feat(server): support http long polling.

global/config/config.go

@@ -86,6 +86,10 @@ type HTTPServer struct {
 	Host        string `yaml:"host"`
 	Port        int    `yaml:"port"`
 	Timeout     int32  `yaml:"timeout"`
+	LongPolling struct {
+		Enabled      bool `yaml:"enabled"`
+		MaxQueueSize int  `yaml:"max-queue-size"`
+	} `yaml:"long-polling"`
 	Post []struct {
 		URL    string `yaml:"url"`
 		Secret string `yaml:"secret"`
@@ -268,6 +272,12 @@ const httpDefault = `  # HTTP 通信设置
       # 反向HTTP超时时间, 单位秒
       # 最小值为5，小于5将会忽略本项设置
       timeout: 5
+      # 长轮询拓展
+      long-polling:
+        # 是否开启
+        enabled: false
+        # 消息队列大小，0 表示不限制队列大小，谨慎使用
+        max-queue-size: 2000
       middlewares:
         <<: *default # 引用默认中间件
       # 反向HTTP POST地址列表

server/http.go

@@ -160,6 +160,9 @@ func RunHTTPServerAndClients(bot *coolq.CQBot, conf *config.HTTPServer) {
 	if conf.RateLimit.Enabled {
 		s.api.use(rateLimit(conf.RateLimit.Frequency, conf.RateLimit.Bucket))
 	}
+	if conf.LongPolling.Enabled {
+		s.api.use(longPolling(bot, conf.LongPolling.MaxQueueSize))
+	}
 
 	go func() {
 		log.Infof("CQ HTTP 服务器已启动: %v", addr)

server/middlewares.go

@@ -1,6 +1,7 @@
 package server
 
 import (
+	"container/list"
 	"context"
 	"os"
 	"sync"
@@ -54,3 +55,37 @@ func findFilter(file string) global.Filter {
 	defer filterMutex.RUnlock()
 	return filters[file]
 }
+
+func longPolling(bot *coolq.CQBot, maxSize int) handler {
+	var mutex sync.Mutex
+	cond := sync.NewCond(&mutex)
+	queue := list.New()
+	bot.OnEventPush(func(event *coolq.Event) {
+		mutex.Lock()
+		defer mutex.Unlock()
+		queue.PushBack(event.RawMsg)
+		for maxSize != 0 && queue.Len() > maxSize {
+			queue.Remove(queue.Front())
+		}
+		cond.Signal()
+	})
+	return func(action string, p resultGetter) coolq.MSG {
+		if action != "get_updates" {
+			return nil
+		}
+		mutex.Lock()
+		defer mutex.Unlock()
+		if queue.Len() == 0 {
+			cond.Wait()
+		}
+		limit := int(p.Get("limit").Int())
+		if limit <= 0 || queue.Len() < limit {
+			limit = queue.Len()
+		}
+		ret := make([]interface{}, limit)
+		for i := 0; i < limit; i++ {
+			ret[i] = queue.Remove(queue.Front())
+		}
+		return coolq.OK(ret)
+	}
+}