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

public class Hyperbola : MonoBehaviour
{
    Mesh mesh;
    public Vector3 center;
    public float a;
    public float b;
    // Start is called before the first frame update
    void Start()
    {
        mesh = new Mesh
        {
            name = "Hyperbola"
        };
    }

    // Update is called once per frame
    void Update()
    {
        
    }

    public void DrawHyperbola()
    {
        mesh.Clear();

        Vector3[] vectors = new Vector3[202];
        int k = 0;
        float step = a / 100;
        float x = -a;
        while (k < 51)
        {
            float y = x * x / (a * a) - 1;
            y *= (b * b);
            y = Mathf.Sqrt(y);
            vectors[50 + k] = new Vector3(x, y, 0);
            if (y != 0)
            {
                vectors[50 - k] = new Vector3(x, -y, 0);
            }
            x -= step;
            step *= 1.1f;
            k++;
        }

        x = a;
        step = a / 100;
        k = 0;
        while (k < 51)
        {
            float y = x * x / (a * a) - 1;
            y *= (b * b);
            y = Mathf.Sqrt(y);
            vectors[151 + k] = new Vector3(x, y, 0);
            if (y != 0)
            {
                vectors[151 - k] = new Vector3(x, -y, 0);
            }
            x += step;
            step *= 1.1f;
            k++;
        }
        mesh.vertices = vectors;

        int[] triangle = new int[400];
        for (int i = 0; i < 100; ++i)
        {
            triangle[2 * i] = i;
            triangle[2 * i + 1] = i + 1;
        }
        for (int i = 100; i < 200; ++i)
        {
            triangle[2 * i] = i + 1;
            triangle[2 * i + 1] = i + 2;
        }

        mesh.SetIndices(triangle, MeshTopology.Lines, 0);

        GetComponent<MeshFilter>().mesh = mesh;
    }

    public void DrawHyperbola3D()
    {
        mesh.Clear();

        Vector3[] vectors = new Vector3[404];
        int k = 0;
        float step = a / 100;
        float x = -a;
        while (k < 101)
        {
            float y = x * x / (a * a) - 1;
            y *= (b * b);
            y = Mathf.Sqrt(y);
            vectors[100 + k] = new Vector3(x, y, -5);
            if (y != 0)
            {
                if(k % 2 == 0)
                    vectors[100 - k] = new Vector3(x, -y, -5);
                else
                    vectors[102 - k] = new Vector3(x, -y, -5);
            }
            k++;
            vectors[100 + k] = new Vector3(x, y, 5);
            if (y != 0)
            {
                if (k % 2 == 0)
                    vectors[100 - k] = new Vector3(x, -y, 5);
                else
                    vectors[102 - k] = new Vector3(x, -y, 5);
            }
            x -= step;
            step *= 1.1f;
            k++;
        }

        x = a;
        step = a / 100;
        k = 0;
        while (k < 101)
        {
            float y = x * x / (a * a) - 1;
            y *= (b * b);
            y = Mathf.Sqrt(y);
            vectors[301 + k] = new Vector3(x, y, -5);
            if (y != 0)
            {
                if (k % 2 == 0)
                    vectors[301 - k] = new Vector3(x, -y, -5);
                else
                    vectors[303 - k] = new Vector3(x, -y, -5);
            }
            k++;
            vectors[301 + k] = new Vector3(x, y, 5);
            if (y != 0)
            {
                if (k % 2 == 0)
                    vectors[301 - k] = new Vector3(x, -y, 5);
                else
                    vectors[303 - k] = new Vector3(x, -y, 5);
            }
            x += step;
            step *= 1.1f;
            k++;
        }
        mesh.vertices = vectors;

        Vector2[] uvs = new Vector2[vectors.Length];
        for (int i = 0; i < uvs.Length; i++)
        {
            uvs[i] = new Vector2(0, vectors[i].y / 100);
        }
        mesh.uv = uvs;

        int[] triangle = new int[1200];
        for (int i = 0; i < 99; ++i)
        {
            triangle[6 * i] = 2 * i;
            triangle[6 * i + 1] = 2 * i + 1;
            triangle[6 * i + 2] = 2 * i + 2;
            triangle[6 * i + 3] = 2 * i + 1;
            triangle[6 * i + 4] = 2 * i + 3;
            triangle[6 * i + 5] = 2 * i + 2;
        }
        for (int i = 101; i < 200; ++i)
        {
            triangle[6 * i] = 2 * i;
            triangle[6 * i + 1] = 2 * i + 1;
            triangle[6 * i + 2] = 2 * i + 2;
            triangle[6 * i + 3] = 2 * i + 1;
            triangle[6 * i + 4] = 2 * i + 3;
            triangle[6 * i + 5] = 2 * i + 2;
        }

        mesh.SetIndices(triangle, MeshTopology.Triangles, 0);

        GetComponent<MeshFilter>().mesh = mesh;
    }

    public void MeshClear()
    {
        mesh.Clear();
        GetComponent<MeshFilter>().mesh = mesh;
    }
}