Canvas support V1

render.go

@@ -7,14 +7,17 @@ import (
 	"net/url"
 	"os"
 	"path"
+	"regexp"
 	"sort"
 	"strings"
 	"time"
 
 	"github.com/yuin/goldmark"
+	"github.com/yuin/goldmark/ast"
 	"github.com/yuin/goldmark/extension"
 	"github.com/yuin/goldmark/parser"
 	"github.com/yuin/goldmark/renderer/html"
+	"github.com/yuin/goldmark/text"
 )
 
 var md goldmark.Markdown
@@ -129,19 +132,61 @@ var (
 	iconAudio   = readIcon("audio")
 	iconArchive = readIcon("archive")
 	iconGeneric = readIcon("generic")
+	iconCanvas  = readIcon("canvas")
 )
 
 // renderMarkdown converts raw markdown to trusted HTML.
 func renderMarkdown(raw []byte) template.HTML {
+	return template.HTML(rewriteTaskCheckboxes(convertMarkdown(raw, "")))
+}
+
+// convertMarkdown renders raw markdown to HTML with the wiki's table styling
+// but leaves task checkboxes as goldmark emits them (disabled), so callers
+// decide how they toggle.
+//
+// base, when set, is the URL path (slash-terminated) relative link and embed
+// destinations resolve against. Pages leave it empty: the browser resolves
+// them against the page URL. Markdown shown somewhere else (a canvas file
+// node showing another folder's page) passes that folder.
+func convertMarkdown(raw []byte, base string) []byte {
 	var buf bytes.Buffer
-	if err := md.Convert(raw, &buf); err != nil {
-		return ""
+	doc := md.Parser().Parse(text.NewReader(raw))
+	if base != "" {
+		rebaseDestinations(doc, base)
+	}
+	if err := md.Renderer().Render(&buf, raw, doc); err != nil {
+		return nil
 	}
-	out := rewriteTaskCheckboxes(buf.Bytes())
 	// Goldmark emits a bare `<table>`; tag it so it picks up the shared
 	// .data-table styling with the grid modifier (per-cell borders + header).
-	out = bytes.ReplaceAll(out, []byte("<table>"), []byte(`<table class="data-table data-table-grid">`))
-	return template.HTML(out)
+	return bytes.ReplaceAll(buf.Bytes(), []byte("<table>"), []byte(`<table class="data-table data-table-grid">`))
+}
+
+// schemeRe matches a URL that starts with a scheme ("https:", "mailto:").
+var schemeRe = regexp.MustCompile(`^[a-zA-Z][a-zA-Z0-9+.-]*:`)
+
+// rebaseDestinations prefixes every relative link and image destination in
+// doc with base. Absolute paths, fragments, queries and URLs with a scheme
+// stay as they are.
+func rebaseDestinations(doc ast.Node, base string) {
+	rebase := func(dest []byte) []byte {
+		if len(dest) == 0 || dest[0] == '/' || dest[0] == '#' || dest[0] == '?' || schemeRe.Match(dest) {
+			return dest
+		}
+		return append([]byte(base), dest...)
+	}
+	ast.Walk(doc, func(n ast.Node, entering bool) (ast.WalkStatus, error) {
+		if !entering {
+			return ast.WalkContinue, nil
+		}
+		switch n := n.(type) {
+		case *ast.Link:
+			n.Destination = rebase(n.Destination)
+		case *ast.Image:
+			n.Destination = rebase(n.Destination)
+		}
+		return ast.WalkContinue, nil
+	})
 }
 
 // extractFirstHeading returns the text of the first ATX heading in raw markdown,
@@ -301,6 +346,8 @@ func fileIcon(name string) template.HTML {
 	switch ext {
 	case ".md", ".pdf":
 		return iconDoc
+	case canvasExt:
+		return iconCanvas
 	case ".png", ".jpg", ".jpeg", ".gif", ".webp", ".svg":
 		return iconImage
 	case ".mp4", ".mkv", ".avi", ".mov":