Home-Assistant-Backup-Script/V3/main.go

// ha-backup: creates a Home Assistant backup over SSH, copies it locally,
// prunes old backups (remote and local) and sends optional ntfy/Discord
// notifications. Go port of home_assistant_backup.sh.
//
// Only the standard library is used. The system `ssh` and `scp` binaries are
// still required (same as the original script), but `jq` and `yq` are not.
package main

import (
	"bufio"
	"bytes"
	"encoding/json"
	"flag"
	"fmt"
	"io/fs"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"regexp"
	"strconv"
	"strings"
	"time"
)

// ---------------------------------------------------------------------------
// Configuration (reads the same KEY="value" # comment format as the .sh script)
// ---------------------------------------------------------------------------

const defaultConfigName = "home_assistant_backup.conf"

type Config struct {
	SSHKey  string
	SSHUser string
	SSHHost string
	SSHPort string

	BackupDest         string
	BackupFileLocation string
	StorageThresholdKB int64
	LocalCleanupDays   int
	RemoteCleanupDays  int

	NtfyEnabled bool
	NtfyServer  string
	NtfyTopic   string

	DiscordEnabled    bool
	DiscordWebhookURL string
}

func parseValue(raw string) string {
	raw = strings.TrimSpace(raw)
	if raw == "" {
		return ""
	}
	if raw[0] == '"' || raw[0] == '\'' {
		q := raw[0]
		if end := strings.IndexByte(raw[1:], q); end >= 0 {
			return raw[1 : 1+end]
		}
		return raw[1:]
	}
	// Unquoted: strip trailing comment (a '#' preceded by whitespace).
	for i := 1; i < len(raw); i++ {
		if raw[i] == '#' && (raw[i-1] == ' ' || raw[i-1] == '\t') {
			raw = raw[:i]
			break
		}
	}
	return strings.TrimSpace(raw)
}

func readConfFile(path string) (map[string]string, error) {
	f, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	defer f.Close()

	vals := map[string]string{}
	sc := bufio.NewScanner(f)
	for sc.Scan() {
		line := strings.TrimSpace(sc.Text())
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}
		line = strings.TrimPrefix(line, "export ")
		k, v, ok := strings.Cut(line, "=")
		if !ok {
			continue
		}
		vals[strings.TrimSpace(k)] = parseValue(v)
	}
	return vals, sc.Err()
}

func loadConfig(path string) (*Config, error) {
	m, err := readConfFile(path)
	if err != nil {
		return nil, err
	}

	get := func(key, def string) string {
		if v, ok := m[key]; ok && v != "" {
			return v
		}
		return def
	}

	cfg := &Config{
		SSHKey:             get("HA_SSH_KEY", ""),
		SSHUser:            get("HA_SSH_USER", ""),
		SSHHost:            get("HA_SSH_HOST", ""),
		SSHPort:            get("HA_SSH_PORT", ""),
		BackupDest:         get("BACKUP_DEST", ""),
		BackupFileLocation: strings.TrimRight(get("BACKUP_FILE_LOCATION", "/backup"), "/"),
		NtfyEnabled:        get("NTFY_ENABLED", "false") == "true",
		NtfyServer:         get("NTFY_SERVER", ""),
		NtfyTopic:          get("NTFY_TOPIC", ""),
		DiscordEnabled:     get("DISCORD_ENABLED", "false") == "true",
		DiscordWebhookURL:  get("DISCORD_WEBHOOK_URL", ""),
	}

	if cfg.StorageThresholdKB, err = strconv.ParseInt(get("STORAGE_THRESHOLD_KB", "2097152"), 10, 64); err != nil {
		return nil, fmt.Errorf("invalid STORAGE_THRESHOLD_KB: %w", err)
	}
	if cfg.LocalCleanupDays, err = strconv.Atoi(get("LOCAL_BACKUP_CLEANUP", "90")); err != nil {
		return nil, fmt.Errorf("invalid LOCAL_BACKUP_CLEANUP: %w", err)
	}
	if cfg.RemoteCleanupDays, err = strconv.Atoi(get("REMOTE_BACKUP_CLEANUP", "30")); err != nil {
		return nil, fmt.Errorf("invalid REMOTE_BACKUP_CLEANUP: %w", err)
	}
	return cfg, nil
}

