Simplify with `fold`

mirai-core-qqandroid/src/commonMain/kotlin/net/mamoe/mirai/qqandroid/QQAndroidBot.kt

@@ -20,6 +20,8 @@ import io.ktor.client.statement.HttpResponse
 import kotlinx.coroutines.CoroutineName
 import kotlinx.coroutines.async
 import kotlinx.coroutines.io.ByteReadChannel
+import kotlinx.coroutines.withContext
+import kotlinx.serialization.UnstableDefault
 import kotlinx.serialization.json.Json
 import kotlinx.serialization.json.JsonConfiguration
 import kotlinx.serialization.json.int
@@ -68,6 +70,7 @@ internal abstract class QQAndroidBotBase constructor(
     override val uin: Long get() = client.uin
 
     companion object {
+        @OptIn(UnstableDefault::class)
         val json = Json(JsonConfiguration(ignoreUnknownKeys = true, encodeDefaults = true))
     }
 
@@ -226,7 +229,7 @@ internal abstract class QQAndroidBotBase constructor(
     @MiraiExperimentalAPI
     override suspend fun _lowLevelGetAnnouncements(groupId: Long, page: Int, amount: Int): GroupAnnouncementList {
         val data = network.async {
-            HttpClient().post<String> {
+            MiraiPlatformUtils.Http.post<String> {
                 url("https://web.qun.qq.com/cgi-bin/announce/list_announce")
                 body = MultiPartFormDataContent(formData {
                     append("qid", groupId)
@@ -254,8 +257,8 @@ internal abstract class QQAndroidBotBase constructor(
     @LowLevelAPI
     @MiraiExperimentalAPI
     override suspend fun _lowLevelSendAnnouncement(groupId: Long, announcement: GroupAnnouncement): String {
-        val rep = network.async {
-            HttpClient().post<String> {
+        val rep = withContext(network.coroutineContext) {
+            MiraiPlatformUtils.Http.post<String> {
                 url("https://web.qun.qq.com/cgi-bin/announce/add_qun_notice")
                 body = MultiPartFormDataContent(formData {
                     append("qid", groupId)
@@ -282,7 +285,7 @@ internal abstract class QQAndroidBotBase constructor(
                 }
             }
         }
-        val jsonObj = json.parseJson(rep.await())
+        val jsonObj = json.parseJson(rep)
         return jsonObj.jsonObject["new_fid"]?.primitive?.content
             ?: throw throw IllegalStateException("Send Announcement fail group:$groupId msg:${jsonObj.jsonObject["em"]} content:${announcement.msg.text}")
     }
@@ -290,8 +293,8 @@ internal abstract class QQAndroidBotBase constructor(
     @LowLevelAPI
     @MiraiExperimentalAPI
     override suspend fun _lowLevelDeleteAnnouncement(groupId: Long, fid: String) {
-        val rep = network.async {
-            HttpClient().post<String> {
+        val data = withContext(network.coroutineContext) {
+            MiraiPlatformUtils.Http.post<String> {
                 url("https://web.qun.qq.com/cgi-bin/announce/del_feed")
                 body = MultiPartFormDataContent(formData {
                     append("qid", groupId)
@@ -310,7 +313,6 @@ internal abstract class QQAndroidBotBase constructor(
                 }
             }
         }
-        val data = rep.await()
         val jsonObj = json.parseJson(data)
         if (jsonObj.jsonObject["ec"]?.int ?: 1 != 0) {
             throw throw IllegalStateException("delete Announcement fail group:$groupId msg:${jsonObj.jsonObject["em"]} fid:$fid")
@@ -361,17 +363,11 @@ internal abstract class QQAndroidBotBase constructor(
     }
 
     /**
-     * 获取 获取群公告 所需的bkn参数
+     * 获取 获取群公告 所需的 bkn 参数
      * */
-    val bkn: Int
-        get() {
-            val str = client.wLoginSigInfo.sKey.data.encodeToString()
-            var magic = 5381
-            for (i in str) {
-                magic += magic.shl(5) + i.toInt()
-            }
-            return Int.MAX_VALUE.and(magic)
-        }
+    private val bkn: Int
+        get() = client.wLoginSigInfo.sKey.data
+            .fold(5381) { acc: Int, b: Byte -> acc + acc.shl(5) + b.toInt() }
 }
 
 @Suppress("DEPRECATION")