From 10e731f260e571c95f785e52c1538dd6078ff4b6 Mon Sep 17 00:00:00 2001
From: Him188 <Him188@mamoe.net>
Date: Sat, 22 Apr 2023 12:02:04 +0100
Subject: [PATCH] [core] CoroutineOnDemandValueScope: remove CreatingProducer
 state

---
 .../auth/CoroutineOnDemandValueScope.kt       | 12 +++++------
 .../kotlin/network/auth/ProducerState.kt      | 21 +++++++------------
 2 files changed, 12 insertions(+), 21 deletions(-)

diff --git a/mirai-core/src/commonMain/kotlin/network/auth/CoroutineOnDemandValueScope.kt b/mirai-core/src/commonMain/kotlin/network/auth/CoroutineOnDemandValueScope.kt
index 5a068a772..9fad94aeb 100644
--- a/mirai-core/src/commonMain/kotlin/network/auth/CoroutineOnDemandValueScope.kt
+++ b/mirai-core/src/commonMain/kotlin/network/auth/CoroutineOnDemandValueScope.kt
@@ -175,12 +175,10 @@ internal class CoroutineOnDemandValueScope<T, V>(
         state.loop { state ->
             when (state) {
                 is ProducerState.JustInitialized -> {
-                    compareAndSetState(state, ProducerState.CreatingProducer { Producer(ticket) })
-                    // loop again
-                }
-
-                is ProducerState.CreatingProducer -> {
-                    compareAndSetState(state, ProducerState.ProducerReady(state.producer))
+                    val ready = ProducerState.ProducerReady { Producer(ticket) }
+                    if (compareAndSetState(state, ready)) {
+                        ready.startProducerIfNotYet()
+                    }
                     // loop again
                 }
 
@@ -193,7 +191,7 @@ internal class CoroutineOnDemandValueScope<T, V>(
                 is ProducerState.Consuming -> throw IllegalProducerStateException(state) // a value is already ready
 
                 is ProducerState.Consumed -> {
-                    if (compareAndSetState(state, ProducerState.ProducerReady(state.producer))) {
+                    if (compareAndSetState(state, ProducerState.ProducerReady { state.producer })) {
                         // wake up producer async.
                         state.producerLatch.resumeWith(Result.success(ticket))
                         // loop again to switch state atomically to Producing. 
diff --git a/mirai-core/src/commonMain/kotlin/network/auth/ProducerState.kt b/mirai-core/src/commonMain/kotlin/network/auth/ProducerState.kt
index 99666a2ed..128ac9ebe 100644
--- a/mirai-core/src/commonMain/kotlin/network/auth/ProducerState.kt
+++ b/mirai-core/src/commonMain/kotlin/network/auth/ProducerState.kt
@@ -32,11 +32,6 @@ internal sealed interface ProducerState<T, V> {
      *                                         |
      *                                         | 调用 [expectMore]
      *                                         |
-     *                                         V 
-     *                                  CreatingProducer 
-     *                                         |
-     *                                         | 
-     *                                         |                                                     
      *                                         V                                                      
      *                                   ProducerReady (从此用户协程作为 producer 在后台运行)             
      *                                         |                                                      
@@ -105,17 +100,15 @@ internal sealed interface ProducerState<T, V> {
         val producer: OnDemandProducerScope<T, V>
     }
 
-    // This is need — to ensure [launchProducer] is called exactly once.
-    class CreatingProducer<T, V>(
-        launchProducer: () -> OnDemandProducerScope<T, V>
-    ) : HasProducer<T, V> {
-        override val producer: OnDemandProducerScope<T, V> by lazy(launchProducer)
-        override fun toString(): String = "CreatingProducer"
-    }
-
     class ProducerReady<T, V>(
-        override val producer: OnDemandProducerScope<T, V>,
+        launchProducer: () -> OnDemandProducerScope<T, V>,
     ) : HasProducer<T, V> {
+        override val producer: OnDemandProducerScope<T, V> by lazy(launchProducer) // `lazy` is synchronized
+
+        fun startProducerIfNotYet() {
+            producer
+        }
+
         override fun toString(): String = "ProducerReady"
     }