go-whosonfirst-geojson-fearturecollection

Tools for working with GeoJSON FeatureCollections and Who's On First documents.

Install

You will need to have both Go (specifically a version of Go more recent than 1.7 so let's just assume you need Go 1.10 or higher) and the make programs installed on your computer. Assuming you do just type:

make bin

All of this package's dependencies are bundled with the code in the vendor directory.

Example

Error handling has been removed, in the examples below, for the sake of brevity.

Simple

Create a GeoJSON FeatureCollection from a single GeoJSON file, writing the results to STDOUT.

package main

import(
	"github.com/whosonfirst/go-whosonfirst-geojson-featurecollection/encode"
	"github.com/whosonfirst/go-whosonfirst-geojson-v2/feature"
)

func main() {

	f, _ := feature.LoadFeatureFromFile("example.geojson")

	opts, _ := encode.DefaultEncoderOptions()
	enc, _ := encode.NewEncoder(opts)

	enc.WriteFeature(f)
	enc.Close()
}	

Fancy

Create a GeoJSON FeatureCollection from all the GeoJSON files processed by a go-whosonfirst-index index, optionally writing the results to a file. This example uses the Listen() which return a channel for sending features (to encode) to and a "done" channel to signal when there are no more features to encode.

The "done" channel will trigger the encoder's Close() method which, in turn, will invoke the underlying writer's Close() method. That might be a little too much magic for anyone's good so this behaviour might change. The Listen() method might also get a different (better?) name...

package main

import (
	"context"
	"flag"
	"github.com/whosonfirst/go-whosonfirst-geojson-featurecollection/encode"
	"github.com/whosonfirst/go-whosonfirst-geojson-v2/feature"
	"github.com/whosonfirst/go-whosonfirst-index"
	"github.com/whosonfirst/go-whosonfirst-index/utils"
	"io"
	"log"
)

func main() {

	var mode = flag.String("mode", "repo", "...")
	var out = flag.String("out", "", "...")	
	var spr = flag.Bool("spr", false, "Encode features as a \"standard places response\" (SPR)")

	flag.Parse()

	opts, _ := encode.DefaultEncoderOptions()
	opts.SPR = *spr

	if *out != "" {
		fh, _ := os.OpenFile(*out, os.O_RDWR|os.O_CREATE, 0644)
	   	opts.Writer = fh
	}
	
	enc, _ := encode.NewEncoder(opts)

	// _, _ are an error channel and any error that may have been
	// triggered when invoking the Listen() method, respectively
	
	feature_ch, done_ch, _, _ := enc.Listen()

	f := func(fh io.Reader, ctx context.Context, args ...interface{}) error {

		ok, _ := utils.IsPrincipalWOFRecord(fh, ctx)

		if !ok {
			return nil
		}

		f, _ := feature.LoadFeatureFromReader(fh)

		feature_ch <- f
		return nil
	}

	i, _ := index.NewIndexer(*mode, f)

	for _, path := range flag.Args() {
		i.IndexPath(path)
	}

	done_ch <- true
}

Options

EncoderOptions

type EncoderOptions struct {
	SPR    bool
	Writer io.Writer
}

Tools

wof-encode-featurecollection

$> ./bin/wof-encode-featurecollection -h
Usage of ./bin/wof-encode-featurecollection:
  -has-property 
    	Ensure that only features matching 'properties.{PROPERTY}={VALUE}' are included. This flag can be passed multiple times.
  -mode string
    	A valid go-whosonfirst-index mode. Valid modes are: directory,feature,feature-collection,files,geojson-ls,meta,path,repo,sqlite (default "repo")
  -out string
    	Write results to this path. If empty results are written to STDOUT.
  -spr
    	Encode features as a "standard places response" (SPR)

For example:

$> ./bin/wof-encode-featurecollection -has-property 'sfomuseum:placetype=gate' /usr/local/data/sfomuseum-data-architecture \
   	| jq '[.["features"][]["properties"]["sfomuseum:placetype"]] | unique'

[
  "gate"
]

See also

• https://github.com/whosonfirst/go-whosonfirst-geojson-v2
• https://github.com/whosonfirst/go-whosonfirst-spr
• https://github.com/whosonfirst/go-whosonfirst-index