package frc.robot.subsystems;

import com.revrobotics.CANSparkMax;

import edu.wpi.first.math.controller.PIDController;
import edu.wpi.first.math.controller.SimpleMotorFeedforward;
import edu.wpi.first.math.geometry.Pose2d;
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.math.proto.Trajectory;
import edu.wpi.first.units.Distance;
import edu.wpi.first.units.Measure;
import edu.wpi.first.units.Velocity;
import edu.wpi.first.units.Voltage;
import edu.wpi.first.units.MutableMeasure;
import edu.wpi.first.wpilibj.Encoder;
import edu.wpi.first.wpilibj.RobotController;
import edu.wpi.first.wpilibj2.command.Command;
import edu.wpi.first.wpilibj2.command.Commands;
import edu.wpi.first.wpilibj2.command.SubsystemBase;
import edu.wpi.first.wpilibj2.command.sysid.SysIdRoutine;

import static edu.wpi.first.units.MutableMeasure.mutable;
import static edu.wpi.first.units.Units.Volts;

import static edu.wpi.first.units.Units.Meters;
import static edu.wpi.first.units.Units.MetersPerSecond;

import frc.robot.Constants;
import frc.robot.util.IMUGyro;

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

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

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

    private SimpleMotorFeedforward m_feedforward = new SimpleMotorFeedforward(1.1, 3.16, 0.17);

    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;

    // For system identification
    private final MutableMeasure<Voltage> m_voltage = mutable(Volts.of(0));
    private final MutableMeasure<Distance> m_distance = mutable(Meters.of(0));
    private final MutableMeasure<Velocity<Distance>> m_velocity = mutable(MetersPerSecond.of(0));
    private final SysIdRoutine m_sysIdRoutine = new SysIdRoutine(
        new SysIdRoutine.Config(), 
        new SysIdRoutine.Mechanism(
            (Measure<Voltage> volts) -> {
                m_motorL_leader.set(-volts.in(Volts));
                m_motorR_leader.set(-volts.in(Volts));
            },
            log -> {
                log.motor("drive-left")
                    .voltage(
                        m_voltage.mut_replace(
                            m_motorL_leader.get() * RobotController.getBatteryVoltage(), Volts)
                    )
                    .linearPosition(m_distance.mut_replace(m_encoderL.getDistance(), Meters))
                    .linearVelocity(m_velocity.mut_replace(m_encoderL.getRate(), MetersPerSecond));
                log.motor("driver-right")
                .voltage(
                        m_voltage.mut_replace(
                            m_motorR_leader.get() * RobotController.getBatteryVoltage(), Volts)
                    )
                    .linearPosition(m_distance.mut_replace(m_encoderR.getDistance(), Meters))
                    .linearVelocity(m_velocity.mut_replace(m_encoderR.getRate(), MetersPerSecond));
            }, this));

    public Drivetrain()
    {
        m_gyro.reset();
        m_gyro.calibrateGyro(10000);

        m_motorR_follower.follow(m_motorR_leader);
        m_motorL_follower.follow(m_motorL_leader);
        
        m_motorR_leader.setInverted(true);
        m_encoderL.setReverseDirection(true);

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

        m_odometry = new DifferentialDriveOdometry(
            m_gyro.toRotation2d(),
            Constants.encoderL.getDistance(),
            Constants.encoderR.getDistance());
    }

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

    // in m/s
    public void tank(double left, double right) 
    {
        speed(new DifferentialDriveWheelSpeeds(left, right));
    }

    public void speed(DifferentialDriveWheelSpeeds speeds) 
    {
        voltage(
            m_pidL.calculate(m_encoderL.getRate(), speeds.leftMetersPerSecond)
              + m_feedforward.calculate(speeds.leftMetersPerSecond),
            m_pidR.calculate(m_encoderR.getRate(), speeds.rightMetersPerSecond)
              + m_feedforward.calculate(speeds.rightMetersPerSecond)
        );
    }

    public void voltage(double leftVolts, double rightVolts)
    {
        m_motorL_leader.setVoltage(leftVolts);
        m_motorR_leader.setVoltage(rightVolts);
    }

    public Pose2d pose2d() 
    {
        return m_odometry.getPoseMeters();
    }

    public void reset() 
    {
        m_gyro.reset();
        m_encoderL.reset();
        m_encoderR.reset();

        m_odometry = new DifferentialDriveOdometry(
            m_gyro.toRotation2d(),
            Constants.encoderL.getDistance(),
            Constants.encoderR.getDistance());
    }    

    @Override
    public void periodic() 
    {
        m_gyro.update();

        m_odometry.update(
            m_gyro.toRotation2d(),
            m_encoderL.getDistance(),
            m_encoderR.getDistance());
    }

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

    public Command trajectory(Trajectory trajectory)
    {
        // TOOD: Implement
        // return this.runOnce(...)   
        return Commands.none();
    }

    public Command sysIdQausistatic(SysIdRoutine.Direction direction)
    {
        return m_sysIdRoutine.quasistatic(direction);
    }

    public Command sysIdDynamic(SysIdRoutine.Direction direction)
    {
        return m_sysIdRoutine.dynamic(direction);
    }
}