using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Plot2D : MonoBehaviour {

    public Function2D Function;

    public Vector4 ArgsBounds = new Vector4(0, 0, 1, 1);
    public Vector4 ViewBounds = new Vector4(0, 0, 1, 1);

    public int USamples = 10;
    public int VSamples = 10;

    private Vector3[] _points;

    private void OnValidate()
    {
        if(USamples < 2) {
            USamples = 2;
        }
        if (VSamples < 2) {
            VSamples = 2;
        }
    }

    private void OnDrawGizmos()
    {
        
        if(Function == null) {
            return;
        }

        var pointsCount = USamples * VSamples;
        if(_points == null || _points.Length != pointsCount) {
            _points = new Vector3[USamples * VSamples];
        }
      

        for (int vI = 0; vI < VSamples; ++vI) {
            double lV = (double)vI / (VSamples - 1);
            for (int uI = 0; uI < USamples; ++uI) {
                double lU = (double)uI / (USamples - 1);

                double u = lU * ArgsBounds.z + ArgsBounds.x;
                double v = lV * ArgsBounds.w + ArgsBounds.y;

                double z = Function.Evaluate(u, v);
                double x = lU * ViewBounds.z + ViewBounds.x;
                double y = lV * ViewBounds.w + ViewBounds.y;

                _points[vI * USamples + uI] = new Vector3((float)x, (float)z, (float)y);
            }
        }


        for(int y = 0; y < VSamples; ++y) {
            for (int x = 1; x < USamples; ++x) {
                Gizmos.DrawLine(_points[y * USamples + (x - 1)], _points[y * USamples + x]);
            }
        }

        for (int y = 1; y < VSamples; ++y) {
            for (int x = 0; x < USamples; ++x) {
                Gizmos.DrawLine(_points[(y - 1) * USamples + x], _points[y * USamples + x]);
            }
        }
    }
}