/* SquashR - Manage backups based on SquashFS, OverlayFS and LUKS
 * Copyright (C) 2025 Leonard Kugis <leonard@kug.is>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published
 * by the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

use anyhow::{anyhow, bail, Context, Result};
use clap::{Parser, Subcommand, ValueHint};
use itertools::Itertools;
use regex::Regex;
use serde::Deserialize;
use std::collections::{BTreeSet, HashMap, HashSet};
use std::env;
use std::fs;
use std::io::{Read, Write};
use std::io::ErrorKind;
use std::path::{Path, PathBuf};
use std::process::{Command, Stdio};
use walkdir::WalkDir;

// kleine Helfer für Verbose-Logs
macro_rules! vlog {
    ($ctx:expr, $($arg:tt)*) => {
        if $ctx.verbose {
            eprintln!($($arg)*);
        }
    };
}

#[derive(Parser, Debug)]
#[command(name="squashr", version, about="Manage backups based on SquashFS, OverlayFS and LUKS")]
struct Cli {
    #[arg(short, long, value_hint=ValueHint::FilePath)]
    config: Option<PathBuf>,

    #[arg(long, value_hint=ValueHint::DirPath)]
    squashr_root: Option<PathBuf>,

    #[arg(long)]
    squashr_n_snapshots_min: Option<usize>,

    #[arg(long)]
    squashr_n_snapshots_max: Option<usize>,

    #[arg(long)]
    squashr_include: Option<String>,

    #[arg(long)]
    squashr_exclude: Option<String>,

    #[arg(long)]
    squashr_truncate: Option<String>,

    #[arg(long)]
    squashr_compression_enable: Option<bool>,

    #[arg(long)]
    squashr_compression_algo: Option<String>,

    #[arg(long, allow_hyphen_values = true)]
    squashr_compression_args: Option<String>,

    #[arg(long)]
    squashr_cryptsetup_enable: Option<bool>,

    #[arg(long, allow_hyphen_values = true)]
    squashr_cryptsetup_create_args: Option<String>,

    #[arg(long, allow_hyphen_values = true)]
    squashr_cryptsetup_open_args: Option<String>,

    /// Passphrase für cryptsetup; ACHTUNG: Sichtbar im Prozesslisting.
    #[arg(long)]
    squashr_cryptsetup_pass: Option<String>,

    /// Datei mit Passphrase (roh, binär möglich); hat Vorrang, wenn beides gesetzt ist.
    #[arg(long, value_hint=ValueHint::FilePath)]
    squashr_cryptsetup_pass_file: Option<PathBuf>,

    /// Mehr Ausgaben, inkl. Auflistung gesicherter Dateien
    #[arg(short, long)]
    verbose: bool,

    #[command(subcommand)]
    cmd: Cmd,
}

#[derive(Subcommand, Debug)]
enum Cmd {
    Backup,
    Minimize { #[arg(short = 'n')] n: Option<usize> },
    New,
    Mount { #[arg(short = 's')] s: Option<usize>, target: PathBuf },
    Delete { #[arg(short = 's')] s: usize },
    /// Hängt SquashR-relevante Mounts aus (ohne Argument: alle; mit Pfad: nur diesen).
    Umount { target: Option<PathBuf> },
}

#[derive(Debug, Clone, Deserialize)]
struct Config {
    SQUASHR_ROOT: Option<PathBuf>,
    SQUASHR_N_SNAPSHOTS_MIN: Option<usize>,
    SQUASHR_N_SNAPSHOTS_MAX: Option<usize>,
    SQUASHR_INCLUDE: Option<Vec<String>>,
    SQUASHR_EXCLUDE: Option<Vec<String>>,
    SQUASHR_TRUNCATE: Option<Vec<String>>,
    SQUASHR_COMPRESSION_ENABLE: Option<bool>,
    SQUASHR_COMPRESSION_ALGO: Option<String>,
    SQUASHR_COMPRESSION_ARGS: Option<String>,
    SQUASHR_CRYPTSETUP_ENABLE: Option<bool>,
    SQUASHR_CRYPTSETUP_CREATE_ARGS: Option<String>,
    SQUASHR_CRYPTSETUP_OPEN_ARGS: Option<String>,
    SQUASHR_CRYPTSETUP_PASS: Option<String>,
    SQUASHR_CRYPTSETUP_PASS_FILE: Option<PathBuf>,
}

