package main

import (
	"flag"
	"fmt"
	"os"
	"time"
)

var (
	zoneinfoPath = flag.String("path", "/usr/share/zoneinfo", "used to parse timezone")
	timezoneName = flag.String("tz", "America/Adak", "the timezone you want transfer")
	localTime    = flag.String("l", "2022-11-01 00:00:00", "local time need to transfer")
)

const (
	envZoneinfo = "ZONEINFO"
	longForm    = "2006-01-02 15:04:05"
)

func main() {
	flag.Parse()
	os.Setenv(envZoneinfo, *zoneinfoPath)
	if path := os.Getenv(envZoneinfo); path != *zoneinfoPath {
		fmt.Println("The env ZONEINFO is not what you set: ", path, *zoneinfoPath)
		return
	}

	// after set the env ZONEINFO to the zoneinfo path
	location, err := time.LoadLocation(*timezoneName)
	if err != nil {
		fmt.Println("Load location fail", *timezoneName, err)
		return
	}
	parseTime, err := time.ParseInLocation(longForm, *localTime, location)
	if err != nil {
		fmt.Println("Parse local time fail", *localTime, err)
		return
	}

	fmt.Println("UTC:", parseTime.UTC())
}