voronoi.js

const MAX_NUMBER_OF_PLACES = 60
const MAX_AREA_FOR_SEARCH = 60000000

const split = rectangle => {
  const firstDistance = turf.distance(...rectangle.slice(0, 2))
  const secondDistance = turf.distance(...rectangle.slice(1, 3))
  if (firstDistance > secondDistance) {
    const firstCenter = turf.midpoint(...rectangle.slice(0, 2)).geometry.coordinates
    const secondCenter = turf.midpoint(...rectangle.slice(2)).geometry.coordinates
    return [
      [...rectangle[0], ...secondCenter ],
      [...firstCenter, ...rectangle[2]]
    ]
  } else {
    const firstCenter = turf.midpoint(...rectangle.slice(1, 3)).geometry.coordinates
    const secondCenter = turf.midpoint(rectangle[3], rectangle[0]).geometry.coordinates
    return [
      [...rectangle[0], ...firstCenter ],
      [...secondCenter, ...rectangle[2]]
    ]
  }
}

export function* selectPlace({ payload }) {
  const { voronoi: { hiddenGoogleMap, cityBoundingBox }} = yield select()

  let researchedRects = []
  let unresearchedRects = [cityBoundingBox.flatten_()]
  try {
    while(unresearchedRects.length) {
      const rect = unresearchedRects[0]
      unresearchedRects = unresearchedRects.slice(1)
      const bboxPolygon = turf.bboxPolygon(rect).geometry.coordinates[0].slice(0, 4)
      const area = turf.area(turf.bboxPolygon(rect))
      if (area > MAX_AREA_FOR_SEARCH) {
        unresearchedRects = [
          ...unresearchedRects,
          ...split(bboxPolygon)
        ]
        continue
      }
      const [minLat, minLng, maxLat, maxLng] = rect
      const request = {
        bounds: new google.maps.LatLngBounds(
          new google.maps.LatLng(minLng, minLat),
          new google.maps.LatLng(maxLng, maxLat),
        ),
        type: payload,
      }
      const service = new google.maps.places.PlacesService(hiddenGoogleMap)
      let placesReceived = false
      let rectPlaces = []
      
      service.nearbySearch(request, (results, status, pagination) => {
        rectPlaces = [...rectPlaces, ...results]
        if(pagination.hasNextPage) {
          pagination.nextPage()
        } else {
          placesReceived = true
        }
      })
      while(!placesReceived) {
        const { voronoi: { stage } } = yield select()
        if (stage !== STAGES.VORONOI) return
        yield call(delay, 500)
      }
      if (rectPlaces.length !== MAX_NUMBER_OF_PLACES) {
        const points = rectPlaces.map(p => new Point(p.geometry.location.lng(), p.geometry.location.lat()))
        const contour = new Contour(bboxPolygon.map(([ x, y ]) => new Point(x, y)))
        researchedRects = [...researchedRects, {
          contour,
          places: points,
          polygons: getPolygons(rect, points)
        }]
        yield put(updateResearchedRectangles(researchedRects))
      }
      else {
        unresearchedRects = [
          ...unresearchedRects,
          ...split(bboxPolygon)
        ]
      }
    }

    const bboxPolygon = turf.bboxPolygon(cityBoundingBox.flatten_()).geometry.coordinates[0].slice(0, 4)
    const contour = new Contour(bboxPolygon.map(([ x, y ]) => new Point(x, y)))
    const places = researchedRects.take_('places').flatten_()
    yield put(updateResearchedRectangles([{
      contour,
      places,
      polygons: getPolygons(cityBoundingBox.flatten_(), places)
    }]))
  } catch(err) {
    yield put(toggleSnackbar('fail to build voronoi diagram'))
    yield put(startSearchingNewPlace())
  }
}