minor changes

data-cursor.go

@@ -133,7 +133,7 @@ func (dc *dataCursor) Current() (item any, err error) { // must return io.EOF at
 	return
 }
 
-func (dc *dataCursor) Next() (item any, err error) { // must return io.EOF after the last item
+func (dc *dataCursor) _Next() (item any, err error) { // must return io.EOF after the last item
 	if dc.resource != nil {
 		ctx := cloneContext(dc.ctx)
 		// fmt.Printf("Entering Inner-Ctx [%p]: %s\n", ctx, CtxToString(ctx, 0))
@@ -153,6 +153,40 @@ func (dc *dataCursor) Next() (item any, err error) { // must return io.EOF after
 	return
 }
 
+const filterName = "filter"
+func (dc *dataCursor) filter(item any) (filterdItem any, err error) {
+	if filter, ok := dc.ds[filterName]; ok {
+		ctx := cloneContext(dc.ctx)
+		filterdItem, err = filter.Invoke(ctx, filterName, []any{item, dc.index});
+	} else {
+		filterdItem = item
+	}
+	return
+}
+
+func (dc *dataCursor) Next() (item any, err error) { // must return io.EOF after the last item
+	if dc.resource != nil {
+		ctx := cloneContext(dc.ctx)
+		// fmt.Printf("Entering Inner-Ctx [%p]: %s\n", ctx, CtxToString(ctx, 0))
+		for item == nil && err == nil {
+			if item, err = dc.nextFunc.Invoke(ctx, nextName, []any{dc.resource}); err == nil {
+				if item == nil {
+					err = io.EOF
+				} else {
+					dc.index++
+					item, err = dc.filter(item)
+				}
+			}
+		}
+		// fmt.Printf("Exiting Inner-Ctx [%p]: %s\n", ctx, CtxToString(ctx, 0))
+		exportObjects(dc.ctx, ctx)
+		// fmt.Printf("Outer-Ctx [%p]: %s\n", dc.ctx, CtxToString(dc.ctx, 0))
+	} else {
+		err = errInvalidDataSource()
+	}
+	return
+}
+
 func (dc *dataCursor) Index() int {
 	return dc.index
 }