go-whosonfirst-validate-wasm

Go package for compiling the Validate method of the go-whosonfirst-validate package to JavaScript-compatible and wasip1 WebAssembly (wasm) binaries. It also provides a net/http middleware packages for appending the necessary static assets and HTML resources to use the wasm binary in web applications.

Important

This package has been deprecated and is no longer maintained. All the functionality has been moved in to the whosonfirst/go-whosonfirst-validate package.

Build

wasmjs

To build the validate_feature WebAssembly binary for use in your JavaSceipt applications run the wasm Makefile target:

$> make wasm
GOOS=js GOARCH=wasm go build -mod vendor -ldflags="-s -w" \
		-o static/wasm/validate_feature.wasm \
		cmd/validate-feature-wasmjs/main.go

Use

To use the validate_feature WebAssembly binary in your applications a JSON-encoded GeoJSON string to the validate_feature function.

The function returns a JavaScript Promise that will return a JSON-encoded Who's On First (WOF) GeoJSON string on success or an error message if there was a problem.

	var str_f = '{"type": "Feature" ... }'	// A valid GeoJSON Feature
	
	validate_feature().then(rsp => {
	    console.log("WOF feature is valid.");
	}).catch(err => {
	    console.log("Failed to validate feature: ", err);
	});

In order to load the validate_feature function you will need to include the wasm_exec.js and whosonfirst.validate.feature.js JavaScript files, or functional equivalents. Both scripts are bundled with this package in the static/javascript folder.

Middleware

The go-whosonfirst-validate-wasm/http package provides methods for appending static assets and HTML resources to existing web applications to facilitate the use of the validate_feature WebAssembly binary. For example:

Note the use of the sfomuseum/go-http-wasm package which is an HTTP middleware package for serving and appending resources to the wasm_exec.js JavaScript library.

package main

import (
	"embed"
	"flag"
	"fmt"
	"log"
	"net/http"

	validate_wasm "github.com/whosonfirst/go-whosonfirst-validate-wasm/http"
	"github.com/sfomuseum/go-http-wasm"	
)

//go:embed index.html example.*
var FS embed.FS

func main() {

	host := flag.String("host", "localhost", "The host name to listen for requests on")
	port := flag.Int("port", 8080, "The host port to listen for requests on")

	flag.Parse()

	mux := http.NewServeMux()

	wasm_opts := wasm.DefaultWASMOptions()
	
	wasm.AppendAssetHandlers(mux, wasm_opts)
	validate_wasm.AppendAssetHandlers(mux)

	http_fs := http.FS(FS)
	example_handler := http.FileServer(http_fs)

	example_handler = wasm.AppendResourcesHandler(example_handler, wasm_opts)

	mux.Handle("/", example_handler)

	addr := fmt.Sprintf("%s:%d", *host, *port)
	log.Printf("Listening for requests on %s\n", addr)

	http.ListenAndServe(addr, mux)
}

Error handling omitted for brevity.

Example

There is a full working example of this application in the cmd/example folder. To run this application type the following command:

$> make example
go run -mod vendor cmd/example/main.go
2023/01/31 15:11:48 Listening for requests on localhost:8080

Then open http://localhost:8080 in a web browser. You should see something like this:

The default document included in the example is invalid so when you click the "Validate" button you should see an error like this:

If you add a "wof:repo":"whosonfirst-data-example" property and resubmit the document the validation will succeed.

wasip

To build the validate_feature WebAssembly WASI (wasip1) binary for use in your applications run the wasi Makefile target:

$> make wasi
GOOS=wasip1 GOARCH=wasm go build -mod vendor -ldflags="-s -w" \
		-o static/wasi/validate_feature.wasm \
		./cmd/validate-feature-wasip/main.go

Use

The validate_feature.wasm binary reads from STDIN and will report any errors found validating that input. For example:

$> cat fixtures/102527513.geojson | wasmer ./static/wasi/validate_feature.wasm

$> cat fixtures/102527513-bunk.geojson | wasmer ./static/wasi/validate_feature.wasm
2024/08/01 12:05:37 Failed to validate feature, Failed to validate ID, Failed to derive wof:id from body, Invalid wof:id '"102527513"'

See also

• https://github.com/whosonfirst/go-whosonfirst-validate
• https://github.com/sfomuseum/go-http-wasm
• https://go.dev/blog/wasi
• https://github.com/golang/go/wiki/WebAssembly