better error handling

internal/client/client.go

@@ -73,7 +73,7 @@ func (c *Client) CreateShare(ctx context.Context, key string) (*types.Share, err
 	}
 
 	if !exists {
-		return nil, errors.New("key does not exist")
+		return nil, types.ErrKeyNotFound
 	}
 
 	err = c.db.CreateShare(ctx, share)

internal/db/mock.go

@@ -31,7 +31,7 @@ func (d *mockDB) CreateShare(ctx context.Context, share *types.Share) error {
 
 func (d *mockDB) DeleteShare(ctx context.Context, slug string) error {
 	if d.shares[slug] == nil {
-		return errors.New("share does not exist")
+		return types.ErrShareNotFound
 	}
 	delete(d.shares, slug)
 	return nil

internal/db/sql.go

@@ -79,10 +79,20 @@ func (db *sqlDB) CreateShare(ctx context.Context, share *types.Share) error {
 }
 
 func (db *sqlDB) DeleteShare(ctx context.Context, slug string) error {
-	_, err := db.db.ExecContext(ctx, "DELETE FROM shares WHERE slug = ?", slug)
+	result, err := db.db.ExecContext(ctx, "DELETE FROM shares WHERE slug = ?", slug)
 	if err != nil {
 		return err
 	}
+
+	rowsAffected, err := result.RowsAffected()
+	if err != nil {
+		return err
+	}
+
+	if rowsAffected == 0 {
+		return types.ErrShareNotFound
+	}
+
 	return nil
 }
 

internal/types/errors.go

@@ -0,0 +1,6 @@
+package types
+
+import "errors"
+
+var ErrKeyNotFound = errors.New("Key not found")
+var ErrShareNotFound = errors.New("Share not found")

internal/web/web.go

@@ -117,6 +117,10 @@ func CreateRouter(client *client.Client, username, password string) *mux.Router
 		share, err := client.CreateShare(r.Context(), shareParams.Key)
 
 		if err != nil {
+			if err == types.ErrKeyNotFound {
+				http.Error(w, "The specified key does not exist", http.StatusBadRequest)
+				return
+			}
 			logrus.Error(err.Error())
 			http.Error(w, err.Error(), http.StatusInternalServerError)
 			return
@@ -136,6 +140,10 @@ func CreateRouter(client *client.Client, username, password string) *mux.Router
 
 		err := client.DeleteShare(r.Context(), vars["slug"])
 		if err != nil {
+			if err == types.ErrShareNotFound {
+				http.NotFound(w, r)
+				return
+			}
 			logrus.Error(err.Error())
 			http.Error(w, err.Error(), http.StatusInternalServerError)
 			return