geohash based spatial index on leveldb

index.js

var plumbdb = require('plumbdb')
var shp2json = require('shp2json')
var tako = require('tako')
var geohash = require('geohash').GeoHash
var JSONStream = require('JSONStream')
var async = require('async')
var gju = require('geostuff')

var t = tako()

t.plumb = plumbdb('data', function(err, db) {
  t.db = db
})

t.route('/', function (req, resp) {
  if (!req.qs) return resp.end()
  var lat = +req.qs.lat
  var lon = +req.qs.lon
  var radius = +req.qs.radius
  if (!lat || !lon || !radius) return resp.end()
  var range = geohashRange(lat, lon, radius)
  var circle = gju.drawCircle(radius, {type: "Point", coordinates: [lon, lat]})
  resp.write('{"rows": [')
  var sep = ""  
  t.plumb.rangeStream(range[0], range[1])
    .on('data', function(key, value) {
      var hash = geohash.decodeGeoHash(key)
      var point = {type: "Point", coordinates: [hash.longitude[2], hash.latitude[2]]}
      if (!gju.pointInPolygon(point, circle)) return
      resp.write(sep + JSON.stringify(point))
      sep = ","
    })
    .on('end', function() {
      resp.end("]}")
    })
})

function geohashRange(lat, lon, radius) {
  var diff = radius / 111034 // convert to degrees
  diff = diff / 2 // square diameter -> radius
  var upper = geohash.encodeGeoHash(lat + diff, lon + diff)
  var lower = geohash.encodeGeoHash(lat - diff, lon - diff)
  return [lower, upper]  
}

t.route('/upload', function (req, resp) {
  var parser = JSONStream.parse(['features', /./])
  shp2json(req).pipe(parser)
  var q = queue(
    store,
    function(err) {
      if (err) resp.end(err)
      resp.end('ok')
    }
  )
  parser.on('data', function(feature) {
    q.push(feature, function(err) {
      if (err) console.log(err)
    })
  })
})

function queue(save, cb) {
  var q = async.queue(save, 1)
  q.drain = cb
  return q
}

function store(feature, cb) {
  var type = feature.geometry.type
  if (type === "Polygon") feature = preparePoly(feature)
  if (type === "Point") feature = preparePoint(feature)
  cb(false)
  // t.plumb._store(feature, function(err, json) {
  //   if (err) cb(err)
  //   cb(false, json)
  // })
}

function preparePoly(feature) {
  var extent = gju.polygonExtent(feature.geometry)
  console.log('extent', extent)
  return feature
}

function preparePoint(feature) {
  var lat = feature.geometry.coordinates[1]
  var lon = feature.geometry.coordinates[0]
  feature._id = geohash.encodeGeoHash(lat, lon)
  return feature
}

t.httpServer.listen(8000, function () {
  console.log('dun runnin')
})