impl Default for Config {
    fn default() -> Self {
        Self {
            SQUASHR_ROOT: None,
            SQUASHR_N_SNAPSHOTS_MIN: Some(5),
            SQUASHR_N_SNAPSHOTS_MAX: Some(30),
            SQUASHR_INCLUDE: None,
            SQUASHR_EXCLUDE: None,
            SQUASHR_TRUNCATE: None,
            SQUASHR_COMPRESSION_ENABLE: Some(true),
            SQUASHR_COMPRESSION_ALGO: Some("zstd".to_string()),
            SQUASHR_COMPRESSION_ARGS: Some("-Xcompression-level 19".to_string()),
            SQUASHR_CRYPTSETUP_ENABLE: Some(false),
            SQUASHR_CRYPTSETUP_CREATE_ARGS: Some("--type luks2".to_string()),
            SQUASHR_CRYPTSETUP_OPEN_ARGS: Some("--type luks".to_string()),
            SQUASHR_CRYPTSETUP_PASS: None,
            SQUASHR_CRYPTSETUP_PASS_FILE: None,
        }
    }
}

fn parse_list(s: &str) -> Vec<String> {
    let mut out: Vec<String> = vec![];
    for line in s.lines() {
        let t = line.trim();
        if !t.is_empty() { out.push(t.to_string()); }
    }
    out = out.into_iter()
        .flat_map(|x| x.split(',').map(|y| y.trim().to_string()).collect::<Vec<_>>())
        .collect();
    out.into_iter().filter(|x| !x.is_empty()).collect()
}

fn load_config(path: Option<&Path>) -> Result<Config> {
    let mut cfg = Config::default();
    if let Some(p) = path {
        if p.exists() {
            let text = fs::read_to_string(p).with_context(|| format!("Konfig lesen: {}", p.display()))?;
            let mut map: HashMap<String, String> = HashMap::new();
            for line in text.lines() {
                let l = line.trim();
                if l.is_empty() || l.starts_with('#') { continue; }
                if let Some((k,v)) = l.split_once('=') {
                    map.insert(k.trim().to_string(), v.trim().to_string());
                }
            }
            let assign = |k:&str, f: &mut dyn FnMut(String)| {
                if let Some(v)=map.get(k).cloned(){ f(v) }
            };
            let set = |k:&str, f:&mut dyn FnMut(String)| assign(k, f);
            set("SQUASHR_ROOT", &mut |v| cfg.SQUASHR_ROOT = Some(PathBuf::from(v)));
            set("SQUASHR_N_SNAPSHOTS_MIN", &mut |v| cfg.SQUASHR_N_SNAPSHOTS_MIN = v.parse().ok());
            set("SQUASHR_N_SNAPSHOTS_MAX", &mut |v| cfg.SQUASHR_N_SNAPSHOTS_MAX = v.parse().ok());
            set("SQUASHR_INCLUDE", &mut |v| cfg.SQUASHR_INCLUDE = Some(parse_list(&v)));
            set("SQUASHR_EXCLUDE", &mut |v| cfg.SQUASHR_EXCLUDE = Some(parse_list(&v)));
            set("SQUASHR_TRUNCATE", &mut |v| cfg.SQUASHR_TRUNCATE = Some(parse_list(&v)));
            set("SQUASHR_COMPRESSION_ENABLE", &mut |v| cfg.SQUASHR_COMPRESSION_ENABLE = v.parse().ok());
            set("SQUASHR_COMPRESSION_ALGO", &mut |v| cfg.SQUASHR_COMPRESSION_ALGO = Some(v));
            set("SQUASHR_COMPRESSION_ARGS", &mut |v| cfg.SQUASHR_COMPRESSION_ARGS = Some(v));
            set("SQUASHR_CRYPTSETUP_ENABLE", &mut |v| cfg.SQUASHR_CRYPTSETUP_ENABLE = v.parse().ok());
            set("SQUASHR_CRYPTSETUP_CREATE_ARGS", &mut |v| cfg.SQUASHR_CRYPTSETUP_CREATE_ARGS = Some(v));
            set("SQUASHR_CRYPTSETUP_OPEN_ARGS", &mut |v| cfg.SQUASHR_CRYPTSETUP_OPEN_ARGS = Some(v));
            set("SQUASHR_CRYPTSETUP_PASS", &mut |v| cfg.SQUASHR_CRYPTSETUP_PASS = Some(v));
            set("SQUASHR_CRYPTSETUP_PASS_FILE", &mut |v| cfg.SQUASHR_CRYPTSETUP_PASS_FILE = Some(PathBuf::from(v)));
        }
    }
    Ok(cfg)
}

fn bool_env(name:&str)->Option<bool>{ env::var(name).ok()?.parse().ok() }
fn str_env(name:&str)->Option<String>{ env::var(name).ok() }
fn list_env(name:&str)->Option<Vec<String>>{ env::var(name).ok().map(|v| parse_list(&v)) }

