Fix sorting events on the client (#47)

(k1 < k2) should have been (k1 < k2 ? -1 : 1), but Array.sort() has been
stable for a long time. We don't compare keys on the server side, so
just remove this on the client side as well.

Also, change tiebreak in the leaderboard as suggested in[1]. Instead of
comparing user IDs, which are arbitrary, compare the times that they
found the last set.

Fixes #46

[1] ekzhang/setwithfriends#153

src/pages/GamePage.js

@@ -143,17 +143,16 @@ function GamePage({ match }) {
   const spectating = !game.users || !(user.id in game.users);
   const maxNumHints = gameMode === "ultraset" ? 4 : 3;
 
-  const { current, scores, history, boardSize } = computeState(
+  const { current, scores, lastEvents, history, boardSize } = computeState(
     gameData,
     gameMode
   );
 
-  const leaderboard = Object.keys(game.users).sort((u1, u2) => {
-    const s1 = scores[u1] || 0;
-    const s2 = scores[u2] || 0;
-    if (s1 !== s2) return s2 - s1;
-    return u1 < u2 ? -1 : 1;
-  });
+  const leaderboard = Object.keys(game.users).sort(
+    (u1, u2) =>
+      (scores[u2] || 0) - (scores[u1] || 0) ||
+      (lastEvents[u1] || 0) - (lastEvents[u2] || 0)
+  );
 
   function handleSet(cards) {
     const event =

src/util.js

@@ -244,8 +244,9 @@ function removeCards(internalGameState, cards) {
 }
 
 function processValidEvent(internalGameState, event, cards) {
-  const { scores, history } = internalGameState;
+  const { scores, lastEvents, history } = internalGameState;
   scores[event.user] = (scores[event.user] || 0) + 1;
+  lastEvents[event.user] = event.time;
   history.push(event);
   removeCards(internalGameState, cards);
 }
@@ -300,21 +301,22 @@ export function computeState(gameData, gameMode = "normal") {
   const used = {}; // set of cards that have been taken
   const history = []; // list of valid events in time order
   const current = gameData.deck.slice(); // remaining cards in the game
+  const lastEvents = {}; // time of the last event for each user
   const internalGameState = {
     used,
     current,
     scores,
     history,
+    lastEvents,
     // Initial deck split
     boardSize: splitDeck(current, gameMode, 12, [])[0].length,
   };
 
   if (gameData.events) {
-    const events = Object.entries(gameData.events)
-      .sort(([k1, e1], [k2, e2]) => {
-        return e1.time !== e2.time ? e1.time - e2.time : k1 < k2;
-      })
-      .map(([_k, e]) => e);
+    // Array.sort() is guaranteed to be stable in since around 2018
+    const events = Object.values(gameData.events).sort(
+      (e1, e2) => e1.time - e2.time
+    );
     const processFn =
       gameMode === "normal"
         ? processEventNormal
@@ -328,7 +330,13 @@ export function computeState(gameData, gameMode = "normal") {
     }
   }
 
-  return { current, scores, history, boardSize: internalGameState.boardSize };
+  return {
+    current,
+    scores,
+    history,
+    lastEvents,
+    boardSize: internalGameState.boardSize,
+  };
 }
 
 export function formatTime(t, hideSubsecond) {