/*
  KFS Smart Farm — field node (ESP32) — HTTP version  (sessions 9-12, 17-21)
  Sensors : DHT22 (GPIO 4), capacitive soil moisture v1.2 (GPIO 34), LDR divider (GPIO 35), battery divider (GPIO 33)
  Actuator: relay module IN1 (GPIO 26) -> irrigation pump, IN2 (GPIO 27) -> greenhouse fan  (active LOW modules)
  Every 30 s: POST /api/v1/readings  then  GET /api/v1/commands/pending  -> drive relays -> ACK
  Libraries: "DHT sensor library" (Adafruit), "ArduinoJson" v7
*/
#include <WiFi.h>
#include <HTTPClient.h>
#include <ArduinoJson.h>
#include <DHT.h>

// ---------- edit for your farm ----------
const char* WIFI_SSID = "KFS-Farm-IoT";
const char* WIFI_PASS = "change-me";
const char* SERVER    = "http://192.168.1.10:5000";   // laptop / Raspberry Pi running app.py
const char* API_KEY   = "kfs-farm-node-key";
const char* NODE_ID   = "field_A";
const int   SOIL_DRY  = 3200;   // ADC in dry air      (calibrate! session 2)
const int   SOIL_WET  = 1300;   // ADC in a cup of water
// -----------------------------------------

#define DHT_PIN 4
#define SOIL_PIN 34
#define LDR_PIN 35
#define BAT_PIN 33
#define PUMP_PIN 26
#define FAN_PIN 27
#define PUMP_MAX_MS (30UL * 60UL * 1000UL)   // hardware safety: never run the pump > 30 min

DHT dht(DHT_PIN, DHT22);
unsigned long lastSend = 0, pumpOffAt = 0, fanOffAt = 0;

int readSoilAdc() {                        // median of 9 samples -> rejects spikes (session 3)
  int v[9];
  for (int i = 0; i < 9; i++) { v[i] = analogRead(SOIL_PIN); delay(5); }
  for (int i = 1; i < 9; i++) { int k = v[i], j = i - 1; while (j >= 0 && v[j] > k) { v[j + 1] = v[j]; j--; } v[j + 1] = k; }
  return v[4];
}

float soilPercent(int adc) {
  float p = (float)(SOIL_DRY - adc) / (SOIL_DRY - SOIL_WET) * 100.0;
  return constrain(p, 0, 100);
}

void relay(int pin, bool on) { digitalWrite(pin, on ? LOW : HIGH); }   // active-LOW relay board

void connectWiFi() {
  if (WiFi.status() == WL_CONNECTED) return;
  WiFi.mode(WIFI_STA);
  WiFi.begin(WIFI_SSID, WIFI_PASS);
  for (int i = 0; i < 40 && WiFi.status() != WL_CONNECTED; i++) delay(250);
  Serial.printf("WiFi %s  IP=%s  RSSI=%d\n", WiFi.status() == WL_CONNECTED ? "OK" : "FAIL",
                WiFi.localIP().toString().c_str(), WiFi.RSSI());
}

void sendReading() {
  float t = dht.readTemperature(), h = dht.readHumidity();
  int soil = readSoilAdc();
  JsonDocument doc;
  doc["node_id"] = NODE_ID;
  if (!isnan(t)) doc["air_temp_c"] = t;            // missing value -> field omitted (server stores NULL)
  if (!isnan(h)) doc["air_humidity_pct"] = h;
  doc["soil_moisture_pct"] = soilPercent(soil);
  doc["light"] = analogRead(LDR_PIN);
  doc["battery_v"] = analogReadMilliVolts(BAT_PIN) * 2 / 1000.0;   // 100k/100k divider
  doc["rssi"] = WiFi.RSSI();
  doc["fw"] = "1.3.0";
  String body; serializeJson(doc, body);

  HTTPClient http;
  http.begin(String(SERVER) + "/api/v1/readings");
  http.addHeader("Content-Type", "application/json");
  http.addHeader("X-API-Key", API_KEY);
  int code = http.POST(body);
  Serial.printf("POST %d  %s\n", code, body.c_str());
  http.end();
}

void pollCommands() {
  HTTPClient http;
  http.begin(String(SERVER) + "/api/v1/commands/pending?node_id=" + NODE_ID);
  http.addHeader("X-API-Key", API_KEY);
  if (http.GET() == 200) {
    JsonDocument doc;
    deserializeJson(doc, http.getString());
    for (JsonObject c : doc["commands"].as<JsonArray>()) {
      bool on = String((const char*)c["action"]) == "on";
      unsigned long ms = min((unsigned long)c["duration_min"].as<int>() * 60000UL, PUMP_MAX_MS);
      if (String((const char*)c["actuator"]) == "pump") { relay(PUMP_PIN, on); pumpOffAt = on ? millis() + ms : 0; }
      else                                             { relay(FAN_PIN, on);  fanOffAt  = on ? millis() + ms : 0; }
      Serial.printf("CMD #%d %s %s\n", (int)c["id"], (const char*)c["actuator"], (const char*)c["action"]);
      HTTPClient ack;
      ack.begin(String(SERVER) + "/api/v1/commands/" + String((int)c["id"]) + "/ack");
      ack.addHeader("X-API-Key", API_KEY);
      ack.POST("{}");
      ack.end();
    }
  }
  http.end();
}

void setup() {
  Serial.begin(115200);
  pinMode(PUMP_PIN, OUTPUT); pinMode(FAN_PIN, OUTPUT);
  relay(PUMP_PIN, false); relay(FAN_PIN, false);       // fail-safe: everything OFF at boot
  analogReadResolution(12);
  dht.begin();
  connectWiFi();
}

void loop() {
  if (pumpOffAt && millis() > pumpOffAt) { relay(PUMP_PIN, false); pumpOffAt = 0; Serial.println("pump auto-off"); }
  if (fanOffAt && millis() > fanOffAt)   { relay(FAN_PIN, false);  fanOffAt = 0; }
  if (millis() - lastSend > 30000 || lastSend == 0) {
    lastSend = millis();
    connectWiFi();
    if (WiFi.status() == WL_CONNECTED) { sendReading(); pollCommands(); }
    else { relay(PUMP_PIN, false); }                    // lost the server -> stop irrigating
  }
}