState == LOW) {
    digitalWrite(RELAY_PIN, LOW);
    
    // Display the stopwatch time without decimals.
    unsigned long elapsedTime = millis() - stopwatchStartTime;
    unsigned long seconds = elapsedTime / 1000;

    display.clearDisplay();
    display.setTextSize(2); // Set text size to 2
    display.setTextColor(SSD1306_WHITE); // Set text color to white
    display.setCursor(0, 0);
    display.println("BREWING...");
    display.setTextSize(4);
    display.setCursor(40, 30);
    display.print(seconds);
    display.display();
  }
  
  // Update the last button state for the next loop.
  lastButtonState = reading;
}