Honor If-Match when deleting documents (#21)

Compare the document ETag and delete it in one datastore operation so a stale If-Match returns 412 and leaves the newer document in place.

Co-authored-by: Cursor Agent <[email protected]>

internal/datastore/badger_datastore/documents.go

@@ -64,20 +64,36 @@ func (r *BadgerDataStore) GetDocument(databaseId string, collectionId string, do
 }
 
 func (r *BadgerDataStore) DeleteDocument(databaseId string, collectionId string, documentId string) datastore.DataStoreStatus {
+	return r.deleteDocument(databaseId, collectionId, documentId, "")
+}
+
+func (r *BadgerDataStore) DeleteDocumentIfMatch(databaseId string, collectionId string, documentId string, ifMatch string) datastore.DataStoreStatus {
+	return r.deleteDocument(databaseId, collectionId, documentId, ifMatch)
+}
+
+func (r *BadgerDataStore) deleteDocument(databaseId string, collectionId string, documentId string, ifMatch string) datastore.DataStoreStatus {
 	documentKey := generateDocumentKey(databaseId, collectionId, documentId)
 
 	txn := r.db.NewTransaction(true)
 	defer txn.Discard()
 
-	exists, err := keyExists(txn, documentKey)
-	if err != nil {
-		return datastore.Unknown
-	}
-	if !exists {
+	var document datastore.Document
+	status := getKey(txn, documentKey, &document)
+	if status == datastore.StatusNotFound {
 		return datastore.StatusNotFound
 	}
+	if status != datastore.StatusOk {
+		return status
+	}
 
-	err = txn.Delete([]byte(documentKey))
+	if ifMatch != "" {
+		etag, _ := document["_etag"].(string)
+		if etag != ifMatch {
+			return datastore.PreconditionFailed
+		}
+	}
+
+	err := txn.Delete([]byte(documentKey))
 	if err != nil {
 		logger.ErrorLn("Error while deleting document:", err)
 		return datastore.Unknown

internal/datastore/datastore.go

@@ -15,6 +15,11 @@ type DataStore interface {
 	GetDocumentIterator(databaseId string, collectionId string) (DocumentIterator, DataStoreStatus)
 	GetDocument(databaseId string, collectionId string, documentId string) (Document, DataStoreStatus)
 	DeleteDocument(databaseId string, collectionId string, documentId string) DataStoreStatus
+	// DeleteDocumentIfMatch removes a document when ifMatch is empty or equals its _etag.
+	// The comparison and delete happen together, so a concurrent update cannot land between them.
+	// A mismatched etag returns PreconditionFailed and leaves the document in place.
+	// A missing document returns StatusNotFound.
+	DeleteDocumentIfMatch(databaseId string, collectionId string, documentId string, ifMatch string) DataStoreStatus
 	CreateDocument(databaseId string, collectionId string, document map[string]interface{}) (Document, DataStoreStatus)
 
 	GetAllTriggers(databaseId string, collectionId string) ([]Trigger, DataStoreStatus)

internal/datastore/json_datastore/documents.go

@@ -45,6 +45,14 @@ func (r *JsonDataStore) GetDocument(databaseId string, collectionId string, docu
 }
 
 func (r *JsonDataStore) DeleteDocument(databaseId string, collectionId string, documentId string) datastore.DataStoreStatus {
+	return r.deleteDocument(databaseId, collectionId, documentId, "")
+}
+
+func (r *JsonDataStore) DeleteDocumentIfMatch(databaseId string, collectionId string, documentId string, ifMatch string) datastore.DataStoreStatus {
+	return r.deleteDocument(databaseId, collectionId, documentId, ifMatch)
+}
+
+func (r *JsonDataStore) deleteDocument(databaseId string, collectionId string, documentId string, ifMatch string) datastore.DataStoreStatus {
 	r.storeState.Lock()
 	defer r.storeState.Unlock()
 
@@ -56,10 +64,18 @@ func (r *JsonDataStore) DeleteDocument(databaseId string, collectionId string, d
 		return datastore.StatusNotFound
 	}
 
-	if _, ok := r.storeState.Documents[databaseId][collectionId][documentId]; !ok {
+	document, ok := r.storeState.Documents[databaseId][collectionId][documentId]
+	if !ok {
 		return datastore.StatusNotFound
 	}
 
+	if ifMatch != "" {
+		etag, _ := document["_etag"].(string)
+		if etag != ifMatch {
+			return datastore.PreconditionFailed
+		}
+	}
+
 	delete(r.storeState.Documents[databaseId][collectionId], documentId)
 
 	return datastore.StatusOk

internal/datastore/models.go

@@ -11,12 +11,13 @@ type Database struct {
 type DataStoreStatus int
 
 const (
-	StatusOk       DataStoreStatus = 1
-	StatusNotFound DataStoreStatus = 2
-	Conflict       DataStoreStatus = 3
-	BadRequest     DataStoreStatus = 4
-	IterEOF        DataStoreStatus = 5
-	Unknown        DataStoreStatus = 6
+	StatusOk           DataStoreStatus = 1
+	StatusNotFound     DataStoreStatus = 2
+	Conflict           DataStoreStatus = 3
+	BadRequest         DataStoreStatus = 4
+	IterEOF            DataStoreStatus = 5
+	Unknown            DataStoreStatus = 6
+	PreconditionFailed DataStoreStatus = 7
 )
 
 type TriggerOperation string