/// <summary>
/// Attempts to parse a markdown link e.g. "[](http://www.reddit.com)".
/// </summary>
/// <param name="markdown"> The markdown text. </param>
/// <param name="start"> The location to start parsing. </param>
/// <param name="maxEnd"> The location to stop parsing. </param>
/// <returns> A parsed markdown link, or <c>null</c> if this is not a markdown link. </returns>
internal static Helpers.Common.InlineParseResult Parse(string markdown, int start, int maxEnd)
{
// Expect a '[' character.
if (start == maxEnd || markdown[start] != '[')
{
return(null);
}
// Find the ']' character, keeping in mind that [test [0-9]](http://www.test.com) is allowed.
int linkTextOpen = start + 1;
int pos = linkTextOpen;
int linkTextClose;
int openSquareBracketCount = 0;
while (true)
{
linkTextClose = markdown.IndexOfAny(new char[] { '[', ']' }, pos, maxEnd - pos);
if (linkTextClose == -1)
{
return(null);
}
if (markdown[linkTextClose] == '[')
{
openSquareBracketCount++;
}
else if (openSquareBracketCount > 0)
{
openSquareBracketCount--;
}
else
{
break;
}
pos = linkTextClose + 1;
}
// Skip whitespace.
pos = linkTextClose + 1;
while (pos < maxEnd && Helpers.Common.IsWhiteSpace(markdown[pos]))
{
pos++;
}
if (pos == maxEnd)
{
return(null);
}
// Expect the '(' character or the '[' character.
int linkOpen = pos;
if (markdown[pos] == '(')
{
// Skip whitespace.
linkOpen++;
while (linkOpen < maxEnd && Helpers.Common.IsWhiteSpace(markdown[linkOpen]))
{
linkOpen++;
}
// Find the ')' character.
pos = linkOpen;
int linkClose = -1;
var openParenthesis = 0;
while (pos < maxEnd)
{
if (markdown[pos] == ')')
{
if (openParenthesis == 0)
{
linkClose = pos;
break;
}
else
{
openParenthesis--;
}
}
if (markdown[pos] == '(')
{
openParenthesis++;
}
pos++;
}
if (pos >= maxEnd)
{
return(null);
}
int end = linkClose + 1;
// Skip whitespace backwards.
while (linkClose > linkOpen && Helpers.Common.IsWhiteSpace(markdown[linkClose - 1]))
{
linkClose--;
}
// If there is no text whatsoever, then this is not a valid link.
if (linkOpen == linkClose)
{
return(null);
}
// Check if there is tooltip text.
string url;
string tooltip = null;
bool lastUrlCharIsDoubleQuote = markdown[linkClose - 1] == '"';
int tooltipStart = Helpers.Common.IndexOf(markdown, " \"", linkOpen, linkClose - 1);
if (tooltipStart == linkOpen)
{
return(null);
}
if (lastUrlCharIsDoubleQuote && tooltipStart != -1)
{
// Extract the URL (resolving any escape sequences).
url = TextRunInline.ResolveEscapeSequences(markdown, linkOpen, tooltipStart).TrimEnd(' ', '\t', '\r', '\n');
tooltip = markdown.Substring(tooltipStart + 2, (linkClose - 1) - (tooltipStart + 2));
}
else
{
// Extract the URL (resolving any escape sequences).
url = TextRunInline.ResolveEscapeSequences(markdown, linkOpen, linkClose);
}
// Check the URL is okay.
if (!IsUrlValid(url))
{
return(null);
}
// We found a regular stand-alone link.
var result = new MarkdownLinkInline();
result.Inlines = Helpers.Common.ParseInlineChildren(markdown, linkTextOpen, linkTextClose, ignoreLinks: true);
result.Url = url.Replace(" ", "%20");
result.Tooltip = tooltip;
return(new Helpers.Common.InlineParseResult(result, start, end));
}
else if (markdown[pos] == '[')
{
// Find the ']' character.
int linkClose = Helpers.Common.IndexOf(markdown, ']', pos + 1, maxEnd);
if (linkClose == -1)
{
return(null);
}
// We found a reference-style link.
var result = new MarkdownLinkInline();
result.Inlines = Helpers.Common.ParseInlineChildren(markdown, linkTextOpen, linkTextClose, ignoreLinks: true);
result.ReferenceId = markdown.Substring(linkOpen + 1, linkClose - (linkOpen + 1));
if (result.ReferenceId == string.Empty)
{
result.ReferenceId = markdown.Substring(linkTextOpen, linkTextClose - linkTextOpen);
}
return(new Helpers.Common.InlineParseResult(result, start, linkClose + 1));
}
return(null);
}
/// <summary>
/// Attempts to parse an image e.g. "".
/// </summary>
/// <param name="markdown"> The markdown text. </param>
/// <param name="start"> The location to start parsing. </param>
/// <param name="end"> The location to stop parsing. </param>
/// <returns> A parsed markdown image, or <c>null</c> if this is not a markdown image. </returns>
internal static Helpers.Common.InlineParseResult Parse(string markdown, int start, int end)
{
// Expect a '!' character.
if (start >= end || markdown[start] != '!')
{
return(null);
}
int pos = start + 1;
// Then a '[' character
if (pos >= end || markdown[pos] != '[')
{
return(null);
}
pos++;
// Find the ']' character
while (pos < end)
{
if (markdown[pos] == ']')
{
break;
}
pos++;
}
if (pos == end)
{
return(null);
}
// Extract the alt.
string tooltip = markdown.Substring(start + 2, pos - (start + 2));
// Expect the '(' character.
pos++;
if (pos == end || markdown[pos] != '(')
{
return(null);
}
// Skip whitespace
pos++;
while (pos < end && Helpers.Common.IsWhiteSpace(markdown[pos]))
{
pos++;
}
if (pos == end)
{
return(null);
}
// Extract the URL.
int urlStart = pos;
while (pos < end && markdown[pos] != ')')
{
pos++;
}
string url = TextRunInline.ResolveEscapeSequences(markdown, urlStart, pos);
// We found something!
var result = new ImageInline
{
Tooltip = tooltip,
Url = url,
Text = markdown.Substring(start, pos + 1 - start),
};
return(new Helpers.Common.InlineParseResult(result, start, end));
}