// Parse reference. Assumes string begins with '[' character.
// Modify refmap if a reference is encountered.
// Return 0 if no reference found, otherwise position of subject
// after reference is parsed.
public static int ParseReference(Subject subj)
{
string title;
var startPos = subj.Position;
// parse label:
var lab = ParseReferenceLabel(subj);
if (lab == null || lab.Value.Length > Reference.MaximumReferenceLabelLength)
{
goto INVALID;
}
if (!Scanner.HasNonWhitespace(lab.Value))
{
goto INVALID;
}
// colon:
if (peek_char(subj) == ':')
{
subj.Position++;
}
else
{
goto INVALID;
}
// parse link url:
spnl(subj);
var matchlen = Scanner.scan_link_url(subj.Buffer, subj.Position, subj.Length);
if (matchlen == 0)
{
goto INVALID;
}
var url = subj.Buffer.Substring(subj.Position, matchlen);
url = CleanUrl(url);
subj.Position += matchlen;
// parse optional link_title
var beforetitle = subj.Position;
spnl(subj);
matchlen = Scanner.scan_link_title(subj.Buffer, subj.Position, subj.Length);
if (matchlen > 0)
{
title = subj.Buffer.Substring(subj.Position, matchlen);
title = CleanTitle(title);
subj.Position += matchlen;
}
else
{
subj.Position = beforetitle;
title = string.Empty;
}
// parse final spaces and newline:
while (peek_char(subj) == ' ')
{
subj.Position++;
}
if (peek_char(subj) == '\n')
{
subj.Position++;
}
else if (peek_char(subj) != '\0')
{
goto INVALID;
}
// insert reference into refmap
AddReference(subj.ReferenceMap, lab.Value, url, title);
return(subj.Position);
INVALID:
subj.Position = startPos;
return(0);
}
// Parse a link or the link portion of an image, or return a fallback.
static Reference ParseLinkDetails(Subject subj)
{
int n;
int sps;
int endlabel, starturl, endurl, starttitle, endtitle, endall;
string url, title;
endlabel = subj.Position;
var c = peek_char(subj);
if (c == '(' &&
((sps = Scanner.scan_spacechars(subj.Buffer, subj.Position + 1, subj.Length)) > -1) &&
((n = Scanner.scan_link_url(subj.Buffer, subj.Position + 1 + sps, subj.Length)) > -1))
{
// try to parse an explicit link:
starturl = subj.Position + 1 + sps; // after (
endurl = starturl + n;
starttitle = endurl + Scanner.scan_spacechars(subj.Buffer, endurl, subj.Length);
// ensure there are spaces btw url and title
endtitle = (starttitle == endurl) ? starttitle :
starttitle + Scanner.scan_link_title(subj.Buffer, starttitle, subj.Length);
endall = endtitle + Scanner.scan_spacechars(subj.Buffer, endtitle, subj.Length);
if (endall < subj.Length && subj.Buffer[endall] == ')')
{
subj.Position = endall + 1;
url = subj.Buffer.Substring(starturl, endurl - starturl);
url = CleanUrl(url);
title = subj.Buffer.Substring(starttitle, endtitle - starttitle);
title = CleanTitle(title);
return(new Reference()
{
Title = title, Url = url
});
}
}
else if (c == '[' || c == ' ' || c == '\n')
{
var label = ParseReferenceLabel(subj);
if (label != null)
{
if (label.Value.Length == 0)
{
return(Reference.SelfReference);
}
var details = LookupReference(subj.ReferenceMap, label.Value);
if (details != null)
{
return(details);
}
// rollback the subject but return InvalidReference so that the caller knows not to
// parse 'foo' from [foo][bar].
subj.Position = endlabel;
return(Reference.InvalidReference);
}
}
// rollback the subject position because didn't match anything.
subj.Position = endlabel;
return(null);
}
