createTileIntersect.js

import intersect from './intersect';

export default function createTileIntersect() {
  let tileCache = {};
  let lastBbox = null;

  return (boundingBox, tile) => {
    if (!boundingBox) {
      return true;
    }

    // bbox changed => invalidate the tile-cache
    if (
      JSON.stringify(lastBbox) !==
      JSON.stringify(boundingBox)
    ) {
      lastBbox = boundingBox;
      tileCache = {};
    }

    // cache look-up
    if (tileCache[tile.uid]) {
      // cache hit
      return tileCache[tile.uid];
    }

    // cache miss
    tileCache[tile.uid] = intersect(
      tileToBounds(tile),
      boundingBox
    );

    return tileCache[tile.uid];
  };
}