/*
 * Secure Temperature and Humidity Monitoring for Agriculture
 *
 * Hardware:
 *   - ESP32 DevKit C V4
 *   - DHT22 sensor (Temperature & Humidity)
 * 
 * Wiring:
 *   - DHT22 VCC  -> ESP32 3.3V
 *   - DHT22 GND  -> ESP32 GND
 *   
 *
 * Functionality:
 *   - Connects to a WiFi network using WPA2.
 *   - Reads temperature and humidity from the DHT22 sensor.
 *   - Securely transmits the sensor data via HTTPS to a remote server.
 *
 * Cybersecurity Features:
 *   - Uses TLS/SSL via WiFiClientSecure for encrypted data transmission.
 *   
 *
 * Note:
 *   - Update WiFi credentials and server details below.
 */

#include <WiFi.h>
#include "DHT.h"

// WiFi Credentials
const char* ssid = "WokwiSSID";
const char* password = "WokwiPassword";

// Server details (use HTTP instead of HTTPS)
const char* host = "example.com"; // Use a placeholder server or your own endpoint
const int httpPort = 80;          // Standard HTTP port

// DHT Sensor Configuration
#define DHTPIN 4       // GPIO pin connected to the DHT22 sensor's data line
#define DHTTYPE DHT22  // DHT22 sensor type
DHT dht(DHTPIN, DHTTYPE);

// Create a WiFi client object (no need for WiFiClientSecure)
WiFiClient client;

void setup() {
  Serial.begin(115200);
  delay(1000);
  Serial.println("\nSecure Temperature & Humidity Monitoring System");

  dht.begin();

  Serial.print("Connecting to WiFi network: ");
  Serial.println(ssid);
  WiFi.begin(ssid, password);
  
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("\nWiFi connected successfully!");
  Serial.print("IP Address: ");
  Serial.println(WiFi.localIP());

  // Optionally, you can also synchronize time using NTP if needed
  configTime(0, 0, "pool.ntp.org", "time.nist.gov");
}

void loop() {
  // Wait 2 seconds between sensor readings
  delay(2000);

  // Read sensor values from the DHT22 sensor
  float humidity = dht.readHumidity();
  float temperature = dht.readTemperature();

  // Check if any reading failed; if so, log an error message.
  if (isnan(humidity) || isnan(temperature)) {
    Serial.println("Error: Failed to read from DHT sensor!");
    return;  // Skip this iteration if readings are invalid.
  }

  // Print the sensor readings to the Serial Monitor
  Serial.print("Temperature: ");
  Serial.print(temperature);
  Serial.print(" °C, Humidity: ");
  Serial.print(humidity);
  Serial.println(" %");

  // **********************************
  // HTTP Data Transmission
  // **********************************
  
  // Try to connect to the remote server using HTTP
  if (!client.connect(host, httpPort)) {
    Serial.println("Error: Connection to server failed!");
    return; // Skip transmission if connection fails
  }

  // Build the HTTP POST request
  String url = "/api/sensor-data";  // Update this endpoint to your server's configuration
  String postData = "temperature=" + String(temperature) + "&humidity=" + String(humidity);

  // Debug: Print the POST data
  Serial.println("Preparing to send data:");
  Serial.println(postData);

  // Construct the HTTP request headers
  client.println("POST " + url + " HTTP/1.1");
  client.println("Host: " + String(host));
  client.println("User-Agent: ESP32-Secure-Client/1.0");
  client.println("Connection: close");
  client.println("Content-Type: application/x-www-form-urlencoded");
  client.print("Content-Length: ");
  client.println(postData.length());
  client.println();  // End of headers

  // Send the POST data (sensor readings) to the server
  client.print(postData);

  // Read and print the server's response (if any)
  Serial.println("Server Response:");
  while (client.connected()) {
    String line = client.readStringUntil('\n');
    if (line == "\r") {
      // End of HTTP response headers reached
      break;
    }
    Serial.println(line);
  }
  
  // Optionally, read the remaining payload from the server:
  String response = client.readString();
  Serial.println(response);

  // Close the connection
  client.stop();
}