#include "LiquidCrystal_I2C.h"

// ===== LCD =====
#define I2C_ADDR    0x27
#define LCD_COLUMNS 20
#define LCD_LINES   4

// ===== Pins =====
const int LED_PIN = D13;        // Діод 2
const int BUTTON_PIN = PC13;    // Кнопка B1

// ===== Constants =====
const unsigned long INFINITE_DURATION = 0xFFFFFFFFUL;
const unsigned long DURATIONS[4] = {
  2000UL,
  1000UL,
  10000UL,
  INFINITE_DURATION
};

const float FREQUENCIES[4] = {
  6.0f,
  12.0f,
  2.0f,
  0.0f
};

unsigned long HALF_MS[4];

// ===== State =====
int currentStage = 0;   // 0..3
int dir = 1;            // +1 = прямий, -1 = реверс
bool finished = false;

unsigned long stageStart = 0;
unsigned long lastToggle = 0;
bool ledState = LOW;

// ===== Debounce =====
const unsigned long DEBOUNCE_MS = 40;
int lastRaw = HIGH;
int stableState = HIGH;
unsigned long lastBounce = 0;

const int PRESSED_LEVEL = LOW;  // при INPUT_PULLUP натиснута -> LOW


// ===== Setup =====
void setup() {
  pinMode(LED_PIN, OUTPUT);
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  digitalWrite(LED_PIN, LOW);

  for (int i = 0; i < 4; ++i) {
    if (FREQUENCIES[i] > 0.0f) {
      HALF_MS[i] = (unsigned long)(500.0f / FREQUENCIES[i] + 0.5f);
    } else {
      HALF_MS[i] = 0;
    }
  }

  Serial.begin(115200);
  delay(50);

  lastRaw = digitalRead(BUTTON_PIN);
  stableState = lastRaw;
  lastBounce = millis();

  stageStart = millis();
  lastToggle = millis();
  ledState = LOW;

  Serial.println("--- START ---");
  Serial.print("Start stage: ");
  Serial.print(currentStage);
  Serial.print(" dir: ");
  Serial.println(dir);
}

// ===== Helpers =====
bool isFinalForDir(int stageIndex, int d) {
  // прямий режим: фінальний stage 3
  if (d == 1 && stageIndex == 3) return true;

  // реверс: фінальний stage 0
  if (d == -1 && stageIndex == 0) return true;

  return false;
}

// ===== Loop =====
void loop() {
  unsigned long now = millis();

  // ----- debounce -----
  int raw = digitalRead(BUTTON_PIN);
  if (raw != lastRaw) lastBounce = now;
  lastRaw = raw;

  if ((now - lastBounce) > DEBOUNCE_MS) {
    if (raw != stableState) {
      stableState = raw;

      if (stableState == PRESSED_LEVEL) {
        // натискання кнопки
        dir = -dir;

        Serial.print("BUTTON pressed -> new dir = ");
        Serial.println(dir == 1 ? "FORWARD" : "REVERSE");

        currentStage = (dir == 1) ? 0 : 3;
        stageStart = now;
        lastToggle = now;
        ledState = LOW;
        digitalWrite(LED_PIN, ledState);
        finished = false;

        Serial.print("Start stage after toggle: ");
        Serial.println(currentStage);
      }
    }
  }

  if (finished) {
    digitalWrite(LED_PIN, HIGH);
    delay(2);
    return;
  }

  // ----- stage timing -----
  unsigned long rawDuration = DURATIONS[currentStage];
  bool finalForDir = isFinalForDir(currentStage, dir);
  unsigned long durationForCheck = rawDuration;

  // INFINITE_DURATION застосовуємо лише для фінального етапу
  if (rawDuration == INFINITE_DURATION && !finalForDir) {
    durationForCheck = 1;
  }

  unsigned long elapsed = now - stageStart;

  if (durationForCheck != INFINITE_DURATION && elapsed >= durationForCheck) {
    int next = currentStage + dir;

    if (next < 0 || next > 3) {
      finished = true;
      digitalWrite(LED_PIN, HIGH);
      Serial.println("Reached sequence end -> finished (LED ON).");
    } else {
      currentStage = next;
      stageStart = now;
      lastToggle = now;
      ledState = LOW;
      digitalWrite(LED_PIN, ledState);

      Serial.print("Transition -> now stage ");
      Serial.print(currentStage);
      Serial.print(" (freq=");
      Serial.print(FREQUENCIES[currentStage]);
      Serial.println(" Hz)");
    }
  }

  // ----- frequency selection -----
  float freq;

  if (dir == 1) {
    // прямий режим
    freq = FREQUENCIES[currentStage];
  } else {
    // реверс:
    // stage 3 -> постійно
    // stage 2 -> 2 Гц
    // stage 1 -> 12 Гц
    // stage 0 -> 6 Гц
    switch (currentStage) {
      case 3: freq = 0.0f;  break;
      case 2: freq = 2.0f;  break;
      case 1: freq = 12.0f; break;
      case 0: freq = 6.0f;  break;
    }
  }

  // ----- LED control -----
  if (freq > 0.0f) {
    unsigned long half = (unsigned long)(500.0f / freq + 0.5f);

    if (now - lastToggle >= half) {
      ledState = !ledState;
      digitalWrite(LED_PIN, ledState);
      lastToggle = now;
    }
  } else {
    // постійне світло
    digitalWrite(LED_PIN, HIGH);
  }

  delay(2);
}