fix(server): appropriately handle empty slots at game start

Author: xeruf

sdk/src/main/server-api/sc/framework/plugins/Player.kt

@@ -7,6 +7,7 @@ import com.thoughtworks.xstream.annotations.XStreamOmitField
 import org.slf4j.LoggerFactory
 import sc.api.plugins.ITeam
 import sc.api.plugins.host.IPlayerListener
+import sc.networking.clients.XStreamClient.DisconnectCause
 import sc.protocol.room.MoveRequest
 import sc.protocol.room.RoomMessage
 import sc.util.PlayerConverter
@@ -37,9 +38,9 @@ class Player @JvmOverloads constructor(
     var canTimeout: Boolean = false
 
     @XStreamOmitField
-    var left = false
+    var left: DisconnectCause? = null
 
-    fun hasLeft() = left
+    fun hasLeft() = left != null
 
     @XStreamOmitField
     var softTimeout = false

sdk/src/main/server-api/sc/protocol/RemovedFromGame.kt

@@ -8,4 +8,4 @@ import com.thoughtworks.xstream.annotations.XStreamAsAttribute
 data class RemovedFromGame(
         @XStreamAsAttribute
         val roomId: String
-): ProtocolPacket
+): ResponsePacket

server/src/main/java/sc/server/gaming/GameRoom.java

@@ -367,7 +367,10 @@ public synchronized void step(boolean forced) {
     if (getStatus() == GameStatus.CREATED) {
       if (forced) {
         logger.warn("Forcing game start for {}", game);
-        start();
+        if(getClients().size() < 2)
+          cancel();
+        else
+          start();
       } else {
         logger.info("Game isn't active yet, step was not forced.");
       }
@@ -406,7 +409,10 @@ protected void setStatus(GameStatus status) {
   /** Remove a player and stop the game. */
   public void removePlayer(Player player, XStreamClient.DisconnectCause cause) {
     logger.info("Removing {} from {}", player, this);
-    player.setLeft(true);
+    // Mark all non-joined players as left to trigger a draw when noone joined
+    // Might be superfluous through the check in "step", but keeping for safety
+    playerSlots.forEach(slot -> slot.getPlayer().setLeft(slot.isEmpty() ? cause : null));
+    player.setLeft(cause);
     if (!isOver())
       cancel();
   }

server/src/test/java/sc/server/network/LobbyGameTest.kt

@@ -10,6 +10,7 @@ import io.kotest.matchers.collections.*
 import io.kotest.matchers.nulls.*
 import io.kotest.matchers.string.*
 import sc.api.plugins.Team
+import sc.protocol.RemovedFromGame
 import sc.protocol.ResponsePacket
 import sc.protocol.requests.JoinPreparedRoomRequest
 import sc.protocol.requests.PrepareGameRequest
@@ -95,6 +96,18 @@ class LobbyGameTest: WordSpec({
                 room.clients.shouldBeEmpty()
                 room.isPauseRequested shouldBe true
             }
+    
+            "return GameResult on step" {
+                val roomListener = observeRoom(room.id)
+                admin.control(room.id).step(true)
+                val result = roomListener.waitForMessage(GameResult::class)
+                withClue("No Winner") {
+                    result.winner shouldBe null
+                }
+                adminListener.waitForMessage(RemovedFromGame::class)
+                roomListener.clearMessages() shouldBe 0
+                admin.closed shouldBe false
+            }
 
             val reservations = prepared.reservations
             players[0].joinGameWithReservation(reservations[0])