/******************************************************************************
 * Copyright (C) Ultraleap, Inc. 2011-2021.                                   *
 *                                                                            *
 * Use subject to the terms of the Apache License 2.0 available at            *
 * http://www.apache.org/licenses/LICENSE-2.0, or another agreement           *
 * between Ultraleap and you, your company or other organization.             *
 ******************************************************************************/

namespace Leap
{
    using System;

    /// <summary>
    /// The Bone class represents a tracked bone.
    /// 
    /// All fingers contain 4 bones that make up the anatomy of the finger.
    /// Get valid Bone objects from a Finger object.
    /// 
    /// Bones are ordered from base to tip, indexed from 0 to 3.  Additionally, the
    /// bone's Type enum may be used to index a specific bone anatomically.
    /// 
    /// The thumb does not have a base metacarpal bone and therefore contains a valid,
    /// zero length bone at that location.
    /// @since 2.0
    /// </summary>
    [Serializable]
    public class Bone : IEquatable<Bone>
    {

        /// <summary>
        /// Constructs a default invalid Bone object.
        /// 
        /// @since 2.0
        /// </summary>
        public Bone()
        {
            Type = BoneType.TYPE_INVALID;
        }

        /// <summary>
        /// Constructs a new Bone object.
        /// @since 3.0
        /// </summary>
        public Bone(Vector prevJoint,
                    Vector nextJoint,
                    Vector center,
                    Vector direction,
                    float length,
                    float width,
                    Bone.BoneType type,
                    LeapQuaternion rotation)
        {
            PrevJoint = prevJoint;
            NextJoint = nextJoint;
            Center = center;
            Direction = direction;
            Rotation = rotation;
            Length = length;
            Width = width;
            Type = type;
        }

        /// <summary>
        /// Compare Bone object equality.
        /// 
        /// Two Bone objects are equal if and only if both Bone objects represent the
        /// exact same physical bone in the same frame and both Bone objects are valid.
        /// @since 2.0
        /// </summary>
        public bool Equals(Bone other)
        {
            return Center == other.Center && Direction == other.Direction && Length == other.Length;
        }

        /// <summary>
        /// A string containing a brief, human readable description of the Bone object.
        /// @since 2.0
        /// </summary>
        public override string ToString()
        {
            return Enum.GetName(typeof(BoneType), this.Type) + " bone";
        }

        /// <summary>
        /// The base of the bone, closest to the wrist.
        /// In anatomical terms, this is the proximal end of the bone.
        /// @since 2.0
        /// </summary>
        public Vector PrevJoint;

        /// <summary>
        /// The end of the bone, closest to the finger tip.
        /// In anatomical terms, this is the distal end of the bone.
        /// @since 2.0
        /// </summary>
        public Vector NextJoint;

        /// <summary>
        /// The midpoint of the bone. 
        /// @since 2.0 
        /// </summary>
        public Vector Center;

        /// <summary>
        /// The normalized direction of the bone from base to tip.
        /// @since 2.0
        /// </summary>
        public Vector Direction;

        /// <summary>
        /// The estimated length of the bone.
        /// @since 2.0
        /// </summary>
        public float Length;

        /// <summary>
        /// The average width of the flesh around the bone.
        /// @since 2.0
        /// </summary>
        public float Width;

        /// <summary>
        /// The type of this bone.
        /// @since 2.0
        /// </summary>
        public BoneType Type;

        /// <summary>
        /// The orientation of this Bone as a Quaternion.
        /// @since 2.0
        /// </summary>
        public LeapQuaternion Rotation;

        /// <summary>
        /// The orthonormal basis vectors for this Bone as a Matrix.
        /// The orientation of this Bone as a Quaternion.
        /// 
        /// Basis vectors specify the orientation of a bone.
        /// 
        /// **xBasis** Perpendicular to the longitudinal axis of the
        ///   bone; exits the sides of the finger.
        /// 
        /// **yBasis or up vector** Perpendicular to the longitudinal
        ///   axis of the bone; exits the top and bottom of the finger. More positive
        ///   in the upward direction.
        /// 
        /// **zBasis** Aligned with the longitudinal axis of the bone.
        ///   More positive toward the base of the finger.
        /// 
        /// The bases provided for the right hand use the right-hand rule; those for
        /// the left hand use the left-hand rule. Thus, the positive direction of the
        /// x-basis is to the right for the right hand and to the left for the left
        /// hand. You can change from right-hand to left-hand rule by multiplying the
        /// z basis vector by -1.
        /// 
        /// You can use the basis vectors for such purposes as measuring complex
        /// finger poses and skeletal animation.
        /// 
        /// Note that converting the basis vectors directly into a quaternion
        /// representation is not mathematically valid. If you use quaternions,
        /// create them from the derived rotation matrix not directly from the bases.
        /// 
        /// @since 2.0
        /// </summary>
        public LeapTransform Basis { get { return new LeapTransform(PrevJoint, Rotation); } }

        /// <summary>
        /// Enumerates the type of bones.
        /// 
        /// Members of this enumeration are returned by Bone.Type() to identify a
        /// Bone object.
        /// @since 2.0
        /// </summary>
        public enum BoneType
        {
            TYPE_INVALID = -1,
            TYPE_METACARPAL = 0,
            TYPE_PROXIMAL = 1,
            TYPE_INTERMEDIATE = 2,
            TYPE_DISTAL = 3
        }
    }
}