Use mora instead of characters, e.g. しゅ

demo/shiritori.js

@@ -25,7 +25,7 @@ ws.onmessage = e => {
     case "word":
       let waiting = data.author === id;
       displayWord(data.word, true);
-      input.placeholder = waiting ? "Waiting for other players..." : `${data.next_char}…`;
+      input.placeholder = waiting ? "Waiting for other players..." : `${data.next_mora}…`;
       input.disabled = waiting;
       if (!waiting) input.focus();
       break;

src/database.rs

@@ -47,7 +47,6 @@ impl Database {
     }
 
     pub fn load_words_before(&self, before_id: i64) -> Result<Vec<Word>> {
-        println!("{}", before_id);
         self.conn
             .prepare("SELECT id, word, reading, timestamp FROM word WHERE id < ? ORDER BY id DESC LIMIT 10")?
             .query_map(params![before_id], |row| {

src/server.rs

@@ -30,7 +30,7 @@ enum MessageResponseData {
     Word {
         author: u64,
         word: Word,
-        next_char: char,
+        next_mora: String,
     },
     History {
         words: Vec<Word>,
@@ -70,7 +70,7 @@ pub struct Server {
     event_hub: EventHub,
     database: Database,
     clients: HashMap<u64, Responder>,
-    next_char: Option<char>,
+    next_mora: Option<String>,
     last_client_id: Option<u64>,
 }
 
@@ -85,13 +85,59 @@ pub enum ServerError {
     DatabaseError(rusqlite::Error),
 }
 
+fn get_starting_mora(word: &str) -> String {
+    if word.is_empty() {
+        return String::from("");
+    }
+    let word = word.to_hiragana();
+    let mut iter = word.chars();
+    let starting_char = iter.next().unwrap();
+    let second_char = iter.next().unwrap();
+    match second_char {
+        'ゃ' | 'ゅ' | 'ょ' => format!("{starting_char}{second_char}"),
+        _ => starting_char.to_string(),
+    }
+}
+
+// Trim off lengtheners and non-kana that are irrelevant to shiritori
+// TODO: Use slices
+fn trim_irrelevant_chars(word: &str) -> String {
+    let mut iter = word.chars().rev().peekable();
+    while let Some(c) = iter.peek() {
+        if *c == 'ー' || !c.to_string().is_kana() {
+            iter.next();
+        } else {
+            break;
+        }
+    }
+    iter.rev().collect()
+}
+
+// Get final mora, which could be multiple chars e.g. しゃ
+// TODO: Use slices
+fn get_final_mora(word: &str) -> String {
+    let word = trim_irrelevant_chars(word).to_hiragana();
+    if word.is_empty() {
+        return String::from("");
+    }
+    let mut iter = word.chars().rev();
+    let final_char = iter.next().unwrap();
+    match final_char {
+        'ゃ' | 'ゅ' | 'ょ' => format!("{}{final_char}", match iter.next() {
+            Some(c) => c.to_string(),
+            None => String::from(""),
+        }),
+        _ => final_char.to_string(),
+    }
+}
+
 impl Server {
     pub fn new(port: u16, testing: bool) -> Result<Self, ServerCreationError> {
         Ok(Server {
             event_hub: simple_websockets::launch(port)?,
             database: Database::new(testing)?,
             clients: HashMap::new(),
-            next_char: None,
+            next_mora: None,
             last_client_id: None,
         })
     }
@@ -153,32 +199,23 @@ impl Server {
         } else {
             match lookup(&message) {
                 Some(entry) => {
+                    println!("{}, {:?}", get_starting_mora(&entry.reading), self.next_mora);
                     if entry.reading.chars().last().unwrap().to_string().to_hiragana() == "ん" {
                         MessageResponseData::Error {
                             message: String::from("Can't end with ん!"),
                         }
-                    } else if self.next_char.is_none() || entry.reading.chars().next().unwrap().to_string().to_hiragana().chars().next().unwrap() == self.next_char.unwrap() {
+                    } else if self.next_mora.is_none() || get_starting_mora(&entry.reading).eq(self.next_mora.as_deref().unwrap()) {
-                        self.next_char = {
-                            // If final character is lengthener or not kana
-                            // Use semifinal
-                            let mut final_chars = entry.reading.chars().rev();
-                            let final_char = final_chars.next().unwrap();
-                            Some(if final_char == 'ー' || !final_char.to_string().is_kana() {
-                                final_chars.next().unwrap()
-                            } else {
-                                final_char
-                            }.to_string().to_hiragana().chars().next().unwrap())
-                        };
                         let word: Word = entry.clone().into();
+                        self.next_mora = Some(get_final_mora(&word.reading));
                         self.database.add_word(&word)?;
                         MessageResponseData::Word {
                             author: client_id,
                             word,
-                            next_char: self.next_char.unwrap(),
+                            next_mora: self.next_mora.as_deref().unwrap().to_owned(),
                         }
                     } else {
                         MessageResponseData::Error {
-                            message: String::from("Wrong starting kana!"),
+                            message: String::from("Wrong starting mora!"),
                         }
                     }
                 }