How do I flip an image and point a gun at the mouse at the same time? (SFML)

I'm making a shooter where the player can shoot at the mouse, so I got the guns to point at the mouse, but I can't figure out how to correctly flip the image once it's turned left. I mean, I did flip the image but it's not aligned right. I'm not really sure how to explain it, here's my code.

void PortalGun::update(Vector2i mPos) {

    float pi = 3.14159265359;

    float rotation = atan2(sprite.getGlobalBounds().top - mPos.y,sprite.getGlobalBounds().left - mPos.x) * 180 / pi;

    int x = player->sprite.getGlobalBounds().left + 16;
    int y = player->sprite.getGlobalBounds().top;

    if (rotation > -90 && rotation < 90) {
        player->dir = -1;
        sprite.setTextureRect(IntRect(0, 32, 64, -32));
    } else {
        player->dir = 1;
        sprite.setTextureRect(IntRect(0, 0, 64, 32));
    }


    sprite.setPosition(x, y + 15);
    sprite.setRotation(rotation + 170);

}

When the mouse is to the left of the gun, it flips the image but keeps rotating upwards so the mouse is 20 ish pixels higher. I can't just change the position when rotating, so what do I do? Sorry for sounding a bit cryptic, it's a bit hard to explain.

Solution

First of all, you should set your sprite's origin to the point where you'd like to rotate the gun (typically the handle or mounting point). To do this, use sf::Sprite::setOrigin(). The passed coordinates are relative to the top left corner of the sprite.
To get or set your sprite's position in the world (where your origin is), you can use sf::Sprite::getPosition() and sf::Sprite::setPosition().
Your rotation can stay as it is. It will rotate around your set origin.
To mirror your sprite, just scale (sf::Sprite::setScale()) it using a negative factor: sprite.setScale(-1, 1); The negative factor will mirror/flip the image at the set origin, without forcing you to update the texture coordinates.