Fix windows

Author: ShayBox

Makefile

@@ -4,7 +4,6 @@ clean:
 	-rm -rf ./output
 	-rm ./build/darwin/MultiMC-Twitch.app/Contents/MacOS/MultiMC-Twitch
 	-rm ./build/linux/usr/bin/multimc-twitch
-	-rm ./build/windows/MultiMC-Twitch.exe
 
 darwin:
 	mkdir -p output

main_windows.go

@@ -1,75 +1,136 @@
 package main
 
 import (
-	"fmt"
 	"os"
+	"path/filepath"
 
+	"golang.org/x/sys/windows"
 	"golang.org/x/sys/windows/registry"
 )
 
 func init() {
+	ex, err := os.Executable()
+	if err != nil {
+		panic(err)
+	}
+
+	exPath := filepath.Dir(ex)
+	err = os.Chdir(exPath)
+	if err != nil {
+		panic(err)
+	}
+
+	hasAdmin, err := CheckAdmin()
+	if err != nil {
+		panic(err)
+	}
+
+	if hasAdmin {
+		err = UpdateRegistry()
+		if err != nil {
+			panic(err)
+		}
+	}
+}
+
+func UpdateRegistry() error {
 	key, _, err := registry.CreateKey(registry.CLASSES_ROOT, "twitch", registry.WRITE)
 	if err != nil {
-		fmt.Println(err)
+		return err
 	}
 
 	defer key.Close()
 
 	err = key.SetStringValue("", "URL: Twitch Handler")
 	if err != nil {
-		fmt.Println(err)
+		return err
 	}
 
 	err = key.SetStringValue("URL Protocol", "")
 	if err != nil {
-		fmt.Println(err)
+		return err
 	}
 
 	iconKey, _, err := registry.CreateKey(key, "DefaultIcon", registry.WRITE)
 	if err != nil {
-		fmt.Println(err)
+		return err
 	}
 
 	defer iconKey.Close()
 
 	dir, err := os.Getwd()
 	if err != nil {
-		fmt.Println(err)
+		return err
 	}
 
 	err = iconKey.SetStringValue("", dir+"\\MultiMC.exe")
 	if err != nil {
-		fmt.Println(err)
+		return err
 	}
 
 	shellKey, _, err := registry.CreateKey(key, "shell", registry.WRITE)
 	if err != nil {
-		fmt.Println(err)
+		return err
 	}
 
 	defer shellKey.Close()
 
 	openKey, _, err := registry.CreateKey(shellKey, "open", registry.WRITE)
 	if err != nil {
-		fmt.Println(err)
+		return err
 	}
 
 	defer openKey.Close()
 
 	commandKey, _, err := registry.CreateKey(openKey, "command", registry.WRITE)
 	if err != nil {
-		fmt.Println(err)
+		return err
 	}
 
 	defer commandKey.Close()
 
 	executable, err := os.Executable()
 	if err != nil {
-		fmt.Println(err)
+		return err
 	}
 
 	err = commandKey.SetStringValue("", "\""+executable+"\" \"%1\"")
 	if err != nil {
-		fmt.Println(err)
+		return err
+	}
+
+	return nil
+}
+
+// CheckAdmin determines if we have administrative privileges.
+// Ref: https://coolaj86.com/articles/golang-and-windows-and-admins-oh-my/
+func CheckAdmin() (bool, error) {
+	var sid *windows.SID
+
+	// Although this looks scary, it is directly copied from the
+	// official windows documentation. The Go API for this is a
+	// direct wrap around the official C++ API.
+	// See https://docs.microsoft.com/en-us/windows/desktop/api/securitybaseapi/nf-securitybaseapi-checktokenmembership
+	err := windows.AllocateAndInitializeSid(
+		&windows.SECURITY_NT_AUTHORITY,
+		2,
+		windows.SECURITY_BUILTIN_DOMAIN_RID,
+		windows.DOMAIN_ALIAS_RID_ADMINS,
+		0, 0, 0, 0, 0, 0,
+		&sid)
+	if err != nil {
+		return false, err
 	}
+
+	// This appears to cast a null pointer so I'm not sure why this
+	// works, but this guy says it does and it Works for Me™:
+	// https://github.com/golang/go/issues/28804#issuecomment-438838144
+	token := windows.Token(0)
+
+	member, err := token.IsMember(sid)
+	if err != nil {
+		return false, err
+	}
+
+	return member, nil
 }