events: add store implementation (#1957)

events/store/store.go

@@ -0,0 +1,103 @@
+package store
+
+import (
+	"encoding/json"
+	"time"
+
+	"github.com/micro/go-micro/v3/events"
+	gostore "github.com/micro/go-micro/v3/store"
+	"github.com/micro/go-micro/v3/store/memory"
+	"github.com/pkg/errors"
+)
+
+const joinKey = "/"
+
+// NewStore returns an initialized events store
+func NewStore(opts ...Option) events.Store {
+	// parse the options
+	var options Options
+	for _, o := range opts {
+		o(&options)
+	}
+	if options.TTL.Seconds() == 0 {
+		options.TTL = time.Hour * 24
+	}
+	if options.Store == nil {
+		options.Store = memory.NewStore()
+	}
+
+	// return the store
+	return &evStore{options}
+}
+
+type evStore struct {
+	opts Options
+}
+
+// Read events for a topic
+func (s *evStore) Read(topic string, opts ...events.ReadOption) ([]*events.Event, error) {
+	// validate the topic
+	if len(topic) == 0 {
+		return nil, events.ErrMissingTopic
+	}
+
+	// parse the options
+	options := events.ReadOptions{
+		Offset: 0,
+		Limit:  250,
+	}
+	for _, o := range opts {
+		o(&options)
+	}
+
+	// execute the request
+	recs, err := s.opts.Store.Read(topic+joinKey,
+		gostore.ReadPrefix(),
+		gostore.ReadLimit(options.Limit),
+		gostore.ReadOffset(options.Offset),
+	)
+	if err != nil {
+		return nil, errors.Wrap(err, "Error reading from store")
+	}
+
+	// unmarshal the result
+	result := make([]*events.Event, len(recs))
+	for i, r := range recs {
+		var e events.Event
+		if err := json.Unmarshal(r.Value, &e); err != nil {
+			return nil, errors.Wrap(err, "Invalid event returned from stroe")
+		}
+		result[i] = &e
+	}
+
+	return result, nil
+}
+
+// Write an event to the store
+func (s *evStore) Write(event *events.Event, opts ...events.WriteOption) error {
+	// parse the options
+	options := events.WriteOptions{
+		TTL: s.opts.TTL,
+	}
+	for _, o := range opts {
+		o(&options)
+	}
+
+	// construct the store record
+	bytes, err := json.Marshal(event)
+	if err != nil {
+		return errors.Wrap(err, "Error mashaling event to JSON")
+	}
+	record := &gostore.Record{
+		Key:    event.Topic + joinKey + event.ID,
+		Value:  bytes,
+		Expiry: options.TTL,
+	}
+
+	// write the record to the store
+	if err := s.opts.Store.Write(record); err != nil {
+		return errors.Wrap(err, "Error writing to the store")
+	}
+
+	return nil
+}