ingest: add wire format for incoming messages

ingest/wire.go

@@ -0,0 +1,31 @@
+package ingest
+
+import (
+	"fmt"
+	"io"
+
+	"github.com/go-json-experiment/json/jsontext"
+)
+
+// NullableString is a string that decodes JSON null as the empty string.
+type NullableString string
+
+func (n *NullableString) UnmarshalJSONFrom(d *jsontext.Decoder) error {
+	t, err := d.ReadToken()
+	switch err {
+	case nil: // do nothing
+	case io.EOF:
+		return io.ErrUnexpectedEOF
+	default:
+		return err
+	}
+	switch t.Kind() {
+	case 'n':
+		*n = ""
+	case '"':
+		*n = NullableString(t.String())
+	default:
+		return fmt.Errorf("invalid token for nullable string %q", t.String())
+	}
+	return nil
+}