Add basic support for drawers

org/drawer.go

@@ -0,0 +1,37 @@
+package org
+
+import (
+	"regexp"
+	"strings"
+)
+
+type Drawer struct {
+	Name     string
+	Children []Node
+}
+
+var beginDrawerRegexp = regexp.MustCompile(`^(\s*):(\S+):\s*$`)
+var endDrawerRegexp = regexp.MustCompile(`^(\s*):END:\s*$`)
+
+func lexDrawer(line string) (token, bool) {
+	if m := endDrawerRegexp.FindStringSubmatch(line); m != nil {
+		return token{"endDrawer", len(m[1]), "", m}, true
+	} else if m := beginDrawerRegexp.FindStringSubmatch(line); m != nil {
+		return token{"beginDrawer", len(m[1]), strings.ToUpper(m[2]), m}, true
+	}
+	return nilToken, false
+}
+
+func (d *Document) parseDrawer(i int, parentStop stopFn) (int, Node) {
+	drawer, start := Drawer{Name: strings.ToUpper(d.tokens[i].content)}, i
+	i++
+	stop := func(d *Document, i int) bool {
+		return parentStop(d, i) || d.tokens[i].kind == "endDrawer" || d.tokens[i].kind == "headline"
+	}
+	consumed, nodes := d.parseMany(i, stop)
+	drawer.Children = nodes
+	if d.tokens[i+consumed].kind == "endDrawer" {
+		consumed++
+	}
+	return i + consumed - start, drawer
+}