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

// -------------------------
// Wi-Fi Settings
// -------------------------
const char* ssid = "Wokwi-GUEST";
const char* password = "";

// -------------------------
// ThingSpeak Settings
// -------------------------
const char* server = "http://api.thingspeak.com/update";
String apiKey = "E3RP71MA6BCU57FY"; // Replace with your API key

// -------------------------
// Ultrasonic Sensor Pins
// -------------------------
const int trigPin = 5;  // Trigger pin
const int echoPin = 18; // Echo pin

// -------------------------
// Tank parameters
// -------------------------
float tankHeight = 100.0;   // Tank height in cm
float fullThreshold = 90.0; // Water level % considered full
float lowThreshold  = 10.0; // Water level % considered low

// Variables
long duration;
float distance;
float waterLevel;
String tankStatus;

void setup() {
  Serial.begin(115200);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);

  // Connect to Wi-Fi
  WiFi.begin(ssid, password);
  Serial.print("Connecting to Wi-Fi");
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("\nConnected to Wi-Fi");
}

void loop() {
  // Measure distance
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  duration = pulseIn(echoPin, HIGH);
  distance = duration * 0.034 / 2;

  // Calculate water level
  waterLevel = ((tankHeight - distance) / tankHeight) * 100;

  // Calculate tank status
  if (waterLevel >= fullThreshold) {
    tankStatus = "Full";
  } else if (waterLevel <= lowThreshold) {
    tankStatus = "Low";
  } else {
    tankStatus = "Normal";
  }

  // Print values on Serial Monitor
  Serial.print("Distance: "); Serial.print(distance); Serial.print(" cm | ");
  Serial.print("Water Level: "); Serial.print(waterLevel, 1); Serial.print("% | ");
  Serial.print("Tank Status: "); Serial.println(tankStatus);

  // Send data to ThingSpeak
  if(WiFi.status() == WL_CONNECTED){
    HTTPClient http;
    String url = server;
    url += "?api_key=" + apiKey;
    url += "&field1=" + String(distance);
    url += "&field2=" + String(waterLevel, 1);
    url += "&field3=" + String(tankStatus == "Full" ? 1 : (tankStatus == "Low" ? -1 : 0));
    
    http.begin(url);
    int httpResponseCode = http.GET();
    if(httpResponseCode>0){
      Serial.println("Data sent to ThingSpeak successfully");
    } else {
      Serial.println("Error sending data to ThingSpeak");
    }
    http.end();
  }

  delay(20000); // Send data every 20 seconds (ThingSpeak free limit: 15s min)
}