Intersects geojson features with a POSTGIS database

augment-geojson-data.js

#!/usr/bin/env node

'use strict';

var through       = require('through2')
  , geojsonStream = require('geojson-stream')
  , fs            = require('fs')
  , chalk         = require('chalk')
  , pg            = require('pg')

var client = new pg.Client({
  user: 'digitalsadhu',
  database: 'tmps'
})

var queries = {
  intersection: 'SELECT count(*) FROM tmps WHERE ST_Intersects(geom, ' +
    'ST_GeomFromGeoJSON($1)) AND type = $2'
}

var weightings = {
  'notsignificant': 4,
  'major': 7,
  'closure': 10
}

function intersection(type, geojson, client, cb) {
  client.query({
    text: queries.intersection,
    values: [geojson.geometry, type]
  }, cb)
}

function calculateIntersection(type) {
  return through.obj(function (chunk, enc, cb) {
    intersection(type, chunk, client, function (err, result) {
      if (result.rows[0].count > 0) {
        chunk.properties.weighting = weightings[type]
      }
      this.push(chunk)
      cb()
    }.bind(this))
  })
}

function removeNonIntersectingChunks() {
  return through.obj(function (chunk, enc, cb) {
    if (chunk.properties.weighting) this.push(chunk)
    cb()
  })
}

client.connect(function(err) {
  if(err) return console.error('could not connect to postgres', err)

  fs.createReadStream(process.argv[2])
    .pipe(geojsonStream.parse())
    .pipe(calculateIntersection('notsignificant'))
    .pipe(calculateIntersection('major'))
    .pipe(calculateIntersection('closure'))
    .pipe(removeNonIntersectingChunks())
    .pipe(geojsonStream.stringify())
    .on('end', function () {
      process.exit(0)
    })
    .pipe(process.stdout)
    .on('error', function (err) {
      console.error(chalk.red(err.message))
      console.trace()
    })
})