// Copyright (c) FIRST and other WPILib contributors.
// Open Source Software; you can modify and/or share it under the terms of
// the WPILib BSD license file in the root directory of this project.

package edu.wpi.first.math.geometry;

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

import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonProperty;
import edu.wpi.first.math.geometry.proto.Pose2dProto;
import edu.wpi.first.math.geometry.struct.Pose2dStruct;
import edu.wpi.first.math.interpolation.Interpolatable;
import edu.wpi.first.units.Distance;
import edu.wpi.first.units.Measure;
import edu.wpi.first.util.protobuf.ProtobufSerializable;
import edu.wpi.first.util.struct.StructSerializable;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.Objects;

/** Represents a 2D pose containing translational and rotational elements. */
@JsonIgnoreProperties(ignoreUnknown = true)
@JsonAutoDetect(getterVisibility = JsonAutoDetect.Visibility.NONE)
public class Pose2d implements Interpolatable<Pose2d>, ProtobufSerializable, StructSerializable {
  /**
   * A preallocated Pose2d representing the origin.
   *
   * <p>This exists to avoid allocations for common poses.
   */
  public static final Pose2d kZero = new Pose2d();

  private final Translation2d m_translation;
  private final Rotation2d m_rotation;

  /** Constructs a pose at the origin facing toward the positive X axis. */
  public Pose2d() {
    m_translation = Translation2d.kZero;
    m_rotation = Rotation2d.kZero;
  }

  /**
   * Constructs a pose with the specified translation and rotation.
   *
   * @param translation The translational component of the pose.
   * @param rotation The rotational component of the pose.
   */
  @JsonCreator
  public Pose2d(
      @JsonProperty(required = true, value = "translation") Translation2d translation,
      @JsonProperty(required = true, value = "rotation") Rotation2d rotation) {
    m_translation = translation;
    m_rotation = rotation;
  }

  /**
   * Constructs a pose with x and y translations instead of a separate Translation2d.
   *
   * @param x The x component of the translational component of the pose.
   * @param y The y component of the translational component of the pose.
   * @param rotation The rotational component of the pose.
   */
  public Pose2d(double x, double y, Rotation2d rotation) {
    m_translation = new Translation2d(x, y);
    m_rotation = rotation;
  }

  /**
   * Constructs a pose with x and y translations instead of a separate Translation2d. The X and Y
   * translations will be converted to and tracked as meters.
   *
   * @param x The x component of the translational component of the pose.
   * @param y The y component of the translational component of the pose.
   * @param rotation The rotational component of the pose.
   */
  public Pose2d(Measure<Distance> x, Measure<Distance> y, Rotation2d rotation) {
    this(x.in(Meters), y.in(Meters), rotation);
  }

  /**
   * Transforms the pose by the given transformation and returns the new transformed pose.
   *
   * <pre>
   * [x_new]    [cos, -sin, 0][transform.x]
   * [y_new] += [sin,  cos, 0][transform.y]
   * [t_new]    [  0,    0, 1][transform.t]
   * </pre>
   *
   * @param other The transform to transform the pose by.
   * @return The transformed pose.
   */
  public Pose2d plus(Transform2d other) {
    return transformBy(other);
  }

  /**
   * Returns the Transform2d that maps the one pose to another.
   *
   * @param other The initial pose of the transformation.
   * @return The transform that maps the other pose to the current pose.
   */
  public Transform2d minus(Pose2d other) {
    final var pose = this.relativeTo(other);
    return new Transform2d(pose.getTranslation(), pose.getRotation());
  }

  /**
   * Returns the translation component of the transformation.
   *
   * @return The translational component of the pose.
   */
  @JsonProperty
  public Translation2d getTranslation() {
    return m_translation;
  }

  /**
   * Returns the X component of the pose's translation.
   *
   * @return The x component of the pose's translation.
   */
  public double getX() {
    return m_translation.getX();
  }

  /**
   * Returns the Y component of the pose's translation.
   *
   * @return The y component of the pose's translation.
   */
  public double getY() {
    return m_translation.getY();
  }

  /**
   * Returns the rotational component of the transformation.
   *
   * @return The rotational component of the pose.
   */
  @JsonProperty
  public Rotation2d getRotation() {
    return m_rotation;
  }

  /**
   * Multiplies the current pose by a scalar.
   *
   * @param scalar The scalar.
   * @return The new scaled Pose2d.
   */
  public Pose2d times(double scalar) {
    return new Pose2d(m_translation.times(scalar), m_rotation.times(scalar));
  }

  /**
   * Divides the current pose by a scalar.
   *
   * @param scalar The scalar.
   * @return The new scaled Pose2d.
   */
  public Pose2d div(double scalar) {
    return times(1.0 / scalar);
  }

  /**
   * Rotates the pose around the origin and returns the new pose.
   *
   * @param other The rotation to transform the pose by.
   * @return The transformed pose.
   */
  public Pose2d rotateBy(Rotation2d other) {
    return new Pose2d(m_translation.rotateBy(other), m_rotation.rotateBy(other));
  }

  /**
   * Transforms the pose by the given transformation and returns the new pose. See + operator for
   * the matrix multiplication performed.
   *
   * @param other The transform to transform the pose by.
   * @return The transformed pose.
   */
  public Pose2d transformBy(Transform2d other) {
    return new Pose2d(
        m_translation.plus(other.getTranslation().rotateBy(m_rotation)),
        other.getRotation().plus(m_rotation));
  }

