package render

import ( "html"

"github.com/yuin/goldmark/ast"
"github.com/yuin/goldmark/parser"
"github.com/yuin/goldmark/renderer"
"github.com/yuin/goldmark/text"
"github.com/yuin/goldmark/util"

)

// Mermaid support: a fenced ```mermaid code block is rendered as //

…diagram source…

instead of being syntax // highlighted, so the client-side mermaid script (loaded by the page template // only when such an element is present) can draw it. The diagram source is // HTML-escaped here and passes through the bluemonday sanitizer as plain text; // mermaid reads it back via the element's textContent.

// kindMermaid is the AST node kind for a mermaid diagram block. var kindMermaid = ast.NewNodeKind("Mermaid")

type mermaidNode struct { ast.BaseBlock source []byte }

func (n *mermaidNode) Kind() ast.NodeKind { return kindMermaid }

func (n *mermaidNode) Dump(source []byte, level int) { ast.DumpHelper(n, source, level, nil, nil) }

// mermaidTransformer rewrites ```mermaid fenced code blocks into mermaidNode, // before the highlighting renderer would otherwise turn them into code. type mermaidTransformer struct{}

func (mermaidTransformer) Transform(doc *ast.Document, reader text.Reader, _ parser.Context) { source := reader.Source() var found []*ast.FencedCodeBlock _ = ast.Walk(doc, func(n ast.Node, entering bool) (ast.WalkStatus, error) { if !entering { return ast.WalkContinue, nil } if fc, ok := n.(*ast.FencedCodeBlock); ok && string(fc.Language(source)) == "mermaid" { found = append(found, fc) } return ast.WalkContinue, nil }) for _, fc := range found { var buf []byte for i := 0; i < fc.Lines().Len(); i++ { seg := fc.Lines().At(i) buf = append(buf, seg.Value(source)...) } m := &mermaidNode{source: buf} if p := fc.Parent(); p != nil { p.ReplaceChild(p, fc, m) } } }

// mermaidHTMLRenderer renders a mermaidNode. type mermaidHTMLRenderer struct{}

func (mermaidHTMLRenderer) RegisterFuncs(reg renderer.NodeRendererFuncRegisterer) { reg.Register(kindMermaid, renderMermaid) }

func renderMermaid(w util.BufWriter, _ []byte, n ast.Node, entering bool) (ast.WalkStatus, error) { if !entering { return ast.WalkContinue, nil } m := n.(*mermaidNode) _, _ = w.WriteString(<pre class="mermaid">) _, _ = w.WriteString(html.EscapeString(string(m.source))) _, _ = w.WriteString("\n") return ast.WalkSkipChildren, nil }