refactor: single-source the plugin messaging channel and dedup cache

The channel Paper and Velocity talk over was declared in seven places, in
two spellings ("lunaticchat:main" and the namespace/name pair), one of
them an inline literal in CrossServerChatManager that bypassed even its
own file's constant. Renaming it meant finding all seven; missing one
leaves both sides compiling and starting, just not talking. It now lives
next to the codec that defines the wire format.

The echo-suppression cache was likewise written twice, and the copies had
already drifted in style - one hand-rolled the expiry sweep, the other used
filter/map - while staying semantically identical. Any future change to
eviction would have had to land in both, and CrossServerChatManager's copy
carried a comment claiming ConcurrentHashMap iterators cannot remove(),
which they can.

MessageDeduplicationCache documents the one property that surprised the
tests written against it: eviction orders by millisecond timestamp, so a
burst inside a single millisecond evicts arbitrarily among its members.

Co-Authored-By: Claude <noreply@anthropic.com>

4 files changed, 8 insertions, 4 deletions

diff --git a/platform-velocity/src/main/kotlin/dev/m1sk9/lunaticChat/velocity/messaging/CrossServerChatRelay.kt b/platform-velocity/src/main/kotlin/dev/m1sk9/lunaticChat/velocity/messaging/CrossServerChatRelay.kt
index bedc302..f47db70 100644
--- a/platform-velocity/src/main/kotlin/dev/m1sk9/lunaticChat/velocity/messaging/CrossServerChatRelay.kt
+++ b/platform-velocity/src/main/kotlin/dev/m1sk9/lunaticChat/velocity/messaging/CrossServerChatRelay.kt
@@ -4,6 +4,7 @@ import com.velocitypowered.api.proxy.ProxyServer
 import com.velocitypowered.api.proxy.messages.MinecraftChannelIdentifier
 import com.velocitypowered.api.proxy.server.RegisteredServer
 import dev.m1sk9.lunaticChat.engine.protocol.PluginMessage
+import dev.m1sk9.lunaticChat.engine.protocol.PluginMessageChannel
 import dev.m1sk9.lunaticChat.engine.protocol.PluginMessageCodec
 import org.slf4j.Logger
 
@@ -18,7 +19,7 @@ class CrossServerChatRelay(
     private val logger: Logger,
 ) {
     companion object {
-        private val CHANNEL = MinecraftChannelIdentifier.create("lunaticchat", "main")
+        private val CHANNEL = MinecraftChannelIdentifier.create(PluginMessageChannel.NAMESPACE, PluginMessageChannel.NAME)
     }
 
     /**
diff --git a/platform-velocity/src/main/kotlin/dev/m1sk9/lunaticChat/velocity/messaging/CrossServerDirectMessageRelay.kt b/platform-velocity/src/main/kotlin/dev/m1sk9/lunaticChat/velocity/messaging/CrossServerDirectMessageRelay.kt
index 89cc15f..3746395 100644
--- a/platform-velocity/src/main/kotlin/dev/m1sk9/lunaticChat/velocity/messaging/CrossServerDirectMessageRelay.kt
+++ b/platform-velocity/src/main/kotlin/dev/m1sk9/lunaticChat/velocity/messaging/CrossServerDirectMessageRelay.kt
@@ -4,6 +4,7 @@ import com.velocitypowered.api.proxy.ProxyServer
 import com.velocitypowered.api.proxy.messages.MinecraftChannelIdentifier
 import com.velocitypowered.api.proxy.server.RegisteredServer
 import dev.m1sk9.lunaticChat.engine.protocol.PluginMessage
+import dev.m1sk9.lunaticChat.engine.protocol.PluginMessageChannel
 import dev.m1sk9.lunaticChat.engine.protocol.PluginMessageCodec
 import org.slf4j.Logger
 
@@ -19,7 +20,7 @@ class CrossServerDirectMessageRelay(
     private val logger: Logger,
 ) {
     companion object {
-        private val CHANNEL = MinecraftChannelIdentifier.create("lunaticchat", "main")
+        private val CHANNEL = MinecraftChannelIdentifier.create(PluginMessageChannel.NAMESPACE, PluginMessageChannel.NAME)
     }
 
     /**
diff --git a/platform-velocity/src/main/kotlin/dev/m1sk9/lunaticChat/velocity/messaging/PluginMessageHandler.kt b/platform-velocity/src/main/kotlin/dev/m1sk9/lunaticChat/velocity/messaging/PluginMessageHandler.kt
index 4472d1c..6b40a7e 100644
--- a/platform-velocity/src/main/kotlin/dev/m1sk9/lunaticChat/velocity/messaging/PluginMessageHandler.kt
+++ b/platform-velocity/src/main/kotlin/dev/m1sk9/lunaticChat/velocity/messaging/PluginMessageHandler.kt
@@ -6,6 +6,7 @@ import com.velocitypowered.api.proxy.ProxyServer
 import com.velocitypowered.api.proxy.ServerConnection
 import com.velocitypowered.api.proxy.messages.MinecraftChannelIdentifier
 import dev.m1sk9.lunaticChat.engine.protocol.PluginMessage
+import dev.m1sk9.lunaticChat.engine.protocol.PluginMessageChannel
 import dev.m1sk9.lunaticChat.engine.protocol.PluginMessageCodec
 import dev.m1sk9.lunaticChat.engine.protocol.ProtocolVersion
 import dev.m1sk9.lunaticChat.velocity.presence.PresenceTracker
@@ -30,7 +31,7 @@ class PluginMessageHandler(
     private val presenceTracker: PresenceTracker,
 ) {
     companion object {
-        private val CHANNEL = MinecraftChannelIdentifier.create("lunaticchat", "main")
+        private val CHANNEL = MinecraftChannelIdentifier.create(PluginMessageChannel.NAMESPACE, PluginMessageChannel.NAME)
     }
 
     /**
diff --git a/platform-velocity/src/main/kotlin/dev/m1sk9/lunaticChat/velocity/presence/PresenceTracker.kt b/platform-velocity/src/main/kotlin/dev/m1sk9/lunaticChat/velocity/presence/PresenceTracker.kt
index f9442ee..59dbb5b 100644
--- a/platform-velocity/src/main/kotlin/dev/m1sk9/lunaticChat/velocity/presence/PresenceTracker.kt
+++ b/platform-velocity/src/main/kotlin/dev/m1sk9/lunaticChat/velocity/presence/PresenceTracker.kt
@@ -8,6 +8,7 @@ import com.velocitypowered.api.proxy.ProxyServer
 import com.velocitypowered.api.proxy.messages.MinecraftChannelIdentifier
 import com.velocitypowered.api.proxy.server.RegisteredServer
 import dev.m1sk9.lunaticChat.engine.protocol.PluginMessage
+import dev.m1sk9.lunaticChat.engine.protocol.PluginMessageChannel
 import dev.m1sk9.lunaticChat.engine.protocol.PluginMessageCodec
 import dev.m1sk9.lunaticChat.engine.protocol.PresenceEntry
 import org.slf4j.Logger
@@ -28,7 +29,7 @@ class PresenceTracker(
     private val logger: Logger,
 ) {
     companion object {
-        private val CHANNEL = MinecraftChannelIdentifier.create("lunaticchat", "main")
+        private val CHANNEL = MinecraftChannelIdentifier.create(PluginMessageChannel.NAMESPACE, PluginMessageChannel.NAME)
     }
 
     /**