Source Blocks

In order to extract the documentation from the code, LiterateCS needs to split a source file into blocks which represent either text or code. Blocks capture parts of a source file and make it easier to process them differently depending on their kind.

namespace LiterateCS
{
using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using ExtensionCord;


Block Kinds

A block can capture either documentation written in markdown or C# code. The enumeration below indicates which one we are dealing with.

	public enum BlockKind { Markdown, Code }


The block data structure itself is a simple singly-linked list. It implements IEnumerable<T> to make traversing the structure easier.

	public class BlockList : IEnumerable<BlockList>
{


The properties below describe the data associated with a block. Kind tells the whether it is a code or text block. Contents is the part of the source file that was extracted. Comment delimiters are excluded from the text, so that contents is valid markdown. Next points to the following block. Obviously code blocks are in the same order as they appear in the source file.

		public BlockKind Kind { get; private set; }
public string Contents { get; private set; }
public BlockList Next { get; internal set; }


The following constants describe how the code blocks are decorated in the outputted markdown or HTML. In the case of markdown output, the code blocks are surrounded by standard triple backticks followed by the language designator. In HTML output the header and footer contain tags which have the required CSS classes in order for the syntax highlighting to work.

		private const string _mdCodeHeader = @" csharp";
private const string _mdCodeFooter = @"";
private const string _htmlCodeHeader = @"<pre class=""csharp""><code class=""csharp"">";
private const string _htmlCodeFooter = @"</code></pre>";


The string builder is used to construct contents of a block. It is discarded after its content is extracted.

		internal StringBuilder _builder;


Creating a Block

Blocks are constructed dynamically as the source file is parsed. When creating a new block only the kind of the block and the output format needs to be specified. Based on those the constructor initializes a new block and inserts a correct header to it.

In markdown output whitespace is a bit more important than in HTML. That is why we sometimes need to add additional line breaks to the output.

		public BlockList (BlockKind kind, OutputFormat format)
{
Kind = kind;
_builder = new StringBuilder ();
}


Create a new markdown block.

		public BlockList (string contents)
{
Kind = BlockKind.Markdown;
Contents = contents;
}


Cloning a single block.

		public BlockList (BlockList block)
{
Kind = block.Kind;
Contents = block.Contents;
}


Closing a Block

After a block is filled with its content it can be closed. Closing involves adding the correct header and footer to the output. Code blocks are trimmed before these are added. If they do not contain any text after trimming, then we don't add the header and footer at all. After the StringBuilder object has converted the contents to string, it can be disposed by assigning null to the field.

		public void Close (OutputFormat format)
{
if (Kind == BlockKind.Code)
{
TrimStart ();
TrimEnd ();
if (_builder.Length > 0)
{
_builder.Insert (0, format == OutputFormat.html ?
_builder.Append (Environment.NewLine);
_builder.AppendLine (format == OutputFormat.html ?
_htmlCodeFooter :
_mdCodeFooter);
}
}
Contents = _builder.ToString ();
_builder = null;
}


Code blocks are trimmed to get rid of extra white space at the beginning and end of them. This makes the verbatim output more compact and readable. The following methods trim all whitespace from the beginning and from the end of the block. Note that we don't remove the whitespace before the first non-empty line, so indentation is preserved.

		private void TrimStart ()
{
while (RemoveFirstEmptyLine ());
}

private void TrimEnd ()
{
var last = _builder.Length - 1;
var i = last;
while (i >= 0 && char.IsWhiteSpace (_builder[i]))
i--;
if (i < last)
_builder.Remove (i + 1, last - i);
}


The method below removes the first line of a block, if it contains just whitespace. It handles both Windows and Unix style line delimiters. The method returns true, if it removed a line, and false if it did not.

		private bool RemoveFirstEmptyLine ()
{
var i = 0;
while (i < _builder.Length && char.IsWhiteSpace (_builder[i]) &&
!_builder[i].In ('\r', '\n'))
i++;
if (i == _builder.Length || !_builder[i].In ('\r', '\n'))
return false;
_builder.Remove (0, i + 1);
return true;
}


IEnumerable Implementation

Iterator is used to implement IEnumerable<BlockList> interface.

		public IEnumerator<BlockList> GetEnumerator ()
{
for (var block = this; block != null; block = block.Next)
yield return block;
}

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