Need to realize FIFO (queue) with an option of node expiration time. Please write the code.

Question

Sigiloso · Accepted Answer

using System;
using System.Collections;
using System.Collections.Generic;
using TEST;

namespace TEST
{
    public class Node
    {
        public Node(T? value, DateTime? exprirationDateTime = null)
        {
            this.Id = Guid.NewGuid();
            this.Value = value;
            this.ExprirationDateTime = exprirationDateTime;
        }

public Guid Id { get; }
        public T? Value { get; set; }
        public DateTime? ExprirationDateTime { get; set; }
        internal Node? Next { get; set; }
    }

internal interface IFIFOEngine
    {
        Node Peek();
        Node Pop();
        bool Push(Node node);
    }

internal class FIFOEngine : IFIFOEngine, IEnumerable>
    {
        private Node? _thresholder = null;
        private Node? _last = null;

IEnumerator IEnumerable.GetEnumerator()
        {
            return GetEnumerator();
        }

public IEnumerator> GetEnumerator()
        {
            if (_thresholder == null)
            {
                throw new InvalidOperationException(String.Format("The operation has failed.{0}The queue is empty!", Environment.NewLine));
            }

RemoveExpiredNodes();

return _thresholder;
        }
        public Node Pop()
        {
            if (_thresholder is null)
            {
                throw new InvalidOperationException(String.Format("The operation has failed.{0}The queue is empty!", Environment.NewLine));
            }

RemoveExpiredNodes();

var tmp = _thresholder;

_thresholder = _thresholder.Next;

if (_thresholder is null)
            {
                _last = null;
            }

tmp.Next = null;

return tmp;
        }
        public bool Push(Node node)
        {
            if (node is null)
            {
                throw new ArgumentNullException(String.Format("The operation has failed.{0}The item {1} is null!", Environment.NewLine, nameof(node)));
            }

if (_thresholder is null)
            {
                _thresholder = _last = node;
                return true;
            }

_last!.Next = node;
            _last = node;

return true;
        }

private void RemoveExpiredNodes()
        {
            while (_thresholder != null && _thresholder.ExprirationDateTime.HasValue && _thresholder.ExprirationDateTime.Value < DateTime.Now)
            {
                var tmp = _thresholder;
                _thresholder = _thresholder.Next;

if (_thresholder == null)
                {
                    _last = null;
                }
                tmp.Next = null;
            }
        }

}

public partial class Program
{
    public static void Main()
    {
        var node1 = new Node("Test1");
        var node2 = new Node("Test2", DateTime.Now.AddMinutes(1));
        var node3 = new Node(null, DateTime.Now.AddMinutes(2));

FIFOEngine queue = new FIFOEngine();

queue.Push(node1);
        queue.Push(node2);
        queue.Push(node3);

var t = queue.Peek();
        queue.Pop();
        t = queue.Peek();

foreach (var node in queue)
        {
            var z = node.Value;
        }
    }

}

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