package main

import "fmt"

// MyListElement contains custom-attributes and internal data
type MyListElement struct {
	Name string
	Age  int

	next *MyListElement
	prev *MyListElement
}

// Next iterates to the next list element, or nil if end of list
func (i *MyListElement) Next() *MyListElement {
	return i.next
}

// MyList structure, pointer for begin and end element
type MyList struct {
	head *MyListElement
	tail *MyListElement
}

// Append item to end of list
func (list *MyList) Append(item *MyListElement) {
	if list.head == nil && list.tail == nil {
		list.head = item
		list.tail = item

		item.next = nil
		item.prev = nil
		return
	}

	list.tail.next = item
	item.prev = list.tail

	item.next = nil

	list.tail = item

}

func (list *MyList) Delete(item *MyListElement) {
	if list.head == item && list.tail == item && item.prev == nil && item.next == nil {
		list.head = nil
		list.tail = nil
		return
	}

	item.prev = item.next
	item.next = item.prev	
}

// Count elements in list
func (list *MyList) Count() int {
	count := 0

	for i := list.head; i != nil; i = i.next {
		count++
	}
	return count
}

func main() {
	list := MyList{}

	{
		a := &MyListElement{Name: "Max", Age: 23}

		list.Append(a)
	}
	{
		b := &MyListElement{Name: "Hans", Age: 42}

		list.Append(b)
	}

	fmt.Println(list.Count())
}