Add versioning, update tool, and soft-delete

Schema: public_id + version columns with UNIQUE constraint,
delete_timestamp for soft-delete.

Tools: store_flashcard accepts optional public_id, update_flashcard
creates a new version preserving history, delete_flashcard inserts
a tombstone row and removes the Qdrant point.

Qdrant: point ID is public_id (only latest version indexed).

.env.example

@@ -7,4 +7,4 @@ OPENAI_API_KEY=sk-...
 EMBEDDING_MODEL=text-embedding-3-small
 MCP_TOKEN=change-me
 PORT=8080
-SQLITE_PATH=knowledge.db
+SQLITE_PATH=flashcard.db

README.md

@@ -1,12 +1,12 @@
-# St-Pierre - Knowledge MCP Server
+# St-Pierre - Flashcard MCP Server
 
-Remote MCP server that stores and retrieves knowledge using Qdrant vector
+Remote MCP server that stores and retrieves flashcards using Qdrant vector
 database and OpenAI embeddings.
 
 ## Tools
 
-### `store_knowledge`
-Store a piece of knowledge for later retrieval. Automatically generates
+### `store_flashcard`
+Store a flashcard for later retrieval. Automatically generates
 embeddings via OpenAI and persists them in Qdrant.
 
 Parameters:
@@ -17,8 +17,8 @@ Parameters:
 - `user` (string, optional): User identifier
 - `context` (string, optional): What triggered this
 
-### `search_knowledge`
-Semantic search across stored knowledge.
+### `search_flashcard`
+Semantic search across stored flashcards.
 
