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snapshotter.go
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snapshotter.go
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// Copyright 2022 Monoskope Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package formatters
import (
"context"
"errors"
"io"
esApi "github.com/finleap-connect/monoskope/pkg/api/eventsourcing"
es "github.com/finleap-connect/monoskope/pkg/eventsourcing"
"github.com/google/uuid"
)
// Snapshotter implements basic snapshot creation for audit formatters
type Snapshotter[T es.Projection] struct {
esClient esApi.EventStoreClient
projector es.Projector[T]
}
func NewSnapshotter[T es.Projection](esClient esApi.EventStoreClient, projector es.Projector[T]) *Snapshotter[T] {
return &Snapshotter[T]{esClient, projector}
}
// CreateSnapshot creates a snapshot based on an event-filter and the corresponding projector for
// the aggregate of which the id is used in the filter.
// This is a temporary implementation until snapshots are fully implemented,
// and it is not meant to be used extensively.
func (s *Snapshotter[T]) CreateSnapshot(ctx context.Context, eventFilter *esApi.EventFilter) (T, error) {
var nilResult T
id, err := uuid.Parse(eventFilter.AggregateId.Value)
if err != nil {
id = uuid.New()
}
projection := s.projector.NewProjection(id)
aggregateEvents, err := s.esClient.Retrieve(ctx, eventFilter)
if err != nil {
return nilResult, err
}
for {
e, err := aggregateEvents.Recv()
if err == io.EOF {
break
}
if err != nil {
return nilResult, err
}
event, err := es.NewEventFromProto(e)
if err != nil {
return nilResult, err
}
projection, err = s.projector.Project(ctx, event, projection)
if err != nil {
return nilResult, err
}
}
if projection.Version() == 0 {
return nilResult, errors.New("no events found to create a snapshot for aggregate ID: " + eventFilter.AggregateId.Value)
}
return projection, nil
}