Cesium entity bounds checking function

bounds.ts

// Check some commonly-used shapes and compute a bounding rectangle that
// encloses all the various graphics the Entity might be showing.
// NB: Remember to update this function if we start using more graphics
export function entityBounds(ent: Entity, time: JulianDate): Cartesian3 | Rectangle | undefined {
    // Start with all position-independent graphics types
    const corr: Cartesian3[] = ent.corridor?.positions?.getValue(time) || [];
    const line: Cartesian3[] = ent.polyline?.positions?.getValue(time) || [];
    const lineVol: Cartesian3[] = ent.polylineVolume?.positions?.getValue(time) || [];
    const poly: Cartesian3[] = ent.polygon?.hierarchy?.getValue(time)?.positions || [];
    const wall: Cartesian3[] = ent.wall?.positions?.getValue(time) || [];

    const all = [
        ...corr,
        ...poly,
        ...line,
        ...lineVol,
        ...wall,
    ];

    // If there was a `position`, we need that
    const pos: Cartesian3 | undefined = ent.position?.getValue(time);
    if (pos) { all.push(pos); }

    // The entity might also define a rectangle graphic
    const rect: Rectangle | undefined = ent.rectangle?.coordinates?.getValue(time);

    // This gets a little complex
    if (rect) {
        const first = all[0];
        if (all.length > 1) {
            // If there's a rectangle graphic plus multiple points, the overall
            // bound is the union the rectangle dimensions and a rectangle
            // covering all points
            const cover = Rectangle.fromCartesianArray(all);
            return Rectangle.union(rect, cover);
        } else if (first) {
            // If there's exactly one point, expand the rectangle to include it
            return Rectangle.expand(rect, Cartographic.fromCartesian(first));
        } else {
            // If there were no points just use the rectangle
            return rect;
        }
    } else {
        if (all.length > 1) {
            // If there were multiple points, return a covering rectangle
            return Rectangle.fromCartesianArray(all);
        } else {
            // There was only one position (or none) and no rectangle, return that
            return all[0];
        }
    }
}