overpass-frontend/src/BBoxQueryCache.js

A JavaScript (NodeJS/Browser) library to easily access data from OpenStreetMap via Overpass API or from an OSM File. The objects can directly be used with LeafletJS or exported to GeoJSON. Data will be cached in the browser memory.

const BoundingBox = require('boundingbox')
const turf = require('./turf')

const Filter = require('./Filter')

class BBoxQueryCache {
  constructor (overpass) {
    this.overpass = overpass
    this.list = {}
  }

  get (id) {
    if (!(id in this.list)) {
      this.list[id] = new BBoxQueryCacheItem(this, id)
    }

    return this.list[id]
  }

  clear () {
    for (const k in this.list) {
      delete this.list[k]
    }
  }
}

class BBoxQueryCacheItem {
  constructor (main, id) {
    this.main = main
    this.id = id
    this.filter = new Filter(id)
    this.area = null
  }

  /**
   * make another part of the map known
   */
  add (bbox, cacheDescriptors = null) {
    // ignore requests for IDs
    if (cacheDescriptors && cacheDescriptors.ids) {
      return
    }

    bbox = new BoundingBox(bbox).toGeoJSON()

    if (cacheDescriptors && cacheDescriptors.bounds) {
      bbox = turf.intersect(bbox, cacheDescriptors.bounds)
    }

    if (this.area === null) {
      this.area = bbox
    } else {
      this.area = turf.union(bbox, this.area)
    }
  }

  /**
   * is the whole area known?
   */
  check (bbox, cacheDescriptors = null) {
    if (cacheDescriptors && cacheDescriptors.invalid) {
      return true
    }

    if (cacheDescriptors && cacheDescriptors.ids) {
      let types = [cacheDescriptors.id.match(/^(node|way|relation|nwr)/)[1]]
      if (types[0] === 'nwr') {
        types = ['node', 'way', 'relation']
      }

      return types.every(type =>
        cacheDescriptors.ids.every(id =>
          (type.substr(0, 1) + id) in this.main.overpass.cacheElements
        )
      )
    }

    bbox = new BoundingBox(bbox).toGeoJSON()

    if (cacheDescriptors && cacheDescriptors.bounds) {
      bbox = turf.intersect(bbox, cacheDescriptors.bounds)
    }

    if (this.area) {
      const remaining = turf.difference(bbox, this.area)

      if (!remaining) {
        return true
      }
    }

    // check if a superset matches
    return Object.values(this.main.list).some(cache => {
      if (cache.id === this.id) { return false }

      if (cache.filter.isSupersetOf(this.filter)) {
        if (cache.area) {
          return !turf.difference(bbox, cache.area)
        }
      }

      return false
    })
  }

  /**
   * clear this cache
   */
  clear () {
    this.area = null
    delete this.main.list[this.id]
  }

  /**
   * return area as (multi)polygon
   */
  toGeoJSON () {
    return this.area
  }
}

module.exports = BBoxQueryCache