#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <WiFi.h>
#include <PubSubClient.h>

// ------- Pins -------
#define LED_GREEN 23
#define LED_RED   19

// ------- LCD (I2C) -------
LiquidCrystal_I2C lcd(0x27, 20, 4);   // 20x4 at address 0x27

// ------- Wi‑Fi (Wokwi virtual AP) -------
const char* ssid     = "Wokwi-GUEST";
const char* password = "";

// ------- MQTT (EMQX Public Broker) -------
const char* mqttHost = "broker.emqx.io";
const int   mqttPort = 1883;

// Unique topics for you
const char* mqttTopic = "kutrrh/joseph/parking/status"; // telemetry
const char* mqttLwt   = "kutrrh/joseph/parking/lwt";    // presence

WiFiClient   wifiClient;
PubSubClient mqtt(wifiClient);

// ---- Global state ----
int freeSlots = 23;          // initial value
int lastPublishedSlots = -1; // force first publish

// ---- Helpers ----
void connectWiFi() {
  if (WiFi.status() == WL_CONNECTED) return;
  Serial.print("Connecting WiFi");
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(300);
    Serial.print(".");
  }
  Serial.println();
  Serial.print("WiFi connected. IP: ");
  Serial.println(WiFi.localIP());
}

void connectMQTT() {
  mqtt.setServer(mqttHost, mqttPort);

  int attempt = 0;
  while (!mqtt.connected()) {
    String clientId = "esp32-parking-" + String((uint32_t)ESP.getEfuseMac(), HEX);
    Serial.printf("MQTT connect try %d ... ", ++attempt);

    // Set LWT via connect()
    bool ok = mqtt.connect(
      clientId.c_str(),
      mqttLwt,           // willTopic
      0,                 // willQoS
      true,              // willRetain
      "device:esp32-entrance-A status:offline" // willMessage
    );

    if (ok) {
      Serial.println("OK");
      // Announce online (retained)
      mqtt.publish(mqttLwt, "device:esp32-entrance-A status:online", true);
      break;
    } else {
      Serial.printf("failed rc=%d; retrying...\n", mqtt.state());
      delay(min(500 * attempt, 4000)); // incremental backoff
    }
  }
}

void updateUI() {
  // LEDs
  digitalWrite(LED_GREEN, freeSlots > 0 ? HIGH : LOW);
  digitalWrite(LED_RED,   freeSlots > 0 ? LOW  : HIGH);

  // LCD
  lcd.setCursor(0, 0); lcd.print("Parking Status:    ");
  lcd.setCursor(0, 1); lcd.print("Free Slots:        ");
  lcd.setCursor(12,1); lcd.print("    ");
  lcd.setCursor(12,1); lcd.print(freeSlots);
}

void publishStatusIfChanged() {
  if (!mqtt.connected()) return;

  if (freeSlots != lastPublishedSlots) {
    char json[160];
    snprintf(json, sizeof(json),
             "{\"device\":\"esp32-entrance-A\",\"freeSlots\":%d,\"status\":\"%s\"}",
             freeSlots, freeSlots > 0 ? "OPEN" : "FULL");

    bool ok = mqtt.publish(mqttTopic, json, true); // retain=true
    Serial.printf("MQTT publish (changed) -> topic='%s' payload=%s | ok=%d\n",
                  mqttTopic, json, ok);
    lastPublishedSlots = freeSlots;
  }
}

// Optional: clears retained message on the broker (call once if needed)
void clearRetained() {
  // Publish empty payload with retain=true to delete retained message on this topic
  bool ok = mqtt.publish(mqttTopic, "", true);
  Serial.printf("Cleared retained on '%s' | ok=%d\n", mqttTopic, ok);
}

void setup() {
  Serial.begin(115200);

  pinMode(LED_GREEN, OUTPUT);
  pinMode(LED_RED,   OUTPUT);

  Wire.begin(21, 22);
  lcd.init();
  lcd.backlight();

  connectWiFi();
  connectMQTT();

  updateUI();
  publishStatusIfChanged();

  Serial.println("\nType 's0' or 's10' in Serial to change freeSlots for testing.");
}

void loop() {
  if (WiFi.status() != WL_CONNECTED) connectWiFi();
  if (!mqtt.connected()) connectMQTT();
  mqtt.loop();

  // --- Demo: read simple serial commands to change the value live ---
  // Type s0  -> sets freeSlots=0
  // Type s10 -> sets freeSlots=10
  if (Serial.available()) {
    String cmd = Serial.readStringUntil('\n');
    cmd.trim();
    if (cmd.equalsIgnoreCase("s0")) {
      freeSlots = 0;
      updateUI();
      publishStatusIfChanged();
    } else if (cmd.equalsIgnoreCase("s10")) {
      freeSlots = 10;
      updateUI();
      publishStatusIfChanged();
    } else if (cmd.equalsIgnoreCase("clear")) {
      clearRetained(); // optional: remove retained message on broker
    }
  }

 }