Suprise Me

#include <Arduino.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <ESP32Servo.h>


// Hoisted type definitions
enum TimerState { READY, LOCKED_RUNNING, FINISHED };


// Forward declarations
void moveLock(bool lockBox);
void drawScreen();
void startSession();
void handleButtonPress();

constexpr int OLED_SDA = 21;
constexpr int OLED_SCL = 22;
constexpr int BUTTON_PIN = 27;
constexpr int SERVO_PIN = 26;
constexpr uint32_t SESSION_SECONDS = 25UL * 60UL;
constexpr uint32_t DEBOUNCE_MS = 35;
constexpr int UNLOCK_ANGLE = 15;
constexpr int LOCK_ANGLE = 105;



Adafruit_SSD1306 display(128, 64, &Wire, -1);
Servo lockServo;
TimerState timerState = READY;
uint32_t remainingSeconds = SESSION_SECONDS;
uint32_t lastTickMs = 0;
bool lastButtonReading = HIGH;
bool stableButtonState = HIGH;
uint32_t lastDebounceMs = 0;

void moveLock(bool lockBox) {
  lockServo.write(lockBox ? LOCK_ANGLE : UNLOCK_ANGLE);
}

void drawScreen() {
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(1);
  display.setCursor(25, 1);
  display.print("PHONE LOCKBOX");
  display.drawLine(0, 12, 127, 12, SSD1306_WHITE);

  const uint32_t minutes = remainingSeconds / 60;
  const uint32_t seconds = remainingSeconds % 60;
  char timeText[6];
  snprintf(timeText, sizeof(timeText), "%02lu:%02lu", static_cast<unsigned long>(minutes), static_cast<unsigned long>(seconds));
  display.setTextSize(3);
  display.setCursor(18, 22);
  display.print(timeText);

  display.setTextSize(1);
  display.setCursor(5, 54);
  if (timerState == READY) display.print("Place phone in; press to lock");
  else if (timerState == LOCKED_RUNNING) display.print("Locked until timer ends");
  else display.print("Unlocked! Press for new session");
  display.display();
}

void startSession() {
  remainingSeconds = SESSION_SECONDS;
  moveLock(true);
  delay(350);
  timerState = LOCKED_RUNNING;
  lastTickMs = millis();
  drawScreen();
}

void handleButtonPress() {
  if (timerState == READY || timerState == FINISHED) startSession();
}

void setup() {
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  Wire.begin(OLED_SDA, OLED_SCL);
  lockServo.setPeriodHertz(50);
  lockServo.attach(SERVO_PIN, 500, 2400);
  moveLock(false);
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) while (true) delay(1000);
  drawScreen();
}

void loop() {
  const uint32_t now = millis();
  const bool reading = digitalRead(BUTTON_PIN);
  if (reading != lastButtonReading) lastDebounceMs = now;
  if (now - lastDebounceMs >= DEBOUNCE_MS && reading != stableButtonState) {
    stableButtonState = reading;
    if (stableButtonState == LOW) handleButtonPress();
  }
  lastButtonReading = reading;

  if (timerState == LOCKED_RUNNING && now - lastTickMs >= 1000) {
    const uint32_t elapsedSeconds = (now - lastTickMs) / 1000;
    lastTickMs += elapsedSeconds * 1000;
    if (elapsedSeconds >= remainingSeconds) {
      remainingSeconds = 0;
      timerState = FINISHED;
      moveLock(false);
    } else {
      remainingSeconds -= elapsedSeconds;
    }
    drawScreen();
  }
}