Beginning to hand out footnote ids.

src/intermediate/registry.rs

@@ -1,10 +1,13 @@
 use std::collections::HashMap;
 
+use organic::types::Object;
+
 type IdCounter = u16;
 
-pub(crate) struct Registry<'parse> {
+pub(crate) struct Registry<'intermediate, 'parse> {
     id_counter: IdCounter,
     targets: HashMap<&'parse str, String>,
+    footnote_ids: Vec<(Option<&'parse str>, &Vec<Object<'parse>>)>,
 }
 
 impl<'parse> Registry<'parse> {
@@ -12,6 +15,7 @@ impl<'parse> Registry<'parse> {
         Registry {
             id_counter: 0,
             targets: HashMap::new(),
+            footnote_ids: Vec::new(),
         }
     }
 
@@ -21,4 +25,37 @@ impl<'parse> Registry<'parse> {
             format!("target_{}", self.id_counter)
         })
     }
+
+    /// Get a 0-indexed ID for a footnote.
+    ///
+    /// This needs to be incremented to be 1-indexed for render.
+    pub(crate) fn get_footnote_reference_id<'b>(
+        &'b mut self,
+        label: Option<&'parse str>,
+        definition: &'parse Vec<Object<'parse>>,
+    ) -> usize {
+        if let None = label {
+            // If it has no label then it must always get a new ID.
+            self.footnote_ids.push((None, definition));
+            return self.footnote_ids.len();
+        }
+
+        if let Some(existing_id) = self
+            .footnote_ids
+            .iter()
+            .position(|(id, _definition)| *id == label)
+        {
+            if !definition.is_empty() {
+                let entry = self
+                    .footnote_ids
+                    .get_mut(existing_id)
+                    .expect("If-statement proves this to be Some.");
+                entry.1 = definition;
+            }
+            existing_id
+        } else {
+            self.footnote_ids.push((label, definition));
+            self.footnote_ids.len()
+        }
+    }
 }