/*
  Session 20 — Over-The-Air (OTA) firmware updates + health heartbeat (ESP32)
  After the first USB upload, the node appears in Arduino IDE -> Tools -> Port -> "kfs-field-a at 192.168.1.x".
  Upload again over Wi-Fi without removing the node from the field. The OTA password protects it.
  Heartbeat: every 5 min publish uptime, free heap, RSSI, reset reason, firmware version (retained MQTT).
*/
#include <WiFi.h>
#include <ArduinoOTA.h>
#include <PubSubClient.h>
#include <esp_system.h>

#define FW_VERSION "1.4.0"
const char* WIFI_SSID = "KFS-Farm-IoT";
const char* WIFI_PASS = "change-me";
const char* HOSTNAME  = "kfs-field-a";
const char* OTA_PASS  = "farm-ota-2026";
const char* BROKER    = "192.168.1.10";

WiFiClient net;
PubSubClient mqtt(net);
unsigned long lastBeat = 0;

void setup() {
  Serial.begin(115200);
  WiFi.setHostname(HOSTNAME);
  WiFi.begin(WIFI_SSID, WIFI_PASS);
  while (WiFi.status() != WL_CONNECTED) delay(300);

  ArduinoOTA.setHostname(HOSTNAME);
  ArduinoOTA.setPassword(OTA_PASS);
  ArduinoOTA.onStart([]() { digitalWrite(26, HIGH); Serial.println("OTA start - pump relay forced OFF"); });
  ArduinoOTA.onProgress([](unsigned int p, unsigned int t) { Serial.printf("OTA %u%%\r", p * 100 / t); });
  ArduinoOTA.onEnd([]() { Serial.println("\nOTA done, rebooting"); });
  ArduinoOTA.onError([](ota_error_t e) { Serial.printf("OTA error %u\n", e); });
  ArduinoOTA.begin();

  mqtt.setServer(BROKER, 1883);
  Serial.printf("fw %s ready at %s\n", FW_VERSION, WiFi.localIP().toString().c_str());
}

void loop() {
  ArduinoOTA.handle();                       // must be called often
  if (!mqtt.connected()) mqtt.connect(HOSTNAME);
  mqtt.loop();
  if (millis() - lastBeat > 300000 || lastBeat == 0) {
    lastBeat = millis();
    char buf[200];
    snprintf(buf, sizeof(buf),
             "{\"fw\":\"%s\",\"uptime_s\":%lu,\"heap\":%u,\"rssi\":%d,\"reset_reason\":%d}",
             FW_VERSION, millis() / 1000, ESP.getFreeHeap(), WiFi.RSSI(), (int)esp_reset_reason());
    mqtt.publish("kfs/farm/field_A/health", buf, true);   // retained: the dashboard always sees the last state
  }
}