#include <Wire.h>

const int MPU_ADDR = 0x68;

// MPU6050 register addresses
const int PWR_MGMT_1 = 0x6B;
const int ACCEL_XOUT_H = 0x3B;
const int GYRO_XOUT_H = 0x43;
const int TEMP_OUT_H = 0x41;

// Calibration offsets
float accelOffsetX = 0;
float accelOffsetY = 0;
float accelOffsetZ = 0;
float gyroOffsetX = 0;
float gyroOffsetY = 0;
float gyroOffsetZ = 0;

// Adaptive thresholds - will adjust based on normal motion
float adaptiveAccelThreshold = 3.0;    // Start with reasonable value
float adaptiveGyroThreshold = 50.0;    // Start with reasonable value

// Impact detection
const unsigned long IMPACT_WINDOW = 100;    // Time to analyze impact (ms)
const unsigned long HIT_COOLDOWN = 2000;    // Prevent multiple detections
const float SUDDEN_CHANGE_FACTOR = 3.0;     // Must be 3x normal motion

// Fall detection parameters
const float FREE_FALL_THRESHOLD = 0.5;      // Low G-force for free fall
const float FALL_IMPACT_THRESHOLD = 4.0;    // G-force for fall impact
const unsigned long FALL_TIME_WINDOW = 3000; // Max time for fall sequence
const unsigned long FALL_COOLDOWN = 5000;   // Cooldown between fall detections

// State variables
bool hitDetected = false;
bool fallDetected = false;
unsigned long lastHitTime = 0;
unsigned long lastFallTime = 0;
unsigned long impactStartTime = 0;
bool analyzingImpact = false;

// Fall detection states
bool inFreeFall = false;
unsigned long fallStartTime = 0;
bool waitingForFallImpact = false;

// For adaptive threshold calculation
float normalAccelMax = 0;
float normalGyroMax = 0;
unsigned long lastNormalUpdate = 0;
const unsigned long NORMAL_LEARNING_TIME = 5000; // Learn normal motion for 5 sec

// Impact analysis
float impactAccelPeaks[10] = {0};
float impactGyroPeaks[10] = {0};
int peakCount = 0;

// Filtering
const int MOVING_AVERAGE_SAMPLES = 5;
float accelBuffer[MOVING_AVERAGE_SAMPLES] = {0};
float gyroBuffer[MOVING_AVERAGE_SAMPLES] = {0};
int bufferIndex = 0;

bool calibrated = false;
const int CALIBRATION_SAMPLES = 100;
bool learningPhase = true;

void setup() {
  Serial.begin(115200);
  Wire.begin();

  // Wake up MPU6050
  Wire.beginTransmission(MPU_ADDR);
  Wire.write(PWR_MGMT_1);
  Wire.write(0);
  Wire.endTransmission(true);

  Serial.println("HEAD IMPACT & FALL DETECTION SYSTEM");
  Serial.println("Learning normal motion for 5 seconds...");
  Serial.println("Please walk around normally");
  calibrateSensor();
  Serial.println("Calibration complete!");
  Serial.println("======================================");
  lastNormalUpdate = millis();
}

void calibrateSensor() {
  float accelXSum = 0, accelYSum = 0, accelZSum = 0;
  float gyroXSum = 0, gyroYSum = 0, gyroZSum = 0;

  for (int i = 0; i < CALIBRATION_SAMPLES; i++) {
    int16_t accelX = readSensor(ACCEL_XOUT_H);
    int16_t accelY = readSensor(ACCEL_XOUT_H + 2);
    int16_t accelZ = readSensor(ACCEL_XOUT_H + 4);
    int16_t gyroX = readSensor(GYRO_XOUT_H);
    int16_t gyroY = readSensor(GYRO_XOUT_H + 2);
    int16_t gyroZ = readSensor(GYRO_XOUT_H + 4);

    accelXSum += accelX / 16384.0;
    accelYSum += accelY / 16384.0;
    accelZSum += accelZ / 16384.0;
    gyroXSum += gyroX / 131.0;
    gyroYSum += gyroY / 131.0;
    gyroZSum += gyroZ / 131.0;

    delay(10);
  }

  accelOffsetX = accelXSum / CALIBRATION_SAMPLES;
  accelOffsetY = accelYSum / CALIBRATION_SAMPLES;
  accelOffsetZ = accelZSum / CALIBRATION_SAMPLES - 1.0;

