#include <Wire.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_BMP280.h>

#define BMP_SCK  (13)
#define BMP_MISO (12)
#define BMP_MOSI (11)
#define BMP_CS   (10)

// Mock MPU6050 class
class MPU6050 {
public:
    void initialize() {
        Serial.println("MPU6050 initialized.");
    }
    bool testConnection() {
        return true;
    }
    void update() {}
    double getGyroZ() {
        // Simulate 0.5 Hz roll about Z-axis (1 cycle every 2 seconds)
        static double angle = 0;
        double frequency = 0.5; // 0.5 Hz
        angle += 360 * frequency / 100; // Increment angle for each loop
        if (angle > 180) angle = -180; // Simulate angle wrap around
        return angle;
    }
};

Adafruit_BMP280 bmp;
MPU6050 mpu;
double gyroZ_bias = 0;

// Kalman filter variables for altitude estimation
double altitude_estimate = 0;
double velocity_estimate = 12.0; // 12 m/s upwards
double accel_bias = 0;
double P[2][2] = { {1, 0}, {0, 1} };
double Q[2][2] = { {0.001, 0}, {0, 0.003} };
double R = 0.03;
double K[2];

// Calibration function for MPU6050
void calibrateMPU6050() {
    long gyroZ_sum = 0;
    int samples = 1000;
    for (int i = 0; i < samples; i++) {
        mpu.update();
        gyroZ_sum += mpu.getGyroZ();
        delay(2);
    }
    gyroZ_bias = gyroZ_sum / samples;
}

// Kalman filter update function for altitude
void kalmanUpdate(double measured_altitude) {
    // Predict step
    altitude_estimate += velocity_estimate * 0.1; // dt = 0.1s
    P[0][0] += P[1][1] + Q[0][0];
    P[0][1] += P[1][1];
    P[1][0] += P[1][1];
    P[1][1] += Q[1][1];

    // Update step
    double y = measured_altitude - altitude_estimate;
    double S = P[0][0] + R;
    K[0] = P[0][0] / S;
    K[1] = P[1][0] / S;

    altitude_estimate += K[0] * y;
    velocity_estimate += K[1] * y;

    double P00_temp = P[0][0];
    double P01_temp = P[0][1];

    P[0][0] -= K[0] * P00_temp;
    P[0][1] -= K[0] * P01_temp;
    P[1][0] -= K[1] * P00_temp;
    P[1][1] -= K[1] * P01_temp;
}

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

    if (!bmp.begin(0x77)) { // Assuming the I2C address is 0x76
        Serial.println("Could not find a valid BMP280 sensor, check wiring!");
        while (1);
    }

    mpu.initialize();
    if (!mpu.testConnection()) {
        Serial.println("MPU6050 connection failed!");
        while (1);
    }

    Serial.println("Calibrating MPU6050...");
    calibrateMPU6050();
    Serial.print("Gyro Z Bias: ");
    Serial.println(gyroZ_bias);

    // BMP280 settings
    bmp.setSampling(Adafruit_BMP280::MODE_NORMAL,
                    Adafruit_BMP280::SAMPLING_X2,
                    Adafruit_BMP280::SAMPLING_X16,
                    Adafruit_BMP280::FILTER_X16,
                    Adafruit_BMP280::STANDBY_MS_1);
}

void loop() {
    mpu.update();
    double gyroZ = mpu.getGyroZ() - gyroZ_bias;

    // Calculate roll angle based on gyroZ readings
    static double roll_angle = 0;
    double dt = 0.1; // Assume a fixed time step for simplicity
    roll_angle += gyroZ * dt;
    if (roll_angle > 180) roll_angle = -180;

    // Simulate altitude change
    double measured_altitude = bmp.readAltitude(1013.25) + velocity_estimate * dt; // Simulate altitude change

    // Update Kalman filter for altitude
    kalmanUpdate(measured_altitude);

    Serial.print("Gyro Z: ");
    Serial.print(gyroZ);
    Serial.print(", Roll Angle: ");
    Serial.print(roll_angle);
    Serial.print(", Measured Altitude: ");
    Serial.print(measured_altitude);
    Serial.print(", Estimated Altitude: ");
    Serial.println(altitude_estimate);

    delay(100); // Adjust delay as needed
}