fix: correct division by 0 issue in web percentage (#661)

internal/sync/http.go

@@ -37,33 +37,30 @@ func (w *worker) handleRoot(c *gin.Context) {
 		"Build":      version.Build,
 		"SyncStatus": w.status(),
 		"Stats": map[string]any{
-			"Labels":  getLast24Hours(),
-			"DNS":     dns,
-			"Blocked": blocked,
-			"BlockedPercentage": fmt.Sprintf(
-				"%.2f",
-				(float64(*total.NumBlockedFiltering)*100.0)/float64(*total.NumDnsQueries),
-			),
-			"Malware": malware,
-			"MalwarePercentage": fmt.Sprintf(
-				"%.2f",
-				(float64(*total.NumReplacedSafebrowsing)*100.0)/float64(*total.NumDnsQueries),
-			),
-			"Adult": adult,
-			"AdultPercentage": fmt.Sprintf(
-				"%.2f",
-				(float64(*total.NumReplacedParental)*100.0)/float64(*total.NumDnsQueries),
-			),
-
-			"TotalDNS":     total.NumDnsQueries,
-			"TotalBlocked": total.NumBlockedFiltering,
-			"TotalMalware": total.NumReplacedSafebrowsing,
-			"TotalAdult":   total.NumReplacedParental,
+			"Labels":            getLast24Hours(),
+			"DNS":               dns,
+			"Blocked":           blocked,
+			"BlockedPercentage": percent(total.NumBlockedFiltering, total.NumDnsQueries),
+			"Malware":           malware,
+			"MalwarePercentage": percent(total.NumReplacedSafebrowsing, total.NumDnsQueries),
+			"Adult":             adult,
+			"AdultPercentage":   percent(total.NumReplacedParental, total.NumDnsQueries),
+			"TotalDNS":          total.NumDnsQueries,
+			"TotalBlocked":      total.NumBlockedFiltering,
+			"TotalMalware":      total.NumReplacedSafebrowsing,
+			"TotalAdult":        total.NumReplacedParental,
 		},
 	},
 	)
 }
 
+func percent(a, b *int) string {
+	if a == nil || b == nil || *b == 0 {
+		return "0.00"
+	}
+	return fmt.Sprintf("%.2f", (float64(*a)*100.0)/float64(*b))
+}
+
 func (w *worker) handleLogs(c *gin.Context) {
 	c.Data(http.StatusOK, "text/plain", []byte(strings.Join(log.Logs(), "")))
 }

internal/sync/http_test.go

@@ -0,0 +1,30 @@
+package sync
+
+import (
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("Percent", func() {
+	DescribeTable("calculating percentage",
+		func(a, b *int, want string) {
+			Expect(percent(a, b)).To(Equal(want))
+		},
+		Entry("both inputs are nil", nil, nil, "0.00"),
+		Entry("a is nil, b is non-zero", nil, intPtr(10), "0.00"),
+		Entry("b is nil, a is non-zero", intPtr(10), nil, "0.00"),
+		Entry("b is zero", intPtr(10), intPtr(0), "0.00"),
+		Entry("normal case with positive int values", intPtr(25), intPtr(100), "25.00"),
+		Entry("a and b are equal", intPtr(50), intPtr(50), "100.00"),
+		Entry("a is zero, b is positive", intPtr(0), intPtr(50), "0.00"),
+		Entry("large positive values", intPtr(1000), intPtr(4000), "25.00"),
+		Entry("a greater than b", intPtr(150), intPtr(100), "150.00"),
+		Entry("negative values for a and b", intPtr(-25), intPtr(-50), "50.00"),
+		Entry("a is positive, b is negative", intPtr(25), intPtr(-50), "-50.00"),
+		Entry("a is negative, b is positive", intPtr(-25), intPtr(50), "-50.00"),
+	)
+})
+
+func intPtr(i int) *int {
+	return &i
+}