// ─────────────────────────────────────────────
// LIBRARIES (these add features to your ESP32)
// ─────────────────────────────────────────────
#include <WiFi.h>          // allows ESP32 to connect to WiFi
#include <PubSubClient.h>  // allows MQTT communication
#include <HTTPClient.h>    // allows API calls over HTTP
#include <ArduinoJson.h>   // allows parsing JSON data
#include <DHT.h>           // allows reading DHT22 sensor

// ─────────────────────────────────────────────
// WIFI SETTINGS
// ─────────────────────────────────────────────
const char* ssid = "Wokwi-GUEST";   // WiFi name
const char* password = "";          // WiFi password

// ─────────────────────────────────────────────
// MQTT SETTINGS
// ─────────────────────────────────────────────
const char* mqtt_server = "broker.hivemq.com"; // public MQTT broker

// MQTT topics (channels)
const char* mqtt_topic_weather   = "weather/suburbs";   // weather data
const char* mqtt_topic_summary   = "weather/summary";   // summary data
const char* mqtt_topic_pollution = "weather/Pollution"; // pollution data

const char* mqtt_topic_alert     = "alert/threshold";   // alert messages
const char* mqtt_topic_sensor    = "alert/sensor";      // sensor readings
const char* mqtt_topic_threshold = "alert/set";         // slider input
const char* mqtt_topic_buzzer    = "alert/buzzer";      // remote buzzer

const char* mqtt_pwm_topic = "Moola"; // LED brightness control

// ─────────────────────────────────────────────
// SENSOR SETUP
// ─────────────────────────────────────────────
#define DHTPIN 26      // DHT22 connected to GPIO 26
#define DHTTYPE DHT22 // sensor type
DHT dht(DHTPIN, DHTTYPE); // create sensor object

// ─────────────────────────────────────────────
// HARDWARE DEFINITIONS
// ─────────────────────────────────────────────
#define BUZZERPIN 15   // buzzer connected to GPIO 15
#define LEDPIN 13      // LED connected to GPIO 13

#define BUZZ_FREQ 1000      // buzzer tone (1kHz sound)
#define BUZZ_RESOLUTION 8   // PWM resolution

// ─────────────────────────────────────────────
// VARIABLES
// ─────────────────────────────────────────────
float USER_THRESHOLD = 30.0;   // temperature limit set by user
float ALERT_THRESHOLD = 3.0;   // deviation threshold

bool lastBuzzerState = false;  // remembers buzzer state

// PWM settings (for LED brightness)
const int pwmChannel = 0;
const int pwmFreq = 5000;
const int pwmResolution = 8;

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

// ─────────────────────────────────────────────
// STRUCT (used to store suburb info)
// ─────────────────────────────────────────────
struct Suburb {
  const char* name;    // suburb name
  const char* query;   // used in API request
  float lat;           // latitude
  float lon;           // longitude
};

// list of suburbs
Suburb suburbs[] = {
  {"Bellville", "Bellville,ZA", 0, 0},
  {"Belhar", "Belhar,ZA", 0, 0},
  {"Cape Town CBD", NULL, -33.9249, 18.4241},
  {"Kuilsrivier", "Kuilsrivier,ZA", 0, 0}
};

const int suburbCount = 4; // number of suburbs

// ─────────────────────────────────────────────
// NETWORK OBJECTS
// ─────────────────────────────────────────────
WiFiClient espClient;            // WiFi connection
PubSubClient client(espClient);  // MQTT client

// ─────────────────────────────────────────────
// BUZZER FUNCTIONS
// ─────────────────────────────────────────────
void buzzerOn() {
  ledcWriteTone(BUZZERPIN, BUZZ_FREQ); // start sound
}

void buzzerOff() {
  ledcWriteTone(BUZZERPIN, 0); // stop sound
}

// ─────────────────────────────────────────────
// CONNECT TO WIFI
// ─────────────────────────────────────────────
void connectWiFi() {
  WiFi.begin(ssid, password);   // start connection
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);                // wait 1 second
    Serial.println("Connecting to WiFi...");
  }
  Serial.println("WiFi Connected");
}

// ─────────────────────────────────────────────
// MQTT MESSAGE HANDLER
// ─────────────────────────────────────────────
void mqttCallback(char* topic, byte* payload, unsigned int length) {

  String message = "";

  // convert incoming bytes into a readable string
  for (int i = 0; i < length; i++) {
    message += (char)payload[i];
  }

