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

// iter-list.go
package expr

import (
	"fmt"
	"io"
)

type ListIterator struct {
	a     *ListType
	index int
}

func NewListIterator(list *ListType) *ListIterator {
	return &ListIterator{a: list, index: 0}
}

func NewArrayIterator(array []any) *ListIterator {
	return &ListIterator{a: (*ListType)(&array), index: 0}
}

func NewAnyIterator(value any) (it *ListIterator) {
	if value == nil {
		it = NewArrayIterator([]any{})
	} else if list, ok := value.(*ListType); ok {
		it = NewListIterator(list)
	} else if array, ok := value.([]any); ok {
		it = NewArrayIterator(array)
	} else if it1, ok := value.(*ListIterator); ok {
		it = it1
	} else {
		it = NewArrayIterator([]any{value})
	}
	return
}

func (it *ListIterator) String() string {
	var l = 0
	if it.a != nil {
		l = len(*it.a)
	}
	return fmt.Sprintf("$(#%d)", l)
}

func (it *ListIterator) HasOperation(name string) bool {
	yes := name == resetName || name == indexName
	return yes
}

func (it *ListIterator) CallOperation(name string, args []any) (v any, err error) {
	switch name {
	case resetName:
		v, err = it.Reset()
	case indexName:
		v = it.Index()
	default:
		err = errNoOperation(name)
	}
	return
}

func (it *ListIterator) Current() (item any, err error) {
	a := *(it.a)
	if it.index >= 0 && it.index < len(a) {
		item = a[it.index]
	} else {
		err = io.EOF
	}
	return
}

func (it *ListIterator) Next() (item any, err error) {
	if item, err = it.Current(); err != io.EOF {
		it.index++
	}
	return
}

func (it *ListIterator) Index() int {
	return it.index - 1
}

func (it *ListIterator) Reset() (bool, error) {
	it.index = 0
	return true, nil
}