// ============================================================
// SMART DRAINAGE SYSTEM - ESP32
// FEATURES: Self-Correction (Moving Average) + Adaptive Sampling
// ============================================================

#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <WiFi.h>
#include <HTTPClient.h>

// LCD Setup
LiquidCrystal_I2C lcd(0x27, 16, 2); 

// WiFi Configuration
const char* ssid = "YOUR_WIFI_NAME";
const char* password = "YOUR_WIFI_PASSWORD";

// ThingSpeak Configuration
String thingspeakKey = "YOUR_WRITE_API_KEY";
String server = "http://api.thingspeak.com/update";

// Ultrasonic pins - Reverting to ESP32 GPIOs
#define TRIG_PIN 5   // GPIO 5
#define ECHO_PIN 18  // GPIO 18

// Thresholds [cite: 26]
#define SAFE_DISTANCE 150
#define WARNING_DISTANCE 50

// Location [cite: 28]
float manholeLat = 12.9716;
float manholeLon = 77.5946;

// Variables
float distance_cm;
float readings[3] = {150.0, 150.0, 150.0}; // Array for Self-Correction
int readIndex = 0;
bool alertSent = false;
unsigned long lastSend = 0;
int statusCode = 0; 
int samplingInterval = 10000; 

void setup() {
  Serial.begin(115200);
  
  // LCD Init
  lcd.init();
  lcd.backlight();
  lcd.clear();
  lcd.print("Smart Drainage");
  lcd.setCursor(0, 1);
  lcd.print("Booting...");
  
  // WiFi Connection
  int attempts = 0;
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED && attempts < 15) {
    delay(500);
    Serial.print(".");
    attempts++;
  }

  lcd.clear();
  if (WiFi.status() == WL_CONNECTED) {
    lcd.print("WiFi OK!");
    Serial.println("\nWiFi Connected!");
  } else {
    lcd.print("WiFi Failed!");
  }
  delay(2000);
  
  // Ultrasonic Sensor Setup
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  
  lcd.clear();
  lcd.print("System Ready");
  delay(1000);
}

void loop() {
  // ----- 1. READ SENSOR -----
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
  
  long duration = pulseIn(ECHO_PIN, HIGH, 30000);
  float currentReading;

  if (duration == 0) {
    currentReading = 2.0; // Fail-safe for submerged sensor
  } else {
    currentReading = (duration * 0.0343) / 2;
  }

  // ----- 2. SELF-CORRECTION (Moving Average) -----
  readings[readIndex] = currentReading;
  readIndex = (readIndex + 1) % 3; 

  float total = 0;
  for (int i = 0; i < 3; i++) {
    total += readings[i];
  }
  distance_cm = total / 3;

  // ----- 3. STATUS & ADAPTIVE SAMPLING -----
  String status = "";
  if (distance_cm > SAFE_DISTANCE) {
    status = "SAFE";
    statusCode = 0;
    alertSent = false;
    samplingInterval = 10000; // Normal Mode
  }
  else if (distance_cm >= WARNING_DISTANCE && distance_cm <= SAFE_DISTANCE) {
    status = "WARNING";
    statusCode = 1;
    alertSent = false;
    samplingInterval = 2000;  // Burst Mode
  }
  else if (distance_cm < WARNING_DISTANCE) {
    status = "CRITICAL!";
    statusCode = 2;
    samplingInterval = 2000;  // Burst Mode
    
    if (!alertSent) {
      sendToThingSpeak(true);
      alertSent = true;
    }
  }

  // ----- 4. DISPLAY & LOG -----
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Dist: ");
  lcd.print(distance_cm, 0);
  lcd.print(" cm");
  
  lcd.setCursor(0, 1);
  lcd.print(status);
  
  if (samplingInterval < 5000) {
    lcd.setCursor(12, 1);
    lcd.print("FAST");
  }

  Serial.print("Avg Dist: "); Serial.print(distance_cm);
  Serial.print(" | Interval: "); Serial.println(samplingInterval);

  // Periodic ThingSpeak Update
  if (millis() - lastSend > 20000) {
    sendToThingSpeak(false);
    lastSend = millis();
  }
  
  delay(samplingInterval); 
}

void sendToThingSpeak(bool isAlert) {
  if (WiFi.status() != WL_CONNECTED) return;
  
  String url = server + "?api_key=" + thingspeakKey + 
               "&field1=" + String(distance_cm, 0) + 
               "&field2=" + String(statusCode) + 
               "&field3=" + String(isAlert ? 1 : 0) +
               "&field4=" + String(manholeLat, 4) +
               "&field5=" + String(manholeLon, 4);
  
  HTTPClient http;
  http.begin(url);
  int httpCode = http.GET();
  http.end();
}