// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
// All rights reserved.

// operator-map.go
package expr

import (
	"fmt"

	"git.portale-stac.it/go-pkg/expr/kern"
	"git.portale-stac.it/go-pkg/expr/scan"
)

//-------- map term

func newMapTerm(tk *scan.Token) (inst *scan.Term) {
	return &scan.Term{
		Tk:       *tk,
		Children: make([]*scan.Term, 0, 2),
		Position: scan.PosInfix,
		Priority: scan.PriIterOp,
		EvalFunc: evalMap,
	}
}

func evalMap(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
	// var leftValue, rightValue any
	var leftValue any
	var it kern.Iterator
	// var item any
	var ok bool

	if err = opTerm.CheckOperands(); err != nil {
		return
	}

	if leftValue, err = opTerm.Children[0].Compute(ctx); err != nil {
		return
	}

	if it, ok = leftValue.(kern.Iterator); !ok {
		if it, err = NewIterator(ctx, leftValue, nil); err != nil {
			return nil, fmt.Errorf("left operand of MAP must be an iterable data-source; got %s", kern.TypeName(leftValue))
		}
	}

	// values := kern.NewListA()
	// for item, err = it.Next(); err == nil; item, err = it.Next() {
	// 	ctx.SetVar("_", item)
	// 	ctx.SetVar("__", it.Index())
	// 	ctx.SetVar("_#", it.Count())
	// 	if rightValue, err = opTerm.Children[1].Compute(ctx); err == nil {
	// 		values.AppendItem(rightValue)
	// 	}
	// 	ctx.DeleteVar("_#")
	// 	ctx.DeleteVar("__")
	// 	ctx.DeleteVar("_")
	// 	if err != nil {
	// 		break
	// 	}
	// }
	// if err == io.EOF {
	// 	err = nil
	// }
	// if err == nil {
	// 	v = values
	// }
	v, err = NewIterIter(it, ctx, opTerm.Children[1:])
	return
}

// init
func init() {
	scan.RegisterTermConstructor(scan.SymKwMap, newMapTerm)
}