fix docker healthcheck formatting

internal/watcher/health/monitor/docker.go

@@ -1,8 +1,6 @@
 package monitor
 
 import (
-	"bytes"
-
 	"github.com/yusing/go-proxy/internal/docker"
 	"github.com/yusing/go-proxy/internal/net/types"
 
@@ -36,16 +34,10 @@ func (mon *DockerHealthMonitor) CheckHealth() (result *health.HealthCheckResult,
 	}
 	result = new(health.HealthCheckResult)
 	result.Healthy = cont.State.Health.Status == dockerTypes.Healthy
-	detail := new(bytes.Buffer)
-	for _, status := range cont.State.Health.Log {
-		detail.WriteString(status.Output)
-		detail.WriteString("\n")
-	}
-	result.Detail = detail.String()
 	if len(cont.State.Health.Log) > 0 {
-		last := cont.State.Health.Log[len(cont.State.Health.Log)-1].End
-		first := cont.State.Health.Log[0].Start
-		result.Latency = last.Sub(first)
+		lastLog := cont.State.Health.Log[len(cont.State.Health.Log)-1]
+		result.Detail = lastLog.Output
+		result.Latency = lastLog.End.Sub(lastLog.Start)
 	}
 	return
 }

internal/watcher/health/monitor/json.go

@@ -28,6 +28,10 @@ func (jsonRepr *JSONRepresentation) MarshalJSON() ([]byte, error) {
 	if url == "http://:0" {
 		url = ""
 	}
+	lastSeen := "never"
+	if !jsonRepr.LastSeen.IsZero() {
+		lastSeen = strutils.FormatTime(jsonRepr.LastSeen)
+	}
 	return json.Marshal(map[string]any{
 		"name":        jsonRepr.Name,
 		"config":      jsonRepr.Config,
@@ -39,7 +43,7 @@ func (jsonRepr *JSONRepresentation) MarshalJSON() ([]byte, error) {
 		"latency":     jsonRepr.Latency.Seconds(),
 		"latencyStr":  strconv.Itoa(int(jsonRepr.Latency.Milliseconds())) + " ms",
 		"lastSeen":    jsonRepr.LastSeen.Unix(),
-		"lastSeenStr": strutils.FormatTime(jsonRepr.LastSeen),
+		"lastSeenStr": lastSeen,
 		"detail":      jsonRepr.Detail,
 		"url":         url,
 		"extra":       jsonRepr.Extra,