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reader.go
60 lines (53 loc) · 1.26 KB
/
reader.go
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package dalgo2datastore
import (
"cloud.google.com/go/datastore"
"errors"
"fmt"
"github.com/dal-go/dalgo/dal"
"google.golang.org/api/iterator"
)
var _ dal.Reader = (*datastoreReader)(nil)
type datastoreReader struct {
i int // iteration
query dal.Query
iterator *datastore.Iterator
}
func (d *datastoreReader) Close() error {
return nil
}
func (d *datastoreReader) Next() (record dal.Record, err error) {
if limit := d.query.Limit(); limit > 0 && d.i >= limit {
return nil, dal.ErrNoMoreRecords
}
if into := d.query.Into(); into == nil {
from := d.query.From()
record = dal.NewRecordWithIncompleteKey(from.Name, d.query.IDKind(), nil)
} else {
record = into()
}
record.SetError(nil)
data := record.Data()
if rd, ok := data.(dal.DataWrapper); ok {
data = rd.Data()
}
var key *datastore.Key
if key, err = d.iterator.Next(data); err != nil {
if errors.Is(err, iterator.Done) {
err = fmt.Errorf("%w: %v", dal.ErrNoMoreRecords, err)
}
return record, err
}
k := record.Key()
if k.ID, err = idFromDatastoreKey(key, k.IDKind); err != nil {
return record, err
}
d.i++
return
}
func (d *datastoreReader) Cursor() (string, error) {
cursor, err := d.iterator.Cursor()
if err != nil {
return "", err
}
return cursor.String(), nil
}