/*----------------------------------------------------------------------------*/
/* Copyright (c) 2017-2018 FIRST. All Rights Reserved.                        */
/* Open Source Software - may be modified and shared by FRC teams. The code   */
/* must be accompanied by the FIRST BSD license file in the root directory of */
/* the project.                                                               */
/*----------------------------------------------------------------------------*/

package frc.robot;

import edu.wpi.first.wpilibj.TimedRobot;
import edu.wpi.first.wpilibj.smartdashboard.SmartDashboard;
import edu.wpi.first.wpilibj.Encoder;
import edu.wpi.first.wpilibj.Talon;
import edu.wpi.first.wpilibj.Timer;

/**
 * The VM is configured to automatically run this class, and to call the
 * functions corresponding to each mode, as described in the TimedRobot
 * documentation. If you change the name of this class or the package after
 * creating this project, you must also update the build.gradle file in the
 * project.
 */
public class Robot extends TimedRobot {
  private Talon leftMotor, rightMotor;
  private Encoder leftEncoder, rightEncoder;
  private double  leftPower, rightPower;
  private Timer   autoTimer;
  private boolean autoDone; 

  /**
   * This function is run when the robot is first started up and should be
   * used for any initialization code.
   */
  @Override
  public void robotInit() {
   // Quadrature encoder has A and B channels connected to DIO0,1, DIO2,3
   leftEncoder = new Encoder(0, 1);
   rightEncoder = new Encoder(2, 3, true); // right side turns in opposite direction
   // Peanut wheels are 7.5" in diameter
   // Encoders provide 1 count per degree of rotation
   leftEncoder.setDistancePerPulse((3.141592*7.5)/360);
   rightEncoder.setDistancePerPulse((3.141592*7.5)/360);
   // PWM motor controllers connected to PWM0, PWM1
   leftMotor = new Talon(0);
   rightMotor = new Talon(1);
   // right motor turns in opposite direction
   rightMotor.setInverted(true);
   // timer to manage autonomous direction updates
   autoTimer = new Timer();
  }

  /**
   * This function is called every robot packet, no matter the mode. Use
   * this for items like diagnostics that you want ran during disabled,
   * autonomous, teleoperated and test.
   *
   * <p>This runs after the mode specific periodic functions, but before
   * LiveWindow and SmartDashboard integrated updating.
   */
  @Override
  public void robotPeriodic() {
    SmartDashboard.putNumber("Left Distance", leftEncoder.getDistance());
    SmartDashboard.putNumber("Right Distance", rightEncoder.getDistance());
    SmartDashboard.putNumber("Left Power", leftPower);
    SmartDashboard.putNumber("Right Power", rightPower);
  }

  /**
   * Initialize the motor powers and start the timer we created so we can
   * periodically adjust the motor power to keep the robot going straight
   */
  @Override
  public void autonomousInit() {
    // Reset encoder counts to 0
    leftEncoder.reset();
    rightEncoder.reset();
    // start motors turning forward at 20% power
    leftPower = 0.20;
    leftMotor.set(leftPower);
    rightPower = 0.20;
    rightMotor.set(rightPower);

    autoTimer.start();
    autoDone = false;  
  }

  /**
   * This function is called regularly during autonomous.
   * Periodically adjust the motor powers and stop if we've gone the desired distance.
   */
  @Override
  public void autonomousPeriodic() {
    if (!autoDone) {
      // adjust motor power every 1/4 second to keep us going straight
      if (autoTimer.hasPeriodPassed(0.125)) {
        // if we're going straight, leftDistance == rightDistance
        // otherwise, compute the error and adjust the motor powers to minimize it
        double error = leftEncoder.getDistance() - rightEncoder.getDistance();
        double kP = 0.005; // proportion of error used to correct motor power
        // adjust motor power to try to keep left/right distances same
        leftPower  -= kP*error; // positive error means left is going too fast
        rightPower += kP*error; // right motor spins opposite direction of left
        leftMotor.set(leftPower);
        rightMotor.set(rightPower);
      }

      if ((leftEncoder.getDistance() > 36.0) || 
          (rightEncoder.getDistance() > 36.0)) {
          leftMotor.stopMotor();
          rightMotor.stopMotor();
          autoDone = true;
      }
    }
  }

  /**
   * This function is called periodically during operator control.
   */
  @Override
  public void teleopPeriodic() {
  }

  /**
   * This function is called periodically during test mode.
   */
  @Override
  public void testPeriodic() {
  }
}