// Smart Garbage Bin (Wokwi) - ESP32
// HC-SR04 (fill level) + POT (simulated gas sensor on ADC35)
// Publishes JSON to Serial and to MQTT if available.

/* Add libraries.txt to Wokwi:
   knolleary/PubSubClient@^2.8
*/

#include <WiFi.h>
#include <PubSubClient.h>

// -------- CONFIG ----------
const char* WIFI_SSID = "REPLACE_WITH_SSID";
const char* WIFI_PASS = "REPLACE_WITH_PASSWORD";
const char* MQTT_BROKER = "test.mosquitto.org";
const uint16_t MQTT_PORT = 1883;
const char* DEVICE_ID = "BIN-0001";

#define TRIG_PIN 25
#define ECHO_PIN 26
#define GAS_PIN 35   // ADC input (POT wiper)
#define ALERT_LED 16

const float BIN_DEPTH_CM = 40.0;   // distance from sensor to bin bottom when EMPTY
const float FULL_THRESHOLD_PCT = 80.0; // consider full above this percent
const float GAS_THRESHOLD_PCT = 45.0;  // consider smell high above this percent

const unsigned long PUBLISH_INTERVAL_MS = 10000UL; // 10 seconds

WiFiClient wifiClient;
PubSubClient mqtt(wifiClient);
unsigned long lastPublish = 0;

// ---------- Helpers ----------
float measureDistanceCm() {
  // Trigger 10us pulse
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  // wait for echo (timeout 30000 us)
  unsigned long dur = pulseIn(ECHO_PIN, HIGH, 30000UL);
  if (dur == 0) return -1.0; // no echo
  float dist = dur / 58.0; // us -> cm (approx)
  return dist;
}

float distanceToFillPct(float distCm) {
  if (distCm < 0) return -1.0;         // invalid
  if (distCm >= BIN_DEPTH_CM) return 0.0; // empty
  float pct = (1.0 - (distCm / BIN_DEPTH_CM)) * 100.0;
  if (pct < 0) pct = 0;
  if (pct > 100) pct = 100;
  return pct;
}

float readGasPct() {
  // ADC returns 0..4095 (12-bit) on ESP32 by default in Arduino core
  int raw = analogRead(GAS_PIN); // 0..4095
  float pct = (raw / 4095.0) * 100.0; // 0..100%
  return pct;
}

void connectWiFiOnce() {
  if (WiFi.status() == WL_CONNECTED) return;
  Serial.print("Connecting WiFi...");
  WiFi.mode(WIFI_STA);
  WiFi.begin(WIFI_SSID, WIFI_PASS);
  unsigned long start = millis();
  while (WiFi.status() != WL_CONNECTED && millis() - start < 20000UL) {
    delay(500); Serial.print(".");
  }
  if (WiFi.status() == WL_CONNECTED) {
    Serial.println("\nWiFi OK: " + WiFi.localIP().toString());
  } else {
    Serial.println("\nWiFi not connected (will retry later).");
  }
}

void mqttCallback(char* topic, byte* payload, unsigned int length) {
  Serial.print("MQTT Rx: "); Serial.println(topic);
  String s;
  for (unsigned int i = 0; i < length; i++) s += (char)payload[i];
  Serial.println("Payload: " + s);
}

void connectMQTT() {
  if (WiFi.status() != WL_CONNECTED) return;
  if (mqtt.connected()) return;
  mqtt.setServer(MQTT_BROKER, MQTT_PORT);
  mqtt.setCallback(mqttCallback);
  Serial.print("Connecting MQTT...");
  if (mqtt.connect(DEVICE_ID)) {
    Serial.println("connected");
    String cmdTopic = String("waste/bin/") + DEVICE_ID + "/cmd";
    mqtt.subscribe(cmdTopic.c_str());
  } else {
    Serial.print("failed rc="); Serial.println(mqtt.state());
  }
}

void publishTelemetry(float fillPct, float dist, float gasPct, float tempMock, float humMock) {
  String payload = "{";
  payload += "\"device_id\":\"" + String(DEVICE_ID) + "\"";
  payload += ",\"ts\":" + String((unsigned long)(millis() / 1000));
  payload += ",\"fill_level_pct\":" + String(fillPct,1);
  payload += ",\"distance_cm\":" + String(dist,1);
  payload += ",\"gas_pct\":" + String(gasPct,1);
  payload += ",\"temp_c\":" + String(tempMock,1);
  payload += ",\"humidity_pct\":" + String(humMock,1);
  payload += "}";

  String topic = "waste/bin/" + String(DEVICE_ID) + "/telemetry";
  Serial.println("MQTT Publish -> " + topic + " : " + payload);

  // Try MQTT publish if connected
  if (WiFi.status() == WL_CONNECTED && mqtt.connected()) {
    bool ok = mqtt.publish(topic.c_str(), payload.c_str());
    if (!ok) Serial.println("MQTT publish failed");
  } else {
    Serial.println("MQTT not connected (Serial only).");
  }
}

// ---------- Setup / Loop ----------
void setup() {
  Serial.begin(115200);
  delay(50);
  Serial.println("Smart Bin (Wokwi) starting...");

  pinMode(TRIG_PIN, OUTPUT); digitalWrite(TRIG_PIN, LOW);
  pinMode(ECHO_PIN, INPUT);
  pinMode(ALERT_LED, OUTPUT); digitalWrite(ALERT_LED, LOW);

  analogReadResolution(12); // ensure 0..4095 (default)
  // Attempt WiFi (optional)
  connectWiFiOnce();
  connectMQTT();
}

void loop() {
  // Maintain MQTT
  if (WiFi.status() == WL_CONNECTED) {
    if (!mqtt.connected()) connectMQTT();
    mqtt.loop();
  } else {
    static unsigned long lastWiFiTry = 0;
    if (millis() - lastWiFiTry > 30000UL) { lastWiFiTry = millis(); connectWiFiOnce(); }
  }

  // Read sensors
  float dist = measureDistanceCm();
  float fillPct = distanceToFillPct(dist);
  float gasPct = readGasPct();

  // simple mocked temp/humidity (use real sensors in hardware)
  float tempMock = 30.0; 
  float humMock  = 60.0;

  // Decide alert
  bool full = (fillPct >= FULL_THRESHOLD_PCT && fillPct >= 0);
  bool smelly = (gasPct >= GAS_THRESHOLD_PCT);
  if (full || smelly) digitalWrite(ALERT_LED, HIGH); else digitalWrite(ALERT_LED, LOW);

  // Publish periodically
  if (millis() - lastPublish >= PUBLISH_INTERVAL_MS) {
    lastPublish = millis();
    publishTelemetry(fillPct < 0 ? 0 : fillPct, dist, gasPct, tempMock, humMock);
  }

  delay(200); // short pause
}