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

namespace LineNodeDemo
{
 class Program
 {
  static void Main(string[] args)
  {
   LineNodeCollection lineNodes = new LineNodeCollection();
   lineNodes.Add(new LineNode("N1") { Name = "Microsoft" });
   lineNodes.Add(new LineNode("N2") { Name = "Lenovo" });
   lineNodes.Add(new LineNode("N3") { Name = "Apple" });
   lineNodes.Add(new LineNode("N4") { Name = "China Mobile" });
   Console.WriteLine("1、顯示全部：");
   lineNodes.ForEach(x => { Console.WriteLine(x.Name); });
   Console.WriteLine("2、刪除編號為N2的元素：");
   lineNodes.Remove("N2");
   lineNodes.ForEach(x => { Console.WriteLine(x.Name); });
   Console.WriteLine("3、刪除索引為1的元素：");
   lineNodes.RemoveAt(1);
   lineNodes.ForEach(x => { Console.WriteLine(x.Name); });
   Console.WriteLine("4、顯示索引為0元素的名稱：");
   Console.WriteLine(lineNodes[0].Name);
   Console.WriteLine("5、顯示編號為N4元素的名稱：");
   Console.WriteLine(lineNodes["N4"].Name);
   Console.WriteLine("6、清空");
   lineNodes.Clear();
   lineNodes.ForEach(x => { Console.WriteLine(x.Name); });
   Console.ReadKey();
  }
 }

 static class Utility
 {
  public static void ForEach<T>(this IEnumerable<T> source, Action<T> action)
  {
   foreach(var r in source)
   {
    action(r);
   }
  }
 }

 class LineNodeCollection : IEnumerable<LineNode>
 {
  public IEnumerator<LineNode> GetEnumerator()
  {
   return new LineNodeEnumerator(this.firstLineNode);
  }

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

  public LineNode this[int index]
  {
   get
   {
    LineNode _lineNode= this.firstLineNode;
    for (int i=0;i<=index;i++)
    {
     if (_lineNode != null)
     {
      if(i<index)
      {
       _lineNode = _lineNode.Next;
       continue;
      }
      else
      {
       return _lineNode;
      }
     }
     else break;
    }
    throw new IndexOutOfRangeException("超出集合索引范圍");
   }
  }

  public LineNode this[string id]
  {
   get
   {
    LineNode _lineNode = this.firstLineNode;
    for (int i = 0; i < this.Count; i++)
    {
     if(_lineNode.ID == id)
     {
      return _lineNode;
     } 
     else
     {
      _lineNode = _lineNode.Next;
     }
    }
    throw new IndexOutOfRangeException("未能在集合中找到該元素");
   }
  }

  LineNode firstLineNode;
  LineNode lastLineNode;
  public void Add(LineNode lineNode)
  {
   this.Count++;
   if(this.firstLineNode == null)
   {
    this.firstLineNode = lineNode;
   }
   else
   {
    if (this.firstLineNode.Next == null)
    {
     lineNode.Previous = this.firstLineNode;
     this.firstLineNode.Next = lineNode;
     this.lastLineNode = this.firstLineNode.Next;
    }
    else
    {
     lineNode.Previous = this.lastLineNode;
     this.lastLineNode.Next = lineNode;
     this.lastLineNode = this.lastLineNode.Next;
    }
   }
  }

  public int Count
  {
   private set;get;
  }

  public int IndexOf(string id)
  {
   LineNode _lineNode = this.firstLineNode;
   for (int i = 0; i < this.Count; i++)
   {
    if (_lineNode.ID == id)
    {
     return i;
    }
    else
    {
     _lineNode = _lineNode.Next;
    }
   }
   throw new IndexOutOfRangeException("未能在集合中找到該元素");
  }

  public void Clear()
  {
   this.firstLineNode = null;
   this.lastLineNode = null;
   this.Count = 0;
   this.GetEnumerator().Reset();
  }

  public void RemoveAt(int index)
  {
   if (this.Count < index) throw new InvalidOperationException("超出集合索引范圍");
   LineNode _currentLineNode = this[index];
   if (_currentLineNode.Previous == null)
   {
    _currentLineNode = _currentLineNode.Next;
    this.firstLineNode = _currentLineNode;
   }
   else 
   { 
    LineNode _lineNode = this.firstLineNode;
    for (int i = 0; i <= index - 1; i++)
    {
     if (i < index - 1)
     {
      _lineNode = _lineNode.Next;
      continue;
     }
     if (i == index - 1)
     {
      if (_currentLineNode.Next != null)
      {
       _lineNode.Next = _lineNode.Next.Next;
      }
      else
      {
       this.lastLineNode = _lineNode;
       _lineNode.Next = null;
      }
      break;
     }
    }
   }
   this.Count--;
  }

  public void Remove(string id)
  {
   int _index = this.IndexOf(id);
   this.RemoveAt(_index);
  }

  public LineNode TopLineNode { get { return this.firstLineNode; } }
  public LineNode LastLineNode { get { return this.lastLineNode; } }
 }

 class LineNodeEnumerator : IEnumerator<LineNode>
 {
  LineNode topLineNode;
  public LineNodeEnumerator(LineNode topLineNode)
  {
   this.topLineNode = topLineNode;
  }
  public LineNode Current
  {
   get
   {
    return this.lineNode;
   }
  }

  object IEnumerator.Current
  {
   get
   {
    return this.Current;
   }
  }

  public void Dispose()
  {
   this.lineNode = null;
  }

  LineNode lineNode;

  public bool MoveNext()
  {
   if(this.lineNode == null)
   {
    this.lineNode = this.topLineNode;
    if (this.lineNode == null) return false;
    if (this.lineNode.Next == null)
     return false;
    else
     return true;
   }
   else
   {
    if(this.lineNode.Next !=null)
    {
     this.lineNode = this.lineNode.Next;
     return true;
    }
    return false;
   }
  }

  public void Reset()
  {
   this.lineNode = null;
  }
 }


 class LineNode
 {
  public LineNode(string id)
  {
   this.ID = id;
  }
  public string ID { private set; get; }
  public string Name {set; get; }
  public LineNode Next { set; get; }
  public LineNode Previous { set; get; }
 }
}