value.go

// +build js,wasm

package vecty

import (
	"reflect"
	"strings"

	"syscall/js"
)

const (
	structTag = "js"

	structTagOptionIncludeEmpty = "includeEmpty"
)

const valueFieldName = "Value"

var jsValueType = reflect.TypeOf(js.Value{})

type JSValuer interface {
	JSValue() js.Value
}

// Value Returns the js value of a type
func Value(p interface{}) js.Value {
	vr, ok := p.(JSValuer)
	if ok {
		return vr.JSValue()
	}

	t := reflect.TypeOf(p)
	rv := reflect.ValueOf(p)

	switch t.Kind() {
	case reflect.Struct:
		// If the struct has an embedded js.Value then we return that.
		f, ok := t.FieldByName(valueFieldName)
		if ok && f.Anonymous && f.Type == jsValueType {
			return rv.FieldByName(valueFieldName).Interface().(js.Value)
		}

		v := js.Global().Get("Object").New()
		structValue(v, p)
		return v
	case reflect.Ptr:
		return Value(rv.Elem().Interface())
	default:
		return js.ValueOf(p)
	}
}

func structValue(v js.Value, p interface{}) {
	t := reflect.TypeOf(p)
	rv := reflect.ValueOf(p)

	for i := 0; i < t.NumField(); i++ {
		field := t.Field(i)
		fv := rv.Field(i)
		if !fv.CanInterface() {
			continue
		}

		fn := field.Name

		tag := strings.Split(field.Tag.Get(structTag), ",")

		if len(tag[0]) > 0 {
			fn = tag[0]
		}

		if field.Anonymous {
			structValue(v, fv.Interface())
			continue
		}

		includeEmpty := len(tag) > 1 && tag[1] == structTagOptionIncludeEmpty

		if !includeEmpty && fv.Interface() == reflect.Zero(field.Type).Interface() {
			continue
		}

		v.Set(fn, Value(fv.Interface()))
	}
}