fix TimedSlidingWindowI64 bug of start index incorrectly wraped around (#24)

Author: jf-tech

times/timedSlidingWindow.go

@@ -2,8 +2,6 @@ package times
 
 import (
 	"time"
-
-	"github.com/jf-tech/go-corelib/maths"
 )
 
 /*
@@ -108,9 +106,10 @@ func (t *TimedSlidingWindowI64) Add(amount int64) {
 			t.buckets[i%t.n] = 0
 		}
 		t.end = (t.start + idx) % t.n
-		newStart := maths.MaxInt(t.start+idx-t.n+1, t.start)
-		t.startTime = t.startTime.Add(time.Duration(newStart-t.start) * t.bucket)
-		t.start = newStart
+		if idx >= t.n {
+			t.startTime = t.startTime.Add(time.Duration(idx-t.n+1) * t.bucket)
+			t.start = (t.start + idx - t.n + 1) % t.n
+		}
 		t.buckets[t.end] += amount
 		t.total += amount
 	} else {

times/timedSlidingWindow_test.go

@@ -65,6 +65,26 @@ func TestTimedSlidingWindowI64(t *testing.T) {
 	})
 }
 
+func TestTimedSlidingWindowI64_ContinousIncr(t *testing.T) {
+	tc := &testClock{}
+	sw := NewTimedSlidingWindowI64(5*time.Second, 1*time.Second, tc)
+	test := func(adv time.Duration, add int64, expected []int64) {
+		tc.adv(adv)
+		sw.Add(add)
+		assert.Equal(t, expected, sw.buckets)
+		total := int64(0)
+		for i := 0; i < len(expected); i++ {
+			total += expected[i]
+		}
+		assert.Equal(t, total, sw.Total())
+	}
+	expected := []int64{0, 0, 0, 0, 0}
+	for i := 0; i < 100; i++ {
+		expected[(i+1)%len(expected)] = int64(i)
+		test(time.Second, int64(i), expected)
+	}
+}
+
 const (
 	tswBenchSeed          = int64(1234)
 	tswBenchWindow        = time.Minute