new iter-iter iterator and kern.func-info module

iter-iter.go

@@ -0,0 +1,132 @@
+// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
+// All rights reserved.
+
+// iter-iter.go
+package expr
+
+import (
+	"fmt"
+	"io"
+
+	"git.portale-stac.it/go-pkg/expr/kern"
+)
+
+type IterIter struct {
+	it      kern.Iterator
+	count   int64
+	index   int64
+	ctx     kern.ExprContext
+	op      kern.Functor
+	opName  string
+	args    map[string]any
+	current any
+}
+
+func NewIterIter(it kern.Iterator, ctx kern.ExprContext, op kern.Functor, args map[string]any) (iter kern.Iterator, err error) {
+	var opName string
+	if op != nil {
+		if f := op.GetFunc(); f != nil {
+			opName = f.Name()
+			// } else {
+			// 	return nil, fmt.Errorf("invalid functor argument for iter-iter: expected kern.Functor, got %T", args["op"])
+		}
+	}
+	if len(opName) == 0 {
+		opName = "anonymous"
+	}
+	iter = &IterIter{it: it, count: 0, index: -1, ctx: ctx, op: op, opName: opName, args: args}
+
+	return
+}
+
+func (it *IterIter) String() string {
+	return fmt.Sprintf("$(%s)", it.it)
+}
+
+func (it *IterIter) TypeName() string {
+	return "IterIter"
+}
+
+func (it *IterIter) HasOperation(name string) bool {
+	return HasStandardOperation(name)
+}
+
+func (it *IterIter) CallOperation(name string, args map[string]any) (v any, err error) {
+	switch name {
+	case kern.NextName:
+		v, err = it.Next()
+	case kern.ResetName:
+		err = it.Reset()
+	case kern.CleanName:
+		err = it.Clean()
+	case kern.IndexName:
+		v = int64(it.Index())
+	case kern.CurrentName:
+		v, err = it.Current()
+	case kern.CountName:
+		v = it.count
+	default:
+		err = kern.ErrNoOperation(name)
+	}
+	return
+}
+
+func (it *IterIter) Current() (item any, err error) {
+	if it.current != nil {
+		item = it.current
+	} else if it.op != nil {
+		if item, err = it.op.InvokeNamed(it.ctx, it.opName, it.args); err == nil {
+			it.current = item
+		}
+	} else {
+		var exists bool
+		if it.current, exists = it.ctx.GetVar("_"); !exists {
+			err = fmt.Errorf("current item not available")
+		} else {
+			item = it.current
+		}
+	}
+	return
+}
+
+func (it *IterIter) Next() (item any, err error) {
+	var src any
+
+	it.current = nil
+	ctx := it.ctx
+	for src, err = it.it.Next(); src == nil && err == nil; src, err = it.it.Next() {
+	}
+
+	if err == nil {
+		if src == nil {
+			err = io.EOF
+		} else {
+			ctx.UnsafeSetVar("_", src)
+			ctx.UnsafeSetVar("__", it.it.Index())
+			ctx.UnsafeSetVar("_#", it.it.Count())
+			item, err = it.Current()
+			ctx.DeleteVar("_#")
+			ctx.DeleteVar("__")
+			ctx.DeleteVar("_")
+		}
+	}
+	return
+}
+
+func (it *IterIter) Index() int64 {
+	return it.index
+}
+
+func (it *IterIter) Count() int64 {
+	return it.count
+}
+
+func (it *IterIter) Reset() error {
+	it.index = -1
+	it.count = 0
+	return nil
+}
+
+func (it *IterIter) Clean() error {
+	return nil
+}