/******************************************************************************
 * 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.             *
 ******************************************************************************/

using UnityEngine;

namespace Leap.Unity.Geometry
{

    public struct Bezier
    {

        public Vector3 a;
        public Vector3 b;
        public Vector3 c;

        public Bezier(Vector3 a, Vector3 b, Vector3 c)
        {
            this.a = a; this.b = b; this.c = c;
        }

        public BezierPointEnumerator Points(int numPoints)
        {
            return new BezierPointEnumerator(this, numPoints);
        }

        public BezierLineEnumerator Lines(int numLines)
        {
            return new BezierLineEnumerator(this, numLines);
        }

        public struct BezierPointEnumerator
        {
            Bezier bez; int numPoints; int idx;
            public BezierPointEnumerator(Bezier bez, int numPoints)
            {
                this.bez = bez;
                this.numPoints = Mathf.Max(2, numPoints);
                this.idx = -1;
            }
            public Vector3 Current
            {
                get
                {
                    var t = Mathf.Max(0, idx) / (float)numPoints;
                    return Vector3.Lerp(
                      Vector3.Lerp(bez.a, bez.b, t),
                      Vector3.Lerp(bez.b, bez.c, t),
                      t
                    );
                }
            }
            public bool MoveNext()
            {
                if (idx == numPoints) { return false; }
                idx += 1;
                return true;
            }
            public BezierPointEnumerator GetEnumerator() { return this; }
        }

        public struct BezierLineEnumerator
        {
            BezierPointEnumerator points;
            Vector3? lastPoint;
            public BezierLineEnumerator(Bezier bez, int numLines)
            {
                numLines = Mathf.Max(1, numLines);
                this.points = new BezierPointEnumerator(bez, numLines + 1);
                lastPoint = null;
            }
            public LocalSegment3 Current
            {
                get
                {
                    if (!lastPoint.HasValue)
                    {
                        return new LocalSegment3(points.Current, points.Current);
                    }
                    else
                    {
                        return new LocalSegment3(lastPoint.Value, points.Current);
                    }
                }
            }
            public bool MoveNext()
            {
                if (!lastPoint.HasValue)
                {
                    if (!points.MoveNext()) { return false; }
                }
                lastPoint = points.Current;
                if (!points.MoveNext()) { return false; }
                return true;
            }
            public BezierLineEnumerator GetEnumerator() { return this; }
        }

    }

}