Improve template helper (#24417)

It seems that we really need the "context function" soon. So we should
clean up the helper functions first.

Major changes:

* Improve StringUtils and add JsonUtils
* Remove one-time-use helper functions like CompareLink
* Move other code (no change) to util_avatar/util_render/util_misc (no
need to propose changes for them)

I have tested the changed templates:


![image](https://user-images.githubusercontent.com/2114189/235283862-608dbf6b-2da3-4d06-8157-b523ca93edb4.png)


![image](https://user-images.githubusercontent.com/2114189/235283888-1dfc0471-e622-4d64-9d76-7859819580d3.png)


![image](https://user-images.githubusercontent.com/2114189/235283903-d559f14d-4abb-4a50-915f-2b9cbc381a7a.png)


![image](https://user-images.githubusercontent.com/2114189/235283955-b7b5adea-aca3-4758-b38a-3aae3f7c6048.png)

---------

Co-authored-by: Giteabot <teabot@gitea.io>

1 files changed, 254 insertions, 0 deletions

diff --git a/modules/templates/util_render.go b/modules/templates/util_render.go
new file mode 100644
index 0000000000..a59ddd3f17
--- /dev/null
+++ b/modules/templates/util_render.go
@@ -0,0 +1,254 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package templates
+
+import (
+	"context"
+	"encoding/hex"
+	"fmt"
+	"html/template"
+	"math"
+	"net/url"
+	"regexp"
+	"strings"
+	"unicode"
+
+	issues_model "code.gitea.io/gitea/models/issues"
+	"code.gitea.io/gitea/modules/emoji"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/markup"
+	"code.gitea.io/gitea/modules/markup/markdown"
+	"code.gitea.io/gitea/modules/setting"
+)
+
+// RenderCommitMessage renders commit message with XSS-safe and special links.
+func RenderCommitMessage(ctx context.Context, msg, urlPrefix string, metas map[string]string) template.HTML {
+	return RenderCommitMessageLink(ctx, msg, urlPrefix, "", metas)
+}
+
+// RenderCommitMessageLink renders commit message as a XXS-safe link to the provided
+// default url, handling for special links.
+func RenderCommitMessageLink(ctx context.Context, msg, urlPrefix, urlDefault string, metas map[string]string) template.HTML {
+	cleanMsg := template.HTMLEscapeString(msg)
+	// we can safely assume that it will not return any error, since there
+	// shouldn't be any special HTML.
+	fullMessage, err := markup.RenderCommitMessage(&markup.RenderContext{
+		Ctx:         ctx,
+		URLPrefix:   urlPrefix,
+		DefaultLink: urlDefault,
+		Metas:       metas,
+	}, cleanMsg)
+	if err != nil {
+		log.Error("RenderCommitMessage: %v", err)
+		return ""
+	}
+	msgLines := strings.Split(strings.TrimSpace(fullMessage), "\n")
+	if len(msgLines) == 0 {
+		return template.HTML("")
+	}
+	return template.HTML(msgLines[0])
+}
+
+// RenderCommitMessageLinkSubject renders commit message as a XXS-safe link to
+// the provided default url, handling for special links without email to links.
+func RenderCommitMessageLinkSubject(ctx context.Context, msg, urlPrefix, urlDefault string, metas map[string]string) template.HTML {
+	msgLine := strings.TrimLeftFunc(msg, unicode.IsSpace)
+	lineEnd := strings.IndexByte(msgLine, '\n')
+	if lineEnd > 0 {
+		msgLine = msgLine[:lineEnd]
+	}
+	msgLine = strings.TrimRightFunc(msgLine, unicode.IsSpace)
+	if len(msgLine) == 0 {
+		return template.HTML("")
+	}
+
+	// we can safely assume that it will not return any error, since there
+	// shouldn't be any special HTML.