fn apply_env_overrides(mut cfg: Config)->Result<Config>{
    if let Some(v)=str_env("SQUASHR_ROOT"){ cfg.SQUASHR_ROOT=Some(PathBuf::from(v)); }
    if let Some(v)=env::var("SQUASHR_N_SNAPSHOTS_MIN").ok().and_then(|x| x.parse().ok()){ cfg.SQUASHR_N_SNAPSHOTS_MIN=Some(v); }
    if let Some(v)=env::var("SQUASHR_N_SNAPSHOTS_MAX").ok().and_then(|x| x.parse().ok()){ cfg.SQUASHR_N_SNAPSHOTS_MAX=Some(v); }
    if let Some(v)=list_env("SQUASHR_INCLUDE"){ cfg.SQUASHR_INCLUDE=Some(v); }
    if let Some(v)=list_env("SQUASHR_EXCLUDE"){ cfg.SQUASHR_EXCLUDE=Some(v); }
    if let Some(v)=list_env("SQUASHR_TRUNCATE"){ cfg.SQUASHR_TRUNCATE=Some(v); }
    if let Some(v)=bool_env("SQUASHR_COMPRESSION_ENABLE"){ cfg.SQUASHR_COMPRESSION_ENABLE=Some(v); }
    if let Some(v)=str_env("SQUASHR_COMPRESSION_ALGO"){ cfg.SQUASHR_COMPRESSION_ALGO=Some(v); }
    if let Some(v)=str_env("SQUASHR_COMPRESSION_ARGS"){ cfg.SQUASHR_COMPRESSION_ARGS=Some(v); }
    if let Some(v)=bool_env("SQUASHR_CRYPTSETUP_ENABLE"){ cfg.SQUASHR_CRYPTSETUP_ENABLE=Some(v); }
    if let Some(v)=str_env("SQUASHR_CRYPTSETUP_CREATE_ARGS"){ cfg.SQUASHR_CRYPTSETUP_CREATE_ARGS=Some(v); }
    if let Some(v)=str_env("SQUASHR_CRYPTSETUP_OPEN_ARGS"){ cfg.SQUASHR_CRYPTSETUP_OPEN_ARGS=Some(v); }
    if let Some(v)=str_env("SQUASHR_CRYPTSETUP_PASS"){ cfg.SQUASHR_CRYPTSETUP_PASS=Some(v); }
    if let Some(v)=str_env("SQUASHR_CRYPTSETUP_PASS_FILE"){ cfg.SQUASHR_CRYPTSETUP_PASS_FILE=Some(PathBuf::from(v)); }
    Ok(cfg)
}

fn apply_cli_overrides(mut cfg: Config, cli:&Cli)->Result<Config>{
    if let Some(v)=cli.squashr_root.clone(){ cfg.SQUASHR_ROOT=Some(v); }
    if let Some(v)=cli.squashr_n_snapshots_min{ cfg.SQUASHR_N_SNAPSHOTS_MIN=Some(v); }
    if let Some(v)=cli.squashr_n_snapshots_max{ cfg.SQUASHR_N_SNAPSHOTS_MAX=Some(v); }
    if let Some(v)=cli.squashr_include.as_ref(){ cfg.SQUASHR_INCLUDE=Some(parse_list(v)); }
    if let Some(v)=cli.squashr_exclude.as_ref(){ cfg.SQUASHR_EXCLUDE=Some(parse_list(v)); }
    if let Some(v)=cli.squashr_truncate.as_ref(){ cfg.SQUASHR_TRUNCATE=Some(parse_list(v)); }
    if let Some(v)=cli.squashr_compression_enable{ cfg.SQUASHR_COMPRESSION_ENABLE=Some(v); }
    if let Some(v)=cli.squashr_compression_algo.clone(){ cfg.SQUASHR_COMPRESSION_ALGO=Some(v); }
    if let Some(v)=cli.squashr_compression_args.clone(){ cfg.SQUASHR_COMPRESSION_ARGS=Some(v); }
    if let Some(v)=cli.squashr_cryptsetup_enable{ cfg.SQUASHR_CRYPTSETUP_ENABLE=Some(v); }
    if let Some(v)=cli.squashr_cryptsetup_create_args.clone(){ cfg.SQUASHR_CRYPTSETUP_CREATE_ARGS=Some(v); }
    if let Some(v)=cli.squashr_cryptsetup_open_args.clone(){ cfg.SQUASHR_CRYPTSETUP_OPEN_ARGS=Some(v); }
    if let Some(v)=cli.squashr_cryptsetup_pass.clone(){ cfg.SQUASHR_CRYPTSETUP_PASS=Some(v); }
    if let Some(v)=cli.squashr_cryptsetup_pass_file.clone(){ cfg.SQUASHR_CRYPTSETUP_PASS_FILE=Some(v); }
    Ok(cfg)
}

