StringBuilderPlus Improves Upon StringBuilder

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;


namespace Zigrem.Text
{

	/// <summary>
	/// Acts like a StringBuilder, with the added benefits that strings
	/// can be added to the beginning of the builder+ without a significant
	/// performance hit and a builder+ can be added to another builder+ without
	/// a significant performance hit.
	/// </summary>
	public partial class StringBuilderPlus
	{

		#region Delegates

		private delegate void AffixDelegate(IString str);

		#endregion


		#region Variables

		private LinkedList<IString> strings;
		private int length;

		#endregion


		#region Properties

		/// <summary>
		/// The strings this builder+ is composed of.
		/// </summary>
		private LinkedList<IString> Strings
		{
			get
			{
				return this.strings;
			}
			set
			{
				this.strings = value;
			}
		}


		/// <summary>
		/// Returns the string stored by this builder+.
		/// </summary>
		public string Value
		{
			get
			{
				string str;
				if (this.Strings.Count == 0)
				{
					str = null;
				}
				else
				{
					StringBuilder builder = this.ToBuilder();
					str = builder.ToString();
					this.Strings.Clear();
					this.Strings.AddLast(new PlainString(str));
				}
				return str;
			}
		}


		/// <summary>
		/// The length of the string stored by this builder+.
		/// </summary>
		public int Length
		{
			get
			{
				return this.length;
			}
			private set
			{
				this.length = value;
			}
		}

		#endregion


		#region Constructors

		/// <summary>
		/// Creates a builder+ that contains a null string.
		/// </summary>
		public StringBuilderPlus()
			: this(null as string)
		{
		}


		/// <summary>
		/// Creates a builder+ that contains the specified string.
		/// </summary>
		/// <param name="str">The initial string.</param>
		public StringBuilderPlus(string str)
		{
			this.Strings = new LinkedList<IString>();
			if (str == null)
			{
				this.Length = 0;
				
			}
			else
			{
				this.Suffix(str);
				this.Length = str.Length;
			}
		}

		#endregion


		#region Methods


		/// <summary>
		/// Adds the specified builder+ to the beginning of this builder+.
		/// </summary>
		/// <param name="builder">The builder+ to prefix.</param>
		public void Prefix(StringBuilderPlus builder)
		{
			this.Affix(builder, AffixType.Before);
		}


		/// <summary>
		/// Adds the specified builder+ to the end of this builder+.
		/// </summary>
		/// <param name="builder">The builder+ to suffix.</param>
		public void Suffix(StringBuilderPlus builder)
		{
			this.Affix(builder, AffixType.After);
		}


		/// <summary>
		/// Adds the specified string to the beginning of this builder+.
		/// </summary>
		/// <param name="str">The string to prefix.</param>
		public void Prefix(string str)
		{
			this.Affix(str, AffixType.Before);
		}


		/// <summary>
		/// Adds the specified string to the end of this builder=.
		/// </summary>
		/// <param name="str">The string to suffix.</param>
		public void Suffix(string str)
		{
			this.Affix(str, AffixType.After);
		}


		/// <summary>
		/// Affixes a string to the beginning or end of this builder+.
		/// </summary>
		/// <param name="str">The string to affix.</param>
		/// <param name="type">Prefix or suffix?</param>
		private void Affix(string str, AffixType type)
		{

			// Prefix or suffix?
			AffixDelegate affix;
			if (type == AffixType.Before)
			{
				affix = new AffixDelegate(delegate(IString val)
				{
					this.Strings.AddFirst(val);
				});
			}
			else
			{
				affix = new AffixDelegate(delegate(IString val)
				{
					this.Strings.AddLast(val);
				});
			}


			// Nulls and empties require special handling.
			if (str != null)
			{
				if (str == string.Empty)
				{

					// Optimization: avoid affixing empty strings.
					if (this.Strings.Count == 0)
					{
						affix(PlainString.Empty);
					}

				}
				else
				{
					affix(new PlainString(str));
				}
				this.Length = this.Length + str.Length;
			}

		}


		/// <summary>
		/// Affixes a builder+ to the beginning or end of this builder+.
		/// </summary>
		/// <param name="builder">The builder+ to affix.</param>
		/// <param name="type">Prefix or suffix?</param>
		private void Affix(StringBuilderPlus builder, AffixType type)
		{

			// Prefix or suffix?
			AffixDelegate affix;
			if (type == AffixType.Before)
			{
				affix = new AffixDelegate(delegate(IString val)
				{
					this.Strings.AddFirst(val);
				});
			}
			else
			{
				affix = new AffixDelegate(delegate(IString val)
				{
					this.Strings.AddLast(val);
				});
			}


			// Wrap collection and affix.
			if (builder != null && builder.Strings.Count > 0)
			{
				StringsWrapper wrapper = new StringsWrapper(builder.Strings, builder.Length);
				builder.Strings = new LinkedList<IString>();
				builder.Strings.AddLast(wrapper);
				affix(wrapper);
				this.Length = this.Length + builder.Length;
			}

		}


		/// <summary>
		/// Appends all the strings this builder+ contains to a string builder.
		/// </summary>
		/// <param name="builder">The string builder to append to.</param>
		public void AppendTo(StringBuilder builder)
		{
			foreach (IString str in this.Strings)
			{
				str.AppendTo(builder);
			}
		}


		/// <summary>
		/// Creates a string builder from this builder+.
		/// </summary>
		/// <returns>The string builder.</returns>
		public StringBuilder ToBuilder()
		{
			StringBuilder builder = new StringBuilder();
			this.AppendTo(builder);
			return builder;
		}


		/// <summary>
		/// Returns the string stored by this builder+.
		/// </summary>
		/// <returns>The string.</returns>
		public override string ToString()
		{
			return this.Value;
		}

		#endregion

	}

}