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

// operator-post-inc-dec.go
package expr

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

// -------- post increment term

func newPostIncTerm(tk *scan.Token) *scan.Term {
	return &scan.Term{
		Tk:       *tk,
		Children: make([]*scan.Term, 0, 1),
		Position: scan.PosPostfix,
		Priority: scan.PriIncDec,
		EvalFunc: evalPostInc,
	}
}

func evalPostInc(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
	var childValue any
	if childValue, err = opTerm.EvalPrefix(ctx); err != nil {
		return
	}

	if it, ok := childValue.(kern.Iterator); ok {
		var namePrefix string
		v, err = it.Next()

		if opTerm.Children[0].Symbol() == scan.SymVariable {
			namePrefix = opTerm.Children[0].Source()
		}
		ctx.UnsafeSetVar(namePrefix+"_index", it.Index())
		if c, err1 := it.Current(); err1 == nil {
			ctx.UnsafeSetVar(namePrefix+"_current", c)
		}

		if it.HasOperation(kern.KeyName) {
			if k, err1 := it.CallOperation(kern.KeyName, nil); err1 == nil {
				ctx.UnsafeSetVar(namePrefix+"_key", k)
			}
		}
		if it.HasOperation(kern.ValueName) {
			if v1, err1 := it.CallOperation(kern.ValueName, nil); err1 == nil {
				ctx.UnsafeSetVar(namePrefix+"_value", v1)
			}
		}
	} else if kern.IsInteger(childValue) && opTerm.Children[0].Symbol() == scan.SymVariable {
		v = childValue
		i, _ := childValue.(int64)
		ctx.SetVar(opTerm.Children[0].Source(), i+1)
	} else {
		err = opTerm.ErrIncompatiblePrefixPostfixType(childValue)
	}
	return
}

// -------- post decrement term

func newPostDecTerm(tk *scan.Token) *scan.Term {
	return &scan.Term{
		Tk:       *tk,
		Children: make([]*scan.Term, 0, 1),
		Position: scan.PosPostfix,
		Priority: scan.PriIncDec,
		EvalFunc: evalPostDec,
	}
}

func evalPostDec(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
	var childValue any
	if childValue, err = opTerm.EvalPrefix(ctx); err != nil {
		return
	}

	/* if it, ok := childValue.(Iterator); ok {
		v, err = it.Next()
	} else  */if kern.IsInteger(childValue) && opTerm.Children[0].Symbol() == scan.SymVariable {
		v = childValue
		i, _ := childValue.(int64)
		ctx.SetVar(opTerm.Children[0].Source(), i-1)
	} else {
		err = opTerm.ErrIncompatiblePrefixPostfixType(childValue)
	}
	return
}

// init
func init() {
	scan.RegisterTermConstructor(scan.SymDoublePlus, newPostIncTerm)
	scan.RegisterTermConstructor(scan.SymDoubleMinus, newPostDecTerm)
}