Snake Rectangle Vector Collision - c++

Question

I'm new to SFML and C++ so I'm trying to learn both at the same time. I've decided to write a Snake game. For my snakes body I am using a vector of RectangleShapes. I've drawn a berry in the center of the screen and I can detect when the head of my snake is in collision with the berry, however I have no idea how to test if the snake is colliding with itself.
I've thought about testing collision between the head of the snake against the entire vector of blocks, but this will always return true as the head of the snake is in collision with itself.
I would appreciate any suggestions and criticisms of my code, Thanks!
#include <iostream>
#include <SFML/Window.hpp>
#include <SFML/Graphics.hpp>
#include <string>
#include <sstream>
using namespace sf;
constexpr int windowWidth{800}, windowHeight{600};
Vector2f blockLocation{0, 0};
struct Block
{
RectangleShape shape;
Vector2f blockSize{15,15};
Block(float posX, float posY)
{
shape.setPosition(posX, posY);
shape.setSize(blockSize);
shape.setFillColor(Color::Blue);
shape.setOutlineColor(Color::Green);
shape.setOutlineThickness(3);
}
};
struct Berry
{
CircleShape shape;
Berry(float posX, float posY)
{
shape.setPosition(posX, posY);
shape.setRadius(8);
shape.setFillColor(Color::Red);
shape.setOutlineColor(Color::Magenta);
shape.setOutlineThickness(3);
}
};
bool keyUp(void)
{
if(Keyboard::isKeyPressed(Keyboard::Key::Up)) return true;
return false;
}
bool keyDown(void)
{
if(Keyboard::isKeyPressed(Keyboard::Key::Down)) return true;
return false;
}
bool keyLeft(void)
{
if(Keyboard::isKeyPressed(Keyboard::Key::Left)) return true;
return false;
}
bool keyRight(void)
{
if(Keyboard::isKeyPressed(Keyboard::Key::Right)) return true;
return false;
}
int stat(std::vector<Block> *blocks, RenderWindow *window)
{
sf::Font font;
if(!font.loadFromFile("Oswald-Bold.ttf"))
{
std::cerr << "Cannot load font!" << std::endl;
return 1;
}
sf::Text text;
text.setFont(font);
std::ostringstream message;
message << "x: " << blockLocation.x << std::endl
<< "y: " << blockLocation.y << std::endl
<< "blocks: " << blocks->size() << std::endl;
text.setString(message.str());
text.setCharacterSize(24);
text.setColor(sf::Color::Magenta);
text.setOrigin(0, 0);
window->draw(text);
return 0;
}
bool collision(Block *shapeA, Berry *shapeB)
{
if( shapeA->shape.getGlobalBounds().intersects(shapeB->shape.getGlobalBounds()) )
{
std::cout << "collision with ";
std::cout << "x: " << shapeA->shape.getPosition().x << "y: " <<
shapeA->shape.getPosition().y << "and x: " << shapeB->shape.getPosition().x << "y: " << shapeB->shape.getPosition().y << std::endl;
return true;
}
else
return false;
}
int main(void)
{
Clock clock;
Time timeSinceLastUpdate = Time::Zero;
const Time TimePerFrame = seconds(3.0f/30.f);
std::vector<Block> blocks;
RenderWindow window{ {windowWidth, windowHeight} , "blocks!"};
bool up(false);
bool down(false);
bool left(false);
bool right(false);
window.setFramerateLimit(60);
Berry berry(400, 300);
blocks.emplace_back(blockLocation.x, blockLocation.y);
while(window.isOpen())
{
if(Keyboard::isKeyPressed(Keyboard::Key::Escape)) return 0;
Time elapsedTime = clock.restart();
timeSinceLastUpdate += elapsedTime;
while(timeSinceLastUpdate > TimePerFrame)
{
timeSinceLastUpdate -= TimePerFrame;
window.clear(Color::Black);
// Get the Head of the snake
auto first = blocks.back();
if(keyUp())
{
up = true;
down = false, left = false, right = false;
blocks.emplace_back(blockLocation.x, blockLocation.y);
blocks.erase(blocks.begin());
}
else if(keyDown())
{
down = true;
up = false, left = false, right = false;
blocks.emplace_back(blockLocation.x, blockLocation.y);
blocks.erase(blocks.begin());
}
else if(keyLeft())
{
left = true;
right = false, up = false, down = false;
blocks.emplace_back(blockLocation.x, blockLocation.y);
blocks.erase(blocks.begin());
}
else if(keyRight())
{
right = true;
left = false, up = false, down = false;
blocks.emplace_back(blockLocation.x, blockLocation.y);
blocks.erase(blocks.begin());
}
if(up) { blockLocation.y-=19; blocks.emplace_back(blockLocation.x, blockLocation.y); blocks.erase(blocks.begin());
}
if(down) { blockLocation.y+=19; blocks.emplace_back(blockLocation.x, blockLocation.y); blocks.erase(blocks.begin());
}
if(left) { blockLocation.x-=19; blocks.emplace_back(blockLocation.x, blockLocation.y); blocks.erase(blocks.begin());
}
if(right){ blockLocation.x+=19; blocks.emplace_back(blockLocation.x, blockLocation.y); blocks.erase(blocks.begin());
}
if (collision(&first, &berry)) blocks.emplace_back(blockLocation.x, blockLocation.y);
if(blocks.size() > 50)
{
blocks.erase(blocks.begin());
}
for(auto a : blocks)
{
window.draw(a.shape);
}
window.draw(berry.shape);
stat(&blocks, &window);
window.display();
}
}
return 0;
}