// Unity C# reference source
// Copyright (c) Unity Technologies. For terms of use, see
// https://unity3d.com/legal/licenses/Unity_Reference_Only_License

using System;
using System.Runtime.InteropServices;
using scm = System.ComponentModel;
using uei = UnityEngine.Internal;

namespace UnityEngine
{
    // Representation of 3D vectors and points.
    [StructLayout(LayoutKind.Sequential)]
    public partial struct Vector3
    {
        public const float kEpsilon = 0.00001F;

        // X component of the vector.
        public float x;
        // Y component of the vector.
        public float y;
        // Z component of the vector.
        public float z;

        // Linearly interpolates between two vectors.
        public static Vector3 Lerp(Vector3 a, Vector3 b, float t)
        {
            t = Mathf.Clamp01(t);
            return new Vector3(
                a.x + (b.x - a.x) * t,
                a.y + (b.y - a.y) * t,
                a.z + (b.z - a.z) * t
                );
        }

        // Linearly interpolates between two vectors without clamping the interpolant
        public static Vector3 LerpUnclamped(Vector3 a, Vector3 b, float t)
        {
            return new Vector3(
                a.x + (b.x - a.x) * t,
                a.y + (b.y - a.y) * t,
                a.z + (b.z - a.z) * t
                );
        }

        // Moves a point /current/ in a straight line towards a /target/ point.
        public static Vector3 MoveTowards(Vector3 current, Vector3 target, float maxDistanceDelta)
        {
            Vector3 toVector = target - current;
            float dist = toVector.magnitude;
            if (dist <= maxDistanceDelta || dist < float.Epsilon)
                return target;
            return current + toVector / dist * maxDistanceDelta;
        }

        [uei.ExcludeFromDocs]
        public static Vector3 SmoothDamp(Vector3 current, Vector3 target, ref Vector3 currentVelocity, float smoothTime, float maxSpeed)
        {
            float deltaTime = Time.deltaTime;
            return SmoothDamp(current, target, ref currentVelocity, smoothTime, maxSpeed, deltaTime);
        }

        [uei.ExcludeFromDocs]
        public static Vector3 SmoothDamp(Vector3 current, Vector3 target, ref Vector3 currentVelocity, float smoothTime)
        {
            float deltaTime = Time.deltaTime;
            float maxSpeed = Mathf.Infinity;
            return SmoothDamp(current, target, ref currentVelocity, smoothTime, maxSpeed, deltaTime);
        }

        // Gradually changes a vector towards a desired goal over time.
        public static Vector3 SmoothDamp(Vector3 current, Vector3 target, ref Vector3 currentVelocity, float smoothTime, [uei.DefaultValue("Mathf.Infinity")]  float maxSpeed, [uei.DefaultValue("Time.deltaTime")]  float deltaTime)
        {
            smoothTime = Mathf.Max(0.0001F, smoothTime);
            float omega = 2F / smoothTime;

            float x = omega * deltaTime;
            float exp = 1F / (1F + x + 0.48F * x * x + 0.235F * x * x * x);
            Vector3 change = current - target;
            Vector3 originalTo = target;

            float maxChange = maxSpeed * smoothTime;
            change = Vector3.ClampMagnitude(change, maxChange);
            target = current - change;

            Vector3 temp = (currentVelocity + omega * change) * deltaTime;
            currentVelocity = (currentVelocity - omega * temp) * exp;
            Vector3 output = target + (change + temp) * exp;

            if (Vector3.Dot(originalTo - current, output - originalTo) > 0)
            {
                output = originalTo;
                currentVelocity = (output - originalTo) / deltaTime;
            }

            return output;
        }

        // Access the x, y, z components using [0], [1], [2] respectively.
        public float this[int index]
        {
            get
            {
                switch (index)
                {
                    case 0: return x;
                    case 1: return y;
                    case 2: return z;
                    default:
                        throw new IndexOutOfRangeException("Invalid Vector3 index!");
                }
            }

            set
            {
                switch (index)
                {
                    case 0: x = value; break;
                    case 1: y = value; break;
                    case 2: z = value; break;
                    default:
                        throw new IndexOutOfRangeException("Invalid Vector3 index!");
                }
            }
        }

        // Creates a new vector with given x, y, z components.
        public Vector3(float x, float y, float z) { this.x = x; this.y = y; this.z = z; }
        // Creates a new vector with given x, y components and sets /z/ to zero.
        public Vector3(float x, float y) { this.x = x; this.y = y; z = 0F; }

        // Set x, y and z components of an existing Vector3.
        public void Set(float newX, float newY, float newZ) { x = newX; y = newY; z = newZ; }

        // Multiplies two vectors component-wise.
        public static Vector3 Scale(Vector3 a, Vector3 b) { return new Vector3(a.x * b.x, a.y * b.y, a.z * b.z); }

        // Multiplies every component of this vector by the same component of /scale/.
        public void Scale(Vector3 scale) { x *= scale.x; y *= scale.y; z *= scale.z; }

