Allow image embedding
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@@ -0,0 +1,254 @@
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package main
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import (
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"bytes"
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"path"
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"regexp"
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"strings"
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"github.com/yuin/goldmark"
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"github.com/yuin/goldmark/ast"
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"github.com/yuin/goldmark/parser"
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"github.com/yuin/goldmark/renderer"
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"github.com/yuin/goldmark/text"
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"github.com/yuin/goldmark/util"
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)
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// wikiEmbedRe matches an ![[...]] token anchored at the current inline reader.
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// The inner blob forbids brackets and newlines but allows ':' so the whole
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// target::caption::align payload travels as one capture — the caption and
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// alignment tail is split apart in Go (parseEmbedFields). This mirrors
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// wikiLinkPattern's shape so the move rewriter needs no embed-specific changes.
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var wikiEmbedRe = regexp.MustCompile(`^!\[\[([^\[\]\n]+)\]\]`)
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const (
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alignLeft = "left"
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alignRight = "right"
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alignCenter = "center"
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)
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// wikiEmbedNode is the AST node produced by wikiEmbedParser.
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type wikiEmbedNode struct {
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ast.BaseInline
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Target string
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Caption string
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Align string
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}
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var kindWikiEmbed = ast.NewNodeKind("WikiEmbed")
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func (n *wikiEmbedNode) Kind() ast.NodeKind { return kindWikiEmbed }
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func (n *wikiEmbedNode) Dump(source []byte, level int) {
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ast.DumpHelper(n, source, level, map[string]string{
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"Target": n.Target,
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"Caption": n.Caption,
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"Align": n.Align,
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}, nil)
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}
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// alignKeyword reports whether s (trimmed) is one of the alignment keywords.
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func alignKeyword(s string) (string, bool) {
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switch strings.TrimSpace(s) {
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case alignLeft:
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return alignLeft, true
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case alignRight:
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return alignRight, true
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case alignCenter:
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return alignCenter, true
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}
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return "", false
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}
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// parseEmbedFields splits the inner ![[...]] blob into target, caption, and
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// alignment per the embed syntax rules. The target is the field before the
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// first "::". The trailing "::"-fields are interpreted as:
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// - none: no caption, default alignment (right)
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// - one keyword field: that alignment, no caption
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// - one non-keyword field: that caption, default alignment
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// - two or more: the last field is the alignment slot (default when it is not
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// a keyword) and the earlier fields re-join with "::" as the caption, so a
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// caption may contain a literal "::" as long as an alignment field trails it.
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func parseEmbedFields(inner string) (target, caption, align string) {
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fields := strings.Split(inner, "::")
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target = strings.TrimSpace(fields[0])
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tail := fields[1:]
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align = alignRight
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switch len(tail) {
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case 0:
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// target only
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case 1:
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if kw, ok := alignKeyword(tail[0]); ok {
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align = kw
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} else {
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caption = strings.TrimSpace(tail[0])
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}
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default:
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if kw, ok := alignKeyword(tail[len(tail)-1]); ok {
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align = kw
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}
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caption = strings.TrimSpace(strings.Join(tail[:len(tail)-1], "::"))
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}
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return target, caption, align
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}
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type wikiEmbedParser struct{}
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func (p *wikiEmbedParser) Trigger() []byte { return []byte{'!'} }
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func (p *wikiEmbedParser) Parse(parent ast.Node, block text.Reader, pc parser.Context) ast.Node {
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line, _ := block.PeekLine()
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// Require the exact "")
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// falls through to goldmark's default image parser at priority 200.
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if len(line) < 5 || line[0] != '!' || line[1] != '[' || line[2] != '[' {
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return nil
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}
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m := wikiEmbedRe.FindSubmatchIndex(line)
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if m == nil {
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return nil
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}
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target, caption, align := parseEmbedFields(string(line[m[2]:m[3]]))
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if !isValidWikiTarget([]byte(target)) {
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return nil
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}
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block.Advance(m[1])
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return &wikiEmbedNode{Target: target, Caption: caption, Align: align}
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}
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// embedBlockTransformer lifts an embed that sits alone in a paragraph up to
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// block level. Goldmark wraps inline content in <p>, but the embed renders a
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// <figure> (block), and a <figure> inside a <p> is auto-closed by the browser —
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// which strands empty <p> elements (they still carry .content paragraph margins)
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// and breaks the float layout once several embeds share a page. Dissolving the
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// wrapping paragraph makes each embed render as a clean block sibling with no
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// stray <p>.
