package main

import (
	"flag"
	"fmt"
	"strings"
)

// Environment 运行环境枚举类型
type Environment string

const (
	EnvDev  Environment = "dev"
	EnvTest Environment = "test"
	EnvProd Environment = "prod"
)

// 合法环境白名单
var validEnvs = map[Environment]bool{
	EnvDev:  true,
	EnvTest: true,
	EnvProd: true,
}

func (e *Environment) Set(s string) error {
	env := Environment(strings.ToLower(s))
	if !validEnvs[env] {
		return fmt.Errorf("无效运行环境，仅支持 dev/test/prod")
	}
	*e = env
	return nil
}

func (e *Environment) String() string {
	if *e == "" {
		return string(EnvDev)
	}
	return string(*e)
}

func (e *Environment) Get() any {
	return *e
}

func main() {
	var env Environment = EnvDev // 默认值为 dev
	flag.Var(&env, "env", "运行环境：dev/test/prod")
	flag.Parse()

	fmt.Printf("当前运行环境：%s\n", env)
}