Feat: collapsible help

src/model/docs.rs

@@ -122,6 +122,53 @@ pub fn topic_count() -> usize {
     DOCS.iter().filter(|e| matches!(e, Topic(_, _))).count()
 }
 
+pub fn section_count() -> usize {
+    DOCS.iter().filter(|e| matches!(e, Section(_))).count()
+}
+
+pub fn section_index_for_topic(topic_idx: usize) -> usize {
+    let mut section: usize = 0;
+    let mut topic: usize = 0;
+    for entry in DOCS.iter() {
+        match entry {
+            Section(_) => section += 1,
+            Topic(_, _) => {
+                if topic == topic_idx {
+                    return section.saturating_sub(1);
+                }
+                topic += 1;
+            }
+        }
+    }
+    section.saturating_sub(1)
+}
+
+pub fn first_topic_in_section(section_idx: usize) -> Option<usize> {
+    let mut section: usize = 0;
+    let mut topic: usize = 0;
+    let mut in_target = false;
+    for entry in DOCS.iter() {
+        match entry {
+            Section(_) => {
+                if in_target {
+                    return None;
+                }
+                if section == section_idx {
+                    in_target = true;
+                }
+                section += 1;
+            }
+            Topic(_, _) => {
+                if in_target {
+                    return Some(topic);
+                }
+                topic += 1;
+            }
+        }
+    }
+    None
+}
+
 pub fn get_topic(index: usize) -> Option<(&'static str, &'static str)> {
     DOCS.iter()
         .filter_map(|e| match e {