util.go

/*
Copyright © 2019 Florian Imdahl <git@ffflorian.de>

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/

package util

import (
	"errors"
	"fmt"
	"os"

	"github.com/simonleung8/flags"
)

// Util is a configuration struct for the util
type Util struct {
	Description string
	FlagContext flags.FlagContext
	Name        string
	Version     string
}

// New returns a new instance of Util
func New(name string, version string, description string) *Util {
	flagContext := flags.New()
	util := &Util{
		Description: description,
		FlagContext: flagContext,
		Name:        name,
		Version:     version,
	}
	return util
}

// CheckFlags checks which command line flags are set
func (util *Util) CheckFlags() {
	util.FlagContext.NewBoolFlag("offline", "o", "enable offline mode (disables city matching)")
	util.FlagContext.NewStringFlagWithDefault("server", "s", "set the NTP server (default is \"pool.ntp.org\")", "pool.ntp.org")
	util.FlagContext.NewIntFlagWithDefault("timeout", "t", "set a custom timeout for HTTP requests (default is 2000ms)", 2000)
	util.FlagContext.NewBoolFlag("debug", "d", "enable debug mode")
	util.FlagContext.NewBoolFlag("version", "v", "output the version number")
	util.FlagContext.NewBoolFlag("help", "h", "output usage information")

	parseError := util.FlagContext.Parse(os.Args...)
	util.CheckError(parseError, false)
}

// GetArgsLocation returns the location provided via arguments
func (util *Util) GetArgsLocation() (string, error) {
	args := util.FlagContext.Args()

	if len(args) == 2 {
		return args[1], nil
	}

	return "", errors.New("Argument for \"location\" not provided")
}

// CheckError checks the error and if it exists, exits with exit code 1
func (util *Util) CheckError(err error, printUsage bool) {
	if err != nil {
		fmt.Fprintln(os.Stderr, "Error:", err)
		if printUsage {
			fmt.Fprintln(os.Stderr, util.GetUsage())
		}
		os.Exit(1)
	}
}

// GetUsage returns the usage text
func (util *Util) GetUsage() string {
	return fmt.Sprintf(
		"%s\n\n%s.\n\nUsage:\n  %s [options] [location]\n\nOptions:\n%s",
		util.Description,
		"For the `location` argument you can either use coordinates (e.g. 52.5502,13.4304)\nor a city name (e.g. \"Berlin, Germany\")",
		util.Name,
		util.FlagContext.ShowUsage(2),
	)
}

// LogAndExit logs one or more messages and exits with exit code 0
func (util *Util) LogAndExit(messages ...interface{}) {
	fmt.Println(messages...)
	os.Exit(0)
}