// Copyright (c) Tailscale Inc & contributors
// SPDX-License-Identifier: BSD-3-Clause

// Package def parses strings and environment variables with fallback default values.
package def

import (
	"os"
	"strconv"
	"time"
)

// Bool parses s as a bool, returning def when s is empty or invalid.
func Bool(s string, def bool) bool {
	if s == "" {
		return def
	}
	v, err := strconv.ParseBool(s)
	if err != nil {
		return def
	}
	return v
}

// Duration parses s as a time.Duration, returning def when s is empty or invalid.
func Duration(s string, def time.Duration) time.Duration {
	if s == "" {
		return def
	}
	v, err := time.ParseDuration(s)
	if err != nil {
		return def
	}
	return v
}

// LookupEnv retrieves the value of the environment variable named by the key.
// If the variable is present in the environment the value (which may be
// empty) is returned. Otherwise, it returns def.
func LookupEnv(key, def string) string {
	if v, ok := os.LookupEnv(key); ok {
		return v
	}
	return def
}