From ea8dfc488069987834e0db3ef4443398b0bb4934 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Vytautas=20=C5=A0altenis?= <vytas@rtfb.lt>
Date: Mon, 29 Aug 2016 23:57:59 +0300
Subject: [PATCH] Move reference extraction to paragraph parser

Move reference and footnote extraction code from firstPass to a
paragraph block parser. This makes firstPass a little bit slimmer, ergo
closer to elimination.
---
 block.go    | 13 ++++++++++++-
 markdown.go | 10 +++++-----
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/block.go b/block.go
index 4a7df43..42bed26 100644
--- a/block.go
+++ b/block.go
@@ -1380,7 +1380,10 @@ func (p *parser) paragraph(data []byte) int {
 	// line: index of 1st char of current line
 	// i: index of cursor/end of current line
 	var prev, line, i int
-
+	tabSize := TabSizeDefault
+	if p.flags&TabSizeEight != 0 {
+		tabSize = TabSizeDouble
+	}
 	// keep going until we find something to mark the end of the paragraph
 	for i < len(data) {
 		// mark the beginning of the current line
@@ -1388,6 +1391,14 @@ func (p *parser) paragraph(data []byte) int {
 		current := data[i:]
 		line = i
 
+		// did we find a reference or a footnote? If so, end a paragraph
+		// preceding it and report that we have consumed up to the end of that
+		// reference:
+		if refEnd := isReference(p, current, tabSize); refEnd > 0 {
+			p.renderParagraph(data[:i])
+			return i + refEnd
+		}
+
 		// did we find a blank line marking the end of the paragraph?
 		if n := p.isEmpty(current); n > 0 {
 			// did this blank line followed by a definition list item?
diff --git a/markdown.go b/markdown.go
index 0bf1c12..13a18d3 100644
--- a/markdown.go
+++ b/markdown.go
@@ -453,7 +453,6 @@ func (p *parser) parseRefsToAST() {
 
 // first pass:
 // - normalize newlines
-// - extract references (outside of fenced code blocks)
 // - expand tabs (outside of fenced code blocks)
 // - copy everything else
 func firstPass(p *parser, input []byte) []byte {
@@ -485,9 +484,6 @@ func firstPass(p *parser, input []byte) []byte {
 		if end > beg {
 			if end < lastFencedCodeBlockEnd { // Do not expand tabs while inside fenced code blocks.
 				out.Write(input[beg:end])
-			} else if refEnd := isReference(p, input[beg:], tabSize); refEnd > 0 {
-				beg += refEnd
-				continue
 			} else {
 				expandTabs(&out, input[beg:end], tabSize)
 			}
@@ -593,7 +589,11 @@ func isReference(p *parser, data []byte, tabSize int) int {
 		return 0
 	}
 	idEnd := i
-
+	// footnotes can have empty ID, like this: [^], but a reference can not be
+	// empty like this: []. Break early if it's not a footnote and there's no ID
+	if noteID == 0 && idOffset == idEnd {
+		return 0
+	}
 	// spacer: colon (space | tab)* newline? (space | tab)*
 	i++
 	if i >= len(data) || data[i] != ':' {