Adds a GetEnvIntWithRange utility function (#102)

* Adds a GetEnvIntWithRange utility function

Signed-off-by: Elena Kolevska <elena@kolevska.com>

* Fixes linter

Signed-off-by: Elena Kolevska <elena@kolevska.com>

* Update to using time duration instead of int for seconds

Signed-off-by: Elena Kolevska <elena@kolevska.com>

---------

Signed-off-by: Elena Kolevska <elena@kolevska.com>

utils/env.go

@@ -0,0 +1,29 @@
+package utils
+
+import (
+	"fmt"
+	"os"
+	"time"
+)
+
+// GetEnvDurationWithRange returns the time.Duration value of the environment variable specified by `envVar`.
+// If the environment variable is not set, it returns `defaultValue`.
+// If the value is set but is not valid (not a valid time.Duration or falls outside the specified range
+// [minValue, maxValue] inclusively), it returns `defaultValue` and an error.
+func GetEnvDurationWithRange(envVar string, defaultValue, min, max time.Duration) (time.Duration, error) {
+	v := os.Getenv(envVar)
+	if v == "" {
+		return defaultValue, nil
+	}
+
+	val, err := time.ParseDuration(v)
+	if err != nil {
+		return defaultValue, fmt.Errorf("invalid time.Duration value %s for the %s env variable: %w", val, envVar, err)
+	}
+
+	if val < min || val > max {
+		return defaultValue, fmt.Errorf("invalid value for the %s env variable: value should be between %s and %s, got %s", envVar, min, max, val)
+	}
+
+	return val, nil
+}

utils/env_test.go

@@ -0,0 +1,83 @@
+package utils
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestGetEnvIntWithRangeWrongValues(t *testing.T) {
+	testValues := []struct {
+		name      string
+		envVarVal string
+		min       time.Duration
+		max       time.Duration
+		error     string
+	}{
+		{
+			"should error if value is not a valid time.Duration",
+			"0.5",
+			time.Second,
+			2 * time.Second,
+			"invalid time.Duration value 0s for the MY_ENV env variable",
+		},
+		{
+			"should error if value is lower than 1s",
+			"0s",
+			time.Second,
+			10 * time.Second,
+			"value should be between 1s and 10s",
+		},
+		{
+			"should error if value is higher than 10s",
+			"2m",
+			time.Second,
+			10 * time.Second,
+			"value should be between 1s and 10s",
+		},
+	}
+
+	defaultValue := 3 * time.Second
+	for _, tt := range testValues {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Setenv("MY_ENV", tt.envVarVal)
+
+			val, err := GetEnvDurationWithRange("MY_ENV", defaultValue, tt.min, tt.max)
+			require.Error(t, err)
+			require.Contains(t, err.Error(), tt.error)
+			require.Equal(t, defaultValue, val)
+		})
+	}
+}
+
+func TestGetEnvDurationWithRangeValidValues(t *testing.T) {
+	testValues := []struct {
+		name      string
+		envVarVal string
+		result    time.Duration
+	}{
+		{
+			"should return default value if env variable is not set",
+			"",
+			3 * time.Second,
+		},
+		{
+			"should return result is env variable value is valid",
+			"4s",
+			4 * time.Second,
+		},
+	}
+
+	for _, tt := range testValues {
+		t.Run(tt.name, func(t *testing.T) {
+			if tt.envVarVal != "" {
+				t.Setenv("MY_ENV", tt.envVarVal)
+			}
+
+			val, err := GetEnvDurationWithRange("MY_ENV", 3*time.Second, time.Second, 5*time.Second)
+			require.NoError(t, err)
+			require.Equal(t, tt.result, val)
+		})
+	}
+}