#include <Wire.h> 
#include <Adafruit_BMP085.h> 
#include <Adafruit_GFX.h> 
#include <Adafruit_SSD1306.h>
#include <Fonts/FreeSansBold9pt7b.h>
#include <Encoder.h> 

// --- I2C OLED Display Definitions ---
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, 0x3C);

// --- Sensor Object Initialization ---
Adafruit_BMP085 bmp;

// --- Pin Definitions ---
// Pins 2 and 3 are used for external interrupts (by Encoder library).
const int ENCODER_CLK_PIN = 2; // Clock (CLK)
const int ENCODER_DT_PIN = 3;  // Data (DT)
const int ENCODER_SW_PIN = 6;  // Switch (SW) - Now handled via polling

const int BUZZER_PIN = 8;    
const int LED_GREEN = 9;     
const int LED_YELLOW = 10;   
const int LED_RED = 11;      

// --- Rotary Encoder Initialization ---
Encoder knob(ENCODER_DT_PIN, ENCODER_CLK_PIN);

// --- Global Variables & Constants ---
const float MAX_UPPER_RANGE = 1095.0;
const float MIN_LOWER_RANGE = 900.0;
const int ALERT_TONE = 1000;

// Encoder State Variables
long oldEncoderPosition = 0; 

// Menu State Machine
enum MenuState { MONITOR, SET_UPPER, SET_LOWER };
MenuState currentState = MONITOR;

int currentMenuSelection = 0; // 0=Upper, 1=Lower

// User-set Limits (hPa) 
float setpointPressure = 1000.0;
float upperLimitSet = 1010.0; 
float lowerLimitSet = 990.0;

// --- FUNCTION PROTOTYPES ---
void handleEncoderRotation();
void handleSwitchPolling(); // New polling function
void updateOLED();
void updateAlerts(float currentP, float lowerL, float upperL);

// =========================================================
// SETUP FUNCTION
// =========================================================
void setup() {
  Serial.begin(9600);
  
  // --- Initialize I/O Pins ---
  pinMode(BUZZER_PIN, OUTPUT);
  pinMode(LED_GREEN, OUTPUT);
  pinMode(LED_YELLOW, OUTPUT);
  pinMode(LED_RED, OUTPUT);

  // Initialize Encoder Switch Pin with PULLUP
  // This is required for the polling function to work correctly.
  pinMode(ENCODER_SW_PIN, INPUT_PULLUP); 
  
  // --- Attach Interrupts ---
  // Rotary switch interrupt REMOVED. Polling will handle it in the loop().
  
  noTone(BUZZER_PIN); 
  digitalWrite(LED_GREEN, HIGH);

  if (!bmp.begin()) {
    digitalWrite(LED_RED, HIGH);
    while (1);
  }
  
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { 
    while (true); 
  }
  display.display();
  delay(1000); 
  display.clearDisplay();
}

// =========================================================
// LOOP FUNCTION (Main Logic)
// =========================================================
void loop() {
  handleEncoderRotation(); // Rotation is fast (interrupt-based)
  handleSwitchPolling();   // Switch is polled (software debounced)
  
  float currentPressure = bmp.readPressure() / 100.0F; 
  
  updateAlerts(currentPressure, lowerLimitSet, upperLimitSet);

  updateOLED();
  
  delay(50); 
}

// =========================================================
// CUSTOM FUNCTIONS
// =========================================================

/**
 * @brief Polling function with software debounce to handle encoder switch presses.
 */
void handleSwitchPolling() {
  // Static variable to store the time of the last valid press
  static unsigned long lastPressTime = 0;
  
  // Check if the button is pressed (LOW, due to INPUT_PULLUP)
  if (digitalRead(ENCODER_SW_PIN) == LOW) { 
    // Check if enough time (200ms) has passed since the last press (debounce)
    if (millis() - lastPressTime > 200) { 
      
