/*
Smart Water Tank Management System
Working Principle:
This program uses an ultrasonic sensor to measure water level in a tank. 
The ESP32 sends data to ThingSpeak using its Wi-Fi capability.
The data is visualized in a line chart on ThingSpeak.

Hardware Required:
- ESP32
- HC-SR04 ultrasonic sensor
- Jumper wires
- Breadboard
*/

// Include necessary libraries
#include <WiFi.h>
#include <HTTPClient.h>

// Wi-Fi credentials
const char* ssid = "Wokwi-GUEST"; // Replace with your Wi-Fi SSID
const char* password = ""; // Replace with your Wi-Fi password

// ThingSpeak settings
const char* server = "http://api.thingspeak.com/update";
String apiKey = "NX09U7D677P2EDJS"; // Replace with your ThingSpeak Write API Key

// Ultrasonic sensor pins
const int trigPin = 13; // Trigger pin connected to GPIO 5
const int echoPin = 12; // Echo pin connected to GPIO 18

// Tank dimensions (in cm)
const int tankHeight = 400; // Maximum height of the tank in cm

void setup() {
  Serial.begin(115200); // Start serial communication for debugging
  pinMode(trigPin, OUTPUT); // Set trigger pin as output
  pinMode(echoPin, INPUT);  // Set echo pin as input

  // Connect to Wi-Fi
  Serial.print("Connecting to Wi-Fi");
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.print(".");
  }
  Serial.println("\nConnected to Wi-Fi");
}

void loop() {
  // Measure water level
  float waterLevel = getWaterLevel();
  Serial.print("Water Level: ");
  Serial.print(waterLevel);
  Serial.println(" cm");

  // Send data to ThingSpeak
  if (WiFi.status() == WL_CONNECTED) {
    HTTPClient http;
    String url = String(server) + "?api_key=" + apiKey + "&field1=" + String(waterLevel);
    http.begin(url); // Start connection
    int httpCode = http.GET(); // Send HTTP GET request

    if (httpCode > 0) {
      Serial.println("Data sent to ThingSpeak");
    } else {
      Serial.println("Error sending data");
    }
    http.end(); // End connection
  } else {
    Serial.println("Wi-Fi Disconnected");
  }

  delay(15000); // Send data every 15 seconds
}

// Function to calculate water level
float getWaterLevel() {
  // Trigger the ultrasonic sensor
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Measure the duration of the echo pulse
  long duration = pulseIn(echoPin, HIGH);

  // Calculate distance in cm
  float distance = (duration * 0.0343) / 2;

  // Calculate water level
  float waterLevel = tankHeight - distance;
  if (waterLevel < 0) {
    waterLevel = 0; // Ensure water level doesn't go below zero
  } else if (waterLevel > tankHeight) {
    waterLevel = tankHeight; // Ensure water level doesn't exceed the tank height
  }

  return waterLevel;
}