added groups

src/diagram.typ

@@ -1,3 +1,4 @@
+#import "utils.typ": get-group-span
 #import "renderer.typ": render
 
 #let _seq(
@@ -37,9 +38,40 @@
   return false
 }
 
+#let _grp(name, desc: none, type: "default", elmts) = {
+  return ((
+    type: "grp",
+    name: name,
+    desc: desc,
+    grp-type: type,
+    elmts: elmts
+  ),)
+}
+
 #let diagram(elements) = {
   let participants = ()
-  for elmt in elements {
+  let elmts = elements
+  let i = 0
+  let a = elmts.len()
+  while i < elmts.len() {
+    let elmt = elmts.at(i)
+    if elmt.type == "grp" {
+      elmts = (
+        elmts.slice(0, i + 1) +
+        elmt.elmts +
+        ((
+          type: "grp-end"
+        ),) +
+        elmts.slice(i+1)
+      )
+    }
+    i += 1
+  }
+  let b = elmts.len()
+  [#a / #b]
+  [#elmts.map(e => e.type)]
+
+  for elmt in elmts {
     if elmt.type == "par" {
       participants.push(elmt)
     } else if elmt.type == "seq" {
@@ -52,7 +84,15 @@
     }
   }
 
-  render(participants, elements)
+  for (i, elmt) in elmts.enumerate() {
+    if elmt.type == "grp" {
+      let (min-i, max-i) = get-group-span(participants, elmt)
+      elmts.at(i).insert("min-i", min-i)
+      elmts.at(i).insert("max-i", max-i)
+    }
+  }
+
+  render(participants, elmts)
 }
 
 #let from-plantuml(code) = {