package frc.robot.subsystems;

import edu.wpi.first.math.controller.PIDController;
import edu.wpi.first.math.controller.SimpleMotorFeedforward;
import edu.wpi.first.math.kinematics.ChassisSpeeds;
import edu.wpi.first.math.kinematics.DifferentialDriveKinematics;
import edu.wpi.first.math.kinematics.DifferentialDriveOdometry;
import edu.wpi.first.math.kinematics.DifferentialDriveWheelSpeeds;
import edu.wpi.first.wpilibj.AnalogGyro;
import edu.wpi.first.wpilibj.Encoder;
import edu.wpi.first.wpilibj.motorcontrol.PWMSparkMax;
import edu.wpi.first.wpilibj2.command.SubsystemBase;
import frc.robot.Constants;

public class Drivetrain extends SubsystemBase 
{
    private AnalogGyro m_gyro = Constants.gyro;

    private PWMSparkMax m_motorL_leader = Constants.motorL_leader;
    private PWMSparkMax m_motorL_follower = Constants.motorL_follower;
    private PWMSparkMax m_motorR_leader = Constants.motorR_leader;
    private PWMSparkMax m_motorR_follower = Constants.motorR_follower;

    private Encoder m_encoderL = Constants.encoderL;
    private Encoder m_encoderR = Constants.encoderR;

    private SimpleMotorFeedforward m_feedforward = Constants.feedforward;

    private final PIDController m_pidL = new PIDController(1, 0, 0);
    private final PIDController m_pidR = new PIDController(1, 0, 0);
    
    private DifferentialDriveKinematics m_kinematics = 
        new DifferentialDriveKinematics(Constants.TrackWidth);

    private DifferentialDriveOdometry m_odometry;

    public Drivetrain()
    {
        m_gyro.reset();        

        m_motorL_leader.addFollower(m_motorL_follower);
        m_motorR_leader.addFollower(m_motorR_follower);

        // perhaps invert
        // m_motorR_leader.setInverted(true);

        m_encoderL.setDistancePerPulse(2 * Math.PI * Constants.WheelRadius / Constants.EncoderResolution);
        m_encoderR.setDistancePerPulse(2 * Math.PI * Constants.WheelRadius / Constants.EncoderResolution);
        
        m_encoderL.reset();
        m_encoderR.reset();

        m_odometry = new DifferentialDriveOdometry(
            m_gyro.getRotation2d(),
            Constants.encoderL.getDistance(),
            Constants.encoderR.getDistance());
    }

    // speed - linear velocity in m/s
    // rot   - angular velocity in rad/s
    public void drive(double speed, double rot) 
    {
        speed(m_kinematics.toWheelSpeeds(new ChassisSpeeds(speed, 0.0, rot)));
    }

    public void speed(DifferentialDriveWheelSpeeds speeds) 
    {
        m_motorL_leader.setVoltage(
            m_pidL.calculate(m_encoderL.getRate(), speeds.leftMetersPerSecond)
            + m_feedforward.calculate(speeds.leftMetersPerSecond)
        );

        m_motorR_leader.setVoltage(
            m_pidR.calculate(m_encoderR.getRate(), speeds.rightMetersPerSecond)
            + m_feedforward.calculate(speeds.rightMetersPerSecond)
        );
    }

    @Override
    public void periodic() 
    {
        m_odometry.update(
            Constants.gyro.getRotation2d(),
            Constants.encoderL.getDistance(),
            Constants.encoderR.getDistance());
    }

    @Override
    public void simulationPeriodic() {
        // This method will be called once per scheduler run during simulation
    }
}