 Parameters:
 - `query` (string, required): Search query
@@ -106,7 +106,7 @@ Add to your MCP client config:
 ```json
 {
   "mcpServers": {
-    "knowledge": {
+    "flashcard": {
       "url": "http://your-server:8080/mcp",
       "headers": {
         "Authorization": "Bearer my-secret-token"

flake.nix

@@ -1,5 +1,5 @@
 {
-  description = "St-Pierre - MCP Knowledge Server";
+  description = "St-Pierre - MCP Flashcard Server";
 
   inputs = {
     nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
@@ -33,7 +33,7 @@
         in
         {
           options.services.st-pierre = {
-            enable = lib.mkEnableOption "St-Pierre knowledge MCP server";
+            enable = lib.mkEnableOption "St-Pierre flashcard MCP server";
 
             port = lib.mkOption {
               type = lib.types.port;

main.go

@@ -55,7 +55,7 @@ func main() {
 	emb := newEmbedder(openAIKey, embeddingModel, embeddingBaseURL)
 	qdrantStore := newQdrantStore(qdrantClient, emb)
 
-	sqlitePath := envOrDefault("SQLITE_PATH", "knowledge.db")
+	sqlitePath := envOrDefault("SQLITE_PATH", "flashcard.db")
 	sqliteStore, err := newSqliteStore(sqlitePath)
 	if err != nil {
 		logger.Fatal("failed to init sqlite", zap.Error(err))
@@ -67,14 +67,16 @@ func main() {
 	}
 
 	mcpServer := server.NewMCPServer(
-		"knowledge-mcp",
+		"flashcard-mcp",
 		version,
 		server.WithToolCapabilities(true),
 		server.WithLogging(),
 	)
 
-	registerStoreKnowledge(mcpServer, sqliteStore, qdrantStore, logger)
-	registerSearchKnowledge(mcpServer, sqliteStore, qdrantStore, logger)
+	registerStoreFlashcard(mcpServer, sqliteStore, qdrantStore, logger)
+	registerSearchFlashcard(mcpServer, sqliteStore, qdrantStore, logger)
+	registerUpdateFlashcard(mcpServer, sqliteStore, qdrantStore, logger)
+	registerDeleteFlashcard(mcpServer, sqliteStore, qdrantStore, logger)
 
 	streamableServer := server.NewStreamableHTTPServer(mcpServer)
 
@@ -119,14 +121,17 @@ func main() {
 	}
 }
 
-func registerStoreKnowledge(mcpServer *server.MCPServer, sqlite *sqliteStore, qdrant *qdrantStore, logger *zap.Logger) {
+func registerStoreFlashcard(mcpServer *server.MCPServer, sqlite *sqliteStore, qdrant *qdrantStore, logger *zap.Logger) {
 	mcpServer.AddTool(
-		mcp.NewTool("store_knowledge",
-			mcp.WithDescription("Store a piece of knowledge for later retrieval. Use this to persist useful information discovered during a session."),
+		mcp.NewTool("store_flashcard",
+			mcp.WithDescription("Store a flashcard for later retrieval. Use this to persist useful information discovered during a session."),
 			mcp.WithString("note",
 				mcp.Required(),
 				mcp.Description("The markdown body — keep it concise, one paragraph usually"),
 			),
+			mcp.WithNumber("public_id",
+				mcp.Description("Optional public identifier. Auto-generated if omitted."),
+			),
 			mcp.WithArray("repos",
 				mcp.Description("Optional list of repository names"),
 			),
@@ -143,14 +148,14 @@ func registerStoreKnowledge(mcpServer *server.MCPServer, sqlite *sqliteStore, qd
 				mcp.Description("Optional context — what triggered this"),
 			),
 		),
-		handleStoreKnowledge(sqlite, qdrant, logger),
+		handleStoreFlashcard(sqlite, qdrant, logger),
 	)
 }
 
-func registerSearchKnowledge(mcpServer *server.MCPServer, sqlite *sqliteStore, qdrant *qdrantStore, logger *zap.Logger) {
+func registerSearchFlashcard(mcpServer *server.MCPServer, sqlite *sqliteStore, qdrant *qdrantStore, logger *zap.Logger) {
 	mcpServer.AddTool(
-		mcp.NewTool("search_knowledge",
-			mcp.WithDescription("Search previously stored knowledge using semantic search. Returns the most relevant knowledge entries for the given query."),
+		mcp.NewTool("search_flashcard",
+			mcp.WithDescription("Search previously stored flashcards using semantic search. Returns the most relevant entries for the given query."),
 			mcp.WithString("query",
 				mcp.Required(),
 				mcp.Description("The search query"),
@@ -159,34 +164,94 @@ func registerSearchKnowledge(mcpServer *server.MCPServer, sqlite *sqliteStore, q