// validate mirrors sanity_check() from the shell script.
func (c *Config) validate() error {
	type req struct{ val, placeholder, name string }
	checks := []req{
		{c.SSHKey, "SSH_PRIVATE_KEY", "HA_SSH_KEY"},
		{c.SSHUser, "SSH_USER", "HA_SSH_USER"},
		{c.SSHHost, "SSH_HOST_IP_OR_HOSTNAME", "HA_SSH_HOST"},
		{c.SSHPort, "SSH_PORT", "HA_SSH_PORT"},
		{c.BackupDest, "BACKUP_FILE_DESTINATION", "BACKUP_DEST"},
	}
	if c.NtfyEnabled {
		checks = append(checks,
			req{c.NtfyServer, "NTFY_SERVER_FQDN_ADDRESS", "NTFY_SERVER"},
			req{c.NtfyTopic, "NTFY_TOPIC", "NTFY_TOPIC"})
	}
	if c.DiscordEnabled {
		checks = append(checks, req{c.DiscordWebhookURL, "DISCORD_WEBHOOK_URL", "DISCORD_WEBHOOK_URL"})
	}
	for _, r := range checks {
		if r.val == "" || r.val == r.placeholder {
			return fmt.Errorf("%s is not set", r.name)
		}
	}
	for _, bin := range []string{"ssh", "scp"} {
		if _, err := exec.LookPath(bin); err != nil {
			return fmt.Errorf("%s is not installed or not in PATH", bin)
		}
	}
	return nil
}

// ---------------------------------------------------------------------------
// Notifications
// ---------------------------------------------------------------------------

type Notifier struct {
	cfg    *Config
	client *http.Client
}

func NewNotifier(cfg *Config) *Notifier {
	return &Notifier{cfg: cfg, client: &http.Client{Timeout: 15 * time.Second}}
}

func (n *Notifier) post(url, contentType string, body []byte) {
	resp, err := n.client.Post(url, contentType, bytes.NewReader(body))
	if err != nil {
		fmt.Fprintf(os.Stderr, "notification failed (%s): %v\n", url, err)
		return
	}
	resp.Body.Close()
	if resp.StatusCode >= 300 {
		fmt.Fprintf(os.Stderr, "notification failed (%s): HTTP %d\n", url, resp.StatusCode)
	}
}

// Send delivers msg to every enabled notification channel.
func (n *Notifier) Send(msg string) {
	if n.cfg.NtfyEnabled {
		url := strings.TrimRight(n.cfg.NtfyServer, "/") + "/" + n.cfg.NtfyTopic
		n.post(url, "text/plain", []byte(msg))
	}
	if n.cfg.DiscordEnabled {
		body, _ := json.Marshal(map[string]string{"content": msg})
		n.post(n.cfg.DiscordWebhookURL, "application/json", body)
	}
}

// ---------------------------------------------------------------------------
// SSH / SCP helpers (shell out to the system OpenSSH client)
// ---------------------------------------------------------------------------

type Remote struct{ cfg *Config }

func (r Remote) target() string { return r.cfg.SSHUser + "@" + r.cfg.SSHHost }

// run executes a command on the Home Assistant host and returns its stdout.
// stderr is passed through to the terminal.
func (r Remote) run(remoteCmd string) (string, error) {
	cmd := exec.Command("ssh", "-i", r.cfg.SSHKey, "-p", r.cfg.SSHPort, r.target(), remoteCmd)
	var out bytes.Buffer
	cmd.Stdout = &out
	cmd.Stderr = os.Stderr
	err := cmd.Run()
	return out.String(), err
}

func (r Remote) copyFrom(remotePath, localPath string) error {
	cmd := exec.Command("scp", "-i", r.cfg.SSHKey, "-P", r.cfg.SSHPort,
		r.target()+":"+remotePath, localPath)
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	return cmd.Run()
}

