fix wsSongListRoutes

- duplicated session is not permited.
- re-tx logic add

webserver/src/main/kotlin/space/mori/chzzk_bot/webserver/routes/WSSongListRoutes.kt

@@ -7,6 +7,7 @@ import io.ktor.websocket.*
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.channels.ClosedReceiveChannelException
+import kotlinx.coroutines.delay
 import kotlinx.coroutines.launch
 import kotlinx.serialization.Serializable
 import kotlinx.serialization.json.Json
@@ -19,23 +20,52 @@ import space.mori.chzzk_bot.common.services.UserService
 import space.mori.chzzk_bot.common.utils.getYoutubeVideo
 import space.mori.chzzk_bot.webserver.UserSession
 import java.util.concurrent.ConcurrentHashMap
-import java.util.concurrent.ConcurrentLinkedQueue
 
 fun Routing.wsSongListRoutes() {
-    val sessions = ConcurrentHashMap<String, ConcurrentLinkedQueue<WebSocketServerSession>>()
+    val sessions = ConcurrentHashMap<String, WebSocketServerSession>()
     val status = ConcurrentHashMap<String, SongType>()
     val logger = LoggerFactory.getLogger("WSSongListRoutes")
 
     val dispatcher: CoroutinesEventBus by inject(CoroutinesEventBus::class.java)
 
     fun addSession(uid: String, session: WebSocketServerSession) {
-        sessions.computeIfAbsent(uid) { ConcurrentLinkedQueue() }.add(session)
+        if(sessions[uid] != null) {
+            CoroutineScope(Dispatchers.Default).launch {
+                sessions[uid]?.close(
+                    CloseReason(CloseReason.Codes.VIOLATED_POLICY,
+                    "Duplicated sessions."
+                ))
+            }
+        }
+        sessions[uid] = session
     }
 
-    fun removeSession(uid: String, session: WebSocketServerSession) {
-        sessions[uid]?.remove(session)
-        if(sessions[uid]?.isEmpty() == true) {
-            sessions.remove(uid)
+    fun removeSession(uid: String) {
+        sessions.remove(uid)
+    }
+
+    suspend fun sendWithRetry(ws: WebSocketServerSession, res: SongResponse, maxRetries: Int, delayMillis: Long = 3000L) {
+        var attempt = 0
+        var sentSuccessfully = false
+
+        while (attempt < maxRetries && !sentSuccessfully) {
+            try {
+                // Attempt to send the message
+                ws.sendSerialized(res)
+                sentSuccessfully = true // If no exception, mark as sent successfully
+                logger.debug("Message sent successfully on attempt $attempt")
+            } catch (e: Exception) {
+                attempt++
+                logger.warn("Failed to send message on attempt $attempt. Retrying in $delayMillis ms.")
+                logger.warn(e.stackTraceToString())
+
+                // Wait before retrying
+                delay(delayMillis)
+            }
+        }
+
+        if (!sentSuccessfully) {
+            logger.error("Failed to send message after $maxRetries attempts.")
         }
     }
 
@@ -63,7 +93,7 @@ fun Routing.wsSongListRoutes() {
                     null,
                 ))
             }
-            removeSession(uid, this)
+            removeSession(uid)
         }
 
         try {
@@ -164,7 +194,7 @@ fun Routing.wsSongListRoutes() {
         } catch(e: ClosedReceiveChannelException) {
             logger.error("Error in WebSocket: ${e.message}")
         } finally {
-            removeSession(uid, this)
+            removeSession(uid)
         }
     }
 
@@ -173,18 +203,16 @@ fun Routing.wsSongListRoutes() {
         CoroutineScope(Dispatchers.Default).launch {
             val user = UserService.getUser(it.uid)
             if(user != null) {
-                sessions[user.token ?: ""]?.forEach { ws ->
-                    ws.sendSerialized(
-                        SongResponse(
-                            it.type.value,
-                            it.uid,
-                            it.reqUid,
-                            it.name,
-                            it.author,
-                            it.time,
-                            it.url
-                        )
-                    )
+                sessions[user.token ?: ""]?.let { ws ->
+                    sendWithRetry(ws, SongResponse(
+                        it.type.value,
+                        it.uid,
+                        it.reqUid,
+                        it.name,
+                        it.author,
+                        it.time,
+                        it.url
+                    ), 3)
                 }
             }
         }
@@ -194,9 +222,8 @@ fun Routing.wsSongListRoutes() {
             CoroutineScope(Dispatchers.Default).launch {
                 val user = UserService.getUser(it.uid)
                 if(user != null) {
-                    sessions[user.token]?.forEach { ws ->
-                        ws.sendSerialized(
-                            SongResponse(
+                    sessions[user.token ?: ""]?.let { ws ->
+                        sendWithRetry(ws, SongResponse(
                                 it.type.value,
                                 it.uid,
                                 null,
@@ -204,9 +231,8 @@ fun Routing.wsSongListRoutes() {
                                 null,
                                 null,
                                 null
-                            )
-                        )
-                        removeSession(user.token ?: "", ws)
+                            ), 3)
+                        removeSession(user.token ?: "")
                     }
                 }
             }