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store.go
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store.go
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package short
import (
"context"
"errors"
"fmt"
"sync"
"time"
"github.com/google/uuid"
"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"
"go.mongodb.org/mongo-driver/x/mongo/driver/connstring"
)
type Store interface {
// Insert adds a record to the storage.
// url, id and override are passed via an insertConfig struct.
Insert(ctx context.Context, ic *insertConfig) error
// GetUrl returns the url given an id.
GetUrl(ctx context.Context, id string) (string, error)
}
type insertConfig struct {
url string
id string
override bool
expiration *time.Time
}
type store struct {
name string
collection *mongo.Collection
}
const collectionsMapName = "collections_map"
// used as a cache to store MongoDB clients.
var mongoDbClientMap = map[string]*mongo.Client{}
var mongoDbClientMapLock sync.Mutex
func getMongoClient(ctx context.Context, mongoUri string) (*mongo.Client, error) {
mongoDbClientMapLock.Lock()
defer mongoDbClientMapLock.Unlock()
if c, ok := mongoDbClientMap[mongoUri]; ok {
return c, nil
}
c, err := mongo.Connect(ctx, options.Client().ApplyURI(mongoUri))
if err != nil {
return nil, fmt.Errorf("failed to connect to %s: %w", mongoUri, err)
}
mongoDbClientMap[mongoUri] = c
return c, nil
}
func getMongoCollection(ctx context.Context, database *mongo.Database, name string) (*mongo.Collection, error) {
collectionsMap := database.Collection(collectionsMapName)
// Index the collectionsMap collection.
if _, err := collectionsMap.Indexes().CreateOne(ctx, mongo.IndexModel{
Keys: bson.M{"name": 1},
Options: options.Index().SetUnique(true),
}); err != nil {
return nil, fmt.Errorf("failed to create an index for collection %s: %w", collectionsMapName, err)
}
id := uuid.New().String()
// Find the collection name in the collections map.
res := collectionsMap.FindOneAndUpdate(
ctx,
bson.M{"name": name},
bson.M{"$setOnInsert": bson.M{"collectionName": id, "name": name}},
options.FindOneAndUpdate().SetUpsert(true).SetReturnDocument(options.After),
)
if res.Err() != nil {
return nil, fmt.Errorf("failed to find and/or insert a collection mapping for %s: %w", name, res.Err())
}
var payload struct {
CollectionName string `bson:"collectionName"`
}
if err := res.Decode(&payload); err != nil {
return nil, fmt.Errorf("failed to decode a collection mapping document for %s: %w", name, err)
}
collection := database.Collection(payload.CollectionName)
// Index the collection.
if _, err := collection.Indexes().CreateMany(ctx, []mongo.IndexModel{
{
Keys: bson.M{"url": 1},
},
{
Keys: bson.M{"id": 1},
Options: options.Index().SetUnique(true),
},
{
Keys: bson.M{"expireAt": 1},
Options: options.Index().SetExpireAfterSeconds(0),
}}); err != nil {
return nil, fmt.Errorf("failed to create an index for collection %s: %w", payload.CollectionName, err)
}
return collection, nil
}
func newStore(mongoUri string, name string) (Store, error) {
ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
defer cancel()
client, err := getMongoClient(ctx, mongoUri)
if err != nil {
return nil, err
}
if err := client.Ping(ctx, readpref.PrimaryPreferred()); err != nil {
return nil, err
}
cs, err := connstring.Parse(mongoUri)
if err != nil {
return nil, fmt.Errorf("failed to parse %s: %w", mongoUri, err)
}
if cs.Database == "" {
cs.Database = "short"
}
database := client.Database(cs.Database)
collection, err := getMongoCollection(ctx, database, name)
if err != nil {
return nil, err
}
return &store{
name: name,
collection: collection,
}, nil
}
func (s *store) Insert(ctx context.Context, ic *insertConfig) error {
toSet := bson.M{"id": ic.id, "url": ic.url}
if ic.expiration != nil {
toSet["expireAt"] = ic.expiration.Unix()
}
if ic.override {
if _, err := s.collection.UpdateOne(
ctx,
bson.M{"id": ic.id},
bson.M{"$set": toSet},
options.Update().SetUpsert(true),
); err != nil {
return fmt.Errorf("failed to update or insert id %s: %w", ic.id, err)
}
return nil
}
if _, err := s.collection.InsertOne(ctx, toSet); err != nil {
if mongo.IsDuplicateKeyError(err) {
return &ConflictError{}
}
return fmt.Errorf("failed to insert id %s: %w", ic.id, err)
}
return nil
}
func (s *store) GetUrl(ctx context.Context, id string) (string, error) {
res := s.collection.FindOne(ctx, bson.M{"id": id})
if res.Err() != nil {
if errors.Is(res.Err(), mongo.ErrNoDocuments) {
return "", &IdNotFoundError{id: id}
}
return "", fmt.Errorf("error when calling FindOne in the store %s: %w", s.name, res.Err())
}
var payload struct {
Url string `bson:"url"`
ExpireAt *int64 `bson:"expireAt,omitempty"`
}
if err := res.Decode(&payload); err != nil {
return "", fmt.Errorf("failed to decode record: %w", err)
}
if payload.ExpireAt != nil && time.Now().Unix() > *payload.ExpireAt {
return "", &IdNotFoundError{id: id}
}
return payload.Url, nil
}