log if discord messages are dropped because of full buffer

Author: Distortions81

fact/util.go

@@ -12,6 +12,7 @@ import (
 	"sort"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/bwmarrin/discordgo"
@@ -34,6 +35,9 @@ var (
 	banLock         sync.Mutex
 	AutoLaunchLock  sync.Mutex
 	FactRunningLock sync.Mutex
+
+	cmsDropCount           uint64
+	cmsLastDropLogUnixNano int64
 )
 
 func GetFactUPS() (float64, float64, float64) {
@@ -1389,11 +1393,30 @@ func CMS(channel string, text string) {
 	lines := strings.Split(text, "\n")
 
 	for _, line := range lines {
-		var item disc.CMSBuf
-		item.Channel = channel
-		item.Text = line
-
-		disc.CMSChan <- item
+		item := disc.CMSBuf{Channel: channel, Text: line}
+
+		select {
+		case disc.CMSChan <- item:
+		default:
+			// Buffer is full; drop the oldest message to make room, otherwise drop this one.
+			select {
+			case <-disc.CMSChan:
+			default:
+			}
+			select {
+			case disc.CMSChan <- item:
+			default:
+				atomic.AddUint64(&cmsDropCount, 1)
+				now := time.Now().UnixNano()
+				last := atomic.LoadInt64(&cmsLastDropLogUnixNano)
+				if now-last > int64(10*time.Second) && atomic.CompareAndSwapInt64(&cmsLastDropLogUnixNano, last, now) {
+					dropped := atomic.SwapUint64(&cmsDropCount, 0)
+					if dropped > 0 {
+						cwlog.DoLogCW("Discord CMS buffer full; dropped %d messages (Discord down or rate-limited).", dropped)
+					}
+				}
+			}
+		}
 	}
 }