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

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

// Initialize BMP280 sensor (hardware SPI)
Adafruit_BMP280 bmp(BMP_CS);

// Mock MPU6050 class
class MPU6050 {
public:
    void initialize() {
        Serial.println("MPU6050 initialized.");
    }
    bool testConnection() {
        return true;
    }
    void update() {}
    double getGyroZ() {
        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;
        return angle;
    }
};

MPU6050 mpu;
double gyroZ_bias = 0;

// Kalman filter variables for altitude estimation
double altitude_estimate = 0;
double velocity_estimate = 2.0;
double accel_bias = 0;
double P[2][2] = { {1, 0}, {0, 1} };
double Q[2][2] = { {0.01, 0}, {0, 0.02} };
double R = 0.01;
double K[2];

// Approximate thrust data derived from the simulation graph
const int thrust_data_length = 240;
double thrust_data[thrust_data_length];

// Function to approximate thrust data from the graph
void initializeThrustData() {
    for (int i = 0; i < thrust_data_length; i++) {
        if (i < 15) {
            thrust_data[i] = 200 - (i * 10); // Example values for initial thrust
        } else {
            thrust_data[i] = -9.8; // Gravity after burnout
        }
    }
}

// Rocket and simulation parameters
double rocket_mass = 50.0; // Mass of the rocket in kg
double time_step = 1.0; // Time step for the simulation in seconds
int thrust_index = 0;

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

    if (!bmp.begin(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);

    initializeThrustData();
}

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

    static double roll_angle = 0;
    double dt = time_step;
    roll_angle += gyroZ * dt;
    if (roll_angle > 180) roll_angle = -180;

    static double simulated_altitude = 0;
    static double simulated_velocity = 0;
    if (thrust_index < thrust_data_length) {
        double thrust = thrust_data[thrust_index];
        double acceleration = thrust / rocket_mass;
        simulated_velocity += acceleration * dt;
        simulated_altitude += simulated_velocity * dt;
        thrust_index++;
    }

    double measured_altitude = simulated_altitude;

    kalmanUpdate(measured_altitude);

    Serial.print("Simulated Altitude: ");
    Serial.print(simulated_altitude);
    Serial.print(", Estimated Altitude: ");
    Serial.println(altitude_estimate);

    delay(100);
}

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;
}

void kalmanUpdate(double measured_altitude) {
    altitude_estimate += velocity_estimate * 1.0; // dt = 1.0s
    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];

    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;
}