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read_policy.go
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read_policy.go
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package gcs_event_store
import (
"errors"
gcs "cloud.google.com/go/storage"
"google.golang.org/api/iterator"
)
type ObjectIterator interface {
Next() (*gcs.ObjectAttrs, error)
}
// ReadPolicy defines the actions that the GCSEventStore takes when it got the object iterator via list query.
type ReadPolicy interface {
Apply(ObjectIterator) (*gcs.ObjectAttrs, error)
}
// takeFirstCreated take the earliest created object under the same key/source/ path
type takeFirstCreated struct{}
func TakeFirstCreated() ReadPolicy {
return takeFirstCreated{}
}
func (t takeFirstCreated) Apply(objectIterator ObjectIterator) (*gcs.ObjectAttrs, error) {
if objectIterator == nil {
return nil, errors.New("objectIterator is nil")
}
var result *gcs.ObjectAttrs
for {
object, err := objectIterator.Next()
if errors.Is(err, iterator.Done) {
break
}
if err != nil {
return nil, err
}
if result == nil || object.Created.Before(result.Created) {
result = object
}
}
return result, nil
}
// takeLastCreated take the latest created object under the same key/source/ path
type takeLastCreated struct{}
func TakeLastCreated() ReadPolicy {
return takeLastCreated{}
}
func (t takeLastCreated) Apply(objectIterator ObjectIterator) (*gcs.ObjectAttrs, error) {
if objectIterator == nil {
return nil, errors.New("objectIterator is nil")
}
var result *gcs.ObjectAttrs
for {
object, err := objectIterator.Next()
if errors.Is(err, iterator.Done) {
break
}
if err != nil {
return nil, err
}
if result == nil || object.Created.After(result.Created) {
result = object
}
}
return result, nil
}