Transformalizing NorthWind

//===============================================================================
// Microsoft patterns & practices Enterprise Library
// Core
//===============================================================================
// Copyright © Microsoft Corporation.  All rights reserved.
// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY
// OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT
// LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
// FITNESS FOR A PARTICULAR PURPOSE.
//===============================================================================

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

namespace Transformalize.Libs.EnterpriseLibrary.Common
{
    /// <summary>
    /// This class provides an engine to process a string that contains
    /// replacement tokens of the form "{token}" and replace them with
    /// calculated value later.
    /// </summary>
    public class ReplacementFormatter
    {
        private List<ReplacementToken> tokens = new List<ReplacementToken>();

        /// <summary>
        /// Create a new <see cref="ReplacementFormatter"/>.
        /// </summary>
        public ReplacementFormatter()
        {
        }

        /// <summary>
        /// Create a new <see cref="ReplacementFormatter"/>.
        /// </summary>
        /// <param name="tokens">List of tokens to replace.</param>
        public ReplacementFormatter(params ReplacementToken[] tokens)
        {
            AddRange(tokens);
        }
        
        /// <summary>
        /// Create a new <see cref="ReplacementFormatter"/>.
        /// </summary>
        /// <param name="tokens">List of tokens to replace.</param>
        public ReplacementFormatter(IEnumerable<ReplacementToken> tokens)
        {
            AddRange(tokens);
        }

        /// <summary>
        /// Add a new set of replacement tokens.
        /// </summary>
        /// <param name="tokens">Tokens to add to the list.</param>
        public void Add(params ReplacementToken[] tokens)
        {
            AddRange(tokens);    
        }

        /// <summary>
        /// Add new tokens to the set of replacements.
        /// </summary>
        /// <param name="tokens">Tokens to add to the list.</param>
        public void AddRange(IEnumerable<ReplacementToken> tokens)
        {
            this.tokens.AddRange(tokens);
        }

        /// <summary>
        /// Format the given template, replacing any tokens present.
        /// </summary>
        /// <param name="template">The string to format, containing the replacement tokens.</param>
        /// <returns>The formatted string, with tokens replaced.</returns>
        public string Format(string template)
        {
            StringBuilder templateBuilder = new StringBuilder(template);
            // Escape literal backslash
            templateBuilder.Replace(@"\\", @"\\.");
            // Escape the \{ sequence
            templateBuilder.Replace(@"\{", @"\{.");
            foreach(ReplacementToken token in tokens)
            {
                token.ReplaceToken(templateBuilder);
            }
            templateBuilder.Replace(@"\{.", "{");
            templateBuilder.Replace(@"\\.", @"\");
            return templateBuilder.ToString();
        }
    }

    /// <summary>
    /// A single replacement token used by the <see cref="ReplacementFormatter"/>. A
    /// token consists of two things:
    /// <list type="bullet">
    /// <item><description>The actual text of the token (including the {})</description></item>
    /// <item><description>A delegate to retrieve the value to replace the token.</description></item>
    /// </list>
    /// </summary>
    public class ReplacementToken
    {
        private string token;
        private ReplacementTextDelegate getReplacementText;

        /// <summary>
        /// Create a new <see cref="ReplacementToken"/>.
        /// </summary>
        /// <param name="token">The string marking where the token should be replaced.</param>
        /// <param name="getReplacementText">Delegate to return the value that replaces the token.</param>
        public ReplacementToken(string token, ReplacementTextDelegate getReplacementText)
        {
            this.token = token;
            this.getReplacementText = getReplacementText;
        }

        /// <summary>
        /// The token string.
        /// </summary>
        /// <value>The token string.</value>
        public string Token
        {
            get { return token; }
        }

        /// <summary>
        /// The text to replace this token with.
        /// </summary>
        /// <value>Replacement text.</value>
        public string ReplacementText
        {
            get { return getReplacementText(); }
        }

        /// <summary>
        /// Replace this token in the given stringbuilder.
        /// </summary>
        /// <param name="sb"><see cref="StringBuilder"/> holding the template to perform the token replacement on.</param>
        public void ReplaceToken(StringBuilder sb)
        {
            if (sb == null) throw new ArgumentNullException("sb");

            sb.Replace(token, ReplacementText);
        }
    }

    /// <summary>
    /// Delegate type giving a function that returns the replacement text for a token.
    /// </summary>
    /// <returns>The replacement text.</returns>
    public delegate string ReplacementTextDelegate();
}