Add markdown support

providers/markdown/markdown.go

@@ -0,0 +1,50 @@
+package markdown
+
+import "fmt"
+import "bytes"
+import "strings"
+import "html/template"
+import "github.com/yuin/goldmark"
+import "github.com/yuin/goldmark/parser"
+import "git.tebibyte.media/sashakoshka/step"
+
+var _ step.FuncProvider = new(Provider)
+
+// Provider provides Markdown functions.
+type Provider struct {
+	// Options contains parse options that are passed to the converter.
+	Options []parser.ParseOption
+}
+
+// FuncMap fulfills the step.FuncProvider interface.
+func (this *Provider) FuncMap () template.FuncMap {
+	stat := &state {
+		options: this.Options,
+	}
+	return template.FuncMap {
+		"markdown": stat.funcMarkdown,
+	}
+}
+
+type state struct {
+	options []parser.ParseOption
+}
+
+func (this *state) funcMarkdown (input any) (template.HTML, error) {
+	builder := strings.Builder { }
+	err := goldmark.Convert(toBytes(input), &builder, this.options...)
+	if err != nil { return "", nil }
+	return template.HTML(builder.String()), nil
+}
+
+func toBytes (data any) []byte {
+	switch data := data.(type) {
+	case []byte:        return data
+	case string:        return []byte(data)
+	case template.HTML: return []byte(data)
+	default:
+		buffer := bytes.Buffer { }
+		fmt.Fprint(&buffer, data)
+		return buffer.Bytes()
+	}
+}