feat(server): support long polling timeout.

server/middlewares.go

@@ -5,6 +5,8 @@ import (
 	"context"
 	"os"
 	"sync"
+	"sync/atomic"
+	"time"
 
 	"github.com/Mrs4s/go-cqhttp/coolq"
 	"github.com/Mrs4s/go-cqhttp/global"
@@ -73,19 +75,39 @@ func longPolling(bot *coolq.CQBot, maxSize int) handler {
 		if action != "get_updates" {
 			return nil
 		}
-		mutex.Lock()
-		defer mutex.Unlock()
-		if queue.Len() == 0 {
-			cond.Wait()
+		var (
+			ok      int32
+			ch      = make(chan []interface{}, 1)
+			timeout = time.Duration(p.Get("timeout").Int()) * time.Second
+		)
+		defer close(ch)
+		go func() {
+			mutex.Lock()
+			defer mutex.Unlock()
+			if queue.Len() == 0 {
+				cond.Wait()
+			}
+			if atomic.CompareAndSwapInt32(&ok, 0, 1) {
+				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())
+				}
+				ch <- ret
+			}
+		}()
+		if timeout != 0 {
+			select {
+			case <-time.After(timeout):
+				atomic.StoreInt32(&ok, 1)
+				return coolq.OK([]interface{}{})
+			case ret := <-ch:
+				return coolq.OK(ret)
+			}
 		}
-		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)
+		return coolq.OK(<-ch)
 	}
 }