Introduce experimental `whileSelectMessages` and `selectMessages`

mirai-core/src/commonMain/kotlin/net.mamoe.mirai/event/select.kt

+/*
+ * Copyright 2020 Mamoe Technologies and contributors.
+ *
+ * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ *
+ * https://github.com/mamoe/mirai/blob/master/LICENSE
+ */
+
+package net.mamoe.mirai.event
+
+import kotlinx.coroutines.*
+import net.mamoe.mirai.message.MessagePacket
+import net.mamoe.mirai.utils.MiraiExperimentalAPI
+import net.mamoe.mirai.utils.SinceMirai
+import kotlin.experimental.ExperimentalTypeInference
+import kotlin.jvm.JvmName
+
+/**
+ *
+ */
+@SinceMirai("0.29.0")
+@Suppress("unused")
+@MiraiExperimentalAPI
+suspend inline fun <reified T : MessagePacket<*, *>> T.whileSelectMessages(
+    timeoutMillis: Long = -1,
+    crossinline selectBuilder: @MessageDsl MessageSelectBuilder<T, Boolean>.() -> Unit
+) {
+    require(timeoutMillis == -1L || timeoutMillis > 0) { "timeoutMillis must be -1 or > 0 " }
+
+    return coroutineScope {
+        var deferred: CompletableDeferred<Boolean> = CompletableDeferred()
+
+        MessageSelectBuilder<T, Boolean>(SELECT_MESSAGE_STUB) { filter: T.(String) -> Boolean, listener: MessageListener<T, Any?> ->
+            subscribeAlways<T> {
+                val toString = it.message.toString()
+                if (filter.invoke(it, toString)) {
+                    val value = listener.invoke(it, toString)
+                    if (value !== SELECT_MESSAGE_STUB) {
+                        while (deferred.isCompleted)
+                            delay(1)
+
+                        deferred.complete(value as Boolean)
+                    }
+                }
+            }
+        }.apply(selectBuilder)
+
+        while (deferred.await()) {
+            deferred = CompletableDeferred()
+        }
+        coroutineContext[Job]!!.cancelChildren()
+    }
+}
+
+@OptIn(ExperimentalTypeInference::class)
+@MiraiExperimentalAPI
+@SinceMirai("0.29.0")
+@JvmName("selectMessages1")
+suspend inline fun <reified T : MessagePacket<*, *>> T.selectMessagesUnit(
+    timeoutMillis: Long = -1,
+    crossinline selectBuilder: @MessageDsl MessageSelectBuilder<T, Unit>.() -> Unit
+) = selectMessages(timeoutMillis, selectBuilder)
+
+
+/**
+ * @param timeoutMillis 超时. 单位为毫秒. `-1` 为不限制
+ */
+@MiraiExperimentalAPI
+@SinceMirai("0.29.0")
+@Suppress("unused") // false positive
+@OptIn(ExperimentalTypeInference::class)
+@BuilderInference
+suspend inline fun <reified T : MessagePacket<*, *>, R> T.selectMessages(
+    timeoutMillis: Long = -1,
+    @BuilderInference
+    crossinline selectBuilder: @MessageDsl MessageSelectBuilder<T, R>.() -> Unit
+): R {
+    require(timeoutMillis == -1L || timeoutMillis > 0) { "timeoutMillis must be -1 or > 0 " }
+
+    return coroutineScope {
+        val deferred = CompletableDeferred<R>()
+
+        MessageSelectBuilder<T, R>(SELECT_MESSAGE_STUB) { filter: T.(String) -> Boolean, listener: MessageListener<T, Any?> ->
+            subscribeAlways<T> {
+                val toString = it.message.toString()
+                if (filter.invoke(it, toString)) {
+                    val value = listener.invoke(it, toString)
+                    if (value !== SELECT_MESSAGE_STUB) {
+                        @Suppress("UNCHECKED_CAST")
+                        deferred.complete(value as R)
+                    }
+                }
+            }
+        }.apply(selectBuilder)
+
+        deferred.await().also { coroutineContext[Job]!!.cancelChildren() }
+    }
+}
+
+@PublishedApi
+internal val SELECT_MESSAGE_STUB = Any()
+
+@SinceMirai("0.29.0")
+class MessageSelectBuilder<M : MessagePacket<*, *>, R>(
+    stub: Any?,
+    subscriber: (M.(String) -> Boolean, MessageListener<M, Any?>) -> Unit
+) : MessageSubscribersBuilder<M, Unit, R, Any?>(stub, subscriber)
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