Reintroduce searchable attributes and reordering

meilisearch-core/src/reordered_attrs.rs

@@ -1,27 +1,31 @@
+use std::cmp;
+
 #[derive(Default, Clone)]
 pub struct ReorderedAttrs {
-    count: usize,
     reorders: Vec<Option<u16>>,
+    reverse: Vec<u16>,
 }
 
 impl ReorderedAttrs {
     pub fn new() -> ReorderedAttrs {
-        ReorderedAttrs {
-            count: 0,
-            reorders: Vec::new(),
-        }
+        ReorderedAttrs { reorders: Vec::new(), reverse: Vec::new() }
     }
 
     pub fn insert_attribute(&mut self, attribute: u16) {
-        self.reorders.resize(attribute as usize + 1, None);
-        self.reorders[attribute as usize] = Some(self.count as u16);
-        self.count += 1;
+        let new_len = cmp::max(attribute as usize + 1, self.reorders.len());
+        self.reorders.resize(new_len, None);
+        self.reorders[attribute as usize] = Some(self.reverse.len() as u16);
+        self.reverse.push(attribute);
     }
 
     pub fn get(&self, attribute: u16) -> Option<u16> {
-        match self.reorders.get(attribute as usize) {
-            Some(Some(attribute)) => Some(*attribute),
-            _ => None,
+        match self.reorders.get(attribute as usize)? {
+            Some(attribute) => Some(*attribute),
+            None => None,
         }
     }
+
+    pub fn reverse(&self, attribute: u16) -> Option<u16> {
+        self.reverse.get(attribute as usize).copied()
+    }
 }