  Serial.print("Received: ");
  Serial.println(message);

  // ───── THRESHOLD CONTROL
  if (String(topic) == mqtt_topic_threshold) {
    USER_THRESHOLD = message.toFloat(); // update user threshold
  }

  // ───── BUZZER REMOTE CONTROL
  if (String(topic) == mqtt_topic_buzzer) {
    if (message == "ON") {
      buzzerOn();
    } else if (message == "OFF") {
      buzzerOff();
    }
  }

  // ───── LED BRIGHTNESS CONTROL (PWM)
  if (String(topic) == mqtt_pwm_topic) {
    int duty = constrain(message.toInt(), 0, 255); // limit value
    ledcWrite(pwmChannel, duty); // apply brightness
  }
}

// ─────────────────────────────────────────────
// CONNECT TO MQTT
// ─────────────────────────────────────────────
void connectMQTT() {
  while (!client.connected()) {

    String clientId = "ESP32-" + String(random(0xffff), HEX);

    if (client.connect(clientId.c_str())) {

      // subscribe to incoming topics
      client.subscribe(mqtt_topic_threshold);
      client.subscribe(mqtt_topic_buzzer);
      client.subscribe(mqtt_pwm_topic);

    }
  }
}

// ─────────────────────────────────────────────
// FETCH WEATHER FROM API
// ─────────────────────────────────────────────
float fetchWeather(Suburb s) {

  HTTPClient http;
  char url[200];

  // build request URL
  if (s.query != NULL) {
    sprintf(url,
      "https://api.openweathermap.org/data/2.5/weather?q=%s&appid=%s&units=metric",
      s.query, apiKey);
  }

  http.begin(url);        // start HTTP request
  int code = http.GET();  // send GET request

  // if successful
  if (code == 200) {

    StaticJsonDocument<1024> doc;

    // parse JSON response
    deserializeJson(doc, http.getString());

    float temp = doc["main"]["temp"]; // extract temperature

    // create MQTT message
    char payload[200];
    sprintf(payload,
      "{\"suburb\":\"%s\",\"temp\":%.1f}",
      s.name, temp);

    client.publish(mqtt_topic_weather, payload); // send data

    return temp;
  }

  return -999; // error value
}

// ─────────────────────────────────────────────
// SETUP (runs once at start)
// ─────────────────────────────────────────────
void setup() {

  Serial.begin(115200); // start serial monitor

  dht.begin(); // initialize sensor

  // setup buzzer
  ledcAttach(BUZZERPIN, BUZZ_FREQ, BUZZ_RESOLUTION);

  // setup LED PWM
  ledcSetup(pwmChannel, pwmFreq, pwmResolution);
  ledcAttachPin(LEDPIN, pwmChannel);

  connectWiFi(); // connect to internet

  client.setServer(mqtt_server, 1883); // set MQTT broker
  client.setCallback(mqttCallback);    // set message handler

  connectMQTT(); // connect to MQTT
}

// ─────────────────────────────────────────────
// MAIN LOOP (runs forever)
// ─────────────────────────────────────────────
void loop() {

  client.loop(); // keep MQTT alive

  if (!client.connected()) {
    connectMQTT(); // reconnect if needed
  }

  float totalTemp = 0;
  int count = 0;

  // get weather for all suburbs
  for (int i = 0; i < suburbCount; i++) {

    float t = fetchWeather(suburbs[i]);

    if (t != -999) { // valid data
      totalTemp += t;
      count++;
    }
  }

  if (count > 0) {

    float avgTemp = totalTemp / count; // calculate average

    // read sensor
    float temp = dht.readTemperature();
    float hum  = dht.readHumidity();

    // retry if failed
    if (isnan(temp)) {
      delay(2000);
      temp = dht.readTemperature();
    }

    if (!isnan(temp)) {

      // check alert condition
      bool alert = temp > USER_THRESHOLD;

      // control buzzer locally
      if (alert) {
        buzzerOn();
      } else {
        buzzerOff();
      }

      // send sensor data
      char payload[200];
      sprintf(payload,
        "{\"sensor_temp\":%.1f,\"humidity\":%.1f}",
        temp, hum);

      client.publish(mqtt_topic_sensor, payload);

      // send alert message
      if (alert) {
        client.publish(mqtt_topic_alert, "{\"alert\":true}");
      }
    }
  }

  delay(30000); // wait 30 seconds
}