Refactor markdown attention render (#29984)

Follow #29833 and add tests

modules/markup/markdown/transform_blockquote.go

@@ -0,0 +1,67 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markdown
+
+import (
+	"strings"
+
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/text"
+	"golang.org/x/text/cases"
+	"golang.org/x/text/language"
+)
+
+func (g *ASTTransformer) transformBlockquote(v *ast.Blockquote, reader text.Reader) (ast.WalkStatus, error) {
+	// We only want attention blockquotes when the AST looks like:
+	// > Text("[") Text("!TYPE") Text("]")
+
+	// grab these nodes and make sure we adhere to the attention blockquote structure
+	firstParagraph := v.FirstChild()
+	g.applyElementDir(firstParagraph)
+	if firstParagraph.ChildCount() < 3 {
+		return ast.WalkContinue, nil
+	}
+	node1, ok1 := firstParagraph.FirstChild().(*ast.Text)
+	node2, ok2 := node1.NextSibling().(*ast.Text)
+	node3, ok3 := node2.NextSibling().(*ast.Text)
+	if !ok1 || !ok2 || !ok3 {
+		return ast.WalkContinue, nil
+	}
+	val1 := string(node1.Segment.Value(reader.Source()))
+	val2 := string(node2.Segment.Value(reader.Source()))
+	val3 := string(node3.Segment.Value(reader.Source()))
+	if val1 != "[" || val3 != "]" || !strings.HasPrefix(val2, "!") {
+		return ast.WalkContinue, nil
+	}
+
+	// grab attention type from markdown source
+	attentionType := strings.ToLower(val2[1:])
+	if !g.AttentionTypes.Contains(attentionType) {
+		return ast.WalkContinue, nil
+	}
+
+	// color the blockquote
+	v.SetAttributeString("class", []byte("attention-header attention-"+attentionType))
+
+	// create an emphasis to make it bold
+	attentionParagraph := ast.NewParagraph()
+	g.applyElementDir(attentionParagraph)
+	emphasis := ast.NewEmphasis(2)
+	emphasis.SetAttributeString("class", []byte("attention-"+attentionType))
+
+	attentionAstString := ast.NewString([]byte(cases.Title(language.English).String(attentionType)))
+
+	// replace the ![TYPE] with a dedicated paragraph of icon+Type
+	emphasis.AppendChild(emphasis, attentionAstString)
+	attentionParagraph.AppendChild(attentionParagraph, NewAttention(attentionType))
+	attentionParagraph.AppendChild(attentionParagraph, emphasis)
+	firstParagraph.Parent().InsertBefore(firstParagraph.Parent(), firstParagraph, attentionParagraph)
+	firstParagraph.RemoveChild(firstParagraph, node1)
+	firstParagraph.RemoveChild(firstParagraph, node2)
+	firstParagraph.RemoveChild(firstParagraph, node3)
+	if firstParagraph.ChildCount() == 0 {
+		firstParagraph.Parent().RemoveChild(firstParagraph.Parent(), firstParagraph)
+	}
+	return ast.WalkContinue, nil
+}