feat(trial): implement grapheme clustered input

src/trial/history.rs

@@ -101,7 +101,7 @@ impl History {
     }
 
     /// Push a typed grapheme cluster to the history.
-    fn push_typed(&mut self, typed: &str) {
+    pub fn push_typed(&mut self, typed: &str) {
         debug_assert_eq!(typed.graphemes(true).count(), 1);
 
         // Push the index of the cluster.

src/trial/mod.rs

@@ -2,6 +2,8 @@ mod history;
 
 use history::History;
 
+use unicode_segmentation::UnicodeSegmentation;
+
 /// The state of a trial.
 pub struct Trial {
     /// The history of typed grapheme clusters and reference grapheme clusters.
@@ -35,7 +37,9 @@ impl Trial {
     pub fn process(&mut self, input: Input) {
         match input {
             Input::TypeScalar(c) => {
-                self.working_grapheme_cluster.push(c);
+                if let Some(finished_cluster) = push_to_working_cluster(&mut self.working_grapheme_cluster, c) {
+                    self.history.push_typed(&finished_cluster);
+                }
             }
             Input::DeleteGraphemeCluster if self.working_grapheme_cluster.is_empty() => {
                 todo!()
@@ -49,3 +53,63 @@ impl Trial {
         }
     }
 }
+
+/// Push a scalar value to the working grapheme cluster, returning the previous cluster if it was finished.
+fn push_to_working_cluster(working_grapheme_cluster: &mut String, scalar: char) -> Option<String> {
+    working_grapheme_cluster.push(scalar);
+
+    let mut clusters = working_grapheme_cluster.graphemes(true);
+    let first_cluster = clusters.next().unwrap();
+
+    if let Some(new_cluster) = clusters.next() {
+        let first_cluster = first_cluster.to_owned();
+        let new_cluster = new_cluster.to_owned();
+
+        *working_grapheme_cluster = new_cluster;
+
+        Some(first_cluster)
+    } else {
+        None
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn push_to_working_cluster_handles_latin() {
+        let mut working_grapheme_cluster = String::new();
+
+        assert_eq!(
+            push_to_working_cluster(&mut working_grapheme_cluster, 'a'),
+            None
+        );
+        assert_eq!(
+            push_to_working_cluster(&mut working_grapheme_cluster, 'a'),
+            Some("a".to_owned())
+        );
+
+        assert_eq!(
+            push_to_working_cluster(&mut working_grapheme_cluster, 'é'),
+            Some("a".to_owned())
+        );
+        assert_eq!(
+            push_to_working_cluster(&mut working_grapheme_cluster, 'a'),
+            Some("é".to_owned())
+        );
+
+        assert_eq!(
+            push_to_working_cluster(&mut working_grapheme_cluster, 'a'),
+            Some("a".to_owned())
+        );
+        assert_eq!(
+            push_to_working_cluster(&mut working_grapheme_cluster, '\u{0302}'), // combining circumflex accent
+            None
+        );
+        assert_eq!(
+            push_to_working_cluster(&mut working_grapheme_cluster, 'a'),
+            Some("a\u{0302}".to_owned())
+        );
+    }
+}