 				mcp.Description("Maximum number of results to return (default: 5)"),
 			),
 		),
-		handleSearchKnowledge(sqlite, qdrant),
+		handleSearchFlashcard(sqlite, qdrant),
 	)
 }
 
-func handleStoreKnowledge(sqlite *sqliteStore, qdrant *qdrantStore, logger *zap.Logger) server.ToolHandlerFunc {
+func registerUpdateFlashcard(mcpServer *server.MCPServer, sqlite *sqliteStore, qdrant *qdrantStore, logger *zap.Logger) {
+	mcpServer.AddTool(
+		mcp.NewTool("update_flashcard",
+			mcp.WithDescription("Update an existing flashcard. Creates a new version while preserving history."),
+			mcp.WithNumber("public_id",
+				mcp.Required(),
+				mcp.Description("Public identifier of the flashcard to update"),
+			),
+			mcp.WithString("note",
+				mcp.Description("The markdown body"),
+			),
+			mcp.WithArray("repos",
+				mcp.Description("Optional list of repository names"),
+			),
+			mcp.WithString("host",
+				mcp.Description("Optional hostname or null if universal"),
+			),
+			mcp.WithArray("tags",
+				mcp.Description("Optional list of tags"),
+			),
+			mcp.WithString("user",
+				mcp.Description("Optional user identifier"),
+			),
+			mcp.WithString("context",
+				mcp.Description("Optional context — what triggered this"),
+			),
+		),
+		handleUpdateFlashcard(sqlite, qdrant, logger),
+	)
+}
+
+func handleUpdateFlashcard(sqlite *sqliteStore, qdrant *qdrantStore, logger *zap.Logger) server.ToolHandlerFunc {
 	return func(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
 		args, ok := request.Params.Arguments.(map[string]any)
 		if !ok {
 			return mcp.NewToolResultError("invalid arguments"), nil
 		}
 
-		note, ok := args["note"].(string)
-		if !ok || note == "" {
-			return mcp.NewToolResultError("note is required and must be a non-empty string"), nil
+		publicID := parseInt64(args["public_id"])
+		if publicID == 0 {
+			return mcp.NewToolResultError("public_id is required and must be a positive integer"), nil
 		}
 
-		repos := parseStringSlice(args["repos"])
-		host := parseOptionalString(args["host"])
-		tags := parseStringSlice(args["tags"])
-		user := parseOptionalString(args["user"])
-		context_ := parseOptionalString(args["context"])
-
-		id, err := sqlite.save(ctx, note, host, user, context_, repos, tags)
+		latest, err := sqlite.getLatestByPublicID(ctx, publicID)
 		if err != nil {
-			return mcp.NewToolResultError(fmt.Sprintf("failed to persist: %v", err)), nil
+			return mcp.NewToolResultError(fmt.Sprintf("failed to query: %v", err)), nil
+		}
+		if latest == nil {
+			return mcp.NewToolResultError(fmt.Sprintf("no flashcard found with public_id %d", publicID)), nil
 		}
 
-		if err := qdrant.index(ctx, id, note); err != nil {
+		note := latest.Note
+		repos := latest.Repos
+		host := latest.Host
+		tags := latest.Tags
+		user := latest.User
+		context_ := latest.Context
+
+		if v := parseOptionalString(args["note"]); v != "" {
+			note = v
+		}
+		if v := parseStringSlice(args["repos"]); v != nil {
+			repos = v
+		}
+		if v := parseOptionalString(args["host"]); v != "" {
+			host = v
+		}
+		if v := parseStringSlice(args["tags"]); v != nil {
+			tags = v
+		}
+		if v := parseOptionalString(args["user"]); v != "" {
+			user = v
+		}
+		if v := parseOptionalString(args["context"]); v != "" {
+			context_ = v
+		}
+
+		version := latest.Version + 1
+		id, err := sqlite.save(ctx, note, host, user, context_, repos, tags, publicID)
+		if err != nil {
+			return mcp.NewToolResultError(fmt.Sprintf("failed to persist update: %v", err)), nil
+		}
+
+		if err := qdrant.index(ctx, id, publicID, version, note); err != nil {
 			logger.Warn("qdrant index failed (entry in sqlite)", zap.Int64("id", id), zap.Error(err))
 		}
 
@@ -204,7 +269,100 @@ func handleStoreKnowledge(sqlite *sqliteStore, qdrant *qdrantStore, logger *zap.
 	}
 }
 
-func handleSearchKnowledge(sqlite *sqliteStore, qdrant *qdrantStore) server.ToolHandlerFunc {
+func registerDeleteFlashcard(mcpServer *server.MCPServer, sqlite *sqliteStore, qdrant *qdrantStore, logger *zap.Logger) {
+	mcpServer.AddTool(
+		mcp.NewTool("delete_flashcard",