+	renderedMessage, err := markup.RenderCommitMessageSubject(&markup.RenderContext{
+		Ctx:         ctx,
+		URLPrefix:   urlPrefix,
+		DefaultLink: urlDefault,
+		Metas:       metas,
+	}, template.HTMLEscapeString(msgLine))
+	if err != nil {
+		log.Error("RenderCommitMessageSubject: %v", err)
+		return template.HTML("")
+	}
+	return template.HTML(renderedMessage)
+}
+
+// RenderCommitBody extracts the body of a commit message without its title.
+func RenderCommitBody(ctx context.Context, msg, urlPrefix string, metas map[string]string) template.HTML {
+	msgLine := strings.TrimRightFunc(msg, unicode.IsSpace)
+	lineEnd := strings.IndexByte(msgLine, '\n')
+	if lineEnd > 0 {
+		msgLine = msgLine[lineEnd+1:]
+	} else {
+		return template.HTML("")
+	}
+	msgLine = strings.TrimLeftFunc(msgLine, unicode.IsSpace)
+	if len(msgLine) == 0 {
+		return template.HTML("")
+	}
+
+	renderedMessage, err := markup.RenderCommitMessage(&markup.RenderContext{
+		Ctx:       ctx,
+		URLPrefix: urlPrefix,
+		Metas:     metas,
+	}, template.HTMLEscapeString(msgLine))
+	if err != nil {
+		log.Error("RenderCommitMessage: %v", err)
+		return ""
+	}
+	return template.HTML(renderedMessage)
+}
+
+// Match text that is between back ticks.
+var codeMatcher = regexp.MustCompile("`([^`]+)`")
+
+// RenderCodeBlock renders "`…`" as highlighted "<code>" block.
+// Intended for issue and PR titles, these containers should have styles for "<code>" elements
+func RenderCodeBlock(htmlEscapedTextToRender template.HTML) template.HTML {
+	htmlWithCodeTags := codeMatcher.ReplaceAllString(string(htmlEscapedTextToRender), "<code>$1</code>") // replace with HTML <code> tags
+	return template.HTML(htmlWithCodeTags)
+}
+
+// RenderIssueTitle renders issue/pull title with defined post processors
+func RenderIssueTitle(ctx context.Context, text, urlPrefix string, metas map[string]string) template.HTML {
+	renderedText, err := markup.RenderIssueTitle(&markup.RenderContext{
+		Ctx:       ctx,
+		URLPrefix: urlPrefix,
+		Metas:     metas,
+	}, template.HTMLEscapeString(text))
+	if err != nil {
+		log.Error("RenderIssueTitle: %v", err)
+		return template.HTML("")
+	}
+	return template.HTML(renderedText)
+}
+
+// RenderLabel renders a label
+func RenderLabel(ctx context.Context, label *issues_model.Label) template.HTML {
+	labelScope := label.ExclusiveScope()
+
+	textColor := "#111"
+	if label.UseLightTextColor() {
+		textColor = "#eee"
+	}
+
+	description := emoji.ReplaceAliases(template.HTMLEscapeString(label.Description))
+
+	if labelScope == "" {
+		// Regular label
+		s := fmt.Sprintf("<div class='ui label' style='color: %s !important; background-color: %s !important' title='%s'>%s</div>",
+			textColor, label.Color, description, RenderEmoji(ctx, label.Name))
+		return template.HTML(s)
+	}
+
+	// Scoped label
+	scopeText := RenderEmoji(ctx, labelScope)
+	itemText := RenderEmoji(ctx, label.Name[len(labelScope)+1:])
+
+	itemColor := label.Color
+	scopeColor := label.Color
+	if r, g, b, err := label.ColorRGB(); err == nil {
+		// Make scope and item background colors slightly darker and lighter respectively.
+		// More contrast needed with higher luminance, empirically tweaked.
+		luminance := (0.299*r + 0.587*g + 0.114*b) / 255
+		contrast := 0.01 + luminance*0.03
+		// Ensure we add the same amount of contrast also near 0 and 1.
