using UnityEngine;
using UnityEngine.Events;
using System;
using System.Collections.ObjectModel;
using System.Collections.Generic;
using UnityEngine.Serialization;

namespace Obi
{
    [System.Serializable]
    public class PathControlPointEvent : UnityEvent<int>
    {
    }

    [Serializable]
    public class ObiPath
    {
        [HideInInspector] [SerializeField] List<string> m_Names = new List<string>(); 
        [HideInInspector] [SerializeField] public ObiPointsDataChannel m_Points = new ObiPointsDataChannel();
        [HideInInspector] [SerializeField] ObiNormalDataChannel m_Normals = new ObiNormalDataChannel();
        [HideInInspector] [SerializeField] ObiColorDataChannel m_Colors = new ObiColorDataChannel();
        [HideInInspector] [SerializeField] ObiThicknessDataChannel m_Thickness = new ObiThicknessDataChannel();
        [HideInInspector] [SerializeField] ObiMassDataChannel m_Masses = new ObiMassDataChannel();
        [HideInInspector] [SerializeField] ObiRotationalMassDataChannel m_RotationalMasses = new ObiRotationalMassDataChannel();

        [FormerlySerializedAs("m_Phases")]
        [HideInInspector] [SerializeField] ObiPhaseDataChannel m_Filters = new ObiPhaseDataChannel();

        [HideInInspector] [SerializeField] private bool m_Closed = false;

        protected bool dirty = false;
        protected const int arcLenghtSamples = 20;
        [HideInInspector] [SerializeField] protected List<float> m_ArcLengthTable = new List<float>();
        [HideInInspector] [SerializeField] protected float m_TotalSplineLenght = 0.0f;

        public UnityEvent OnPathChanged = new UnityEvent();
        public PathControlPointEvent OnControlPointAdded = new PathControlPointEvent();
        public PathControlPointEvent OnControlPointRemoved = new PathControlPointEvent();
        public PathControlPointEvent OnControlPointRenamed = new PathControlPointEvent();

        private IEnumerable<IObiPathDataChannel> GetDataChannels()
        {
            yield return m_Points;
            yield return m_Normals;
            yield return m_Colors;
            yield return m_Thickness;
            yield return m_Masses;
            yield return m_RotationalMasses;
            yield return m_Filters;
        }

        public ObiPointsDataChannel points { get { return m_Points; }}
        public ObiNormalDataChannel normals { get { return m_Normals; } }
        public ObiColorDataChannel colors { get { return m_Colors; } }
        public ObiThicknessDataChannel thicknesses { get { return m_Thickness; } }
        public ObiMassDataChannel masses { get { return m_Masses; } }
        public ObiRotationalMassDataChannel rotationalMasses { get { return m_RotationalMasses; } }
        public ObiPhaseDataChannel filters { get { return m_Filters; } }

        public ReadOnlyCollection<float> ArcLengthTable
        {
            get { return m_ArcLengthTable.AsReadOnly(); }
        }

        public float Length
        {
            get { return m_TotalSplineLenght; }
        }

        public int ArcLengthSamples
        {
            get { return arcLenghtSamples; }
        }

        public int ControlPointCount
        {
            get { return m_Points.Count;}
        }

        public bool Closed
        {
            get { return m_Closed; }
            set
            {
                if (value != m_Closed)
                {
                    m_Closed = value;
                    dirty = true;
                }
            }
        }

        public int GetSpanCount()
        {
            return m_Points.GetSpanCount(m_Closed);
        }

        public int GetSpanControlPointForMu(float mu, out float spanMu)
        {
            return m_Points.GetSpanControlPointAtMu(m_Closed, mu, out spanMu);
        }

        public int GetClosestControlPointIndex(float mu)
        {
            float spanMu;
            int cp = GetSpanControlPointForMu(mu, out spanMu);

            if (spanMu > 0.5f)
                return (cp + 1) % ControlPointCount;
            else
                return cp % ControlPointCount;
        }

        /**
         * Returns the curve parameter (mu) at a certain length of the curve, using linear interpolation
         * of the values cached in arcLengthTable.
         */
        public float GetMuAtLenght(float length)
        {
            if (length <= 0) return 0;
            if (length >= m_TotalSplineLenght) return 1;

            int i;
            for (i = 1; i < m_ArcLengthTable.Count; ++i)
            {
                if (length < m_ArcLengthTable[i]) break;
            }

            float prevMu = (i - 1) / (float)(m_ArcLengthTable.Count - 1);
            float nextMu = i / (float)(m_ArcLengthTable.Count - 1);

            float s = (length - m_ArcLengthTable[i - 1]) / (m_ArcLengthTable[i] - m_ArcLengthTable[i - 1]);

            return prevMu + (nextMu - prevMu) * s;
        }

        /**
         * Recalculates spline arc lenght in world space using Gauss-Lobatto adaptive integration. 
         * @param acc minimum accuray desired (eg 0.00001f)
         * @param maxevals maximum number of spline evaluations we want to allow per segment.
         */
        public float RecalculateLenght(Matrix4x4 referenceFrame, float acc, int maxevals)
        {
            if (referenceFrame == null) 
            { 
                m_TotalSplineLenght = 0;
                return 0;
            }

            m_TotalSplineLenght = 0.0f;
            m_ArcLengthTable.Clear();
            m_ArcLengthTable.Add(0);

            float step = 1 / (float)(arcLenghtSamples + 1);
            int controlPoints = ControlPointCount;

            if (controlPoints >= 2)
            {

                int spans = GetSpanCount();

                for (int cp = 0; cp < spans; ++cp)
                {
                    int nextCP = (cp + 1) % controlPoints;
                    var wp1 = m_Points[cp];
                    var wp2 = m_Points[nextCP];

