// Copyright The OpenTelemetry Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package metric // import "go.opentelemetry.io/otel/sdk/metric"

import (
	"os"
	"strconv"
	"time"

	"go.opentelemetry.io/otel/internal/global"
)

// Environment variable names.
const (
	// The time interval (in milliseconds) between the start of two export attempts.
	envInterval = "OTEL_METRIC_EXPORT_INTERVAL"
	// Maximum allowed time (in milliseconds) to export data.
	envTimeout = "OTEL_METRIC_EXPORT_TIMEOUT"
)

// envDuration returns an environment variable's value as duration in milliseconds if it is exists,
// or the defaultValue if the environment variable is not defined or the value is not valid.
func envDuration(key string, defaultValue time.Duration) time.Duration {
	v := os.Getenv(key)
	if v == "" {
		return defaultValue
	}
	d, err := strconv.Atoi(v)
	if err != nil {
		global.Error(err, "parse duration", "environment variable", key, "value", v)
		return defaultValue
	}
	if d <= 0 {
		global.Error(errNonPositiveDuration, "non-positive duration", "environment variable", key, "value", v)
		return defaultValue
	}
	return time.Duration(d) * time.Millisecond
}