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.
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
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.
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.
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.
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
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"'