From a4cd634b6ecaa2e04055504d991498b7a094a7de Mon Sep 17 00:00:00 2001
From: Alexander Weinhold <me.git@gutmet.org>
Date: Sun, 4 Nov 2018 23:07:08 +0100
Subject: [PATCH] commands etc

---
 goutil.go | 114 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 114 insertions(+)

diff --git a/goutil.go b/goutil.go
index 62a3cc7..b436c41 100644
--- a/goutil.go
+++ b/goutil.go
@@ -3,11 +3,14 @@ package goutil
 import (
 	"bufio"
 	"errors"
+	"flag"
 	"fmt"
 	"io/ioutil"
 	"os"
+	"os/exec"
 	"path"
 	"path/filepath"
+	"runtime"
 	"strings"
 )
 
@@ -23,6 +26,16 @@ 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
@@ -98,3 +111,104 @@ func StrSlice(sl []string, start int, end int) []string {
 	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:])
+	}
+}