                    Vector3 _p  = referenceFrame.MultiplyPoint3x4(wp1.position);
                    Vector3 p   = referenceFrame.MultiplyPoint3x4(wp1.outTangentEndpoint);
                    Vector3 p_  = referenceFrame.MultiplyPoint3x4(wp2.inTangentEndpoint);
                    Vector3 p__ = referenceFrame.MultiplyPoint3x4(wp2.position);

                    for (int i = 0; i <= Mathf.Max(1, arcLenghtSamples); ++i)
                    {

                        float a = i * step;
                        float b = (i + 1) * step;

                        float segmentLength = GaussLobattoIntegrationStep(_p, p, p_, p__, a, b,
                                                                          m_Points.EvaluateFirstDerivative(_p, p, p_, p__, a).magnitude,
                                                                          m_Points.EvaluateFirstDerivative(_p, p, p_, p__, b).magnitude, 0, maxevals, acc);

                        m_TotalSplineLenght += segmentLength;

                        m_ArcLengthTable.Add(m_TotalSplineLenght);

                    }

                }
            }
            else
            {
                Debug.LogWarning("A path needs at least 2 control points to be defined.");
            }

            return m_TotalSplineLenght;
        }

        /**
         * One step of the adaptive integration method using Gauss-Lobatto quadrature.
         * Takes advantage of the fact that the arc lenght of a vector function is equal to the
         * integral of the magnitude of first derivative.
         */
        private float GaussLobattoIntegrationStep(Vector3 p1, Vector3 p2, Vector3 p3, Vector3 p4,
                                                  float a, float b,
                                                  float fa, float fb, int nevals, int maxevals, float acc)
        {

            if (nevals >= maxevals) return 0;

            // Constants used in the algorithm
            float alpha = Mathf.Sqrt(2.0f / 3.0f);
            float beta = 1.0f / Mathf.Sqrt(5.0f);

            // Here the abcissa points and function values for both the 4-point
            // and the 7-point rule are calculated (the points at the end of
            // interval come from the function call, i.e., fa and fb. Also note
            // the 7-point rule re-uses all the points of the 4-point rule.)
            float h = (b - a) / 2;
            float m = (a + b) / 2;

            float mll = m - alpha * h;
            float ml = m - beta * h;
            float mr = m + beta * h;
            float mrr = m + alpha * h;
            nevals += 5;

            float fmll = m_Points.EvaluateFirstDerivative(p1, p2, p3, p4, mll).magnitude;
            float fml = m_Points.EvaluateFirstDerivative(p1, p2, p3, p4, ml).magnitude;
            float fm = m_Points.EvaluateFirstDerivative(p1, p2, p3, p4, m).magnitude;
            float fmr = m_Points.EvaluateFirstDerivative(p1, p2, p3, p4, mr).magnitude;
            float fmrr = m_Points.EvaluateFirstDerivative(p1, p2, p3, p4, mrr).magnitude;

            // Both the 4-point and 7-point rule integrals are evaluted
            float integral4 = (h / 6) * (fa + fb + 5 * (fml + fmr));
            float integral7 = (h / 1470) * (77 * (fa + fb) + 432 * (fmll + fmrr) + 625 * (fml + fmr) + 672 * fm);

            // The difference betwen the 4-point and 7-point integrals is the
            // estimate of the accuracy

            if ((integral4 - integral7) < acc || mll <= a || b <= mrr)
            {
                if (!(m > a && b > m))
                {
                    Debug.LogError("Spline integration reached an interval with no more machine numbers");
                }
                return integral7;
            }
            else
            {
                return GaussLobattoIntegrationStep(p1, p2, p3, p4, a, mll, fa, fmll, nevals, maxevals, acc)
                        + GaussLobattoIntegrationStep(p1, p2, p3, p4, mll, ml, fmll, fml, nevals, maxevals, acc)
                        + GaussLobattoIntegrationStep(p1, p2, p3, p4, ml, m, fml, fm, nevals, maxevals, acc)
                        + GaussLobattoIntegrationStep(p1, p2, p3, p4, m, mr, fm, fmr, nevals, maxevals, acc)
                        + GaussLobattoIntegrationStep(p1, p2, p3, p4, mr, mrr, fmr, fmrr, nevals, maxevals, acc)
                        + GaussLobattoIntegrationStep(p1, p2, p3, p4, mrr, b, fmrr, fb, nevals, maxevals, acc);

