goutil/goutil.go

package goutil

import (
	"bufio"
	"errors"
	"flag"
	"fmt"
	"io/ioutil"
	"os"
	"os/exec"
	"path"
	"path/filepath"
	"runtime"
	"strings"
)

func DecorateError(s string, err error) error {
	if err != nil {
		return errors.New(s + ": " + err.Error())
	} else {
		return nil
	}
}

func WriteFile(filename string, data string) error {
	return ioutil.WriteFile(filename, []byte(data), 0644)
}

func AppendToFile(filename string, data string) error {
	f, err := os.OpenFile(filename, os.O_APPEND|os.O_WRONLY|os.O_CREATE, 0644)
	if err != nil {
		return errors.New("AppendToFile " + filename + ": " + err.Error())
	}
	defer f.Close()
	_, err = f.WriteString(data)
	return err
}

func ReadFile(filename string) (string, error) {
	data, err := ioutil.ReadFile(filename)
	return string(data), err
}

func TrimExt(path string) string {
	extension := filepath.Ext(path)
	return path[0 : len(path)-len(extension)]
}

func ListFilesExt(dir string, ext string) []string {
	list := make([]string, 0)
	ext = strings.ToUpper(ext)
	files, err := ioutil.ReadDir(dir)
	if err == nil {
		for _, file := range files {
			if !file.IsDir() {
				if strings.ToUpper(filepath.Ext(file.Name())) == ext {
					list = append(list, path.Join(dir, file.Name()))
				}
			}
		}
	}
	return list
}

func PathExists(path string) bool {
	if _, err := os.Stat(path); os.IsNotExist(err) {
		return false
	} else {
		return true
	}
}

func AskFor(question string) (string, error) {
	fmt.Print(question + ": ")
	reader := bufio.NewReader(os.Stdin)
	s, err := reader.ReadString('\n')
	if err == nil {
		return strings.TrimSpace(s), nil
	} else {
		return "", err
	}
}

func IntMin(x, y int) int {
	if x < y {
		return x
	} else {
		return y
	}
}

func IntMax(x, y int) int {
	if x > y {
		return x
	} else {
		return y
	}
}

func StrSliceAt(sl []string, i int) string {
	if i < len(sl) {
		return sl[i]
	} else {
		return ""
	}
}

func StrSlice(sl []string, start int, end int) []string {
	bound := func(i int) int { return IntMin(IntMax(0, i), len(sl)) }
	start = bound(start)
	end = bound(end)
	return sl[start:end]
}

func OpenInDefaultApp(filename string, wait bool) error {
	var cmd *exec.Cmd
	switch goos := runtime.GOOS; goos {
	case "windows":
		cmd = exec.Command(filepath.Join(os.Getenv("SYSTEMROOT"), "System32", "rundll32.exe"), "url.dll,FileProtocolHandler", filename)
	case "darwin":
		cmd = exec.Command("open", filename)
	default:
		cmd = exec.Command("xdg-open", filename)
	}
	if wait {
		return cmd.Run()
	} else {
		return cmd.Start()
	}
}

type CommandFunc func(args []string) error

type CommandFlagsInit func(s *flag.FlagSet)

type CommandInitExecFunc func() (CommandFlagsInit, CommandFunc)

type Command struct {
	cmd   string
	exec  CommandFunc
	desc  string
	flags *flag.FlagSet
}

func NewCommandWithFlags(cmd string, f CommandInitExecFunc, desc string) Command {
	flagsInit, exec := f()
	var flags *flag.FlagSet
	if flagsInit != nil {
		flags = flag.NewFlagSet(cmd, flag.ExitOnError)
		flagsInit(flags)
	}
	c := Command{cmd, exec, desc, flags}
	return c
}

func NewCommand(cmd string, f CommandFunc, desc string) Command {
	return NewCommandWithFlags(cmd, func() (CommandFlagsInit, CommandFunc) { return nil, f }, desc)
}

type commandCollection map[string]Command

func UsageAndExit(cmds commandCollection) {
	fmt.Println(os.Args[0])
	fmt.Println("Possible commands:")
	for _, cmd := range cmds {
		fmt.Println("  " + cmd.cmd)
		fmt.Println("  \t" + cmd.desc)
	}
	fmt.Println()
	fmt.Println("for detailed informationen type use 'help COMMAND'")
	os.Exit(-1)
}

func Execute(possibleCommands []Command) error {
	commands := commandCollection{}
	for _, c := range possibleCommands {
		commands[c.cmd] = c
	}
	arglen := len(os.Args)
	if arglen <= 1 {
		UsageAndExit(commands)
	}
	cmdStr := os.Args[1]
	if cmdStr == "help" {
		if arglen == 2 {
			UsageAndExit(commands)
		} else {
			cmd, ok := commands[os.Args[2]]
			if !ok {
				UsageAndExit(commands)
			} else {
				fmt.Println("Description of " + cmd.cmd + ":")
				fmt.Println("  " + cmd.desc)
				if cmd.flags != nil {
					fmt.Println("Possible flags:")
					cmd.flags.PrintDefaults()
				} else {
					fmt.Println("No flags")
				}
				return nil
			}
		}
	}
	cmd, ok := commands[cmdStr]
	if !ok {
		UsageAndExit(commands)
	}
	if cmd.flags != nil {
		cmd.flags.Parse(os.Args[2:])
		return cmd.exec(cmd.flags.Args())
	} else {
		return cmd.exec(os.Args[2:])
	}
}