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type embedBlockTransformer struct{ root string }
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func (t embedBlockTransformer) Transform(doc *ast.Document, reader text.Reader, pc parser.Context) {
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source := reader.Source()
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var paras []*ast.Paragraph
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ast.Walk(doc, func(n ast.Node, entering bool) (ast.WalkStatus, error) {
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if entering {
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if p, ok := n.(*ast.Paragraph); ok && t.paragraphFiguresOnly(p, source) {
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paras = append(paras, p)
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}
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}
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return ast.WalkContinue, nil
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})
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for _, p := range paras {
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parent := p.Parent()
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if parent == nil {
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continue
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}
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// InsertBefore isolates the embed from p first, so hoist each embed to a
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// block sibling ahead of the (soon removed) paragraph, then drop p.
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for c := p.FirstChild(); c != nil; {
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next := c.NextSibling()
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if _, ok := c.(*wikiEmbedNode); ok {
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parent.InsertBefore(parent, p, c)
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}
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c = next
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}
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parent.RemoveChild(parent, p)
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}
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}
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// paragraphFiguresOnly reports whether p holds at least one figure-rendering
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// embed and nothing else visible — only such embeds and whitespace/line-break
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// text. Only these are safe to dissolve: a paragraph carrying prose, or an embed
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// that degrades to an inline link (missing / non-image target), stays wrapped so
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// the fallback anchor keeps its paragraph.
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func (t embedBlockTransformer) paragraphFiguresOnly(p *ast.Paragraph, source []byte) bool {
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hasFigure := false
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for c := p.FirstChild(); c != nil; c = c.NextSibling() {
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switch n := c.(type) {
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case *wikiEmbedNode:
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if !embedIsImage(t.root, n.Target) {
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return false
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}
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hasFigure = true
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case *ast.Text:
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if len(bytes.TrimSpace(n.Segment.Value(source))) != 0 {
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return false
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}
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default:
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return false
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}
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}
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return hasFigure
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}
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// embedIsImage reports whether target resolves to an existing image file, i.e.
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// the embed will render as a <figure> rather than degrade to a link fallback.
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func embedIsImage(root, target string) bool {
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name := path.Base(normalizeWikiTarget(target))
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return wikiTargetExists(root, target) && isImageFile(name)
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}
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type wikiEmbedRenderer struct {
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root string
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}
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func (r *wikiEmbedRenderer) RegisterFuncs(reg renderer.NodeRendererFuncRegisterer) {
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reg.Register(kindWikiEmbed, r.render)
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}
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func (r *wikiEmbedRenderer) render(w util.BufWriter, source []byte, node ast.Node, entering bool) (ast.WalkStatus, error) {
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if !entering {
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return ast.WalkContinue, nil
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}
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n := node.(*wikiEmbedNode)
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// Embed only when the target exists and is an image we can thumbnail.
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// Anything else — a missing target, or an existing non-image file — degrades
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// to the same anchor a plain [[wikilink]] would render (broken or working).
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if !embedIsImage(r.root, n.Target) {
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writeWikiLink(w, r.root, n.Target, "")
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return ast.WalkContinue, nil
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}
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fileHref := wikiFileHref(n.Target)
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alt := n.Caption
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if alt == "" {
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alt = path.Base(normalizeWikiTarget(n.Target))
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}
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w.WriteString(`<figure class="embed embed-`)
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w.WriteString(n.Align)
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w.WriteString(`"><a class="embed-link" href="`)
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w.WriteString(fileHref)
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w.WriteString(`"><img src="`)
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w.WriteString(thumbURL(fileHref, 300))
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w.WriteString(`" alt="`)
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w.Write(util.EscapeHTML([]byte(alt)))
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w.WriteString(`"></a>`)
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if n.Caption != "" {
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w.WriteString(`<figcaption>`)
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w.Write(util.EscapeHTML([]byte(n.Caption)))
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w.WriteString(`</figcaption>`)
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}
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w.WriteString(`</figure>`)
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return ast.WalkContinue, nil
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}
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type wikiEmbedExt struct{ root string }
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// newWikiEmbedExt returns a goldmark extension that turns ![[...]] tokens into
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// image embeds resolved against root.
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func newWikiEmbedExt(root string) goldmark.Extender {
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return &wikiEmbedExt{root: root}
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}
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func (e *wikiEmbedExt) Extend(m goldmark.Markdown) {
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// Priority 199 — one higher than the default image parser (200) so ![[...]]
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// is consumed as an embed before the default `!` parser sees it.
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m.Parser().AddOptions(parser.WithInlineParsers(
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util.Prioritized(&wikiEmbedParser{}, 199),
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))
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m.Parser().AddOptions(parser.WithASTTransformers(
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util.Prioritized(embedBlockTransformer{root: e.root}, 100),
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))
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m.Renderer().AddOptions(renderer.WithNodeRenderers(
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util.Prioritized(&wikiEmbedRenderer{root: e.root}, 500),
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))
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}
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