appvm/generate.go

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package main
import (
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"errors"
"fmt"
"io/ioutil"
"log"
"os"
"os/exec"
"strings"
"github.com/digitalocean/go-libvirt"
)
var template = `
{pkgs, ...}:
{
imports = [
<nixpkgs/nixos/modules/virtualisation/qemu-vm.nix>
<nix/base.nix>
];
services.xserver.displayManager.sessionCommands =
"while [ 1 ]; do ${pkgs.%s}/bin/%s; done &";
}
`
func isPackageExists(name string) bool {
cmd := exec.Command("nix-env", "-iA", name)
cmd.Stdout = os.Stdout
cmd.Stderr = os.Stderr
err := cmd.Run()
return err == nil
}
func nixPath(name string) (path string, err error) {
command := exec.Command("nix", "path-info", name)
bytes, err := command.Output()
if err != nil {
return
}
path = string(bytes)
return
}
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func guessChannel() (channel string, err error) {
command := exec.Command("nix-channel", "--list")
bytes, err := command.Output()
if err != nil {
return
}
channels := strings.Split(string(bytes), "\n")
for _, line := range channels {
fields := strings.Fields(line)
if len(fields) == 2 {
channel = fields[0]
return
}
}
err = errors.New("No channel found")
return
}
func filterDotfiles(files []os.FileInfo) (notHiddenFiles []os.FileInfo) {
for _, f := range files {
if !strings.HasPrefix(f.Name(), ".") {
notHiddenFiles = append(notHiddenFiles, f)
}
}
return
}
func generate(l *libvirt.Libvirt, pkg, bin, vmname string) {
var name string
if strings.Contains(pkg, ".") {
name = pkg
} else {
log.Println("Package name does not contains channel")
log.Println("Trying to guess")
channel, err := guessChannel()
if err != nil {
log.Println("Cannot guess channel")
log.Println("Check nix-channel --list")
return
}
name = channel + "." + pkg
log.Println("Use", name)
}
if !isPackageExists(name) {
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log.Println("Package", name, "does not exists")
return
}
path, err := nixPath(name)
if err != nil {
log.Println("Cannot find nix path")
return
}
path = strings.TrimSpace(path)
files, err := ioutil.ReadDir(path + "/bin/")
if err != nil {
log.Println(err)
return
}
if bin == "" && len(files) != 1 {
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fmt.Println("There's more than one binary in */bin")
fmt.Println("Files in", path+"/bin/:")
for _, f := range files {
fmt.Println("\t", f.Name())
}
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log.Println("Trying to guess binary")
var found bool = false
notHiddenFiles := filterDotfiles(files)
if len(notHiddenFiles) == 1 {
log.Println("Use", notHiddenFiles[0].Name())
bin = notHiddenFiles[0].Name()
found = true
}
if !found {
for _, f := range files {
if f.Name() == pkg {
log.Println("Use", f.Name())
bin = f.Name()
found = true
}
}
}
if !found {
log.Println("Cannot guess in */bin, " +
"you should specify one of them explicitly")
return
}
}
if bin != "" {
var found bool = false
for _, f := range files {
if bin == f.Name() {
found = true
}
}
if !found {
log.Println("There's no such file in */bin")
return
}
} else {
bin = files[0].Name()
}
realName := strings.Split(name, ".")[1]
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var appFilename string
if vmname != "" {
appFilename = configDir + "/nix/" + vmname + ".nix"
} else {
appFilename = configDir + "/nix/" + realName + ".nix"
}
appNixConfig := fmt.Sprintf(template, realName, bin)
err = ioutil.WriteFile(appFilename, []byte(appNixConfig), 0600)
if err != nil {
log.Println(err)
return
}
fmt.Print(appNixConfig + "\n")
log.Println("Configuration file is saved to", appFilename)
}