OpenStreetBrowser/src/wikidata.js

const OverpassLayer = require('overpass-layer')

var httpGet = require('./httpGet')
var loadClash = {}
var cache = {}

function wikidataLoad (id, callback) {
  if (id in cache) {
    return callback(null, cache[id])
  }

  if (id in loadClash) {
    loadClash[id].push(callback)
    return
  }
  loadClash[id] = []

  httpGet('https://www.wikidata.org/wiki/Special:EntityData/' + id + '.json', {}, function (err, result) {
    if (err) {
      return callback(err, null)
    }

    result = JSON.parse(result.body)

    if (!result.entities || !result.entities[id]) {
      console.log('invalid result', result)
      cache[id] = false
      return callback(err, null)
    }

    cache[id] = result.entities[id]

    callback(null, result.entities[id])

    loadClash[id].forEach(function (d) {
      d(null, result.entities[id])
    })
    delete loadClash[id]
  })
}

module.exports = {
  load: wikidataLoad
}

OverpassLayer.twig.extendFilter('wikidataEntity', function (value, param) {
  const ob = global.currentMapFeature
  if (value in cache) {
    return cache[value]
  }

  wikidataLoad(value, () => {
    if (ob) {
      ob.recalc()
    }
  })

  return null
})