  gyroOffsetX = gyroXSum / CALIBRATION_SAMPLES;
  gyroOffsetY = gyroYSum / CALIBRATION_SAMPLES;
  gyroOffsetZ = gyroZSum / CALIBRATION_SAMPLES;

  calibrated = true;
}

float movingAverage(float buffer[], float newValue) {
  buffer[bufferIndex] = newValue;
  bufferIndex = (bufferIndex + 1) % MOVING_AVERAGE_SAMPLES;

  float sum = 0;
  for (int i = 0; i < MOVING_AVERAGE_SAMPLES; i++) {
    sum += buffer[i];
  }
  return sum / MOVING_AVERAGE_SAMPLES;
}

void loop() {
  // Read sensor data
  int16_t rawAccelX = readSensor(ACCEL_XOUT_H);
  int16_t rawAccelY = readSensor(ACCEL_XOUT_H + 2);
  int16_t rawAccelZ = readSensor(ACCEL_XOUT_H + 4);

  int16_t rawGyroX = readSensor(GYRO_XOUT_H);
  int16_t rawGyroY = readSensor(GYRO_XOUT_H + 2);
  int16_t rawGyroZ = readSensor(GYRO_XOUT_H + 4);

  // Convert and apply calibration
  float accelX_g = rawAccelX / 16384.0 - accelOffsetX;
  float accelY_g = rawAccelY / 16384.0 - accelOffsetY;
  float accelZ_g = rawAccelZ / 16384.0 - accelOffsetZ;

  float gyroX_deg = rawGyroX / 131.0 - gyroOffsetX;
  float gyroY_deg = rawGyroY / 131.0 - gyroOffsetY;
  float gyroZ_deg = rawGyroZ / 131.0 - gyroOffsetZ;

  // Calculate magnitudes with moving average filtering
  float accelMagnitude = sqrt(accelX_g * accelX_g + accelY_g * accelY_g + accelZ_g * accelZ_g);
  float gyroMagnitude = sqrt(gyroX_deg * gyroX_deg + gyroY_deg * gyroY_deg + gyroZ_deg * gyroZ_deg);

  float filteredAccel = movingAverage(accelBuffer, accelMagnitude);
  float filteredGyro = movingAverage(gyroBuffer, gyroMagnitude);

  unsigned long currentTime = millis();

  // Learning phase - understand normal motion
  if (learningPhase) {
    updateNormalMotionLevels(filteredAccel, filteredGyro, currentTime);
  }

  // Run both detection systems
  checkForImpact(filteredAccel, filteredGyro, currentTime);
  checkForFall(filteredAccel, currentTime);

  // Print status
  static unsigned long lastPrint = 0;
  if (currentTime - lastPrint > 1000) {
    printStatus(accelX_g, accelY_g, accelZ_g, gyroX_deg, gyroY_deg, gyroZ_deg,
                filteredAccel, filteredGyro, currentTime);
    lastPrint = currentTime;
  }

  delay(20);
}

void updateNormalMotionLevels(float accel, float gyro, unsigned long currentTime) {
  // Update maximum normal motion levels during learning phase
  if (accel > normalAccelMax) normalAccelMax = accel;
  if (gyro > normalGyroMax) normalGyroMax = gyro;

  // End learning phase after 5 seconds
  if (currentTime - lastNormalUpdate > NORMAL_LEARNING_TIME) {
    learningPhase = false;

    // Set adaptive thresholds based on learned normal motion
    adaptiveAccelThreshold = normalAccelMax * SUDDEN_CHANGE_FACTOR;
    adaptiveGyroThreshold = normalGyroMax * SUDDEN_CHANGE_FACTOR;

    // Ensure minimum thresholds
    if (adaptiveAccelThreshold < 2.0) adaptiveAccelThreshold = 2.0;
    if (adaptiveGyroThreshold < 30.0) adaptiveGyroThreshold = 30.0;

