// ESP32 - Button + SIM800 → Firebase
// Notifications handled by Web App (index.html)
// 100% FREE!
// By: Muhmmad Ali

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

#define WIFI_SSID     "Wokwi-GUEST"
#define WIFI_PASSWORD ""

#define FIREBASE_URL  "https://sim800-controller-default-rtdb.firebaseio.com"
#define FIREBASE_AUTH "YUdjhcfUvLbp9s2ELz1x2wSx1iHhA1QnHAaQMzxw"

#define BUTTON_PIN 4

HardwareSerial sim800Serial(2); // RX=GPIO16, TX=GPIO17
String smsBuffer = "";
bool waitingContent = false;
bool lastButtonState = HIGH;

void connectWiFi() {
  Serial.print("Connecting to WiFi");
  WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
  int tries = 0;
  while (WiFi.status() != WL_CONNECTED && tries < 20) {
    delay(500);
    Serial.print(".");
    tries++;
  }
  if (WiFi.status() == WL_CONNECTED) {
    Serial.println("\n✅ WiFi Connected: " + WiFi.localIP().toString());
  } else {
    Serial.println("\n❌ WiFi failed!");
  }
}

void sendToFirebase(String message) {
  if (WiFi.status() != WL_CONNECTED) { connectWiFi(); return; }

  HTTPClient http;
  String url = String(FIREBASE_URL) + "/alerts.json?auth=" + FIREBASE_AUTH;
  http.begin(url);
  http.addHeader("Content-Type", "application/json");

  String body = "{\"message\":\"" + message + "\",\"timestamp\":" + String(millis()) + "}";
  int code = http.POST(body);

  Serial.println((code == 200 || code == 201) ? "✅ Firebase saved!" : "❌ Firebase error: " + String(code));
  http.end();
}

void parseSIM800(String line) {
  line.trim();
  if (line.length() == 0) return;
  Serial.println("[SIM800] " + line);

  if (line.indexOf("+CMTI:") != -1) {
    Serial.println("📩 New SMS! Reading...");
    int comma = line.indexOf(",");
    String idx = line.substring(comma + 1);
    idx.trim();
    sim800Serial.println("AT+CMGR=" + idx);
    waitingContent = true;
    return;
  }

  if (line.indexOf("+CMGR:") != -1) { waitingContent = true; return; }

  if (waitingContent && line != "OK" && line.length() > 0) {
    waitingContent = false;
    Serial.println("📨 SMS: " + line);
    sendToFirebase(line);
  }
}

void setup() {
  Serial.begin(115200);
  Serial.println("=== SIM800 Alert System ===");

  pinMode(BUTTON_PIN, INPUT_PULLUP);

  sim800Serial.begin(9600, SERIAL_8N1, 16, 17);
  delay(1000);
  sim800Serial.println("AT");                delay(300);
  sim800Serial.println("AT+CMGF=1");         delay(300);
  sim800Serial.println("AT+CNMI=1,2,0,0,0"); delay(300);

  connectWiFi();
  Serial.println("✅ Ready! Press button or wait for SMS...");
}

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

  // Push Button
  bool currentButtonState = digitalRead(BUTTON_PIN);
  if (currentButtonState == LOW && lastButtonState == HIGH) {
    Serial.println("🔴 Button Pressed!");
    sendToFirebase("ALERT: Button pressed!");
    delay(300);
  }
  lastButtonState = currentButtonState;

  // SIM800
  while (sim800Serial.available()) {
    char c = sim800Serial.read();
    if (c == '\n') { parseSIM800(smsBuffer); smsBuffer = ""; }
    else smsBuffer += c;
  }

  delay(10);
}