#pragma once

#include <SFML/Graphics.hpp>

#include <vector>

#include "Particle.hpp"

class ParticleRenderer {

private:

sf::Texture texture;

public:

sf::VertexArray vertices;

ParticleRenderer(const int PARTICLE_COUNT) : vertices(sf::Quads, PARTICLE_COUNT * 4) {

texture.loadFromFile("../assets/circle.png");

texture.setSmooth(true);

}

void build(const std::vector<Particle> &particles) {

const float textureSize = static_cast<float>(texture.getSize().x);

for (int i = 0; i < particles.size(); ++i) {

const auto &p = particles[i];

const float r = p.radius;

const std::size_t base = i*4;

// positions: a quad around particle centre

vertices[base + 0].position = p.position + sf::Vector2f(-r, -r);

vertices[base + 1].position = p.position + sf::Vector2f( r, -r);

vertices[base + 2].position = p.position + sf::Vector2f( r, r);

vertices[base + 3].position = p.position + sf::Vector2f(-r, r);

// full texture

vertices[base + 0].texCoords = {0.f, 0.f};

vertices[base + 1].texCoords = {textureSize, 0.f};

vertices[base + 2].texCoords = {textureSize, textureSize};

vertices[base + 3].texCoords = {0.f, textureSize};

// color per vertex

for (int k = 0; k < 4; ++k) {

vertices[base + k].color = p.color;

}

}

}

void draw(sf::RenderTarget &target) {

sf::RenderStates states;

states.texture = &texture;

target.draw(vertices, states);

}

};