+		darken := contrast + math.Max(luminance+contrast-1.0, 0.0)
+		lighten := contrast + math.Max(contrast-luminance, 0.0)
+		// Compute factor to keep RGB values proportional.
+		darkenFactor := math.Max(luminance-darken, 0.0) / math.Max(luminance, 1.0/255.0)
+		lightenFactor := math.Min(luminance+lighten, 1.0) / math.Max(luminance, 1.0/255.0)
+
+		scopeBytes := []byte{
+			uint8(math.Min(math.Round(r*darkenFactor), 255)),
+			uint8(math.Min(math.Round(g*darkenFactor), 255)),
+			uint8(math.Min(math.Round(b*darkenFactor), 255)),
+		}
+		itemBytes := []byte{
+			uint8(math.Min(math.Round(r*lightenFactor), 255)),
+			uint8(math.Min(math.Round(g*lightenFactor), 255)),
+			uint8(math.Min(math.Round(b*lightenFactor), 255)),
+		}
+
+		itemColor = "#" + hex.EncodeToString(itemBytes)
+		scopeColor = "#" + hex.EncodeToString(scopeBytes)
+	}
+
+	s := fmt.Sprintf("<span class='ui label scope-parent' title='%s'>"+
+		"<div class='ui label scope-left' style='color: %s !important; background-color: %s !important'>%s</div>"+
+		"<div class='ui label scope-right' style='color: %s !important; background-color: %s !important''>%s</div>"+
+		"</span>",
+		description,
+		textColor, scopeColor, scopeText,
+		textColor, itemColor, itemText)
+	return template.HTML(s)
+}
+
+// RenderEmoji renders html text with emoji post processors
+func RenderEmoji(ctx context.Context, text string) template.HTML {
+	renderedText, err := markup.RenderEmoji(&markup.RenderContext{Ctx: ctx},
+		template.HTMLEscapeString(text))
+	if err != nil {
+		log.Error("RenderEmoji: %v", err)
+		return template.HTML("")
+	}
+	return template.HTML(renderedText)
+}
+
+// ReactionToEmoji renders emoji for use in reactions
+func ReactionToEmoji(reaction string) template.HTML {
+	val := emoji.FromCode(reaction)
+	if val != nil {
+		return template.HTML(val.Emoji)
+	}
+	val = emoji.FromAlias(reaction)
+	if val != nil {
+		return template.HTML(val.Emoji)
+	}
+	return template.HTML(fmt.Sprintf(`<img alt=":%s:" src="%s/assets/img/emoji/%s.png"></img>`, reaction, setting.StaticURLPrefix, url.PathEscape(reaction)))
+}
+
+// RenderNote renders the contents of a git-notes file as a commit message.
+func RenderNote(ctx context.Context, msg, urlPrefix string, metas map[string]string) template.HTML {
+	cleanMsg := template.HTMLEscapeString(msg)
+	fullMessage, err := markup.RenderCommitMessage(&markup.RenderContext{
+		Ctx:       ctx,
+		URLPrefix: urlPrefix,
+		Metas:     metas,
+	}, cleanMsg)
+	if err != nil {
+		log.Error("RenderNote: %v", err)
+		return ""
+	}
+	return template.HTML(fullMessage)
+}
+
+func RenderMarkdownToHtml(ctx context.Context, input string) template.HTML { //nolint:revive
+	output, err := markdown.RenderString(&markup.RenderContext{
+		Ctx:       ctx,
+		URLPrefix: setting.AppSubURL,
+	}, input)
+	if err != nil {
+		log.Error("RenderString: %v", err)
+	}
+	return template.HTML(output)
+}
+
+func RenderLabels(ctx context.Context, labels []*issues_model.Label, repoLink string) template.HTML {
+	htmlCode := `<span class="labels-list">`
+	for _, label := range labels {
+		// Protect against nil value in labels - shouldn't happen but would cause a panic if so
+		if label == nil {
+			continue
+		}
+		htmlCode += fmt.Sprintf("<a href='%s/issues?labels=%d'>%s</a> ",
+			repoLink, label.ID, RenderLabel(ctx, label))
+	}
+	htmlCode += "</span>"
+	return template.HTML(htmlCode)
+}