#include <WiFi.h>
#include <HTTPClient.h>

// ---------- WiFi ----------
const char* WIFI_SSID = "Wokwi-GUEST";
const char* WIFI_PWD  = "";

// ---------- ThingSpeak ----------
const char* TS_API_KEY = "UOO5LGZFY0EH4RN8";
const char* TS_URL_BASE = "http://api.thingspeak.com/update";

// ---------- ADC / LDR model ----------
const int   LDR_ADC_PIN = 34;
const float ADC_MAX     = 4095.0;
const float R_FIXED     = 10000.0;

// ---------- LED ----------
const int LED_PIN = 2;

// ---------- Calibration ----------
const double A_CONST = 252618.1571708225;
const double B_CONST = 0.7012322813355019;
const double INV_B   = 1.0 / B_CONST;

// ---------- Timing ----------
const unsigned long POST_INTERVAL_MS = 16000;
unsigned long lastPost = 0;

// ---------- Lux Conversion ----------
double luxFromADC(int adc) {
  adc = constrain(adc, 1, 4094);  // Prevent division by zero
  double Rldr = R_FIXED * (double(adc) / (ADC_MAX - double(adc)));
  return pow(A_CONST / Rldr, INV_B);
}

// ---------- WiFi Connection ----------
void connectWiFi() {
  WiFi.mode(WIFI_STA);
  WiFi.begin(WIFI_SSID, WIFI_PWD);
  Serial.print("Connecting to WiFi");
  while (WiFi.status() != WL_CONNECTED) {
    delay(300);
    Serial.print(".");
  }
  Serial.println();
  Serial.print("WiFi connected. IP: ");
  Serial.println(WiFi.localIP());
}

// ---------- ThingSpeak Upload ----------
bool sendToThingSpeak(double lux, int ledStatus) {
  String url = String(TS_URL_BASE) + "?api_key=" + TS_API_KEY +
               "&field1=" + String(lux, 2) +
               "&field3=" + String(ledStatus);

  HTTPClient http;
  http.begin(url);
  int httpCode = http.GET();

  Serial.print("Request URL: ");
  Serial.println(url);
  Serial.print("ThingSpeak response code: ");
  Serial.println(httpCode);

  String payload = http.getString();
  Serial.println("Response payload: " + payload);

  http.end();
  return (httpCode == 200);
}

// ---------- Setup ----------
void setup() {
  Serial.begin(115200);
  analogReadResolution(12);
  pinMode(LED_PIN, OUTPUT);
  connectWiFi();
}

// ---------- Main Loop ----------
void loop() {
  // Reconnect WiFi if disconnected
  if (WiFi.status() != WL_CONNECTED) {
    Serial.println("WiFi disconnected. Reconnecting...");
    connectWiFi();
  }

  // Read ADC and convert to Lux
  int adc = analogRead(LDR_ADC_PIN);
  double lux = luxFromADC(adc);

  Serial.print("ADC=");
  Serial.print(adc);
  Serial.print(" | Lux=");
  Serial.println(lux, 2);

  // LED control based on Lux
  int ledStatus = (lux < 100.0) ? 1 : 0;
  digitalWrite(LED_PIN, ledStatus ? HIGH : LOW);

  // Post to ThingSpeak
  unsigned long now = millis();
  if (now - lastPost >= POST_INTERVAL_MS) {
    sendToThingSpeak(lux, ledStatus);
    lastPost = now;
  }

  delay(250);
}