      // --- Menu Logic Execution ---
      if (currentState == MONITOR) {
        if (currentMenuSelection == 0) {
          currentState = SET_UPPER;
        } else if (currentMenuSelection == 1) {
          currentState = SET_LOWER;
        }
      } else if (currentState == SET_UPPER || currentState == SET_LOWER) {
        // Save and exit edit mode
        currentState = MONITOR;
        // The selection arrow remains on the item just edited.
      }
      
      lastPressTime = millis(); // Record the time of this valid press
    }
  }
}

void handleEncoderRotation() {
  long newPosition = knob.read();

  if (newPosition != oldEncoderPosition) {
    // Calculate delta and divide by a factor (e.g., 4) for stability/sensitivity
    int delta = (newPosition - oldEncoderPosition) / 4; 
    
    if (delta != 0) {
        // 1. Monitor/Selection State: Rotate between Upper/Lower setting
        if (currentState == MONITOR) {
          currentMenuSelection = (currentMenuSelection + delta) % 2;
          if (currentMenuSelection < 0) currentMenuSelection = 1; 
          
        // 2. Setting State: Rotate changes the limit value
        } else if (currentState == SET_UPPER) {
          upperLimitSet = constrain(upperLimitSet + delta, lowerLimitSet + 1, MAX_UPPER_RANGE);
        } else if (currentState == SET_LOWER) {
          lowerLimitSet = constrain(lowerLimitSet + delta, MIN_LOWER_RANGE, upperLimitSet - 1);
        }
    }
    oldEncoderPosition = newPosition;
  }
}

/**
 * @brief Drives the physical outputs (LEDs and Passive Buzzer) based on status
 */
void updateAlerts(float currentP, float lowerL, float upperL) {
  digitalWrite(LED_GREEN, LOW);
  digitalWrite(LED_YELLOW, LOW);
  digitalWrite(LED_RED, LOW);
  noTone(BUZZER_PIN); 
  
  if (currentP >= upperL) {
    digitalWrite(LED_RED, HIGH);
    tone(BUZZER_PIN, ALERT_TONE);
  } 
  else if (currentP <= lowerL) {
    digitalWrite(LED_YELLOW, HIGH);
    tone(BUZZER_PIN, ALERT_TONE);
  }
  else {
    digitalWrite(LED_GREEN, HIGH);
  }
}

/**
 * @brief Updates the OLED display based on the current Menu State.
 */
void updateOLED() {
  float currentPressure = bmp.readPressure() / 100.0F; 
  
  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);

  // --- 1. Current Pressure (Smooth Font) ---
  display.setFont(&FreeSansBold9pt7b);
  display.setTextSize(1); 
  display.setCursor(0, 15);
  display.print("P: ");
  display.print((int)currentPressure); 
  display.print(" hPa");
  
  // --- Switch back to standard font for menu/status ---
  display.setFont(); 
  display.setTextSize(1);
  int status = (currentPressure >= upperLimitSet) ? 2 : (currentPressure <= lowerLimitSet) ? 1 : 0;
  
  // --- 2. Status Indicator ---
  display.setCursor(0, 25); 
  display.print("Status: ");
  if (status == 2) display.print("HIGH ALERT");
  else if (status == 1) display.print("LOW ALERT");
  else display.print("NORMAL");
  
  // --- 3. Limit Settings Menu ---
  // Print UPPER Limit (Row 40)
  display.setCursor(0, 40);
  display.print("UPPER: ");
  display.print((int)upperLimitSet);
  display.print(" hPa");
  
  // Print LOWER Limit (Row 55)
  display.setCursor(0, 55);
  display.print("LOWER: ");
  display.print((int)lowerLimitSet);
  display.print(" hPa");
  
  // --- 4. Menu Selector / Editor Indicator ---
  if (currentState == MONITOR) {
    // Show arrow indicating selected limit
    display.setCursor(75, (currentMenuSelection == 0) ? 40 : 55); 
    display.print(" <--"); 
  } else if (currentState == SET_UPPER) {
    // In edit mode: flash the value being edited
    if (millis() % 500 < 250) {
      display.setCursor(45, 40); 
      display.fillRect(45, 40, 30, 8, BLACK); 
    }
  } else if (currentState == SET_LOWER) {
    // In edit mode: flash the value being edited
    if (millis() % 500 < 250) {
      display.setCursor(45, 55); 
      display.fillRect(45, 55, 30, 8, BLACK); 
    }
  }
  
  display.display();
}