// Inspired by https://github.com/naokazuterada/MarkdownTOC
// http://pandoc.org/MANUAL.html#extension-auto_identifiers
// Auto-identifiers from Markdig project makes this easier
public static string GenerateToc(this string html)
{
int startOfToc = html.IndexOf("<!-- MarkdownTOC -->");
int endOfToc = html.IndexOf("<!-- /MarkdownTOC -->");
if ((startOfToc < 0) || (endOfToc < 0))
{
return(html);
}
startOfToc = startOfToc + 20;
//HeadingItemCollection coll = new HeadingItemCollection();
//coll.Add("Heading 1", 1);
//coll.Add("Heading 2", 2);
//coll.Add("Heading 3", 3);
//coll.Add("Test 4", 3);
//coll.Add("Test 5", 2);
// Headings before MarkdownTOC tags will be ignored. (You know, the one that says "Table of Contents" <G>)
HeadingItemCollection coll = BuildHeadingCollection(html.Substring(endOfToc + 21));
string insert = FormatToc(coll);
string newHtml = html.Substring(0, startOfToc) + "\n" + insert + "\n" + html.Substring(endOfToc);
return(newHtml);
}
private static HeadingItemCollection BuildHeadingCollection(string html)
{
HeadingItemCollection coll = new HeadingItemCollection();
string[] lines = html.Split('\n');
int level = 1;
string text = string.Empty;
foreach (string str in lines)
{
level = 0;
if (!string.IsNullOrEmpty(str))
{
// there may be "better" ways, but since we are only looking for H1 .. H6, I'm hard coding
if (str.StartsWith("# "))
{
level = 1;
}
else if (str.StartsWith("## "))
{
level = 2;
}
else if (str.StartsWith("### "))
{
level = 3;
}
else if (str.StartsWith("#### "))
{
level = 4;
}
else if (str.StartsWith("##### "))
{
level = 5;
}
else if (str.StartsWith("###### "))
{
level = 6;
}
text = str.Substring(level + 1);
if (level > 0)
{
coll.Add(text, level);
}
}
}
return(coll);
}
private static string FormatToc(HeadingItemCollection coll)
{
StringBuilder sb = new StringBuilder();
int indentLevel = 0;
string indentSpaces = string.Empty;
foreach (HeadingItem hi in coll)
{
indentLevel = hi.Level - 1;
indentSpaces = new string(' ', indentLevel * 4);
sb.AppendFormat("{0}- [{1}]\n", indentSpaces, hi.Text);
}
//sb.AppendLine("- Heading 1");
//sb.AppendLine(" - Heading 2");
return(sb.ToString());
}