2 files changed, 81 insertions, 0 deletions
diff --git a/src/gobang.go b/src/gobang.go
index 921597e..804cd34 100644
--- a/src/gobang.go
+++ b/src/gobang.go
@@ -14,6 +14,7 @@ import (
 	"slices"
 	"strings"
 	"syscall"
+	"time"
 
 	"guuid"
 )
@@ -201,6 +202,36 @@ func metric(type_ string, label string, args ...any) {
 	)
 }
 
+func Timed(label string, thunk func() any, args ...any) any {
+	var (
+		start time.Time
+		end   time.Time
+		ret   any
+	)
+
+
+	{
+		start = time.Now()
+		ret   = thunk()
+		end   = time.Now()
+	}
+
+	duration  := end.Sub(start)
+	metric(
+		"timer", label,
+		slices.Concat(
+			[]any{
+				"start", start,
+				"end", end,
+				"duration", duration,
+			},
+			args,
+		)...,
+	)
+
+	return ret
+}
+
 func MakeCounter(label string) func(...any) {
 	return func(args ...any) {
 		metric(
diff --git a/tests/gobang.go b/tests/gobang.go
index e2dd61b..14fe829 100644
--- a/tests/gobang.go
+++ b/tests/gobang.go
@@ -383,6 +383,55 @@ func test_metric() {
 	})
 }
 
+func test_Timed() {
+	TestStart("Timed()")
+
+	Testing("we can use a noop thunk", func() {
+		savedLogger := slog.Default()
+		savedFlag   := emitMetric
+
+		s := new(strings.Builder)
+		SetLoggerOutput(s)
+		emitMetric = true
+
+		Timed("timer-label", func() any { return nil }, "key-1", "value-1")
+
+		var data map[string]interface{}
+		err := json.Unmarshal([]byte(s.String()), &data)
+		ErrorIf(err)
+
+		AssertEqual(data["type"].(string),  "timer")
+		AssertEqual(data["label"].(string), "timer-label")
+		AssertEqual(data["key-1"].(string), "value-1")
+
+		var ok bool
+		_, ok = data["start"].(string)
+		AssertEqual(ok, true)
+		_, ok = data["end"].(string)
+		AssertEqual(ok, true)
+		_, ok = data["duration"].(float64)
+		AssertEqual(ok, true)
+
+		slog.SetDefault(savedLogger)
+		emitMetric = savedFlag
+	})
+
+	Testing("it propagates the return value", func() {
+		savedLogger := slog.Default()
+		savedFlag   := emitMetric
+
+		s := new(strings.Builder)
+		SetLoggerOutput(s)
+		emitMetric = true
+
+		val := Timed("timer-label", func() any { return 123 }, "key-1", "value-1")
+		AssertEqual(val, 123)
+
+		slog.SetDefault(savedLogger)
+		emitMetric = savedFlag
+	})
+}
+
 func test_MakeCounter() {
 	TestStart("MakeCounter()")
 
@@ -875,6 +924,7 @@ func MainTest() {
 	test_Warning()
 	test_Error()
 	test_metric()
+	test_Timed()
 	test_MakeCounter()
 	test_MakeGauge()
 	test_ErrorIf()