snapshot of https://github.com/ThreeDotsLabs/watermill.git (master, 2026-09-15; blobs > 131072B omitted)

_examples/real-world-examples/server-sent-events/server/feeds_storage.go

@@ -0,0 +1,213 @@
+package main
+
+import (
+	"context"
+	"time"
+
+	"go.mongodb.org/mongo-driver/bson"
+	"go.mongodb.org/mongo-driver/mongo"
+	"go.mongodb.org/mongo-driver/mongo/options"
+	"go.mongodb.org/mongo-driver/mongo/readpref"
+)
+
+const collectionName = "feeds"
+
+type FeedsStorage struct {
+	collection *mongo.Collection
+}
+
+func NewFeedsStorage() FeedsStorage {
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+
+	client, err := mongo.Connect(ctx, options.Client().ApplyURI("mongodb://root:password@mongo:27017"))
+	if err != nil {
+		panic(err)
+	}
+
+	err = client.Ping(ctx, readpref.Primary())
+	if err != nil {
+		panic(err)
+	}
+
+	db := client.Database("example")
+	names, err := db.ListCollectionNames(ctx, bson.M{})
+	if err != nil {
+		panic(err)
+	}
+
+	found := false
+	for _, n := range names {
+		if n == collectionName {
+			found = true
+			break
+		}
+	}
+
+	if !found {
+		err := db.CreateCollection(ctx, collectionName)
+		if err != nil {
+			panic(err)
+		}
+	}
+
+	return FeedsStorage{
+		collection: db.Collection(collectionName),
+	}
+}
+
+func (s FeedsStorage) Add(ctx context.Context, name string) error {
+	feed := Feed{
+		Name:  name,
+		Posts: []Post{},
+	}
+
+	_, err := s.collection.InsertOne(ctx, feed)
+	if err != nil {
+		if !isDuplicateError(err) {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (s FeedsStorage) All(ctx context.Context) ([]Feed, error) {
+	cursor, err := s.collection.Find(ctx, bson.M{})
+	if err != nil {
+		return nil, err
+	}
+
+	var feeds []Feed
+
+	err = cursor.All(ctx, &feeds)
+	if err != nil {
+		return nil, err
+	}
+
+	return feeds, nil
+}
+
+func (s FeedsStorage) ByName(ctx context.Context, name string) (Feed, error) {
+	filter := bson.M{
+		"_id": name,
+	}
+
+	var feed Feed
+	err := s.collection.FindOne(ctx, filter).Decode(&feed)
+	if err != nil {
+		return Feed{}, err
+	}
+
+	return feed, nil
+}
+
+func (s FeedsStorage) AppendPost(ctx context.Context, post Post) error {
+	return s.appendPostIfNotPresent(ctx, post)
+}
+
+func (s FeedsStorage) UpdatePost(ctx context.Context, post Post) error {
+	err := s.updatePostIfPresent(ctx, post)
+	if err != nil {
+		return err
+	}
+
+	err = s.appendPostIfNotPresent(ctx, post)
+	if err != nil {
+		return err
+	}
+
+	err = s.removePostIfNotInFeed(ctx, post)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (s FeedsStorage) updatePostIfPresent(ctx context.Context, post Post) error {
+	if len(post.Tags) == 0 {
+		return nil
+	}
+
+	filter := bson.M{
+		"_id": bson.M{
+			"$in": post.Tags,
+		},
+		"posts.id": post.ID,
+	}
+
+	update := bson.M{
+		"$set": bson.M{
+			"posts.$": post,
+		},
+	}
+
+	_, err := s.collection.UpdateMany(ctx, filter, update)
+	return err
+}
+
+func (s FeedsStorage) appendPostIfNotPresent(ctx context.Context, post Post) error {
+	if len(post.Tags) == 0 {
+		return nil
+	}
+
+	filter := bson.M{
+		"_id": bson.M{
+			"$in": post.Tags,
+		},
+		"posts.id": bson.M{
+			"$ne": post.ID,
+		},
+	}
+
+	update := bson.M{
+		"$push": bson.M{
+			"posts": bson.M{
+				"$each":     bson.A{post},
+				"$position": 0,
+			},
+		},
+	}
+
+	_, err := s.collection.UpdateMany(ctx, filter, update)
+	return err
+}
+
+func (s FeedsStorage) removePostIfNotInFeed(ctx context.Context, post Post) error {
+	tags := post.Tags
+	if tags == nil {
+		tags = []string{}
+	}
+
+	filter := bson.M{
+		"_id": bson.M{
+			"$nin": tags,
+		},
+		"posts.id": post.ID,
+	}
+
+	update := bson.M{
+		"$pull": bson.M{
+			"posts": bson.M{
+				"id": post.ID,
+			},
+		},
+	}
+
+	_, err := s.collection.UpdateMany(ctx, filter, update)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func isDuplicateError(err error) bool {
+	mErr, ok := err.(mongo.WriteException)
+	if !ok {
+		return false
+	}
+
+	return mErr.WriteErrors[0].Code == 11000
+}