            }
        }

        public void SetName(int index, string name)
        {
            m_Names[index] = name;
            if (OnControlPointRenamed != null)
                OnControlPointRenamed.Invoke(index);
            dirty = true;
        }

        public string GetName(int index)
        {
            return m_Names[index];
        }

        public void AddControlPoint(Vector3 position, Vector3 inTangentVector, Vector3 outTangentVector, Vector3 normal, float mass, float rotationalMass, float thickness, int filter, Color color, string name)
        {
            InsertControlPoint(ControlPointCount, position, inTangentVector, outTangentVector, normal,  mass, rotationalMass, thickness, filter, color, name);
        }

        public void InsertControlPoint(int index, Vector3 position, Vector3 inTangentVector, Vector3 outTangentVector, Vector3 normal, float mass, float rotationalMass, float thickness, int filter, Color color, string name)
        {
            m_Points.data.Insert(index, new ObiWingedPoint(inTangentVector,position,outTangentVector));
            m_Colors.data.Insert(index, color);
            m_Normals.data.Insert(index, normal);
            m_Thickness.data.Insert(index, thickness);
            m_Masses.data.Insert(index, mass);
            m_RotationalMasses.data.Insert(index, rotationalMass);
            m_Filters.data.Insert(index, filter);
            m_Names.Insert(index,name);

            if (OnControlPointAdded != null)
                OnControlPointAdded.Invoke(index);

            dirty = true;
        }

        public int InsertControlPoint(float mu)
        {

            int controlPoints = ControlPointCount;
            if (controlPoints >= 2)
            {

                if (!System.Single.IsNaN(mu))
                {

                    float p;
                    int i = GetSpanControlPointForMu(mu, out p);

                    int next = (i + 1) % controlPoints;

                    var wp1 = m_Points[i];
                    var wp2 = m_Points[next];

                    Vector3 P0_1 = (1 - p) * wp1.position + p * wp1.outTangentEndpoint;
                    Vector3 P1_2 = (1 - p) * wp1.outTangentEndpoint + p * wp2.inTangentEndpoint;
                    Vector3 P2_3 = (1 - p) * wp2.inTangentEndpoint + p * wp2.position;

                    Vector3 P01_12 = (1 - p) * P0_1 + p * P1_2;
                    Vector3 P12_23 = (1 - p) * P1_2 + p * P2_3;

                    Vector3 P0112_1223 = (1 - p) * P01_12 + p * P12_23;

                    wp1.SetOutTangentEndpoint(P0_1);
                    wp2.SetInTangentEndpoint(P2_3);

                    m_Points[i] = wp1;
                    m_Points[next] = wp2;

                    Color color = m_Colors.Evaluate(m_Colors[i],
                                                    m_Colors[i],
                                                    m_Colors[next],
                                                    m_Colors[next], p);

                    Vector3 normal = m_Normals.Evaluate(m_Normals[i],
                                                        m_Normals[i],
                                                        m_Normals[next],
                                                        m_Normals[next], p);

                    float thickness = m_Thickness.Evaluate(m_Thickness[i],
                                                           m_Thickness[i],
                                                           m_Thickness[next],
                                                           m_Thickness[next], p);

                    float mass = m_Masses.Evaluate(m_Masses[i],
                                                   m_Masses[i],
                                                   m_Masses[next],
                                                   m_Masses[next], p);

                    float rotationalMass = m_RotationalMasses.Evaluate(m_RotationalMasses[i],
                                                                       m_RotationalMasses[i],
                                                                       m_RotationalMasses[next],
                                                                       m_RotationalMasses[next], p);

                    int filter = m_Filters.Evaluate(m_Filters[i],
                                                    m_Filters[i],
                                                    m_Filters[next],
                                                    m_Filters[next], p);

                    InsertControlPoint(i + 1, P0112_1223, P01_12 - P0112_1223, P12_23 - P0112_1223, normal, mass,rotationalMass, thickness, filter, color, GetName(i));

                    return i + 1;
                }
            }
            return -1;

        }

        public void Clear()
        {
            for (int i = ControlPointCount-1; i >= 0; --i)
                RemoveControlPoint(i);

            m_TotalSplineLenght = 0.0f;
            m_ArcLengthTable.Clear();
            m_ArcLengthTable.Add(0);
        }

        public void RemoveControlPoint(int index)
        {
            foreach (var channel in GetDataChannels())
                channel.RemoveAt(index);

            m_Names.RemoveAt(index);

            if (OnControlPointRemoved != null)
                OnControlPointRemoved.Invoke(index);

            dirty = true;
        }

        public void FlushEvents()
        {
            bool isDirty = dirty;
            foreach (var channel in GetDataChannels())
            {
                isDirty |= channel.Dirty;
                channel.Clean(); 
            }

            if (OnPathChanged != null && isDirty)
            {
                dirty = false;
                OnPathChanged.Invoke();
            }
        }

    }
}