Reduce CombinedStateObserver hierarchy: use List

mirai-core/src/commonMain/kotlin/network/handler/state/CombinedStateObserver.kt

@@ -13,16 +13,14 @@ import net.mamoe.mirai.internal.network.handler.NetworkHandler
 import net.mamoe.mirai.internal.network.handler.NetworkHandlerSupport
 
 internal class CombinedStateObserver(
-    private val first: StateObserver,
+    private val list: List<StateObserver>
-    private val last: StateObserver,
 ) : StateObserver {
     override fun stateChanged(
         networkHandler: NetworkHandlerSupport,
         previous: NetworkHandlerSupport.BaseStateImpl,
         new: NetworkHandlerSupport.BaseStateImpl
     ) {
-        first.stateChanged(networkHandler, previous, new)
+        list.forEach { it.stateChanged(networkHandler, previous, new) }
-        last.stateChanged(networkHandler, previous, new)
     }
 
     override fun exceptionOnCreatingNewState(
@@ -30,13 +28,11 @@ internal class CombinedStateObserver(
         previousState: NetworkHandlerSupport.BaseStateImpl,
         exception: Throwable
     ) {
-        first.exceptionOnCreatingNewState(networkHandler, previousState, exception)
+        list.forEach { it.exceptionOnCreatingNewState(networkHandler, previousState, exception) }
-        last.exceptionOnCreatingNewState(networkHandler, previousState, exception)
     }
 
     override fun beforeStateResume(networkHandler: NetworkHandler, state: NetworkHandlerSupport.BaseStateImpl) {
-        first.beforeStateResume(networkHandler, state)
+        list.forEach { it.beforeStateResume(networkHandler, state) }
-        last.beforeStateResume(networkHandler, state)
     }
 
     override fun afterStateResume(
@@ -44,30 +40,29 @@ internal class CombinedStateObserver(
         state: NetworkHandlerSupport.BaseStateImpl,
         result: Result<Unit>
     ) {
-        first.afterStateResume(networkHandler, state, result)
+        list.forEach { it.afterStateResume(networkHandler, state, result) }
-        last.afterStateResume(networkHandler, state, result)
     }
 
     override fun toString(): String {
-        return asSequence().joinToString(
+        return list.joinToString(
             prefix = "CombinedStateObserver[",
             postfix = "]",
             separator = " -> "
         ) { it.toString() }
     }
 
-    private fun asSequence(): Sequence<StateObserver> = sequence {
-        if (first is CombinedStateObserver) yieldAll(first.asSequence()) else yield(first)
-        if (last is CombinedStateObserver) yieldAll(last.asSequence()) else yield(last)
-    }
-
     companion object {
         operator fun StateObserver?.plus(last: StateObserver?): StateObserver {
             return when {
+                last == null -> this ?: StateObserver.NOP
                 this == null -> last
-                last == null -> this
+                else -> {
-                else -> CombinedStateObserver(this, last)
+                    val result = mutableListOf<StateObserver>()
-            } ?: StateObserver.NOP
+                    if (this is CombinedStateObserver) result.addAll(this.list) else result.add(this)
+                    if (last is CombinedStateObserver) result.addAll(last.list) else result.add(last)
+                    CombinedStateObserver(result)
+                }
+            }
         }
     }
 }

mirai-core/src/commonTest/kotlin/network/handler/StateObserverTest.kt

@@ -12,12 +12,14 @@ package net.mamoe.mirai.internal.network.handler
 import net.mamoe.mirai.internal.network.framework.AbstractMockNetworkHandlerTest
 import net.mamoe.mirai.internal.network.handler.NetworkHandler.State.CONNECTING
 import net.mamoe.mirai.internal.network.handler.NetworkHandler.State.INITIALIZED
+import net.mamoe.mirai.internal.network.handler.state.CombinedStateObserver
 import net.mamoe.mirai.internal.network.handler.state.CombinedStateObserver.Companion.plus
 import net.mamoe.mirai.internal.network.handler.state.StateChangedObserver
 import net.mamoe.mirai.internal.network.handler.state.StateObserver
 import org.junit.jupiter.api.Test
 import org.junit.jupiter.api.TestInstance
 import kotlin.test.assertEquals
+import kotlin.test.assertIs
 
 @TestInstance(TestInstance.Lifecycle.PER_METHOD)
 internal class StateObserverTest : AbstractMockNetworkHandlerTest() {
@@ -85,7 +87,7 @@ internal class StateObserverTest : AbstractMockNetworkHandlerTest() {
     @Test
     fun `can combine`() {
         val called = ArrayList<Pair<NetworkHandlerSupport.BaseStateImpl, NetworkHandlerSupport.BaseStateImpl>>()
-        components[StateObserver] = object : StateChangedObserver(CONNECTING) {
+        val added = object : StateChangedObserver(CONNECTING) {
             override fun stateChanged0(
                 networkHandler: NetworkHandlerSupport,
                 previous: NetworkHandlerSupport.BaseStateImpl,
@@ -93,6 +95,8 @@ internal class StateObserverTest : AbstractMockNetworkHandlerTest() {
             ) {
                 called.add(previous to new)
             }
+
+            override fun toString(): String = "1"
         } + object : StateChangedObserver(CONNECTING) {
             override fun stateChanged0(
                 networkHandler: NetworkHandlerSupport,
@@ -101,7 +105,13 @@ internal class StateObserverTest : AbstractMockNetworkHandlerTest() {
             ) {
                 called.add(previous to new)
             }
+
+            override fun toString(): String = "2"
         }
+        assertIs<CombinedStateObserver>(added)
+        assertEquals("CombinedStateObserver[1 -> 2]", added.toString())
+
+        components[StateObserver] = added
         val handler = createNetworkHandler()
         assertEquals(0, called.size)
         handler.setState(INITIALIZED)