#pragma once

#include <GL/glew.h>
#include <vector>
#include <string>
#include <map>

#include "glm/glm.hpp"

class Icosphere
{
public:
    Icosphere(float radius, int subdivisions, GLuint shaderProgram);
	void render(const float time);

    void setPosition(glm::vec3 position);

	~Icosphere();

private:
	GLuint _vbo;
	GLuint _vao;
	GLuint _ebo;
    GLuint _shaderProgram;

	std::vector<float> _vertices;
	std::vector<unsigned int> _indices;

    glm::vec3 _position;

    // Generating an isosphere
    // https://schneide.blog/2016/07/15/generating-an-icosphere-in-c/
	struct Triangle
	{
		int vertex[3];
	};

	using TriangleList = std::vector<Triangle>;
	using VertexList = std::vector<glm::vec3>;

	const float X=.525731112119133606f;
	const float Z=.850650808352039932f;
	const float N=0.f;

	const VertexList _isocahedronVertices =
	{
		{-X,N,Z}, {X,N,Z}, {-X,N,-Z}, {X,N,-Z},
		{N,Z,X}, {N,Z,-X}, {N,-Z,X}, {N,-Z,-X},
		{Z,X,N}, {-Z,X, N}, {Z,-X,N}, {-Z,-X, N}
	};
	 
	const TriangleList _isocahedronTriangles =
	{
		{0,4,1},{0,9,4},{9,5,4},{4,5,8},{4,8,1},
		{8,10,1},{8,3,10},{5,3,8},{5,2,3},{2,7,3},
		{7,10,3},{7,6,10},{7,11,6},{11,0,6},{0,1,6},
		{6,1,10},{9,0,11},{9,11,2},{9,2,5},{7,2,11}
	};

    using Lookup = std::map<std::pair<int, int>, int>;

    void generateVertices(float radius, int subdivisions);
    int vertexForEdge(Lookup& lookup, VertexList& vertices, int first, int second);
    TriangleList subdivide(VertexList& vertices, TriangleList triangles);

    void updateModelMatrix();
};