+			mcp.WithDescription("Delete a flashcard. Creates a tombstone version and removes it from the vector index."),
+			mcp.WithNumber("public_id",
+				mcp.Required(),
+				mcp.Description("Public identifier of the flashcard to delete"),
+			),
+		),
+		handleDeleteFlashcard(sqlite, qdrant, logger),
+	)
+}
+
+func handleDeleteFlashcard(sqlite *sqliteStore, qdrant *qdrantStore, logger *zap.Logger) server.ToolHandlerFunc {
+	return func(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
+		args, ok := request.Params.Arguments.(map[string]any)
+		if !ok {
+			return mcp.NewToolResultError("invalid arguments"), nil
+		}
+
+		publicID := parseInt64(args["public_id"])
+		if publicID == 0 {
+			return mcp.NewToolResultError("public_id is required and must be a positive integer"), nil
+		}
+
+		latest, err := sqlite.getLatestByPublicID(ctx, publicID)
+		if err != nil {
+			return mcp.NewToolResultError(fmt.Sprintf("failed to query: %v", err)), nil
+		}
+		if latest == nil {
+			return mcp.NewToolResultError(fmt.Sprintf("no flashcard found with public_id %d", publicID)), nil
+		}
+		if latest.DeleteTimestamp != "" {
+			return mcp.NewToolResultError(fmt.Sprintf("flashcard %d is already deleted", publicID)), nil
+		}
+
+		if _, err := sqlite.tombstone(ctx, publicID, latest.Version+1); err != nil {
+			return mcp.NewToolResultError(fmt.Sprintf("failed to tombstone: %v", err)), nil
+		}
+
+		if err := qdrant.delete(ctx, publicID); err != nil {
+			logger.Warn("qdrant delete failed (tombstone in sqlite)", zap.Int64("public_id", publicID), zap.Error(err))
+		}
+
+		return mcp.NewToolResultText(fmt.Sprintf("flashcard %d deleted", publicID)), nil
+	}
+}
+
+func handleStoreFlashcard(sqlite *sqliteStore, qdrant *qdrantStore, logger *zap.Logger) server.ToolHandlerFunc {
+	return func(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
+		args, ok := request.Params.Arguments.(map[string]any)
+		if !ok {
+			return mcp.NewToolResultError("invalid arguments"), nil
+		}
+
+		note, ok := args["note"].(string)
+		if !ok || note == "" {
+			return mcp.NewToolResultError("note is required and must be a non-empty string"), nil
+		}
+
+		repos := parseStringSlice(args["repos"])
+		host := parseOptionalString(args["host"])
+		tags := parseStringSlice(args["tags"])
+		user := parseOptionalString(args["user"])
+		context_ := parseOptionalString(args["context"])
+		publicID := parseInt64(args["public_id"])
+
+		id, err := sqlite.save(ctx, note, host, user, context_, repos, tags, publicID)
+		if err != nil {
+			return mcp.NewToolResultError(fmt.Sprintf("failed to persist: %v", err)), nil
+		}
+
+		if publicID == 0 {
+			publicID = id
+		}
+		if err := qdrant.index(ctx, id, publicID, 1, note); err != nil {
+			logger.Warn("qdrant index failed (entry in sqlite)", zap.Int64("id", id), zap.Error(err))
+		}
+
+		entry, err := sqlite.getByID(ctx, id)
+		if err != nil {
+			return mcp.NewToolResultError(fmt.Sprintf("failed to retrieve: %v", err)), nil
+		}
+
+		output, err := json.MarshalIndent(entry, "", "  ")
+		if err != nil {
+			return mcp.NewToolResultError(fmt.Sprintf("failed to marshal result: %v", err)), nil
+		}
+
+		return mcp.NewToolResultText(string(output)), nil
+	}
+}
+
+func handleSearchFlashcard(sqlite *sqliteStore, qdrant *qdrantStore) server.ToolHandlerFunc {
 	return func(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
 		args, ok := request.Params.Arguments.(map[string]any)
 		if !ok {

migrations/000001_create_flashcard.sql

@@ -0,0 +1,18 @@
+-- +goose Up
+CREATE TABLE IF NOT EXISTS flashcard (
+    _id INTEGER PRIMARY KEY,
+    public_id INTEGER NOT NULL,
+    version INTEGER NOT NULL DEFAULT 1,
+    note TEXT NOT NULL,
+    repos TEXT,
+    host TEXT,
+    tags TEXT,
+    "user" TEXT,
+    context TEXT,
+    delete_timestamp TEXT,
+    created TEXT NOT NULL DEFAULT (datetime('now')),
+    UNIQUE(public_id, version)
+);
+
+-- +goose Down
+DROP TABLE IF EXISTS flashcard;

migrations/000001_create_knowledge.sql

@@ -1,14 +0,0 @@
--- +goose Up
-CREATE TABLE IF NOT EXISTS knowledge (