    Serial.println("\n*** LEARNING PHASE COMPLETE ***");
    Serial.print("Normal motion - Max Accel: "); Serial.print(normalAccelMax, 2); Serial.println("g");
    Serial.print("Normal motion - Max Gyro: "); Serial.print(normalGyroMax, 1); Serial.println("°/s");
    Serial.print("Adaptive thresholds - Accel: "); Serial.print(adaptiveAccelThreshold, 2); Serial.println("g");
    Serial.print("Adaptive thresholds - Gyro: "); Serial.print(adaptiveGyroThreshold, 1); Serial.println("°/s");
    Serial.println("Now monitoring for impacts and falls...");
  }
}

void checkForImpact(float accel, float gyro, unsigned long currentTime) {
  // Check if we have a sudden change that might be an impact
  bool suddenChange = (accel > adaptiveAccelThreshold) || (gyro > adaptiveGyroThreshold);

  if (suddenChange && !analyzingImpact) {
    // Start analyzing potential impact
    analyzingImpact = true;
    impactStartTime = currentTime;
    peakCount = 0;
    impactAccelPeaks[0] = accel;
    impactGyroPeaks[0] = gyro;
    Serial.println("💥 Potential impact detected - analyzing...");
  }

  if (analyzingImpact) {
    // Track peaks during impact window
    if (accel > impactAccelPeaks[peakCount]) impactAccelPeaks[peakCount] = accel;
    if (gyro > impactGyroPeaks[peakCount]) impactGyroPeaks[peakCount] = gyro;

    // Check if impact analysis period is over
    if (currentTime - impactStartTime > IMPACT_WINDOW) {
      analyzeImpactPattern(currentTime);
      analyzingImpact = false;
    }

    // Move to next peak every 20ms
    if (currentTime - impactStartTime > (peakCount + 1) * 20 && peakCount < 9) {
      peakCount++;
      impactAccelPeaks[peakCount] = accel;
      impactGyroPeaks[peakCount] = gyro;
    }
  }

  // Reset hit detection after cooldown
  if (currentTime - lastHitTime > HIT_COOLDOWN) {
    hitDetected = false;
  }
}

void analyzeImpactPattern(unsigned long currentTime) {
  // Find maximum values during impact window
  float maxAccel = 0;
  float maxGyro = 0;

  for (int i = 0; i <= peakCount; i++) {
    if (impactAccelPeaks[i] > maxAccel) maxAccel = impactAccelPeaks[i];
    if (impactGyroPeaks[i] > maxGyro) maxGyro = impactGyroPeaks[i];
  }

  // Determine if this is a real head impact
  bool isHeadImpact = verifyHeadImpact(maxAccel, maxGyro);

  if (isHeadImpact && !hitDetected) {
    hitDetected = true;
    lastHitTime = currentTime;

    Serial.println("🚨 🚨 🚨 🚨 🚨 🚨 🚨 🚨 🚨 🚨 🚨 🚨");
    Serial.println("🚨         HEAD IMPACT DETECTED!        🚨");
    Serial.println("🚨 🚨 🚨 🚨 🚨 🚨 🚨 🚨 🚨 🚨 🚨 🚨");
    Serial.print("Impact Force: "); Serial.print(maxAccel, 1); Serial.println("g");
    Serial.print("Rotational Force: "); Serial.print(maxGyro, 1); Serial.println("°/s");
    Serial.print("Thresholds: "); Serial.print(adaptiveAccelThreshold, 1);
    Serial.print("g / "); Serial.print(adaptiveGyroThreshold, 1); Serial.println("°/s");
    Serial.println("⚠️  CHECK USER FOR CONCUSSION SYMPTOMS!");
    Serial.println();
  } else if (!isHeadImpact) {
    Serial.print("❌ False alarm: ");
    Serial.print(maxAccel, 1); Serial.print("g, ");
    Serial.print(maxGyro, 1); Serial.println("°/s - Normal motion pattern");
  }
}

bool verifyHeadImpact(float maxAccel, float maxGyro) {
  // Real head impacts typically have:
  // 1. Very high acceleration OR very high rotation
  // 2. Both values significantly above normal motion
  // 3. Specific pattern characteristics

  bool highAccel = maxAccel > (normalAccelMax * 4.0);  // 4x normal motion
  bool highGyro = maxGyro > (normalGyroMax * 4.0);     // 4x normal motion

  // Head impact usually has both linear and rotational components
  bool hasBothComponents = (maxAccel > adaptiveAccelThreshold * 1.2) &&
                          (maxGyro > adaptiveGyroThreshold * 1.2);

  // Or extremely high values in one component
  bool extremeSingleComponent = (maxAccel > adaptiveAccelThreshold * 2.0) ||
                               (maxGyro > adaptiveGyroThreshold * 2.0);

  return (hasBothComponents || extremeSingleComponent) && (highAccel || highGyro);
}

void checkForFall(float accel, unsigned long currentTime) {
  // Fall detection logic: Free fall followed by impact

