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

// operator-selector.go
package expr

//-------- export all term

func newSelectorTerm(tk *Token) (inst *term) {
	return &term{
		tk:       *tk,
		children: make([]*term, 0, 3),
		position: posMultifix,
		priority: priSelector,
		evalFunc: evalSelector,
	}
}

func isSelectorCase(ctx ExprContext, exprValue, caseSel any, caseIndex int) (selectedValue any, err error) {
	caseData, _ := caseSel.(*selectorCase)
	if caseData.filterList == nil {
		selectedValue, err = caseData.caseExpr.eval(ctx, false)
	} else {
		filterList := caseData.filterList.children
		if len(filterList) == 0 && exprValue == int64(caseIndex) {
			selectedValue, err = caseData.caseExpr.eval(ctx, false)
		} else {
			var caseValue any
			for _, caseTerm := range filterList {
				if caseValue, err = caseTerm.compute(ctx); err != nil || caseValue == exprValue {
					selectedValue, err = caseData.caseExpr.eval(ctx, false)
					break
				}
			}
		}
	}
	return
}

func evalSelector(ctx ExprContext, self *term) (v any, err error) {
	var exprValue any
	// var caseList []*term

	if err = self.checkOperands(); err != nil {
		return
	}
	exprTerm := self.children[0]
	if exprValue, err = exprTerm.compute(ctx); err != nil {
		return
	}

	caseList := self.children[1:]
	for i, caseTerm := range caseList {
		caseSel := caseTerm.value()
		if v, err = isSelectorCase(ctx, exprValue, caseSel, i); err != nil || v != nil {
			break
		}
	}
	if err == nil && v == nil {
		err = exprTerm.tk.Errorf("no case catches the value (%v) of the selection expression", exprValue)
	}
	return
}

// init
func init() {
	registerTermConstructor(SymSelector, newSelectorTerm)
}