-    id INTEGER PRIMARY KEY,
-    note TEXT NOT NULL,
-    repos TEXT,
-    host TEXT,
-    tags TEXT,
-    "user" TEXT,
-    context TEXT,
-    created TEXT NOT NULL DEFAULT (datetime('now'))
-);
-
--- +goose Down
-DROP TABLE IF EXISTS knowledge;

migrations/000002_add_versioning.sql

@@ -0,0 +1,10 @@
+-- +goose Up
+ALTER TABLE flashcard ADD COLUMN public_id INTEGER NOT NULL DEFAULT 0;
+ALTER TABLE flashcard ADD COLUMN version INTEGER NOT NULL DEFAULT 1;
+UPDATE flashcard SET public_id = _id WHERE public_id = 0;
+CREATE UNIQUE INDEX IF NOT EXISTS idx_flashcard_public_id_version ON flashcard(public_id, version);
+
+-- +goose Down
+DROP INDEX IF EXISTS idx_flashcard_public_id_version;
+ALTER TABLE flashcard DROP COLUMN version;
+ALTER TABLE flashcard DROP COLUMN public_id;

migrations/000003_add_delete_timestamp.sql

@@ -0,0 +1,5 @@
+-- +goose Up
+ALTER TABLE flashcard ADD COLUMN delete_timestamp TEXT;
+
+-- +goose Down
+ALTER TABLE flashcard DROP COLUMN delete_timestamp;

qdrant.go

@@ -8,16 +8,19 @@ import (
 	"github.com/qdrant/go-client/qdrant"
 )
 
-const collectionName = "knowledge"
+const collectionName = "flashcard"
 
 type entry struct {
-	ID      int64    `json:"id"`
+	ID        int64    `json:"_id"`
+	PublicID  int64    `json:"public_id"`
+	Version   int      `json:"version"`
 	Note      string   `json:"note"`
 	Repos     []string `json:"repos,omitempty"`
 	Host      string   `json:"host,omitempty"`
 	Tags      []string `json:"tags,omitempty"`
 	User      string   `json:"user,omitempty"`
 	Context         string   `json:"context,omitempty"`
+	DeleteTimestamp string   `json:"delete_timestamp,omitempty"`
 	Created         string   `json:"created"`
 }
 
@@ -58,14 +61,16 @@ func (s *qdrantStore) ensureCollection(ctx context.Context) error {
 	return nil
 }
 
-func (s *qdrantStore) index(ctx context.Context, id int64, note string) error {
+func (s *qdrantStore) index(ctx context.Context, id, publicID int64, version int, note string) error {
 	vec, err := s.embedder.embedText(ctx, note)
 	if err != nil {
 		return fmt.Errorf("embed text: %w", err)
 	}
 
 	payload := map[string]*qdrant.Value{
-		"id":      qdrant.NewValueString(strconv.FormatInt(id, 10)),
+		"_id":       qdrant.NewValueString(strconv.FormatInt(id, 10)),
+		"public_id": qdrant.NewValueString(strconv.FormatInt(publicID, 10)),
+		"version":   qdrant.NewValueInt(int64(version)),
 		"content":   qdrant.NewValueString(note),
 	}
 
@@ -73,7 +78,7 @@ func (s *qdrantStore) index(ctx context.Context, id int64, note string) error {
 		CollectionName: collectionName,
 		Points: []*qdrant.PointStruct{
 			{
-				Id:      qdrant.NewIDNum(uint64(id)),
+				Id:      qdrant.NewIDNum(uint64(publicID)),
 				Vectors: qdrant.NewVectors(vec...),
 				Payload: payload,
 			},
@@ -86,6 +91,21 @@ func (s *qdrantStore) index(ctx context.Context, id int64, note string) error {
 	return nil
 }
 
+func (s *qdrantStore) delete(ctx context.Context, publicID int64) error {
+	wait := true
+	_, err := s.client.Delete(ctx, &qdrant.DeletePoints{
+		CollectionName: collectionName,
+		Wait:           &wait,
+		Points: qdrant.NewPointsSelector(
+			qdrant.NewIDNum(uint64(publicID)),
+		),
+	})
+	if err != nil {
+		return fmt.Errorf("delete point: %w", err)
+	}
+	return nil
+}
+
 func (s *qdrantStore) search(ctx context.Context, query string, limit uint64) ([]searchResult, error) {
 	vec, err := s.embedder.embedText(ctx, query)
 	if err != nil {
@@ -113,7 +133,7 @@ func (s *qdrantStore) search(ctx context.Context, query string, limit uint64) ([
 		}
 
 		if payload := pt.GetPayload(); payload != nil {
-			if v, ok := payload["id"]; ok {
+			if v, ok := payload["_id"]; ok {
 				if n, err := strconv.ParseInt(v.GetStringValue(), 10, 64); err == nil {
 					r.Entry.ID = n
 				}

sqlite.go

@@ -42,14 +42,14 @@ func newSqliteStore(path string) (*sqliteStore, error) {
 	return &sqliteStore{db: db}, nil
 }
 
-func (s *sqliteStore) save(ctx context.Context, note, host, user, context_ string, repos, tags []string) (int64, error) {
