#define DATA_POINTS 10
float voltageArray[DATA_POINTS];
#define SAMPLE_INTERVAL 1000

int offset = 0;

// Define the analog input pin based on your ESP32 NodeMCU board
#define ANALOG_PIN 34  // Replace with the GPIO pin number corresponding to "VP"

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

// Your Wi-Fi credentials
const char *ssid = "YourWiFiSSID";
const char *password = "YourWiFiPassword";

// Server details
const char *serverAddress = "http://YourServerAddress";  // Replace with your server address
const int serverPort = 80;  // Replace with your server port

Ticker timer;

void voltMeter() {
  int volt = analogRead(ANALOG_PIN);  // read the input
  Serial.print("Analog Input: ");
  Serial.println(volt);

  // Calculate the gradient
  float gradient = calculateGradient();
  Serial.print("Gradient: ");
  Serial.println(gradient);

  // Send the values to the server
  sendToServer(volt, gradient);
}

float calculateGradient() {
  // Use numerical differentiation to estimate the gradient
  // Assuming a simple backward difference method
  float voltageNow = analogRead(ANALOG_PIN) * (5.0 / 4095.0);  // Current voltage reading for ESP32
  float voltagePrevious = voltageArray[DATA_POINTS - 1];  // Previous voltage reading

  // Shift the array to make room for the new value
  for (int i = 0; i < DATA_POINTS - 1; i++) {
    voltageArray[i] = voltageArray[i + 1];
  }

  // Store the current value in the array
  voltageArray[DATA_POINTS - 1] = voltageNow;

  // Calculate the gradient using backward difference
  float gradient = (voltageNow - voltagePrevious) / (DATA_POINTS * SAMPLE_INTERVAL / 1000.0);

  return gradient;
}

void sendToServer(int analogInput, float gradient) {
  // Create an HTTP client object
  HTTPClient http;

  // Construct the server endpoint URL
  String url = String(serverAddress) + ":" + String(serverPort) + "/updateData";

  // Add parameters to the URL
  url += "?analogInput=" + String(analogInput);
  url += "&gradient=" + String(gradient);

  // Start the HTTP request
  http.begin(url);

  // Send the request and check for errors
  int httpCode = http.GET();
  if (httpCode > 0) {
    Serial.printf("HTTP request successful, response code: %d\n", httpCode);
  } else {
    Serial.printf("HTTP request failed, error: %s\n", http.errorToString(httpCode).c_str());
  }

  // End the HTTP request
  http.end();
}

void setup() {
  // Debug console
  Serial.begin(115200);

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

  // Set up the timer for data reporting
  timer.attach(SAMPLE_INTERVAL, voltMeter);
}

void loop() {
  // No need for additional loop logic, as the Ticker handles the interval
}