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use super::{Circle, Point2D, SafeArcSinCos, EPS};
pub enum TangentError {
PointInsideCircle,
PointOnBorder,
}
impl Circle {
pub fn tangent_points(&self, point: &Point2D) -> Result<[Point2D; 2], TangentError> {
let d = self.center - point;
let dist = d.magnitude();
if dist < self.radius + EPS {
return Err(TangentError::PointInsideCircle);
}
if dist < self.radius + EPS {
return Err(TangentError::PointOnBorder);
}
let angle1 = (self.radius / dist).acos_safe();
let angle2 = d.x.atan2(d.y);
let angle = angle2 - angle1;
let p1 = Point2D::new(
self.center.x + self.radius * angle.sin(),
self.center.y + self.radius * -angle.cos(),
);
let p2 = Point2D::new(
self.center.x + self.radius * -angle.sin(),
self.center.y + self.radius * angle.cos(),
);
Ok([p1, p2])
}
}