New command: automatic generate app description

generate.go

@@ -0,0 +1,93 @@
+package main
+
+import (
+	"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
+}
+
+func generate(l *libvirt.Libvirt, name, bin string) {
+	if !isPackageExists(name) {
+		log.Println("Package pkgs."+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 {
+		fmt.Println("There's more than one binary in */bin, " +
+			"you should specify one of them explicitly")
+		fmt.Println("Files in", path+"/bin/:")
+		for _, f := range files {
+			fmt.Println("\t", f.Name())
+		}
+		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]
+
+	fmt.Printf(template, realName, bin)
+}