package llist

import (
  "fmt"
)

type Node struct {
  Data any
  Next *Node
}

type LinkedList struct {
  Front *Node
  End *Node
  Count int
}

func (l *LinkedList) Add(data any) {
  el := Node{data, nil}

  if l.Front == nil {
    l.Front = &el
    l.End = &el
  } else {
    l.End.Next = &el
    l.End = &el
  }

  l.Count++
}

func (l *LinkedList) Find(data any) (*Node) {
  for el := l.Front; el != nil; el = el.Next {
    if el.Data == data {
      return el
    }
  }

  return nil
}

func (l *LinkedList) Delete(target *Node) {
  if l.Front == target {
    l.PopFront()
  } else if l.End == target {
    l.PopBack()
  } else {
    el := l.Front

    for el.Next != target {
      el = el.Next
    }

    el.Next = el.Next.Next
    target.Next = nil
    l.Count--
  }
}

func (l *LinkedList) PopBack() (*Node) {
  el := l.End

  if l.Front == nil {
    return nil
  } else if l.Front == l.End {
    l.Front = nil
    l.End = nil
    l.Count--
  } else {
    new_end := l.Front
    for new_end.Next.Next != nil {
      new_end = new_end.Next
    }

    l.End = new_end
    l.End.Next = nil
    l.Count--
  }

  return el
}

func (l *LinkedList) PopFront() (*Node) {
  el := l.Front

  if l.Front == nil {
    return nil
  } else if l.Front == l.End {
    l.Front = nil
    l.End = nil
    l.Count--
  } else {
    l.Front = l.Front.Next
    l.Count--
  }

  return el
}

func (l *LinkedList) Dump() {
  fmt.Println("----------------", l.Count, "nodes")

  for cur := l.Front; cur != nil; cur = cur.Next {
    fmt.Println(cur.Data)
  }
}