Run processors on whole of text (#16155)

There is an inefficiency in the design of our processors which means that Emoji
and other processors run in order n^2 time.

This PR forces the processors to process the entirety of text node before passing
back up. The fundamental inefficiency remains but it should be significantly
ameliorated.

Signed-off-by: Andrew Thornton <art27@cantab.net>

modules/emoji/emoji.go

@@ -6,6 +6,7 @@
 package emoji
 
 import (
+	"io"
 	"sort"
 	"strings"
 	"sync"
@@ -145,6 +146,8 @@ func (n *rememberSecondWriteWriter) Write(p []byte) (int, error) {
 	if n.writecount == 2 {
 		n.idx = n.pos
 		n.end = n.pos + len(p)
+		n.pos += len(p)
+		return len(p), io.EOF
 	}
 	n.pos += len(p)
 	return len(p), nil
@@ -155,6 +158,8 @@ func (n *rememberSecondWriteWriter) WriteString(s string) (int, error) {
 	if n.writecount == 2 {
 		n.idx = n.pos
 		n.end = n.pos + len(s)
+		n.pos += len(s)
+		return len(s), io.EOF
 	}
 	n.pos += len(s)
 	return len(s), nil

modules/markup/html.go

@@ -89,6 +89,7 @@ func isLinkStr(link string) bool {
 	return validLinksPattern.MatchString(link)
 }
 
+// FIXME: This function is not concurrent safe
 func getIssueFullPattern() *regexp.Regexp {
 	if issueFullPattern == nil {
 		issueFullPattern = regexp.MustCompile(regexp.QuoteMeta(setting.AppURL) +
@@ -566,11 +567,16 @@ func replaceContentList(node *html.Node, i, j int, newNodes []*html.Node) {
 }
 
 func mentionProcessor(ctx *RenderContext, node *html.Node) {
+	start := 0
+	next := node.NextSibling
+	for node != nil && node != next && start < len(node.Data) {
 		// We replace only the first mention; other mentions will be addressed later
-	found, loc := references.FindFirstMentionBytes([]byte(node.Data))
+		found, loc := references.FindFirstMentionBytes([]byte(node.Data[start:]))
 		if !found {
 			return
 		}
+		loc.Start += start
+		loc.End += start
 		mention := node.Data[loc.Start:loc.End]
 		var teams string
 		teams, ok := ctx.Metas["teams"]
@@ -582,10 +588,17 @@ func mentionProcessor(ctx *RenderContext, node *html.Node) {
 			mentionOrgAndTeam := strings.Split(mention, "/")
 			if mentionOrgAndTeam[0][1:] == ctx.Metas["org"] && strings.Contains(teams, ","+strings.ToLower(mentionOrgAndTeam[1])+",") {
 				replaceContent(node, loc.Start, loc.End, createLink(util.URLJoin(setting.AppURL, "org", ctx.Metas["org"], "teams", mentionOrgAndTeam[1]), mention, "mention"))
+				node = node.NextSibling.NextSibling
+				start = 0
+				continue
 			}
-		return
+			start = loc.End
+			continue
 		}
 		replaceContent(node, loc.Start, loc.End, createLink(util.URLJoin(setting.AppURL, mention[1:]), mention, "mention"))
+		node = node.NextSibling.NextSibling
+		start = 0
+	}
 }
 
 func shortLinkProcessor(ctx *RenderContext, node *html.Node) {
@@ -593,6 +606,8 @@ func shortLinkProcessor(ctx *RenderContext, node *html.Node) {
 }
 
 func shortLinkProcessorFull(ctx *RenderContext, node *html.Node, noLink bool) {
+	next := node.NextSibling
+	for node != nil && node != next {
 		m := shortLinkPattern.FindStringSubmatchIndex(node.Data)
 		if m == nil {
 			return
@@ -672,7 +687,7 @@ func shortLinkProcessorFull(ctx *RenderContext, node *html.Node, noLink bool) {
 		switch ext := filepath.Ext(link); ext {
 		// fast path: empty string, ignore
 		case "":
-		break
+			// leave image as false
 		case ".jpg", ".jpeg", ".png", ".tif", ".tiff", ".webp", ".gif", ".bmp", ".ico", ".svg":
 			image = true
 		}
@@ -748,12 +763,17 @@ func shortLinkProcessorFull(ctx *RenderContext, node *html.Node, noLink bool) {
 			linkNode.Attr = []html.Attribute{{Key: "href", Val: link}}
 		}
 		replaceContent(node, m[0], m[1], linkNode)
+		node = node.NextSibling.NextSibling
+	}
 }
 
