starting from scratch

backup.go

@@ -0,0 +1,120 @@
+package main
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"io/fs"
+	"log"
+	"os"
+	"os/exec"
+	"strings"
+)
+
+func parseEnvironment(key string) string {
+	value := os.Getenv(key)
+	if value == "" {
+		log.Panicf("%s is not set\n", key)
+	}
+	if _, err := os.Stat(value); err != nil {
+		if errors.Is(err, fs.ErrNotExist) {
+			log.Panicf("%s does not point to a valid path\n", key)
+		}
+		log.Panicf("trying to stat %s produced an unkown error\n", value)
+	}
+	return value
+}
+
+func parsePacmanConf() string {
+	var path string
+
+	file, err := os.Open("/etc/pacman.conf")
+	if err != nil {
+		log.Panicln(err)
+	}
+	defer func() {
+		if err := file.Close(); err != nil {
+			log.Panicln(err)
+		}
+	}()
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if !strings.Contains(line, "DBPath") {
+			continue
+		}
+		path = strings.TrimSpace(strings.Split(line, "=")[1])
+		break
+	}
+
+	if _, err := os.Stat(path); err != nil {
+		if errors.Is(err, fs.ErrNotExist) {
+			log.Panicln("DBPath in /etc/pacman.conf does not point to a valid path")
+		}
+		log.Panicf("trying to stat %s produced an unkown error\n", path)
+	}
+
+	return fmt.Sprintf("%s%s", path, "local")
+}
+
+func preBackup() {
+	pacmanDb := parsePacmanConf()
+	log.Printf("pacmanDb: %s\n", pacmanDb)
+	tmpPath := "/tmp/update/pre_backup"
+
+	output, err := exec.Command("pacman",  "--verbose", "--query").Output()
+	if err != nil {
+		log.Panicln(err)
+	}
+
+	err = os.MkdirAll(tmpPath, 0755)
+
+	err = os.WriteFile(fmt.Sprintf("%s/%s", tmpPath, "pre_pacman.txt"), output, 0644)
+	if err != nil {
+		log.Panicln(err)
+	}
+
+	defer func() {
+		if r := recover(); r != nil {
+			err := os.RemoveAll(tmpPath)
+			if err != nil {
+				log.Fatal(err)
+			}
+
+			err = CopyDir(pacmanDb, fmt.Sprintf("%s/%s", tmpPath, pacmanDb))
+			if err != nil {
+				log.Panicln(err)
+			}
+
+			log.Println("recovered successfully")
+		}
+	}()
+
+	err = CopyDir(pacmanDb, fmt.Sprintf("%s/%s", tmpPath, pacmanDb))
+	if err != nil {
+		log.Panicln(err)
+	}
+}
+
+func postBackup() {
+	/*
+	 * basic logic for post:
+	 * create new pkg list and delete all lines which are the same as pre
+	 */
+	panic("unimplemented")
+}
+
+func main() {
+	// backup_dir := parseEnvironment("UPDATE_BACKUP_DIR")
+	cmdlineArg := os.Args[1]
+	log.Printf("cmdlineArg: %s\n", cmdlineArg)
+
+	if cmdlineArg == "pre" {
+		preBackup()
+	} else if cmdlineArg == "post" {
+		postBackup()
+	} else {
+		log.Panicf("invalid cmdline argument. supplied value was: %s\n", cmdlineArg)
+	}
+}