  // Step 1: Detect free fall (low acceleration)
  if (accel < FREE_FALL_THRESHOLD && !inFreeFall && !waitingForFallImpact) {
    inFreeFall = true;
    fallStartTime = currentTime;
    Serial.println("⚠️  Free fall detected! Monitoring for impact...");
  }

  // Step 2: If we're in free fall, wait for impact
  if (inFreeFall) {
    // Check if free fall period is too long (might not be a real fall)
    if (currentTime - fallStartTime > FALL_TIME_WINDOW) {
      inFreeFall = false;
      Serial.println("❌ Free fall too long - probably not a real fall");
    }

    // Check for impact after free fall
    if (accel > FALL_IMPACT_THRESHOLD) {
      // This is the impact after a fall
      if (!fallDetected && (currentTime - lastFallTime > FALL_COOLDOWN)) {
        fallDetected = true;
        lastFallTime = currentTime;
        inFreeFall = false;
        waitingForFallImpact = false;

        Serial.println("🚨 🚨 🚨 🚨 🚨 🚨 🚨 🚨 🚨 🚨 🚨 🚨");
        Serial.println("🚨           FALL DETECTED!           🚨");
        Serial.println("🚨 🚨 🚨 🚨 🚨 🚨 🚨 🚨 🚨 🚨 🚨 🚨");
        Serial.print("Fall Impact: "); Serial.print(accel, 1); Serial.println("g");
        Serial.print("Free fall duration: ");
        Serial.print(currentTime - fallStartTime);
        Serial.println("ms");
        Serial.println("⚠️  USER MAY HAVE FALLEN - CHECK IMMEDIATELY!");
        Serial.println();
      }
    }
  }

  // Reset fall detection after cooldown
  if (currentTime - lastFallTime > FALL_COOLDOWN) {
    fallDetected = false;
  }

  // Reset free fall state if acceleration returns to normal
  if (inFreeFall && accel > FREE_FALL_THRESHOLD * 2.0) {
    inFreeFall = false;
    waitingForFallImpact = true;
    // Wait a bit to see if impact comes
    if (currentTime - fallStartTime > 1000) {
      waitingForFallImpact = false;
    }
  }
}

void printStatus(float accelX, float accelY, float accelZ, float gyroX, float gyroY, float gyroZ,
                 float accelMag, float gyroMag, unsigned long currentTime) {
  Serial.print("Accel: ");
  Serial.print(accelX, 2); Serial.print("g, ");
  Serial.print(accelY, 2); Serial.print("g, ");
  Serial.print(accelZ, 2); Serial.print("g");
  Serial.print(" | Total: "); Serial.print(accelMag, 2); Serial.println("g");

  Serial.print("Gyro:  ");
  Serial.print(gyroX, 1); Serial.print("°/s, ");
  Serial.print(gyroY, 1); Serial.print("°/s, ");
  Serial.print(gyroZ, 1); Serial.print("°/s");
  Serial.print(" | Total: "); Serial.print(gyroMag, 1); Serial.println("°/s");

  if (learningPhase) {
    float remaining = (NORMAL_LEARNING_TIME - (currentTime - lastNormalUpdate)) / 1000.0;
    Serial.print("📚 Learning normal motion: ");
    Serial.print(remaining, 0); Serial.println("s remaining");
    Serial.print("Current max - Accel: "); Serial.print(normalAccelMax, 2);
    Serial.print("g, Gyro: "); Serial.print(normalGyroMax, 1); Serial.println("°/s");
  } else {
    Serial.print("🎯 Thresholds: "); Serial.print(adaptiveAccelThreshold, 1);
    Serial.print("g / "); Serial.print(adaptiveGyroThreshold, 1); Serial.println("°/s");

    // Status display for both systems
    if (hitDetected) {
      Serial.println("🚨 HEAD IMPACT DETECTED - CHECK USER!");
    } else if (fallDetected) {
      Serial.println("🚨 FALL DETECTED - USER MAY HAVE FALLEN!");
    } else if (inFreeFall) {
      Serial.println("⚠️  Free fall detected - watching for impact...");
    } else if (analyzingImpact) {
      Serial.println("💥 Analyzing potential impact...");
    } else {
      Serial.println("✅ Normal - Monitoring impacts & falls");
    }
  }

  Serial.println("-----------------------");
}

int16_t readSensor(uint8_t reg) {
  Wire.beginTransmission(MPU_ADDR);
  Wire.write(reg);
  Wire.endTransmission(false);
  Wire.requestFrom(MPU_ADDR, 2, true);
  return (Wire.read() << 8) | Wire.read();
}