Optimize embedded dirs

1 files changed, 18 insertions, 4 deletions

diff --git a/rustlings-macros/src/lib.rs b/rustlings-macros/src/lib.rs
index fc2bcf1..4417a4f 100644
--- a/rustlings-macros/src/lib.rs
+++ b/rustlings-macros/src/lib.rs
@@ -25,14 +25,28 @@ pub fn include_files(_: TokenStream) -> TokenStream {
     let solution_files = exercises
         .iter()
         .map(|exercise| format!("../solutions/{}/{}.rs", exercise.dir, exercise.name));
-    let dirs = exercises.iter().map(|exercise| &exercise.dir);
-    let readmes = exercises
+
+    let mut dirs = Vec::with_capacity(32);
+    let mut dir_inds = vec![0; exercises.len()];
+
+    for (exercise, dir_ind) in exercises.iter().zip(&mut dir_inds) {
+        // The directory is often the last one inserted.
+        if let Some(ind) = dirs.iter().rev().position(|dir| *dir == exercise.dir) {
+            *dir_ind = dirs.len() - 1 - ind;
+            continue;
+        }
+
+        dirs.push(exercise.dir.as_str());
+        *dir_ind = dirs.len() - 1;
+    }
+
+    let readmes = dirs
         .iter()
-        .map(|exercise| format!("../exercises/{}/README.md", exercise.dir));
+        .map(|dir| format!("../exercises/{dir}/README.md"));
 
     quote! {
         EmbeddedFiles {
-            exercise_files: &[#(ExerciseFiles { exercise: include_bytes!(#exercise_files), solution: include_bytes!(#solution_files) }),*],
+            exercise_files: &[#(ExerciseFiles { exercise: include_bytes!(#exercise_files), solution: include_bytes!(#solution_files), dir_ind: #dir_inds }),*],
             exercise_dirs: &[#(ExerciseDir { name: #dirs, readme: include_bytes!(#readmes) }),*]
         }
     }