/*
The MIT License (MIT)
Copyright (c) 2014 Matt DesLauriers

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
OR OTHER DEALINGS IN THE SOFTWARE.
*/

using UnityEngine;

namespace DA_Assets.SVGMeshUnity.Internals
{
    public class BezierToVertex
    {
        // https://github.com/mattdesl/svg-path-contours

        public float Scale = 1f;
        
        public float PathDistanceEpsilon = 1f;
        public int RecursionLimit = 8;
        public float FLTEpsilon = 1.19209290e-7f;

        public float AngleEpsilon = 0.01f;
        public float AngleTolerance = 0f;
        public float CuspLimit = 0f;

        public WorkBufferPool WorkBufferPool;

        private WorkBuffer<Vector2> WorkVertices;
        
        public void GetContours(SVGData svg, MeshData data)
        {
            WorkBufferPool.Get(ref WorkVertices);
            
            var pen = Vector2.zero;
            
            var curves = svg.Curves;
            var l = curves.Count;
            for (var i = 0; i < l; ++i)
            {
                var curve = curves[i];
                if (curve.IsMove)
                {
                    EmitWorkVerticesIfNeeded(data);
                }
                else
                {
                    FillBezier(pen, curve.InControl, curve.OutControl, curve.Position);
                }
                pen = curve.Position;
            }
            
            EmitWorkVerticesIfNeeded(data);
            
            WorkBufferPool.Release(ref WorkVertices);
        }

        private void EmitWorkVerticesIfNeeded(MeshData data)
        {
            if (WorkVertices.UsedSize == 0)
            {
                return;
            }
            
            // TODO: Simplify
            
            data.AddVertices(WorkVertices);
            WorkVertices.Clear();
        }

        ////// Based on:
        ////// https://github.com/pelson/antigrain/blob/master/agg-2.4/src/agg_curves.cpp

        private void FillBezier(Vector2 start, Vector2 c1, Vector2 c2, Vector2 end)
        {
            var distanceTolerance = PathDistanceEpsilon / Scale;
            distanceTolerance *= distanceTolerance;
            BeginFillBezier(start, c1, c2, end, distanceTolerance);
        }
        
        private void BeginFillBezier(Vector2 start, Vector2 c1, Vector2 c2, Vector2 end, float distanceTolerance)
        {
            WorkVertices.Push(ref start);
            RecursiveFillBezier(start, c1, c2, end, distanceTolerance, 0);
            WorkVertices.Push(ref end);
        }

        private void RecursiveFillBezier(Vector2 v1, Vector2 v2, Vector2 v3, Vector2 v4, float distanceTolerance, int level)
        {
            if (level > RecursionLimit)
            {
                return;
            }

            var pi = Mathf.PI;

            // Calculate all the mid-points of the line segments
            //----------------------
            var v12 = (v1 + v2) / 2f;
            var v23 = (v2 + v3) / 2f;
            var v34 = (v3 + v4) / 2f;
            var v123 = (v12 + v23) / 2f;
            var v234 = (v23 + v34) / 2f;
            var v1234 = (v123 + v234) / 2f;
            
            // Enforce subdivision first time
            if (level > 0)
            {
                // Try to approximate the full cubic curve by a single straight line
                //------------------
                var d = v4 - v1;

                var d2 = Mathf.Abs((v2.x - v4.x) * d.y - (v2.y - v4.y) * d.x);
                var d3 = Mathf.Abs((v3.x - v4.x) * d.y - (v3.y - v4.y) * d.x);

                if (d2 > FLTEpsilon && d3 > FLTEpsilon)
                {
                    // Regular care
                    //-----------------
                    if ((d2 + d3) * (d2 + d3) <= distanceTolerance * (d.x * d.x + d.y * d.y))
                    {
                        // If the curvature doesn't exceed the distanceTolerance value
                        // we tend to finish subdivisions.
                        //----------------------
                        if (AngleTolerance < AngleEpsilon)
                        {
                            WorkVertices.Push(ref v1234);
                            return;
                        }

