using UnityEngine;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System;
using UnityEngine.UI;

public class InterpolateurDeSurface : MonoBehaviour
{
    public GameObject particle;
    public float[] X;
    public float[,] Y;
    public float[] Z;
    public bool autoGenerateGrid;
    public float pas;
    private List<List<Vector3>> ListePoints = new List<List<Vector3>>();

    void Start()
    {
        if (true)
        {
            int n = 5;

            X = new float[n];
            Y = new float[n, n];
            Z = new float[n];

            for (int i = 0; i < n; i++)
            {
                X[i] = (float)i / (float)(n - 1);
                Z[i] = (float)i / (float)(n - 1);
            }

            for (int i = 0; i < n; i++)
            {
                float XC2 = (X[i] - (1.0f / 2.0f)) * (X[i] - (1.0f / 2.0f));

                for (int j = 0; j < n; j++)
                {
                    float ZC2 = (Z[j] - (1.0f / 2.0f)) * (Z[j] - (1.0f / 2.0f));

                    Y[i, j] = (float)Math.Exp(-(XC2 + ZC2));
                    Instantiate(particle, new Vector3(X[i], Y[i, j], Z[j]), Quaternion.identity);
                }
            }
        }
        else
        {

        }
    }

    void Update()
    {
        if (Input.GetKeyDown(KeyCode.Return))
        {
            List<float> T = new List<float>();
            List<float> tToEval = new List<float>();

            (T, tToEval) = buildParametrisationReguliere(X.Count(), pas);
            applyLagrangeParametrisation(X, Y, Z, T, tToEval);
        }
    }

    (List<float>, List<float>) buildParametrisationReguliere(int nbElem, float pas)
    {
        // Vecteur des pas temporels
        List<float> T = new List<float>();
        // Echantillonage des pas temporels
        List<float> tToEval = new List<float>();

        // Construction des pas temporels
        for (int i = 0; i < nbElem; i++)
        {
            T.Add(i);
        }

        // Construction des échantillons
        for (float t = 0; t < T.Last(); t += pas)
        {
            tToEval.Add(t);
        }

        return (T, tToEval);
    }

    void applyLagrangeParametrisation(float[] X, float[,] Y, float[] Z, List<float> T, List<float> tToEval)
    {
        ListePoints.Clear();

        float[] newX = new float[tToEval.Count()];
        float[,] newY_interm = new float[tToEval.Count(), Z.Count()];
        float[,] newY = new float[tToEval.Count(), tToEval.Count()];
        float[] newZ = new float[tToEval.Count()];

        for (int i = 0; i < tToEval.Count(); i++)
        {
            float t = tToEval[i];

            newX[i] = lagrange(t, T, X);
            newZ[i] = lagrange(t, T, Z);
        }



        for (int k = 0; k < Z.Count(); k++)
        {
            float[] Yk = GetColumn(Y, k);

            for (int i = 0; i < tToEval.Count(); i++)
            {
                float t = tToEval[i];

                float val = lagrange(t, T, Yk);
                newY[i, k * (int)(1 / pas)] = val;
                newY_interm[i, k] = val;
            }
        }

        // for (int k = 0; k < tToEval.Count(); k++)
        // {
        //     float[] Yk = GetRow(newY_interm, k);

        //     for (int i = 0; i < tToEval.Count(); i++)
        //     {
        //         float t = tToEval[i];

        //         newY[k, i] = lagrange(t, T, Yk);
        //     }
        // }

        for (int i = 0; i < tToEval.Count(); i++)
        {
            List<Vector3> ListePoints_i = new List<Vector3>();

            for (int j = 0; j < tToEval.Count(); j++)
            {
                ListePoints_i.Add(new Vector3(newX[i], newY[i, j], newZ[j]));
            }

            ListePoints.Add(ListePoints_i);
        }

    }

    private float lagrange(float x, List<float> X, float[] Y)
    {
        float sum = 0;
        for (int i = 0; i < X.Count; i++)
        {
            float xi = X[i];

            float prod = 1;
            for (int j = 0; j < X.Count; j++)
            {
                float xj = X[j];

                if (xi != xj)
                {
                    prod *= (x - xj) / (xi - xj);
                }
            }

            sum += prod * Y[i];
        }
        return sum;
    }

    void OnDrawGizmosSelected()
    {
        Gizmos.color = Color.blue;
        if (autoGenerateGrid)
        {

            for (int j = 0; j < ListePoints.Count; ++j)
            {
                for (int i = 0; i < ListePoints[j].Count - 1; ++i)
                {
                    Gizmos.DrawLine(ListePoints[j][i], ListePoints[j][i + 1]);
                }
            }
        }
    }


    public float[] GetColumn(float[,] matrix, int columnNumber)
    {
        return Enumerable.Range(0, matrix.GetLength(0))
                .Select(x => matrix[x, columnNumber])
                .ToArray();
    }

    public float[] GetRow(float[,] matrix, int rowNumber)
    {
        return Enumerable.Range(0, matrix.GetLength(1))
                .Select(x => matrix[rowNumber, x])
                .ToArray();
    }
}