monolith

use crate::geom::Rect;

pub(crate) const LEFT: u8 = 1;

pub(crate) const RIGHT: u8 = 2;

pub(crate) const ABOVE: u8 = 4;

pub(crate) const BELOW: u8 = 8;

pub(crate) const X_BITS: u8 = LEFT | RIGHT;

pub(crate) const Y_BITS: u8 = ABOVE | BELOW;

/// Which ways `a` is apart from `b`. Touching edges count as apart.

pub(crate) fn separation(a: &Rect, b: &Rect, eps: f64) -> u8 {

    let mut s = 0;

    if a.right() <= b.x + eps {

        s |= LEFT;

    }

    if b.right() <= a.x + eps {

        s |= RIGHT;

    }

    if a.bottom() <= b.y + eps {

        s |= ABOVE;

    }

    if b.bottom() <= a.y + eps {

        s |= BELOW;

    }

    s

}

/// Which sides of `a` sit against `b`, at most one gap apart and facing each other.

pub(crate) fn adjacency(a: &Rect, b: &Rect, gap: f64, eps: f64) -> u8 {

    let overlap_x = a.x < b.right() + eps && b.x < a.right() + eps;

    let overlap_y = a.y < b.bottom() + eps && b.y < a.bottom() + eps;

    let near = |d: f64| d.abs() <= gap + eps;

    let mut s = 0;

    if overlap_y && near(b.x - a.right()) {

        s |= LEFT;

    }

    if overlap_y && near(a.x - b.right()) {

        s |= RIGHT;

    }

    if overlap_x && near(b.y - a.bottom()) {

        s |= ABOVE;

    }

    if overlap_x && near(a.y - b.bottom()) {

        s |= BELOW;

    }

    s

}