+func (s *sqliteStore) save(ctx context.Context, note, host, user, context_ string, repos, tags []string, publicID int64) (int64, error) {
 	reposJSON := marshalStringSlice(repos)
 	tagsJSON := marshalStringSlice(tags)
 
 	result, err := s.db.ExecContext(ctx,
-		`INSERT INTO knowledge (note, repos, host, tags, "user", context)
-		 VALUES (?, ?, ?, ?, ?, ?)`,
-		note, reposJSON, host, tagsJSON, user, context_,
+		`INSERT INTO flashcard (public_id, version, note, repos, host, tags, "user", context)
+		 VALUES (?, 1, ?, ?, ?, ?, ?, ?)`,
+		publicID, note, reposJSON, host, tagsJSON, user, context_,
 	)
 	if err != nil {
 		return 0, fmt.Errorf("insert: %w", err)
@@ -60,20 +60,27 @@ func (s *sqliteStore) save(ctx context.Context, note, host, user, context_ strin
 		return 0, fmt.Errorf("last insert id: %w", err)
 	}
 
+	if publicID == 0 {
+		_, err = s.db.ExecContext(ctx, `UPDATE flashcard SET public_id = ? WHERE _id = ?`, id, id)
+		if err != nil {
+			return 0, fmt.Errorf("set public_id: %w", err)
+		}
+	}
+
 	return id, nil
 }
 
 func (s *sqliteStore) getByID(ctx context.Context, id int64) (*entry, error) {
 	row := s.db.QueryRowContext(ctx,
-		`SELECT id, note, repos, host, tags, "user", context, created
-		 FROM knowledge WHERE id = ?`, id,
+		`SELECT _id, public_id, version, note, repos, host, tags, "user", context, delete_timestamp, created
+		 FROM flashcard WHERE _id = ?`, id,
 	)
 
 	var e entry
 	var reposJSON, tagsJSON sql.NullString
-	var host, user, context_ sql.NullString
+	var host, user, context_, deleteTimestamp sql.NullString
 
-	err := row.Scan(&e.ID, &e.Note, &reposJSON, &host, &tagsJSON, &user, &context_, &e.Created)
+	err := row.Scan(&e.ID, &e.PublicID, &e.Version, &e.Note, &reposJSON, &host, &tagsJSON, &user, &context_, &deleteTimestamp, &e.Created)
 	if err == sql.ErrNoRows {
 		return nil, nil
 	}
@@ -96,10 +103,71 @@ func (s *sqliteStore) getByID(ctx context.Context, id int64) (*entry, error) {
 	if context_.Valid {
 		e.Context = context_.String
 	}
+	if deleteTimestamp.Valid {
+		e.DeleteTimestamp = deleteTimestamp.String
+	}
 
 	return &e, nil
 }
 
+func (s *sqliteStore) getLatestByPublicID(ctx context.Context, publicID int64) (*entry, error) {
+	row := s.db.QueryRowContext(ctx,
+		`SELECT _id, public_id, version, note, repos, host, tags, "user", context, delete_timestamp, created
+		 FROM flashcard WHERE public_id = ? ORDER BY version DESC LIMIT 1`, publicID,
+	)
+
+	var e entry
+	var reposJSON, tagsJSON sql.NullString
+	var host, user, context_, deleteTimestamp sql.NullString
+
+	err := row.Scan(&e.ID, &e.PublicID, &e.Version, &e.Note, &reposJSON, &host, &tagsJSON, &user, &context_, &deleteTimestamp, &e.Created)
+	if err == sql.ErrNoRows {
+		return nil, nil
+	}
+	if err != nil {
+		return nil, fmt.Errorf("query: %w", err)
+	}
+
+	if reposJSON.Valid {
+		e.Repos = unmarshalStringSlice(reposJSON.String)
+	}
+	if tagsJSON.Valid {
+		e.Tags = unmarshalStringSlice(tagsJSON.String)
+	}
+	if host.Valid {
+		e.Host = host.String
+	}
+	if user.Valid {
+		e.User = user.String
+	}
+	if context_.Valid {
+		e.Context = context_.String
+	}
+	if deleteTimestamp.Valid {
+		e.DeleteTimestamp = deleteTimestamp.String
+	}
+
+	return &e, nil
+}
+
+func (s *sqliteStore) tombstone(ctx context.Context, publicID int64, version int) (int64, error) {
+	result, err := s.db.ExecContext(ctx,
+		`INSERT INTO flashcard (public_id, version, note, delete_timestamp)
+		 VALUES (?, ?, '', datetime('now'))`,
+		publicID, version,
+	)
+	if err != nil {
+		return 0, fmt.Errorf("tombstone: %w", err)
+	}
+
+	id, err := result.LastInsertId()
+	if err != nil {
+		return 0, fmt.Errorf("last insert id: %w", err)
+	}
+
+	return id, nil
+}
+
 func (s *sqliteStore) close() error {
 	return s.db.Close()
 }
@@ -146,3 +214,18 @@ func parseOptionalString(raw any) string {
 	}
 	return ""
 }
+
+func parseInt64(raw any) int64 {
+	if raw == nil {
+		return 0
+	}
+	switch v := raw.(type) {
+	case float64:
+		return int64(v)
+	case int64:
+		return v
+	case int:
+		return int64(v)
+	}
+	return 0
+}