// availableKB returns free space (in KB) on the remote root filesystem.
func (r Remote) availableKB() (int64, error) {
	out, err := r.run("df -k / | tail -n 1")
	if err != nil {
		return 0, err
	}
	fields := strings.Fields(out)
	if len(fields) < 4 {
		return 0, fmt.Errorf("unexpected df output: %q", out)
	}
	return strconv.ParseInt(fields[3], 10, 64)
}

// ---------------------------------------------------------------------------
// Home Assistant operations
// ---------------------------------------------------------------------------

var slugRe = regexp.MustCompile(`^[A-Za-z0-9_-]+$`)

type backupEntry struct {
	Slug string `json:"slug"`
	Date string `json:"date"`
}

type backupListResp struct {
	Backups []backupEntry `json:"backups"`
	Data    struct {
		Backups []backupEntry `json:"backups"`
	} `json:"data"`
}

func (r Remote) listBackups() ([]backupEntry, error) {
	out, err := r.run("ha backups --raw-json")
	if err != nil {
		return nil, err
	}
	var resp backupListResp
	if err := json.Unmarshal([]byte(out), &resp); err != nil {
		return nil, fmt.Errorf("could not parse 'ha backups' output as JSON: %w", err)
	}
	if len(resp.Data.Backups) > 0 {
		return resp.Data.Backups, nil
	}
	return resp.Backups, nil
}

func removeOldRemoteBackups(r Remote, n *Notifier, days int) {
	fmt.Printf("Removing backups older than %d days on Home Assistant server...\n", days)

	backups, err := r.listBackups()
	if err != nil {
		fmt.Printf("Error: %v\n", err)
		return
	}

	cutoff := time.Now().Add(-time.Duration(days) * 24 * time.Hour)
	removed := 0
	for _, b := range backups {
		t, err := time.Parse(time.RFC3339Nano, b.Date)
		if err != nil {
			fmt.Printf("Skipping backup %s: cannot parse date %q\n", b.Slug, b.Date)
			continue
		}
		if !t.Before(cutoff) {
			continue
		}
		if !slugRe.MatchString(b.Slug) {
			fmt.Printf("Skipping backup with unexpected slug %q\n", b.Slug)
			continue
		}
		fmt.Printf("Removing backup with slug: %s\n", b.Slug)
		if _, err := r.run("ha backups remove " + b.Slug); err != nil {
			fmt.Printf("Failed to remove backup with slug: %s\n", b.Slug)
			continue
		}
		removed++
		fmt.Printf("Successfully removed backup with slug: %s\n", b.Slug)
		n.Send("Old backup removed: " + b.Slug)
	}
	if removed == 0 {
		fmt.Println("No old backups found to remove.")
	}
}

type newBackupResp struct {
	Data struct {
		Slug string `json:"slug"`
	} `json:"data"`
	Slug string `json:"slug"`
}

// createBackup creates a backup and returns its slug.
func (r Remote) createBackup(name string) (string, error) {
	out, err := r.run("ha backup new --name=" + name + " --raw-json")
	if err != nil {
		return "", fmt.Errorf("failed to create backup on Home Assistant server: %w", err)
	}

	var resp newBackupResp
	if json.Unmarshal([]byte(out), &resp) == nil {
		if resp.Data.Slug != "" {
			return strings.TrimSpace(resp.Data.Slug), nil
		}
		if resp.Slug != "" {
			return strings.TrimSpace(resp.Slug), nil
		}
	}

	// Fallback: plain-text "slug: xxxx" line (what the original script parsed).
	for _, line := range strings.Split(out, "\n") {
		line = strings.TrimSpace(strings.TrimRight(line, "\r"))
		if strings.HasPrefix(line, "slug:") {
			if s := strings.TrimSpace(strings.TrimPrefix(line, "slug:")); s != "" {
				return s, nil
			}
		}
	}
	return "", fmt.Errorf("failed to extract backup slug")
}

