Improve network stack (less traffic)

src/game.js

@@ -55,7 +55,8 @@ const POWERUPS = ["bomb", "flame", "speed"];
 const MAX_PLAYERS = 8;
 const NETWORK_PATH = "/ws";
 const PLAYER_NAME_STORAGE_KEY = "gptBomberPlayerName";
-const SNAPSHOT_RATE = 24;
+const SNAPSHOT_RATE = 18;
+const MAP_RESYNC_SECONDS = 1.2;
 
 const canvas = document.getElementById("game");
 const ctx = canvas.getContext("2d");
@@ -142,6 +143,8 @@ const network = {
   lastPingAt: 0,
   lobbyPhase: "lobby",
   hasReceivedSnapshot: false,
+  lastFullMapSnapshotAt: 0,
+  lastSentMapState: null,
 };
 
 let audio = null;
@@ -351,6 +354,7 @@ function resetRoundSingle() {
   state.multiplayerRoundKills = {};
   state.multiplayerRoundDeathTimes = {};
   state.multiplayerRoundTime = 0;
+  resetHostSnapshotMapState();
   closeMenu();
 }
 
@@ -384,6 +388,7 @@ function resetRoundMultiplayer(roster) {
   state.multiplayerRoundKills = {};
   state.multiplayerRoundDeathTimes = {};
   state.multiplayerRoundTime = 0;
+  resetHostSnapshotMapState();
   closeMenu();
   inputState.bombQueued = false;
   network.remoteBombPrev.clear();
@@ -858,6 +863,7 @@ function leaveLobbyInternals() {
   network.inputStateAtClient = { dir: null, bomb: false, bombCell: null };
   network.lastInputSentAt = 0;
   network.hasReceivedSnapshot = false;
+  resetHostSnapshotMapState();
 }
 
 function leaveMultiplayerToMainMenu() {
@@ -878,12 +884,68 @@ function hostStartMatchFromLobby() {
   sendSocketMessage("lobby_start");
 }
 
-function serializeGameState() {
+function resetHostSnapshotMapState() {
+  network.lastSentMapState = null;
+  network.lastFullMapSnapshotAt = 0;
+}
+
+function serializeMapTile(tile) {
+  return { type: tile.type, powerup: tile.powerup || null };
+}
+
+function mapTileSignature(tile) {
+  return tile.type + "|" + (tile.powerup || "");
+}
+
+function buildMapSignatureState() {
+  return state.map.map((row) => row.map((tile) => mapTileSignature(tile)));
+}
+
+function serializeMapPatch() {
+  if (!Array.isArray(network.lastSentMapState) || network.lastSentMapState.length !== state.map.length) {
+    network.lastSentMapState = buildMapSignatureState();
+    return [];
+  }
+
+  const patch = [];
+  for (let y = 0; y < state.map.length; y += 1) {
+    const row = state.map[y];
+    const previousRow = network.lastSentMapState[y];
+    for (let x = 0; x < row.length; x += 1) {
+      const tile = row[x];
+      const signature = mapTileSignature(tile);
+      if (!previousRow || previousRow[x] !== signature) {
+        patch.push({ x, y, type: tile.type, powerup: tile.powerup || null });
+        if (previousRow) {
+          previousRow[x] = signature;
+        }
+      }
+    }
+  }
+
+  return patch;
+}
+
+function serializeGameState(includeFullMap = false) {
+  let map;
+  let mapPatch;
+
+  if (includeFullMap || !Array.isArray(network.lastSentMapState)) {
+    map = state.map.map((row) => row.map((tile) => serializeMapTile(tile)));
+    network.lastSentMapState = buildMapSignatureState();
+  } else {
+    const patch = serializeMapPatch();
+    if (patch.length > 0) {
+      mapPatch = patch;
+    }
+  }
+
   return {
     status: state.status,
     message: state.message,
     time: state.time,
-    map: state.map.map((row) => row.map((tile) => ({ type: tile.type, powerup: tile.powerup || null }))),
+    map,
+    mapPatch,
     players: state.players.map((player) => ({
       id: player.id,
       name: player.name,
@@ -957,20 +1019,33 @@ function playSnapshotSfx(snapshot) {
   }
 
   let powerupCollected = false;
-  for (let y = 0; y < state.map.length; y += 1) {
-    for (let x = 0; x < state.map[y].length; x += 1) {
-      const prevTile = state.map[y][x];
-      const nextTile = snapshot.map[y]?.[x];
-      if (!prevTile || !nextTile) {
-        continue;
+  if (Array.isArray(snapshot.map)) {
+    for (let y = 0; y < state.map.length; y += 1) {
+      for (let x = 0; x < state.map[y].length; x += 1) {
+        const prevTile = state.map[y][x];
+        const nextTile = snapshot.map[y]?.[x];
+        if (!prevTile || !nextTile) {
+          continue;
+        }
+        if (prevTile.type === "floor" && prevTile.powerup && nextTile.type === "floor" && !nextTile.powerup) {
+          powerupCollected = true;
+          break;
+        }
       }
-      if (prevTile.type === "floor" && prevTile.powerup && nextTile.type === "floor" && !nextTile.powerup) {
-        powerupCollected = true;
+      if (powerupCollected) {
         break;
       }
     }
-    if (powerupCollected) {
-      break;
+  } else if (Array.isArray(snapshot.mapPatch)) {
+    for (const change of snapshot.mapPatch) {
+      const prevTile = state.map[change.y]?.[change.x];
+      if (!prevTile) {
+        continue;
+      }
+      if (prevTile.type === "floor" && prevTile.powerup && change.type === "floor" && !change.powerup) {
+        powerupCollected = true;
+        break;
+      }
     }
   }
 
@@ -989,7 +1064,21 @@ function applySnapshot(snapshot) {
   state.status = snapshot.status;
   state.message = snapshot.message;
   state.time = snapshot.time;
-  state.map = snapshot.map.map((row) => row.map((tile) => ({ type: tile.type, powerup: tile.powerup })));
+
+  if (Array.isArray(snapshot.map)) {
+    state.map = snapshot.map.map((row) => row.map((tile) => ({ type: tile.type, powerup: tile.powerup })));
+  } else if (Array.isArray(snapshot.mapPatch) && state.map.length > 0) {
+    for (const change of snapshot.mapPatch) {
+      if (!inBounds(change.x, change.y)) {
+        continue;
+      }
+      const row = state.map[change.y];
+      if (!row || !row[change.x]) {
+        continue;
+      }
+      row[change.x] = { type: change.type, powerup: change.powerup || null };
+    }
+  }
   state.players = snapshot.players.map((player) => {
     const key = player.ownerId || `id:${player.id}`;
     const prev = previousPlayers.get(key);
@@ -1031,12 +1120,23 @@ function broadcastSnapshot(force = false) {
   if (!network.isHost || state.mode !== "multiplayer" || state.screen !== "game") {
     return;
   }
+
   const t = now();
   if (!force && t - network.lastSnapshotSentAt < 1 / SNAPSHOT_RATE) {
     return;
   }
+
+  const includeFullMap =
+    force ||
+    !Array.isArray(network.lastSentMapState) ||
+    t - network.lastFullMapSnapshotAt >= MAP_RESYNC_SECONDS;
+
+  if (includeFullMap) {
+    network.lastFullMapSnapshotAt = t;
+  }
+
   network.lastSnapshotSentAt = t;
-  sendSocketMessage("game_snapshot", { snapshot: serializeGameState(), ts: t });
+  sendSocketMessage("game_snapshot", { snapshot: serializeGameState(includeFullMap), ts: t });
 }
 
 function updateLobbyNetwork(dt) {