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

// operator-context-value.go
package expr

import (
	"io"

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

//-------- context term

func newContextTerm(tk *scan.Token) (inst *scan.Term) {
	return &scan.Term{
		Tk:       *tk,
		Children: make([]*scan.Term, 0, 1),
		Position: scan.PosPrefix,
		Priority: scan.PriIncDec,
		EvalFunc: evalContextValue,
	}
}

func evalContextValue(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
	var childValue any
	var sourceCtx kern.ExprContext

	if len(opTerm.Children) == 0 {
		sourceCtx = ctx
	} else if opTerm.Children[0].Symbol() == scan.SymVariable && opTerm.Children[0].Source() == "global" {
		sourceCtx = ctx.GetGlobal()
	} else if childValue, err = opTerm.EvalPrefix(ctx); err == nil {
		if dc, ok := childValue.(*dataCursor); ok {
			sourceCtx = dc.ctx
		}
	} else {
		return
	}

	if sourceCtx != nil {
		v = sourceCtx.ToDict()
	} else if childValue != nil {
		it, ok := childValue.(kern.Iterator)
		if !ok {
			it, err = NewIterator(ctx, childValue, nil)
		}
		if err == nil {
			var item any
			values := kern.NewLinkedListA()
			for item, err = it.Next(); err == nil; item, err = it.Next() {
				values.PushBack(item)
			}
			if err == io.EOF {
				err = nil
				v = values
			}
		}
	} else {
		err = opTerm.ErrIncompatiblePrefixPostfixType(childValue)
	}
	return
}

// init
func init() {
	scan.RegisterTermConstructor(scan.SymDoubleDollar, newContextTerm)
}