Fix reconnection on client-side timeouts in the JS5 client

Signed-off-by: Graham <gpe@openrs2.org>

archive/src/main/kotlin/org/openrs2/archive/cache/Js5ChannelHandler.kt

@@ -7,6 +7,7 @@ import io.netty.channel.ChannelHandler
 import io.netty.channel.ChannelHandlerContext
 import io.netty.channel.ChannelPipeline
 import io.netty.channel.SimpleChannelInboundHandler
+import io.netty.handler.timeout.ReadTimeoutException
 import kotlinx.coroutines.runBlocking
 import org.openrs2.buffer.crc32
 import org.openrs2.buffer.use
@@ -15,6 +16,7 @@ import org.openrs2.cache.Js5Compression
 import org.openrs2.cache.Js5Index
 import org.openrs2.cache.Js5MasterIndex
 import org.openrs2.cache.MasterIndexFormat
+import java.nio.channels.ClosedChannelException
 import java.time.Instant
 import kotlin.coroutines.Continuation
 import kotlin.coroutines.resume
@@ -46,12 +48,13 @@ public abstract class Js5ChannelHandler(
     )
 
     private enum class State {
-        ACTIVE,
+        CONNECTING,
         CLIENT_OUT_OF_DATE,
+        CONNECTED,
         RESUMING_CONTINUATION
     }
 
-    private var state = State.ACTIVE
+    private var state = State.CONNECTING
     private var buildAttempts = 0
     private var reconnectionAttempts = 0
     private val inFlightRequests = mutableSetOf<InFlightRequest>()
@@ -69,11 +72,22 @@ public abstract class Js5ChannelHandler(
     protected abstract fun incrementVersion()
 
     override fun channelActive(ctx: ChannelHandlerContext) {
+        assert(state == State.CONNECTING)
+
         ctx.writeAndFlush(createInitMessage(), ctx.voidPromise())
         ctx.read()
     }
 
     override fun channelReadComplete(ctx: ChannelHandlerContext) {
+        /*
+         * Wait for us to receive the OK message before we send JS5 requests,
+         * as the RS3 JS5 server ignores any JS5 requests sent before the OK
+         * message is received.
+         */
+        if (state != State.CONNECTED) {
+            return
+        }
+
         var flush = false
 
         while (inFlightRequests.size < maxInFlightRequests) {
@@ -97,7 +111,7 @@ public abstract class Js5ChannelHandler(
 
     override fun channelInactive(ctx: ChannelHandlerContext) {
         if (state == State.CLIENT_OUT_OF_DATE) {
-            state = State.ACTIVE
+            state = State.CONNECTING
             bootstrap.connect(hostname, port)
         } else if (state != State.RESUMING_CONTINUATION) {
             if (isComplete()) {
@@ -132,7 +146,7 @@ public abstract class Js5ChannelHandler(
             inFlightRequests.clear()
 
             // re-connect
-            state = State.ACTIVE
+            state = State.CONNECTING
             bootstrap.connect(hostname, port)
         }
     }
@@ -140,12 +154,26 @@ public abstract class Js5ChannelHandler(
     override fun exceptionCaught(ctx: ChannelHandlerContext, cause: Throwable) {
         releaseGroups()
 
+        if (state == State.RESUMING_CONTINUATION) {
+            logger.warn(cause) { "Swallowing exception as continuation has already resumed" }
+        } else if (cause != ReadTimeoutException.INSTANCE) {
+            /*
+             * We skip continuation resumption if there's a read timeout - this
+             * allows channelInactive() to attempt to reconnect if we haven't
+             * used too many reconnection attempts.
+             */
             state = State.RESUMING_CONTINUATION
-        ctx.close()
             continuation.resumeWithException(cause)
         }
 
+        if (cause !is ClosedChannelException) {
+            ctx.close()
+        }
+    }
+
     protected fun handleOk(ctx: ChannelHandlerContext) {
+        assert(state == State.CONNECTING)
+
         configurePipeline(ctx.pipeline())
 
         val msg = createConnectedMessage()
@@ -153,12 +181,16 @@ public abstract class Js5ChannelHandler(
             ctx.write(msg, ctx.voidPromise())
         }
 
+        state = State.CONNECTED
+
         if (masterIndex == null && pendingRequests.isEmpty()) {
             request(ctx, Js5Archive.ARCHIVESET, Js5Archive.ARCHIVESET, 0, 0)
         }
     }
 
     protected fun handleClientOutOfDate(ctx: ChannelHandlerContext) {
+        assert(state == State.CONNECTING)
+
         if (++buildAttempts > maxBuildAttempts) {
             throw Exception("Failed to identify current version")
         }
@@ -216,8 +248,9 @@ public abstract class Js5ChannelHandler(
             }
 
             state = State.RESUMING_CONTINUATION
-            ctx.close()
             continuation.resume(Unit)
+
+            ctx.close()
         }
     }