// removeOldLocalBackups deletes *.tar files under dir that `find -mtime +days`
// would match (age of at least days+1 full 24h periods).
func removeOldLocalBackups(dir string, days int) error {
	minAge := time.Duration(days+1) * 24 * time.Hour
	now := time.Now()
	return filepath.WalkDir(dir, func(path string, d fs.DirEntry, err error) error {
		if err != nil {
			return err
		}
		if !d.Type().IsRegular() || !strings.HasSuffix(d.Name(), ".tar") {
			return nil
		}
		info, err := d.Info()
		if err != nil {
			return err
		}
		if now.Sub(info.ModTime()) >= minAge {
			return os.Remove(path)
		}
		return nil
	})
}

// ---------------------------------------------------------------------------
// main
// ---------------------------------------------------------------------------

func findConfig(flagPath string) string {
	if flagPath != "" {
		return flagPath
	}
	if exe, err := os.Executable(); err == nil {
		p := filepath.Join(filepath.Dir(exe), defaultConfigName)
		if _, err := os.Stat(p); err == nil {
			return p
		}
	}
	return defaultConfigName // current working directory
}

func main() {
	confFlag := flag.String("config", "", "path to config file (default: "+defaultConfigName+" next to the binary, then current directory)")
	flag.Parse()

	confPath := findConfig(*confFlag)
	cfg, err := loadConfig(confPath)
	if err != nil {
		fmt.Printf("Error: cannot load config file %s: %v\n", confPath, err)
		os.Exit(1)
	}
	if err := cfg.validate(); err != nil {
		fmt.Printf("Error: %v\n", err)
		os.Exit(1)
	}

	notify := NewNotifier(cfg)
	remote := Remote{cfg: cfg}

	fail := func(msg string) {
		full := "Error: " + msg
		notify.Send(full)
		fmt.Println(full)
		os.Exit(1)
	}

	timestamp := time.Now().Format("2006-01-02_15-04-05")
	start := time.Now()

	notify.Send("Backup process started at " + timestamp)

	// Free-space check on the Home Assistant host.
	avail, err := remote.availableKB()
	if err != nil {
		fail("failed to check disk space on Home Assistant server: " + err.Error())
	}
	if avail < cfg.StorageThresholdKB {
		fmt.Printf("Disk space is below the threshold (%d KB available, %d KB required). Proceeding with remote backup cleanup...\n",
			avail, cfg.StorageThresholdKB)
		removeOldRemoteBackups(remote, notify, cfg.RemoteCleanupDays)
	} else {
		fmt.Println("Sufficient disk space available on Home Assistant server. Skipping remote backup cleanup.")
	}

	// Create the backup.
	slug, err := remote.createBackup("auto_backup_" + timestamp)
	if err != nil {
		fail(err.Error() + ".")
	}
	if !slugRe.MatchString(slug) {
		fail(fmt.Sprintf("unexpected backup slug %q.", slug))
	}
	notify.Send("Backup created successfully with slug: " + slug)

	// Copy it locally.
	backupFile := filepath.Join(cfg.BackupDest, fmt.Sprintf("%s_%s.tar", timestamp, slug))
	if err := remote.copyFrom(cfg.BackupFileLocation+"/"+slug+".tar", backupFile); err != nil {
		fail("Failed to copy backup to local machine.")
	}

	info, err := os.Stat(backupFile)
	if err != nil {
		fail("Failed to get backup file size.")
	}

	// Local retention.
	if err := removeOldLocalBackups(cfg.BackupDest, cfg.LocalCleanupDays); err != nil {
		fail("Failed to clean up old backups locally: " + err.Error())
	}
	notify.Send("Old backups cleaned up successfully.")

	fmt.Println("Backup completed successfully: " + backupFile)
	notify.Send("Backup completed successfully: " + backupFile)

	runtime := int(time.Since(start).Seconds())
	notify.Send(fmt.Sprintf("Backup file size: %d bytes. Script runtime: %d seconds.", info.Size(), runtime))
}