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/// Represents a line segment
#[derive(Debug, Clone, Copy)]
pub struct Line {
pub start: (f64, f64),
pub end: (f64, f64),
}
/// Represents a rectangle
#[derive(Debug, Clone, Copy)]
pub struct Rect {
pub x: f64,
pub y: f64,
pub width: f64,
pub height: f64,
}
impl Line {
pub fn new(start: (f64, f64), end: (f64, f64)) -> Self {
Self { start, end }
}
}
impl Rect {
pub fn new(x: f64, y: f64, width: f64, height: f64) -> Self {
Self {
x,
y,
width,
height,
}
}
}
/// Checks if a point is inside a rectangle
pub fn point_in_rect(point: (f64, f64), rect: &Rect) -> bool {
point.0 >= rect.x
&& point.0 <= rect.x + rect.width
&& point.1 >= rect.y
&& point.1 <= rect.y + rect.height
}
/// Checks if two rectangles intersect (AABB collision)
pub fn rect_intersects_rect(r1: &Rect, r2: &Rect) -> bool {
!(r1.x + r1.width < r2.x
|| r2.x + r2.width < r1.x
|| r1.y + r1.height < r2.y
|| r2.y + r2.height < r1.y)
}
/// Checks if two line segments intersect using parametric equations
pub fn line_intersects_line(l1: &Line, l2: &Line) -> bool {
let x1 = l1.start.0;
let y1 = l1.start.1;
let x2 = l1.end.0;
let y2 = l1.end.1;
let x3 = l2.start.0;
let y3 = l2.start.1;
let x4 = l2.end.0;
let y4 = l2.end.1;
let denom = (x1 - x2) * (y3 - y4) - (y1 - y2) * (x3 - x4);
if denom.abs() < 1e-10 {
return false; // Parallel or coincident
}
let t = ((x1 - x3) * (y3 - y4) - (y1 - y3) * (x3 - x4)) / denom;
let u = -((x1 - x2) * (y1 - y3) - (y1 - y2) * (x1 - x3)) / denom;
(0.0..=1.0).contains(&t) && (0.0..=1.0).contains(&u)
}
/// Checks if a line segment intersects a rectangle
pub fn line_intersects_rect(line: &Line, rect: &Rect) -> bool {
// Check if either endpoint is inside the rectangle
if point_in_rect(line.start, rect) || point_in_rect(line.end, rect) {
return true;
}
// Check intersection with all four edges
let edges = [
Line::new((rect.x, rect.y), (rect.x + rect.width, rect.y)), // Top
Line::new(
(rect.x + rect.width, rect.y),
(rect.x + rect.width, rect.y + rect.height),
), // Right
Line::new(
(rect.x + rect.width, rect.y + rect.height),
(rect.x, rect.y + rect.height),
), // Bottom
Line::new((rect.x, rect.y + rect.height), (rect.x, rect.y)), // Left
];
edges.iter().any(|edge| line_intersects_line(line, edge))
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_point_in_rect() {
let rect = Rect::new(10.0, 10.0, 20.0, 20.0);
assert!(point_in_rect((15.0, 15.0), &rect));
assert!(point_in_rect((10.0, 10.0), &rect));
assert!(point_in_rect((30.0, 30.0), &rect));
assert!(!point_in_rect((5.0, 15.0), &rect));
assert!(!point_in_rect((35.0, 15.0), &rect));
}
#[test]
fn test_rect_intersects_rect() {
let r1 = Rect::new(0.0, 0.0, 10.0, 10.0);
let r2 = Rect::new(5.0, 5.0, 10.0, 10.0);
let r3 = Rect::new(20.0, 20.0, 10.0, 10.0);
assert!(rect_intersects_rect(&r1, &r2));
assert!(rect_intersects_rect(&r2, &r1));
assert!(!rect_intersects_rect(&r1, &r3));
}
#[test]
fn test_line_intersects_line() {
let l1 = Line::new((0.0, 0.0), (10.0, 10.0));
let l2 = Line::new((0.0, 10.0), (10.0, 0.0));
let l3 = Line::new((20.0, 20.0), (30.0, 30.0));
assert!(line_intersects_line(&l1, &l2));
assert!(!line_intersects_line(&l1, &l3));
}
#[test]
fn test_line_intersects_rect() {
let rect = Rect::new(10.0, 10.0, 20.0, 20.0);
let l1 = Line::new((0.0, 15.0), (40.0, 15.0)); // Horizontal through
let l2 = Line::new((15.0, 0.0), (15.0, 40.0)); // Vertical through
let l3 = Line::new((0.0, 0.0), (5.0, 5.0)); // Outside
assert!(line_intersects_rect(&l1, &rect));
assert!(line_intersects_rect(&l2, &rect));
assert!(!line_intersects_rect(&l3, &rect));
}
}
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