1 files changed, 73 insertions, 0 deletions
diff --git a/filters.go b/filters.go
new file mode 100644
index 0000000..64a1d21
--- /dev/null
+++ b/filters.go
@@ -0,0 +1,73 @@
+package main
+
+// The two filters: in process for the forge's pages, as programs for cgit.
+
+import (
+	"bytes"
+	"fmt"
+	"html/template"
+	"io"
+	"log"
+	"os"
+	"os/exec"
+	"path"
+
+	"github.com/yuin/goldmark"
+)
+
+// Raw HTML is left unrendered, goldmark's default, which is what makes user
+// text safe to hand it.
+var markdown = goldmark.New()
+
+func renderMarkdown(source string) template.HTML {
+	var buf bytes.Buffer
+	if err := markdown.Convert([]byte(source), &buf); err != nil {
+		log.Printf("markdown: %v", err)
+		return template.HTML(template.HTMLEscapeString(source))
+	}
+	return template.HTML(buf.String())
+}
+
+// runMarkdown is the about-filter: markdown on stdin, HTML on stdout.
+func runMarkdown() int {
+	source, err := io.ReadAll(os.Stdin)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "md:", err)
+		return 1
+	}
+	if err := markdown.Convert(source, os.Stdout); err != nil {
+		// A readable page beats an empty one.
+		fmt.Fprintln(os.Stderr, "md:", err)
+		template.HTMLEscape(os.Stdout, source)
+		return 1
+	}
+	return 0
+}
+
+// runHighlight is the source-filter: cgit's bundled one issues a command line
+// the installed highlight refuses, silently.
+func runHighlight(args []string) int {
+	source, err := io.ReadAll(os.Stdin)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "highlight:", err)
+		return 1
+	}
+	name := "source"
+	if len(args) > 0 && args[0] != "" {
+		name = path.Base(args[0])
+	}
+	// --force: an unknown syntax comes back as escaped text, not as nothing.
+	cmd := exec.Command("highlight", "--fragment", "--force", "--out-format=html", "--syntax-by-name="+name)
+	cmd.Stdin = bytes.NewReader(source)
+	cmd.Stderr = os.Stderr
+	out, err := cmd.Output()
+	if err != nil || len(bytes.TrimSpace(out)) == 0 {
+		if err != nil {
+			fmt.Fprintln(os.Stderr, "highlight:", err)
+		}
+		template.HTMLEscape(os.Stdout, source)
+		return 0
+	}
+	os.Stdout.Write(out)
+	return 0
+}