 func fullIssuePatternProcessor(ctx *RenderContext, node *html.Node) {
 	if ctx.Metas == nil {
 		return
 	}
+
+	next := node.NextSibling
+	for node != nil && node != next {
 		m := getIssueFullPattern().FindStringSubmatchIndex(node.Data)
 		if m == nil {
 			return
@@ -771,23 +791,25 @@ func fullIssuePatternProcessor(ctx *RenderContext, node *html.Node) {
 			// TODO if m[4]:m[5] is not nil, then link is to a comment,
 			// and we should indicate that in the text somehow
 			replaceContent(node, m[0], m[1], createLink(link, id, "ref-issue"))
-
 		} else {
 			orgRepoID := matchOrg + "/" + matchRepo + id
 			replaceContent(node, m[0], m[1], createLink(link, orgRepoID, "ref-issue"))
 		}
+		node = node.NextSibling.NextSibling
+	}
 }
 
 func issueIndexPatternProcessor(ctx *RenderContext, node *html.Node) {
 	if ctx.Metas == nil {
 		return
 	}
-
 	var (
 		found bool
 		ref   *references.RenderizableReference
 	)
 
+	next := node.NextSibling
+	for node != nil && node != next {
 		_, exttrack := ctx.Metas["format"]
 		alphanum := ctx.Metas["style"] == IssueNameStyleAlphanumeric
 
@@ -828,7 +850,8 @@ func issueIndexPatternProcessor(ctx *RenderContext, node *html.Node) {
 
 		if ref.Action == references.XRefActionNone {
 			replaceContent(node, ref.RefLocation.Start, ref.RefLocation.End, link)
-		return
+			node = node.NextSibling.NextSibling
+			continue
 		}
 
 		// Decorate action keywords if actionable
@@ -846,6 +869,8 @@ func issueIndexPatternProcessor(ctx *RenderContext, node *html.Node) {
 			Data: node.Data[ref.ActionLocation.End:ref.RefLocation.Start],
 		}
 		replaceContentList(node, ref.ActionLocation.Start, ref.RefLocation.End, []*html.Node{keyword, spaces, link})
+		node = node.NextSibling.NextSibling.NextSibling.NextSibling
+	}
 }
 
 // fullSha1PatternProcessor renders SHA containing URLs
@@ -853,6 +878,9 @@ func fullSha1PatternProcessor(ctx *RenderContext, node *html.Node) {
 	if ctx.Metas == nil {
 		return
 	}
+
+	next := node.NextSibling
+	for node != nil && node != next {
 		m := anySHA1Pattern.FindStringSubmatchIndex(node.Data)
 		if m == nil {
 			return
@@ -897,14 +925,23 @@ func fullSha1PatternProcessor(ctx *RenderContext, node *html.Node) {
 		}
 
 		replaceContent(node, start, end, createCodeLink(urlFull, text, "commit"))
+		node = node.NextSibling.NextSibling
+	}
 }
 
 // emojiShortCodeProcessor for rendering text like :smile: into emoji
 func emojiShortCodeProcessor(ctx *RenderContext, node *html.Node) {
-	m := EmojiShortCodeRegex.FindStringSubmatchIndex(node.Data)
+	start := 0
+	next := node.NextSibling
+	for node != nil && node != next && start < len(node.Data) {
+		m := EmojiShortCodeRegex.FindStringSubmatchIndex(node.Data[start:])
 		if m == nil {
 			return
 		}
+		m[0] += start
+		m[1] += start
+
+		start = m[1]
 
 		alias := node.Data[m[0]:m[1]]
 		alias = strings.ReplaceAll(alias, ":", "")
@@ -914,25 +951,39 @@ func emojiShortCodeProcessor(ctx *RenderContext, node *html.Node) {
 			s := strings.Join(setting.UI.Reactions, " ") + "gitea"
 			if strings.Contains(s, alias) {
 				replaceContent(node, m[0], m[1], createCustomEmoji(alias, "emoji"))
-			return
+				node = node.NextSibling.NextSibling
+				start = 0
+				continue
 			}
-		return
+			continue
 		}
 
 		replaceContent(node, m[0], m[1], createEmoji(converted.Emoji, "emoji", converted.Description))
+		node = node.NextSibling.NextSibling
+		start = 0
+	}
 }
 
