feat: add initial version

main.go

@@ -0,0 +1,128 @@
+package main
+
+import (
+	"errors"
+	"flag"
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+	"text/template"
+	"time"
+)
+
+type LicensingData struct {
+	AuthorName  string
+	AuthorEmail string
+	Year        int
+}
+
+var GitConfigError = errors.New("Can't read Git config")
+var NotSupportedError = errors.New("Not supported license")
+
+func getGitUserData() (string, string, error) {
+	var userData [2]string
+	for i, v := range []string{"user.name", "user.email"} {
+		cmd := exec.Command("git", "config", "--get", v)
+		out, err := cmd.Output()
+		if err != nil {
+			return "", "", GitConfigError
+		}
+
+		userData[i] = strings.TrimSpace(string(out))
+	}
+
+	return userData[0], userData[1], nil
+}
+
+func getTemplateList() []string {
+	d, err := os.Open("templates")
+	if err != nil {
+		panic(err)
+	}
+	files, err := d.Readdir(0)
+	if err != nil {
+		panic(err)
+	}
+
+	var tmplList []string
+	for _, v := range files {
+		tmplList = append(tmplList, strings.Replace(v.Name(), ".tmpl", "", 1))
+	}
+
+	return tmplList
+}
+
+func listTemplates() {
+	tmplList := getTemplateList()
+	fmt.Println(strings.Join(tmplList, ", "))
+}
+
+func genLicense(lcnsName string, lcnsData LicensingData, outFileName string) error {
+	tmplFile := "templates/" + lcnsName + ".tmpl"
+	tmpl, err := template.ParseFiles(tmplFile)
+	if err != nil {
+		return NotSupportedError
+	}
+
+	outFile, err := os.Create(outFileName)
+	if err != nil {
+		return err
+	}
+	defer outFile.Close()
+
+	err = tmpl.Execute(outFile, lcnsData)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func main() {
+	OutputFile := flag.String("output", "LICENSE", "Specify different output file")
+	License := flag.String("license", "", "Choose a license")
+	authorName := flag.String("name", "", "Set the author name")
+	authorEmail := flag.String("email", "", "Set the author email")
+	ListTemplates := flag.Bool("list", false, "List available licenses")
+	flag.Parse()
+
+	if *ListTemplates {
+		listTemplates()
+    os.Exit(0)
+	}
+
+	if *License == "" {
+		fmt.Printf("Error: No license specified\n\nUse --license LICENSE\n\nAvailable licenses:\n")
+		listTemplates()
+    os.Exit(1)
+	}
+
+	if *authorName == "" || *authorEmail == "" {
+		var err error
+		*authorName, *authorEmail, err = getGitUserData()
+		if err != nil {
+			if errors.Is(err, GitConfigError) {
+				fmt.Printf(
+					"Error: Can't read Git config.\n\nUse --name \"NAME\" and --email EMAIL instead.\n",
+				)
+				os.Exit(3)
+			}
+		}
+	}
+
+	lcnsData := LicensingData{
+		AuthorName:  *authorName,
+		AuthorEmail: *authorEmail,
+		Year:        time.Now().Year(),
+	}
+
+	err := genLicense(*License, lcnsData, *OutputFile)
+	if err != nil {
+		if errors.Is(err, NotSupportedError) {
+			fmt.Printf("Error: There is no '%s' license\n\nAvailable licenses:\n", *License)
+			listTemplates()
+      os.Exit(2)
+		}
+	}
+}