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
}