Allow joining an existing room and validating tile placement

board-shared/src/deck.rs

@@ -1,3 +1,4 @@
+use std::error::Error;
 use crate::tile::Operator;
 use enum_map::EnumMap;
 use rand::{thread_rng, Rng};
@@ -6,7 +7,14 @@ type DeckSize = u16;
 type DigitDeck = [DeckSize; 19];
 
 /// When a deck is empty, new tiles cannot be retrieved.
-pub type EmptyDeckError = ();
+#[derive(Debug)]
+pub struct EmptyDeckError;
+impl Error for EmptyDeckError {}
+impl std::fmt::Display for EmptyDeckError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "Deck is empty")
+    }
+}
 
 /// A entire deck of tiles.
 #[derive(Debug, Clone, Default, PartialEq)]

board-shared/src/game.rs

@@ -35,12 +35,20 @@ impl Hand {
     pub fn complete(&mut self, deck: &mut RngDeck) -> Result<(), EmptyDeckError> {
         for _ in 0..self.count_missing_operators() {
             self.tiles
-                .push(Tile::Operator(deck.rand_operator().ok_or(())?));
+                .push(Tile::Operator(deck.rand_operator().ok_or(EmptyDeckError.into())?));
         }
         for _ in 0..self.count_missing_numbers() {
             self.tiles
-                .push(Tile::Digit(Digit::new(deck.rand_digit().ok_or(())?)));
+                .push(Tile::Digit(Digit::new(deck.rand_digit().ok_or(EmptyDeckError.into())?)));
         }
         Ok(())
     }
+
+    pub fn remove(&mut self, idx: usize) -> Option<Tile> {
+        if idx < self.tiles.len() {
+            Some(self.tiles.remove(idx))
+        } else {
+            None
+        }
+    }
 }