chore: add HumanizeTimestamp; make ConvertToFloat exportable

helpers/templates/time.go

@@ -14,13 +14,18 @@
 package templates
 
 import (
+	"errors"
 	"fmt"
 	"math"
 	"strconv"
 	"time"
+
+	"github.com/prometheus/common/model"
 )
 
-func convertToFloat(i interface{}) (float64, error) {
+var errNaNOrInf = errors.New("value is NaN or Inf")
+
+func ConvertToFloat(i interface{}) (float64, error) {
 	switch v := i.(type) {
 	case float64:
 		return v, nil
@@ -41,8 +46,20 @@ func convertToFloat(i interface{}) (float64, error) {
 	}
 }
 
+func FloatToTime(v float64) (*time.Time, error) {
+	if math.IsNaN(v) || math.IsInf(v, 0) {
+		return nil, errNaNOrInf
+	}
+	timestamp := v * 1e9
+	if timestamp > math.MaxInt64 || timestamp < math.MinInt64 {
+		return nil, fmt.Errorf("%v cannot be represented as a nanoseconds timestamp since it overflows int64", v)
+	}
+	t := model.TimeFromUnixNano(int64(timestamp)).Time().UTC()
+	return &t, nil
+}
+
 func HumanizeDuration(i interface{}) (string, error) {
-	v, err := convertToFloat(i)
+	v, err := ConvertToFloat(i)
 	if err != nil {
 		return "", err
 	}
@@ -87,3 +104,20 @@ func HumanizeDuration(i interface{}) (string, error) {
 	}
 	return fmt.Sprintf("%.4g%ss", v, prefix), nil
 }
+
+func HumanizeTimestamp(i interface{}) (string, error) {
+	v, err := ConvertToFloat(i)
+	if err != nil {
+		return "", err
+	}
+
+	tm, err := FloatToTime(v)
+	switch {
+	case errors.Is(err, errNaNOrInf):
+		return fmt.Sprintf("%.4g", v), nil
+	case err != nil:
+		return "", err
+	}
+
+	return fmt.Sprint(tm), nil
+}

helpers/templates/time_test.go

@@ -14,6 +14,7 @@
 package templates
 
 import (
+	"math"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -139,3 +140,103 @@ func TestHumanizeDurationSecondsInt(t *testing.T) {
 		})
 	}
 }
+
+func TestHumanizeTimestampInt(t *testing.T) {
+	tc := []struct {
+		name     string
+		input    int
+		expected string
+	}{
+		{name: "zero", input: 0, expected: "1970-01-01 00:00:00 +0000 UTC"},
+		{name: "negative", input: -1, expected: "1969-12-31 23:59:59 +0000 UTC"},
+		{name: "one", input: 1, expected: "1970-01-01 00:00:01 +0000 UTC"},
+		{name: "past", input: 1234567, expected: "1970-01-15 06:56:07 +0000 UTC"},
+		{name: "future", input: 9223372036, expected: "2262-04-11 23:47:16 +0000 UTC"},
+	}
+
+	for _, tt := range tc {
+		t.Run(tt.name, func(t *testing.T) {
+			result, err := HumanizeTimestamp(tt.input)
+			require.NoError(t, err)
+			require.Equal(t, tt.expected, result)
+		})
+	}
+}
+
+func TestHumanizeTimestampUint(t *testing.T) {
+	tc := []struct {
+		name     string
+		input    uint64
+		expected string
+	}{
+		{name: "zero", input: 0, expected: "1970-01-01 00:00:00 +0000 UTC"},
+		{name: "one", input: 1, expected: "1970-01-01 00:00:01 +0000 UTC"},
+		{name: "past", input: 1234567, expected: "1970-01-15 06:56:07 +0000 UTC"},
+		{name: "future", input: 9223372036, expected: "2262-04-11 23:47:16 +0000 UTC"},
+	}
+
+	for _, tt := range tc {
+		t.Run(tt.name, func(t *testing.T) {
+			result, err := HumanizeTimestamp(tt.input)
+			require.NoError(t, err)
+			require.Equal(t, tt.expected, result)
+		})
+	}
+}
+
+func TestHumanizeTimestampError(t *testing.T) {
+	_, err := HumanizeTimestamp(math.MaxInt64)
+	require.Error(t, err)
+}
+
+func TestHumanizeTimestampInfNanString(t *testing.T) {
+	tc := []struct {
+		name     string
+		input    string
+		expected string
+	}{
+		{name: "infinity", input: "+Inf", expected: "+Inf"},
+		{name: "minus infinity", input: "-Inf", expected: "-Inf"},
+		{name: "NaN", input: "NaN", expected: "NaN"},
+	}
+
+	for _, tt := range tc {
+		t.Run(tt.name, func(t *testing.T) {
+			result, err := HumanizeTimestamp(tt.input)
+			require.NoError(t, err)
+			require.Equal(t, tt.expected, result)
+		})
+	}
+}
+
+func TestHumanizeTimestampInfNanFloat(t *testing.T) {
+	tc := []struct {
+		name     string
+		input    float64
+		expected string
+	}{
+		{name: "infinity", input: math.Inf(1), expected: "+Inf"},
+		{name: "minus infinity", input: math.Inf(-1), expected: "-Inf"},
+		{name: "NaN", input: math.NaN(), expected: "NaN"},
+	}
+
+	for _, tt := range tc {
+		t.Run(tt.name, func(t *testing.T) {
+			result, err := HumanizeTimestamp(tt.input)
+			require.NoError(t, err)
+			require.Equal(t, tt.expected, result)
+		})
+	}
+}
+
+func TestHumanizeTimestampSampleFloat64(t *testing.T) {
+	result, err := HumanizeTimestamp(1435065584.128)
+	require.NoError(t, err)
+	require.Equal(t, "2015-06-23 13:19:44.128 +0000 UTC", result)
+}
+
+func TestHumanizeTimestampSampleString(t *testing.T) {
+	result, err := HumanizeTimestamp(1435065584.128)
+	require.NoError(t, err)
+	require.Equal(t, "2015-06-23 13:19:44.128 +0000 UTC", result)
+}