Refactor handout.typ

Reviewed-on: #7
Co-authored-by: Mark <mark@betalupi.com>
Co-committed-by: Mark <mark@betalupi.com>

lib/typst/local/handout/0.1.0/object.typ

@@ -0,0 +1,100 @@
+
+/// This module defines all handout "objects"
+/// (problems, theorems, definitions, etc)
+
+/// Core render code for all objects (problems, theorems, etc)
+/// This should never be used directly by client code.
+///
+/// Args:
+/// - kind: the kind of object to make ("Problem", "Definition", etc)
+/// - label_name: a string. If provided, generate metadata for this object
+///   under the given label. Labels must be unique.
+///   This label can then be used to reference this object.
+///
+/// For example:
+/// ```
+/// #problem(label: "problem1")
+/// This is @problem1
+/// ```
+#let _obj_base(kind, ..args, label_name: none) = {
+  counter("obj").step()
+  let n = context counter("obj").get().first()
+
+  // The complete title text of this object,
+  // like "Problem 5:" or "Theorem: "
+  let obj_content = if args.pos().len() == 0 {
+    [#kind #n:]
+  } else {
+    [#kind #n: #args.pos().at(0)]
+  }
+
+  // Render the object
+  block(
+    above: 8mm,
+    below: 2mm,
+    text(weight: "bold", obj_content),
+  )
+
+  // Generate labeled metadata for this object.
+  //
+  // This can be viewed directly with `#context query(<label>).first().value`,
+  // Or referenced with `@label` (we define a custom renderer for this metadata later)
+  if label_name != none {
+    let meta = (
+      "obj_meta_ref_kind": kind,
+      // "obj_content": obj_content,
+      "label": label(label_name),
+      "counter": counter("obj"),
+    )
+    [ #metadata(meta) #label(label_name) ]
+  }
+}
+
+// `ref` implementation for object meta-references.
+// Returns `none` if `it` is not object metadata.
+#let ref_obj(it) = {
+  let magic_key = "obj_meta_ref_kind"
+  if not (
+    it.element != none
+      and it.element.has("value")
+      and type(it.element.value) == "dictionary"
+      and it.element.value.keys().contains(magic_key)
+  ) {
+    // This label is not attached to object metadata
+    return none
+  }
+
+  let v = it.element.value
+  let obj_type = v.at(magic_key)
+
+  // The value of this object's counter at its label
+  let obj_count = v.counter.at(v.label).first()
+
+  // Produces text like "Problem 2",
+  // which takes you to the referenced object when clicked.
+  return link(v.label, [#obj_type #obj_count])
+}
+
+/// Factory function for objects.
+/// Provided for convenience, lets us define objects in one line.
+#let _mkobj(kind) = {
+  let out(..args, label: none) = _obj_base(
+    kind,
+    ..args,
+    label_name: label,
+  )
+
+  return out
+}
+
+
+//
+// MARK: export
+//
+// Functions for client code are defined below
+
+#let problem = _mkobj("Problem")
+#let definition = _mkobj("Definition")
+#let theorem = _mkobj("Theorem")
+#let example = _mkobj("Example")
+#let remark = _mkobj("Remark")