                        // Angle & Cusp Condition
                        //----------------------
                        var a23 = Mathf.Atan2(v3.y - v2.y, v3.x - v2.x);
                        var da1 = Mathf.Abs(a23 - Mathf.Atan2(v2.y - v1.y, v2.x - v1.x));
                        var da2 = Mathf.Abs(Mathf.Atan2(v4.y - v3.y, v4.x - v3.x) - a23);

                        if (da1 >= pi)
                        {
                            da1 = 2 * pi - da1;
                        }

                        if (da2 >= pi)
                        {
                            da2 = 2 * pi - da2;
                        }

                        if (da1 + da2 < AngleTolerance)
                        {
                            // Finally we can stop the recursion
                            //----------------------
                            WorkVertices.Push(ref v1234);
                            return;
                        }

                        if (CuspLimit > 0f)
                        {
                            if (da1 > CuspLimit)
                            {
                                WorkVertices.Push(ref v2);
                                return;
                            }

                            if (da2 > CuspLimit)
                            {
                                WorkVertices.Push(ref v3);
                                return;
                            }
                        }
                    }
                }
                else
                {
                    if (d2 > FLTEpsilon)
                    {
                        // p1,p3,p4 are collinear, p2 is considerable
                        //----------------------
                        if (d2 * d2 <= distanceTolerance * (d.x * d.x + d.y * d.y))
                        {
                            if (AngleTolerance < AngleEpsilon)
                            {
                                WorkVertices.Push(ref v1234);
                                return;
                            }

                            // Angle Condition
                            //----------------------
                            var da1 = Mathf.Abs(Mathf.Atan2(v3.y - v2.y, v3.x - v2.x) -
                                                Mathf.Atan2(v2.y - v1.y, v2.x - v1.x));
                            if (da1 >= pi)
                            {
                                da1 = 2 * pi - da1;
                            }

                            if (da1 < AngleTolerance)
                            {
                                WorkVertices.Push(ref v2);
                                WorkVertices.Push(ref v3);
                                return;
                            }

                            if (CuspLimit > 0f)
                            {
                                if (da1 > CuspLimit)
                                {
                                    WorkVertices.Push(ref v2);
                                    return;
                                }
                            }
                        }
                    }
                    else if (d3 > FLTEpsilon)
                    {
                        // p1,p2,p4 are collinear, p3 is considerable
                        //----------------------
                        if (d3 * d3 <= distanceTolerance * (d.x * d.x + d.y * d.y))
                        {
                            if (AngleTolerance < AngleEpsilon)
                            {
                                WorkVertices.Push(ref v1234);
                                return;
                            }

                            // Angle Condition
                            //----------------------
                            var da1 = Mathf.Abs(Mathf.Atan2(v4.y - v3.y, v4.x - v3.x) -
                                                Mathf.Atan2(v3.y - v2.y, v3.x - v2.x));
                            if (da1 >= pi)
                            {
                                da1 = 2 * pi - da1;
                            }

                            if (da1 < AngleTolerance)
                            {
                                WorkVertices.Push(ref v2);
                                WorkVertices.Push(ref v3);
                                return;
                            }

                            if (CuspLimit > 0f)
                            {
                                if (da1 > CuspLimit)
                                {
                                    WorkVertices.Push(ref v3);
                                    return;
                                }
                            }
                        }
                    }
                    else
                    {
                        // Collinear case
                        //-----------------
                        var dx = v1234.x - (v1.x + v4.x) / 2f;
                        var dy = v1234.y - (v1.y + v4.y) / 2f;
                        if (dx * dx + dy * dy <= distanceTolerance)
                        {
                            WorkVertices.Push(ref v1234);
                            return;
                        }
                    }
                }
            }

            // Continue subdivision
            //----------------------
            RecursiveFillBezier(v1, v12, v123, v1234, distanceTolerance, level + 1);
            RecursiveFillBezier(v1234, v234, v34, v4, distanceTolerance, level + 1);
        }
    }
}