 // emoji processor to match emoji and add emoji class
 func emojiProcessor(ctx *RenderContext, node *html.Node) {
-	m := emoji.FindEmojiSubmatchIndex(node.Data)
+	start := 0
+	next := node.NextSibling
+	for node != nil && node != next && start < len(node.Data) {
+		m := emoji.FindEmojiSubmatchIndex(node.Data[start:])
 		if m == nil {
 			return
 		}
+		m[0] += start
+		m[1] += start
 
 		codepoint := node.Data[m[0]:m[1]]
+		start = m[1]
 		val := emoji.FromCode(codepoint)
 		if val != nil {
 			replaceContent(node, m[0], m[1], createEmoji(codepoint, "emoji", val.Description))
+			node = node.NextSibling.NextSibling
+			start = 0
+		}
 	}
 }
 
@@ -942,10 +993,17 @@ func sha1CurrentPatternProcessor(ctx *RenderContext, node *html.Node) {
 	if ctx.Metas == nil || ctx.Metas["user"] == "" || ctx.Metas["repo"] == "" || ctx.Metas["repoPath"] == "" {
 		return
 	}
-	m := sha1CurrentPattern.FindStringSubmatchIndex(node.Data)
+
+	start := 0
+	next := node.NextSibling
+	for node != nil && node != next && start < len(node.Data) {
+		m := sha1CurrentPattern.FindStringSubmatchIndex(node.Data[start:])
 		if m == nil {
 			return
 		}
+		m[2] += start
+		m[3] += start
+
 		hash := node.Data[m[2]:m[3]]
 		// The regex does not lie, it matches the hash pattern.
 		// However, a regex cannot know if a hash actually exists or not.
@@ -959,32 +1017,46 @@ func sha1CurrentPatternProcessor(ctx *RenderContext, node *html.Node) {
 			if !strings.Contains(err.Error(), "fatal: Needed a single revision") {
 				log.Debug("sha1CurrentPatternProcessor git rev-parse: %v", err)
 			}
-		return
+			start = m[3]
+			continue
 		}
 
 		replaceContent(node, m[2], m[3],
 			createCodeLink(util.URLJoin(setting.AppURL, ctx.Metas["user"], ctx.Metas["repo"], "commit", hash), base.ShortSha(hash), "commit"))
+		start = 0
+		node = node.NextSibling.NextSibling
+	}
 }
 
 // emailAddressProcessor replaces raw email addresses with a mailto: link.
 func emailAddressProcessor(ctx *RenderContext, node *html.Node) {
+	next := node.NextSibling
+	for node != nil && node != next {
 		m := emailRegex.FindStringSubmatchIndex(node.Data)
 		if m == nil {
 			return
 		}
+
 		mail := node.Data[m[2]:m[3]]
 		replaceContent(node, m[2], m[3], createLink("mailto:"+mail, mail, "mailto"))
+		node = node.NextSibling.NextSibling
+	}
 }
 
 // linkProcessor creates links for any HTTP or HTTPS URL not captured by
 // markdown.
 func linkProcessor(ctx *RenderContext, node *html.Node) {
+	next := node.NextSibling
+	for node != nil && node != next {
 		m := common.LinkRegex.FindStringIndex(node.Data)
 		if m == nil {
 			return
 		}
+
 		uri := node.Data[m[0]:m[1]]
 		replaceContent(node, m[0], m[1], createLink(uri, uri, "link"))
+		node = node.NextSibling.NextSibling
+	}
 }
 
 func genDefaultLinkProcessor(defaultLink string) processor {
@@ -1008,12 +1080,17 @@ func genDefaultLinkProcessor(defaultLink string) processor {
 
 // descriptionLinkProcessor creates links for DescriptionHTML
 func descriptionLinkProcessor(ctx *RenderContext, node *html.Node) {
+	next := node.NextSibling
+	for node != nil && node != next {
 		m := common.LinkRegex.FindStringIndex(node.Data)
 		if m == nil {
 			return
 		}
+
 		uri := node.Data[m[0]:m[1]]
 		replaceContent(node, m[0], m[1], createDescriptionLink(uri, uri))
+		node = node.NextSibling.NextSibling
+	}
 }
 
 func createDescriptionLink(href, content string) *html.Node {

modules/markup/html_test.go

@@ -464,3 +464,19 @@ func TestIssue16020(t *testing.T) {
 	assert.NoError(t, err)
 	assert.Equal(t, data, res.String())
 }
+
+func BenchmarkEmojiPostprocess(b *testing.B) {
+	data := "🥰 "
+	for len(data) < 1<<16 {
+		data += data
+	}
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		var res strings.Builder
+		err := PostProcess(&RenderContext{
+			URLPrefix: "https://example.com",
+			Metas:     localMetas,
+		}, strings.NewReader(data), &res)
+		assert.NoError(b, err)
+	}
+}