        // Cross Product of two vectors.
        public static Vector3 Cross(Vector3 lhs, Vector3 rhs)
        {
            return new Vector3(
                lhs.y * rhs.z - lhs.z * rhs.y,
                lhs.z * rhs.x - lhs.x * rhs.z,
                lhs.x * rhs.y - lhs.y * rhs.x);
        }

        // used to allow Vector3s to be used as keys in hash tables
        public override int GetHashCode()
        {
            return x.GetHashCode() ^ (y.GetHashCode() << 2) ^ (z.GetHashCode() >> 2);
        }

        // also required for being able to use Vector3s as keys in hash tables
        public override bool Equals(object other)
        {
            if (!(other is Vector3)) return false;

            Vector3 rhs = (Vector3)other;
            return x.Equals(rhs.x) && y.Equals(rhs.y) && z.Equals(rhs.z);
        }

        // Reflects a vector off the plane defined by a normal.
        public static Vector3 Reflect(Vector3 inDirection, Vector3 inNormal)
        {
            return -2F * Dot(inNormal, inDirection) * inNormal + inDirection;
        }

        // *undoc* --- we have normalized property now
        public static Vector3 Normalize(Vector3 value)
        {
            float mag = Magnitude(value);
            if (mag > kEpsilon)
                return value / mag;
            else
                return zero;
        }

        // Makes this vector have a ::ref::magnitude of 1.
        public void Normalize()
        {
            float mag = Magnitude(this);
            if (mag > kEpsilon)
                this = this / mag;
            else
                this = zero;
        }

        // Returns this vector with a ::ref::magnitude of 1 (RO).
        public Vector3 normalized { get { return Vector3.Normalize(this); } }

        // Dot Product of two vectors.
        public static float Dot(Vector3 lhs, Vector3 rhs) { return lhs.x * rhs.x + lhs.y * rhs.y + lhs.z * rhs.z; }

        // Projects a vector onto another vector.
        public static Vector3 Project(Vector3 vector, Vector3 onNormal)
        {
            float sqrMag = Dot(onNormal, onNormal);
            if (sqrMag < Mathf.Epsilon)
                return zero;
            else
                return onNormal * Dot(vector, onNormal) / sqrMag;
        }

        // Projects a vector onto a plane defined by a normal orthogonal to the plane.
        public static Vector3 ProjectOnPlane(Vector3 vector, Vector3 planeNormal)
        {
            return vector - Project(vector, planeNormal);
        }

        // Returns the angle in degrees between /from/ and /to/. This is always the smallest
        public static float Angle(Vector3 from, Vector3 to)
        {
            return Mathf.Acos(Mathf.Clamp(Vector3.Dot(from.normalized, to.normalized), -1F, 1F)) * Mathf.Rad2Deg;
        }

        // The smaller of the two possible angles between the two vectors is returned, therefore the result will never be greater than 180 degrees or smaller than -180 degrees.
        // If you imagine the from and to vectors as lines on a piece of paper, both originating from the same point, then the /axis/ vector would point up out of the paper.
        // The measured angle between the two vectors would be positive in a clockwise direction and negative in an anti-clockwise direction.
        public static float SignedAngle(Vector3 from, Vector3 to, Vector3 axis)
        {
            Vector3 fromNorm = from.normalized, toNorm = to.normalized;
            float unsignedAngle = Mathf.Acos(Mathf.Clamp(Vector3.Dot(fromNorm, toNorm), -1F, 1F)) * Mathf.Rad2Deg;
            float sign = Mathf.Sign(Vector3.Dot(axis, Vector3.Cross(fromNorm, toNorm)));
            return unsignedAngle * sign;
        }

        // Returns the distance between /a/ and /b/.
        public static float Distance(Vector3 a, Vector3 b)
        {
            Vector3 vec = new Vector3(a.x - b.x, a.y - b.y, a.z - b.z);
            return Mathf.Sqrt(vec.x * vec.x + vec.y * vec.y + vec.z * vec.z);
        }

        // Returns a copy of /vector/ with its magnitude clamped to /maxLength/.
        public static Vector3 ClampMagnitude(Vector3 vector, float maxLength)
        {
            if (vector.sqrMagnitude > maxLength * maxLength)
                return vector.normalized * maxLength;
            return vector;
        }

        // *undoc* --- there's a property now
        public static float Magnitude(Vector3 vector) { return Mathf.Sqrt(vector.x * vector.x + vector.y * vector.y + vector.z * vector.z); }

        // Returns the length of this vector (RO).
        public float magnitude { get { return Mathf.Sqrt(x * x + y * y + z * z); } }

        // *undoc* --- there's a property now
        public static float SqrMagnitude(Vector3 vector) { return vector.x * vector.x + vector.y * vector.y + vector.z * vector.z; }

        // Returns the squared length of this vector (RO).
        public float sqrMagnitude { get { return x * x + y * y + z * z; } }

        // Returns a vector that is made from the smallest components of two vectors.
        public static Vector3 Min(Vector3 lhs, Vector3 rhs)
        {
            return new Vector3(Mathf.Min(lhs.x, rhs.x), Mathf.Min(lhs.y, rhs.y), Mathf.Min(lhs.z, rhs.z));
        }

