#include <Adafruit_MPU6050.h>
#include <Adafruit_Sensor.h>
#include <Wire.h>

Adafruit_MPU6050 mpu;

// Pin Definitions based on your wiring
const int BUZZER_PIN = 25;
const int LED_PIN = 26;
const int BUTTON_PIN = 4;

// Threshold for accident detection (G-force magnitude)
// In simulation, you might need to move sliders quickly to trigger this
const float ACCEL_THRESHOLD = 25.0; 

void setup() {
  Serial.begin(115200);
  
  // Initialize Pins
  pinMode(BUZZER_PIN, OUTPUT);
  pinMode(LED_PIN, OUTPUT);
  pinMode(BUTTON_PIN, INPUT_PULLUP); // Button connects to GND when pressed

  // Initialize MPU6050
  if (!mpu.begin()) {
    Serial.println("Failed to find MPU6050 chip - Check your SDA/SCL wiring!");
    while (1) { delay(10); }
  }
  
  Serial.println("MPU6050 Found! Smart Helmet System is ACTIVE.");
}

void loop() {
  sensors_event_t a, g, temp;
  mpu.getEvent(&a, &g, &temp);

  // Calculate the Resultant Vector (Magnitude) of Acceleration
  // Formula: sqrt(ax^2 + ay^2 + az^2)
  float magnitude = sqrt(a.acceleration.x * a.acceleration.x + 
                         a.acceleration.y * a.acceleration.y + 
                         a.acceleration.z * a.acceleration.z);

  // Check if force exceeds the threshold
  if (magnitude > ACCEL_THRESHOLD) {
    handleAccident();
  }
  
  delay(100); // Small delay for stability
}

void handleAccident() {
  Serial.println("\n--- ALERT: SUDDEN IMPACT DETECTED! ---");
  bool cancelled = false;
  
  // 10-second grace period (100 cycles of 100ms)
  for (int i = 0; i < 100; i++) { 
    // Blink LED and Beep Buzzer
    digitalWrite(BUZZER_PIN, HIGH);
    digitalWrite(LED_PIN, HIGH);
    delay(50);
    digitalWrite(BUZZER_PIN, LOW);
    digitalWrite(LED_PIN, LOW);
    delay(50);

    // If rider presses the button (D4 goes LOW), cancel the alert
    if (digitalRead(BUTTON_PIN) == LOW) {
      cancelled = true;
      break;
    }
  }

  if (cancelled) {
    Serial.println("SAFE: Rider cancelled the alert.");
    digitalWrite(BUZZER_PIN, LOW);
    digitalWrite(LED_PIN, LOW);
  } else {
    sendEmergencyAlert();
  }
}

void sendEmergencyAlert() {
  Serial.println("CRITICAL: NO RESPONSE FROM RIDER.");
  Serial.println("GSM: Initializing SIM800L...");
  Serial.println("GSM: Sending Location Data & SMS to Emergency Contact...");
  Serial.println("GSM: Placing Call to +91XXXXXXXXXX...");
  
  // Solid alert to help rescuers find the helmet
  digitalWrite(BUZZER_PIN, HIGH);
  digitalWrite(LED_PIN, HIGH);
}