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aggregatestore.go
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/
aggregatestore.go
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// Copyright (c) 2017 - The Event Horizon 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 model
import (
"context"
"errors"
eh "github.com/looplab/eventhorizon"
"github.com/looplab/eventhorizon/uuid"
)
// AggregateStore is an aggregate store that uses a read write repo for
// loading and saving aggregates.
type AggregateStore struct {
repo eh.ReadWriteRepo
eventHandler eh.EventHandler
}
var (
// ErrInvalidRepo is when a dispatcher is created with a nil repo.
ErrInvalidRepo = errors.New("invalid repo")
// ErrInvalidAggregate occurs when a loaded aggregate is not an aggregate.
ErrInvalidAggregate = errors.New("invalid aggregate")
)
// NewAggregateStore creates an aggregate store with a read write repo and an
// event handler that can handle any resulting events (for example by publishing
// them on an event bus).
func NewAggregateStore(repo eh.ReadWriteRepo, eventHandler eh.EventHandler) (*AggregateStore, error) {
if repo == nil {
return nil, ErrInvalidRepo
}
d := &AggregateStore{
repo: repo,
eventHandler: eventHandler,
}
return d, nil
}
// Load implements the Load method of the eventhorizon.AggregateStore interface.
func (r *AggregateStore) Load(ctx context.Context, aggregateType eh.AggregateType, id uuid.UUID) (eh.Aggregate, error) {
item, err := r.repo.Find(ctx, id)
if errors.Is(err, eh.ErrEntityNotFound) {
// Create the aggregate.
if item, err = eh.CreateAggregate(aggregateType, id); err != nil {
return nil, err
}
} else if err != nil {
return nil, err
}
aggregate, ok := item.(eh.Aggregate)
if !ok {
return nil, ErrInvalidAggregate
}
return aggregate, nil
}
// Save implements the Save method of the eventhorizon.AggregateStore interface.
func (r *AggregateStore) Save(ctx context.Context, aggregate eh.Aggregate) error {
if err := r.repo.Save(ctx, aggregate); err != nil {
return err
}
// Handle any events optionally provided by the aggregate.
if a, ok := aggregate.(eh.EventSource); ok && r.eventHandler != nil {
events := a.UncommittedEvents()
a.ClearUncommittedEvents()
for _, e := range events {
if err := r.eventHandler.HandleEvent(ctx, e); err != nil {
return err
}
}
}
return nil
}