  /**
   * Returns the current pose relative to the given pose.
   *
   * <p>This function can often be used for trajectory tracking or pose stabilization algorithms to
   * get the error between the reference and the current pose.
   *
   * @param other The pose that is the origin of the new coordinate frame that the current pose will
   *     be converted into.
   * @return The current pose relative to the new origin pose.
   */
  public Pose2d relativeTo(Pose2d other) {
    var transform = new Transform2d(other, this);
    return new Pose2d(transform.getTranslation(), transform.getRotation());
  }

  /**
   * Obtain a new Pose2d from a (constant curvature) velocity.
   *
   * <p>See <a href="https://file.tavsys.net/control/controls-engineering-in-frc.pdf">Controls
   * Engineering in the FIRST Robotics Competition</a> section 10.2 "Pose exponential" for a
   * derivation.
   *
   * <p>The twist is a change in pose in the robot's coordinate frame since the previous pose
   * update. When the user runs exp() on the previous known field-relative pose with the argument
   * being the twist, the user will receive the new field-relative pose.
   *
   * <p>"Exp" represents the pose exponential, which is solving a differential equation moving the
   * pose forward in time.
   *
   * @param twist The change in pose in the robot's coordinate frame since the previous pose update.
   *     For example, if a non-holonomic robot moves forward 0.01 meters and changes angle by 0.5
   *     degrees since the previous pose update, the twist would be Twist2d(0.01, 0.0,
   *     Units.degreesToRadians(0.5)).
   * @return The new pose of the robot.
   */
  public Pose2d exp(Twist2d twist) {
    double dx = twist.dx;
    double dy = twist.dy;
    double dtheta = twist.dtheta;

    double sinTheta = Math.sin(dtheta);
    double cosTheta = Math.cos(dtheta);

    double s;
    double c;
    if (Math.abs(dtheta) < 1E-9) {
      s = 1.0 - 1.0 / 6.0 * dtheta * dtheta;
      c = 0.5 * dtheta;
    } else {
      s = sinTheta / dtheta;
      c = (1 - cosTheta) / dtheta;
    }
    var transform =
        new Transform2d(
            new Translation2d(dx * s - dy * c, dx * c + dy * s),
            new Rotation2d(cosTheta, sinTheta));

    return this.plus(transform);
  }

  /**
   * Returns a Twist2d that maps this pose to the end pose. If c is the output of {@code a.Log(b)},
   * then {@code a.Exp(c)} would yield b.
   *
   * @param end The end pose for the transformation.
   * @return The twist that maps this to end.
   */
  public Twist2d log(Pose2d end) {
    final var transform = end.relativeTo(this);
    final var dtheta = transform.getRotation().getRadians();
    final var halfDtheta = dtheta / 2.0;

    final var cosMinusOne = transform.getRotation().getCos() - 1;

    double halfThetaByTanOfHalfDtheta;
    if (Math.abs(cosMinusOne) < 1E-9) {
      halfThetaByTanOfHalfDtheta = 1.0 - 1.0 / 12.0 * dtheta * dtheta;
    } else {
      halfThetaByTanOfHalfDtheta = -(halfDtheta * transform.getRotation().getSin()) / cosMinusOne;
    }

    Translation2d translationPart =
        transform
            .getTranslation()
            .rotateBy(new Rotation2d(halfThetaByTanOfHalfDtheta, -halfDtheta))
            .times(Math.hypot(halfThetaByTanOfHalfDtheta, halfDtheta));

    return new Twist2d(translationPart.getX(), translationPart.getY(), dtheta);
  }

  /**
   * Returns the nearest Pose2d from a list of poses. If two or more poses in the list have the same
   * distance from this pose, return the one with the closest rotation component.
   *
   * @param poses The list of poses to find the nearest.
   * @return The nearest Pose2d from the list.
   */
  public Pose2d nearest(List<Pose2d> poses) {
    return Collections.min(
        poses,
        Comparator.comparing(
                (Pose2d other) -> this.getTranslation().getDistance(other.getTranslation()))
            .thenComparing(
                (Pose2d other) ->
                    Math.abs(this.getRotation().minus(other.getRotation()).getRadians())));
  }

  @Override
  public String toString() {
    return String.format("Pose2d(%s, %s)", m_translation, m_rotation);
  }

  /**
   * Checks equality between this Pose2d and another object.
   *
   * @param obj The other object.
   * @return Whether the two objects are equal or not.
   */
  @Override
  public boolean equals(Object obj) {
    if (obj instanceof Pose2d) {
      return ((Pose2d) obj).m_translation.equals(m_translation)
          && ((Pose2d) obj).m_rotation.equals(m_rotation);
    }
    return false;
  }

  @Override
  public int hashCode() {
    return Objects.hash(m_translation, m_rotation);
  }

  @Override
  public Pose2d interpolate(Pose2d endValue, double t) {
    if (t < 0) {
      return this;
    } else if (t >= 1) {
      return endValue;
    } else {
      var twist = this.log(endValue);
      var scaledTwist = new Twist2d(twist.dx * t, twist.dy * t, twist.dtheta * t);
      return this.exp(scaledTwist);
    }
  }

  /** Pose2d protobuf for serialization. */
  public static final Pose2dProto proto = new Pose2dProto();

  /** Pose2d struct for serialization. */
  public static final Pose2dStruct struct = new Pose2dStruct();
}