        // Returns a vector that is made from the largest components of two vectors.
        public static Vector3 Max(Vector3 lhs, Vector3 rhs)
        {
            return new Vector3(Mathf.Max(lhs.x, rhs.x), Mathf.Max(lhs.y, rhs.y), Mathf.Max(lhs.z, rhs.z));
        }

        static readonly Vector3 zeroVector = new Vector3(0F, 0F, 0F);
        static readonly Vector3 oneVector = new Vector3(1F, 1F, 1F);
        static readonly Vector3 upVector = new Vector3(0F, 1F, 0F);
        static readonly Vector3 downVector = new Vector3(0F, -1F, 0F);
        static readonly Vector3 leftVector = new Vector3(-1F, 0F, 0F);
        static readonly Vector3 rightVector = new Vector3(1F, 0F, 0F);
        static readonly Vector3 forwardVector = new Vector3(0F, 0F, 1F);
        static readonly Vector3 backVector = new Vector3(0F, 0F, -1F);
        static readonly Vector3 positiveInfinityVector = new Vector3(float.PositiveInfinity, float.PositiveInfinity, float.PositiveInfinity);
        static readonly Vector3 negativeInfinityVector = new Vector3(float.NegativeInfinity, float.NegativeInfinity, float.NegativeInfinity);

        // Shorthand for writing @@Vector3(0, 0, 0)@@
        public static Vector3 zero { get { return zeroVector; } }
        // Shorthand for writing @@Vector3(1, 1, 1)@@
        public static Vector3 one { get { return oneVector; } }
        // Shorthand for writing @@Vector3(0, 0, 1)@@
        public static Vector3 forward { get { return forwardVector; } }
        public static Vector3 back { get { return backVector; } }
        // Shorthand for writing @@Vector3(0, 1, 0)@@
        public static Vector3 up { get { return upVector; } }
        public static Vector3 down { get { return downVector; } }
        public static Vector3 left { get { return leftVector; } }
        // Shorthand for writing @@Vector3(1, 0, 0)@@
        public static Vector3 right { get { return rightVector; } }
        // Shorthand for writing @@Vector3(float.PositiveInfinity, float.PositiveInfinity, float.PositiveInfinity)@@
        public static Vector3 positiveInfinity { get { return positiveInfinityVector; } }
        // Shorthand for writing @@Vector3(float.NegativeInfinity, float.NegativeInfinity, float.NegativeInfinity)@@
        public static Vector3 negativeInfinity { get { return negativeInfinityVector; } }

        // Adds two vectors.
        public static Vector3 operator+(Vector3 a, Vector3 b) { return new Vector3(a.x + b.x, a.y + b.y, a.z + b.z); }
        // Subtracts one vector from another.
        public static Vector3 operator-(Vector3 a, Vector3 b) { return new Vector3(a.x - b.x, a.y - b.y, a.z - b.z); }
        // Negates a vector.
        public static Vector3 operator-(Vector3 a) { return new Vector3(-a.x, -a.y, -a.z); }
        // Multiplies a vector by a number.
        public static Vector3 operator*(Vector3 a, float d) { return new Vector3(a.x * d, a.y * d, a.z * d); }
        // Multiplies a vector by a number.
        public static Vector3 operator*(float d, Vector3 a) { return new Vector3(a.x * d, a.y * d, a.z * d); }
        // Divides a vector by a number.
        public static Vector3 operator/(Vector3 a, float d) { return new Vector3(a.x / d, a.y / d, a.z / d); }

        // Returns true if the vectors are equal.
        public static bool operator==(Vector3 lhs, Vector3 rhs)
        {
            // Returns false in the presence of NaN values.
            return SqrMagnitude(lhs - rhs) < kEpsilon * kEpsilon;
        }

        // Returns true if vectors are different.
        public static bool operator!=(Vector3 lhs, Vector3 rhs)
        {
            // Returns true in the presence of NaN values.
            return !(lhs == rhs);
        }

        public override string ToString()
        {
            return UnityString.Format("({0:F1}, {1:F1}, {2:F1})", x, y, z);
        }

        public string ToString(string format)
        {
            return UnityString.Format("({0}, {1}, {2})", x.ToString(format), y.ToString(format), z.ToString(format));
        }

        [System.Obsolete("Use Vector3.forward instead.")]
        public static Vector3 fwd { get { return new Vector3(0F, 0F, 1F); } }
        [System.Obsolete("Use Vector3.Angle instead. AngleBetween uses radians instead of degrees and was deprecated for this reason")]
        public static float AngleBetween(Vector3 from, Vector3 to) { return Mathf.Acos(Mathf.Clamp(Vector3.Dot(from.normalized, to.normalized), -1F, 1F)); }
        [System.Obsolete("Use Vector3.ProjectOnPlane instead.")]
        public static Vector3 Exclude(Vector3 excludeThis, Vector3 fromThat) { return ProjectOnPlane(fromThat, excludeThis); }
    }
}
