#include <WiFi.h>         // Library to connect ESP32 to WiFi
#include <PubSubClient.h> // Library to connect ESP32 to MQTT broker
#include <HTTPClient.h>   // Library to make HTTP GET requests to OpenWeather API
#include <ArduinoJson.h>  // Library to parse the JSON response from OpenWeather

const char* ssid = "Wokwi-GUEST";  // WiFi network name
const char* password = "";          // WiFi password, empty for Wokwi

const char* mqtt_server = "broker.hivemq.com"; // Public MQTT broker address
const char* mqtt_topic = "Money";              // MQTT topic to publish weather data to

const char* apiKey = "1e4fad19e905cfb8553e1a004d2153d1"; // OpenWeather API key

WiFiClient espClient;            // Creates a WiFi client object for network communication
PubSubClient client(espClient);  // Creates an MQTT client using the WiFi client

void connectWiFi() {
  WiFi.begin(ssid, password);                 // Start connecting to WiFi using the credentials
  while (WiFi.status() != WL_CONNECTED) {     // Keep looping until WiFi is connected
    delay(1000);                              // Wait 1 second between each check
    Serial.println("Connecting to WiFi...");  // Print status to serial monitor
  }
  Serial.println("WiFi Connected");           // Confirm connection once done
}

void connectMQTT() {
  if (client.connected()) return;  // Already connected, exit the function immediately — this prevents unnecessary reconnections
  Serial.print("Attempting MQTT connection...");
  String clientId = "ESP32Client-" + String(random(0xffff), HEX); // Generate a random unique client ID to avoid conflicts on the broker
  if (client.connect(clientId.c_str())) {  // Try to connect to the broker with the generated ID
    Serial.println("Connected to MQTT broker"); // Confirm connection
  } else {
    Serial.print("Failed, state: ");
    Serial.println(client.state()); // Print error code if connection failed
  }
}

void fetchAndPublish(const char* suburbName, const char* query, float coordLat, float coordLon) {
// This function takes four inputs:
// suburbName = the display name published to Node-RED e.g. "Bellville"
// query = the name-based API query e.g. "Bellville,ZA", NULL if using coordinates
// coordLat = latitude, only used when query is NULL e.g. Cape Town CBD
// coordLon = longitude, only used when query is NULL e.g. Cape Town CBD

  HTTPClient http;   // Create an HTTP client object to make the API request
  char url[200];     // Character array to hold the full API URL

  if (query != NULL) {
    sprintf(url, "https://api.openweathermap.org/data/2.5/weather?q=%s&appid=%s&units=metric", query, apiKey);
    // If query is not NULL, build a name-based URL e.g. Bellville,ZA
    // units=metric ensures temperature comes back in Celsius
  } else {
    sprintf(url, "https://api.openweathermap.org/data/2.5/weather?lat=%.4f&lon=%.4f&appid=%s&units=metric", coordLat, coordLon, apiKey);
    // If query is NULL, build a coordinates-based URL using lat and lon
    // This is used for Cape Town CBD because "Cape Town CBD" does not resolve by name on OpenWeather
  }

  http.begin(url);            // Initialize the HTTP request with the built URL
  int httpCode = http.GET();  // Send the GET request and store the HTTP response code

  if (httpCode == 200) {  // 200 means the API request was successful
    String response = http.getString(); // Get the full JSON response as a string

    StaticJsonDocument<1024> doc;   // Create a JSON document with 1024 bytes allocated in memory
    deserializeJson(doc, response); // Parse the JSON string into the document object

    float temp       = doc["main"]["temp"];              // Extract temperature in Celsius
    float humidity   = doc["main"]["humidity"];           // Extract humidity as a percentage
    float lon        = doc["coord"]["lon"];               // Extract longitude from response
    float lat        = doc["coord"]["lat"];               // Extract latitude from response
    const char* desc = doc["weather"][0]["description"]; // Extract weather description from first element of the weather array

    char payload[512]; // Character array to hold the final JSON message to publish
    sprintf(payload,
      "{\"suburb\":\"%s\","      // suburb display name
      "\"temp\":\"%.1f°C\","     // temperature with °C label, 1 decimal place
      "\"humidity\":\"%.1f%%\"," // humidity with % label, %% is needed to print a literal % in sprintf
      "\"desc\":\"%s\","         // weather description
      "\"lon\":%.4f,"            // longitude to 4 decimal places
      "\"lat\":%.4f}",           // latitude to 4 decimal places
      suburbName, temp, humidity, desc, lon, lat); // insert actual values into the format

    client.publish(mqtt_topic, payload); // Publish the JSON payload to the MQTT topic
    Serial.println(payload);             // Print the published message to serial monitor

  } else {
    Serial.print("HTTP Error for ");  // Print error label if request failed
    Serial.print(suburbName);         // Print which suburb failed
    Serial.print(": ");
    Serial.println(httpCode);         // Print the HTTP error code
  }

  http.end();   // Close the HTTP connection to free memory and resources
  delay(1000);  // Wait 1 second before the next suburb to avoid hitting the API rate limit
}

void setup() {
  Serial.begin(115200);                // Start serial monitor at 115200 baud rate
  connectWiFi();                       // Connect to WiFi
  client.setServer(mqtt_server, 1883); // Set the MQTT broker address and port, 1883 is the default unencrypted MQTT port
  connectMQTT();                       // Connect to MQTT broker
}

void loop() {
  client.loop(); // Must be called regularly to keep the MQTT connection alive and process any incoming messages

  if (!client.connected()) { // Check if MQTT connection dropped
    connectMQTT();           // Reconnect only if actually disconnected
  }

  fetchAndPublish("Bellville",     "Bellville,ZA",   0,         0      ); // Fetch and publish Bellville using name query
  fetchAndPublish("Belhar",        "Belhar,ZA",      0,         0      ); // Fetch and publish Belhar using name query
  fetchAndPublish("Cape Town CBD", NULL,             -33.9249,  18.4241); // Fetch and publish Cape Town CBD using coordinates because name does not resolve
  fetchAndPublish("Kuilsrivier",   "Kuilsrivier,ZA", 0,         0      ); // Fetch and publish Kuilsrivier using name query

  delay(30000); // Wait 30 seconds before fetching all four suburbs again
}