#[derive(Clone)]
struct Ctx {
    root: PathBuf,
    state_dir: PathBuf,
    mounts_dir: PathBuf,
    work_dir: PathBuf,
    tar_snapshot: PathBuf, // GNU-tar Snapshot-Datei (materialisiert für tar)
    min_keep: usize,
    max_keep: Option<usize>,
    include: Vec<PathBuf>,
    exclude: Vec<PathBuf>,
    truncate: Vec<PathBuf>,
    comp_enable: bool,
    comp_algo: String,
    comp_args: Option<String>,
    luks_enable: bool,
    luks_create_args: Option<String>,
    luks_open_args: Option<String>,
    luks_pass: Option<Vec<u8>>,
    verbose: bool,
}

impl Ctx {
    fn new(cfg: Config, verbose: bool) -> Result<Self> {
        let root = cfg.SQUASHR_ROOT.ok_or_else(|| anyhow!("SQUASHR_ROOT not set!"))?;
        let state_dir = root.join("state");
        let mounts_dir = root.join("mounts");
        let work_dir = root.join("work");
        fs::create_dir_all(&state_dir)?;
        fs::create_dir_all(&mounts_dir)?;
        fs::create_dir_all(&work_dir)?;
        let tar_snapshot = state_dir.join("tar.snapshot");

        let max_raw = cfg.SQUASHR_N_SNAPSHOTS_MAX.unwrap_or(0);
        let max_keep = if max_raw == 0 { None } else { Some(max_raw) };

        // Passphrase ermitteln (CLI-String hat Vorrang vor Datei)
        let luks_pass = if let Some(p) = cfg.SQUASHR_CRYPTSETUP_PASS {
            Some(p.into_bytes())
        } else if let Some(f) = cfg.SQUASHR_CRYPTSETUP_PASS_FILE {
            Some(fs::read(&f).with_context(|| format!("Pass-Datei lesen: {}", f.display()))?)
        } else {
            None
        };

        Ok(Self {
            root,
            state_dir,
            mounts_dir,
            work_dir,
            tar_snapshot,
            min_keep: cfg.SQUASHR_N_SNAPSHOTS_MIN.unwrap_or(5),
            max_keep,
            include: cfg.SQUASHR_INCLUDE.unwrap_or_default().into_iter().map(PathBuf::from).collect(),
            exclude: cfg.SQUASHR_EXCLUDE.unwrap_or_default().into_iter().map(PathBuf::from).collect(),
            truncate: cfg.SQUASHR_TRUNCATE.unwrap_or_default().into_iter().map(PathBuf::from).collect(),
            comp_enable: cfg.SQUASHR_COMPRESSION_ENABLE.unwrap_or(true),
            comp_algo: cfg.SQUASHR_COMPRESSION_ALGO.unwrap_or_else(|| "zstd".into()),
            comp_args: cfg.SQUASHR_COMPRESSION_ARGS,
            luks_enable: cfg.SQUASHR_CRYPTSETUP_ENABLE.unwrap_or(false),
            luks_create_args: cfg.SQUASHR_CRYPTSETUP_CREATE_ARGS,
            luks_open_args: cfg.SQUASHR_CRYPTSETUP_OPEN_ARGS,
            luks_pass,
            verbose,
        })
    }

    fn list_snapshots(&self) -> Result<Vec<PathBuf>> {
        let mut entries: Vec<_> = fs::read_dir(&self.state_dir)?
            .filter_map(|e| e.ok())
            .map(|e| e.path())
            .filter(|p| p.is_file())
            .filter(|p| {
                p.file_name()
                    .and_then(|n| n.to_str())
                    .map(|s| s.ends_with(".squashfs") || s.ends_with(".squashfs.luks"))
                    .unwrap_or(false)
            })
            .filter(|p| {
                // meta-Container NICHT als "Snapshot" zählen
                let fname = p.file_name().and_then(|s| s.to_str()).unwrap_or("");
                fname != "meta.squashfs" && fname != "meta.squashfs.luks"
            })
            .collect();
        entries.sort();
        Ok(entries)
    }

    fn snapshot_path(&self, idx: usize, encrypted: bool) -> PathBuf {
        let name = format!("{:04}{}", idx, if encrypted { ".squashfs.luks" } else { ".squashfs" });
        self.state_dir.join(name)
    }

    fn manifest_name(idx: usize) -> String {
        format!("manifest_{:04}.txt", idx)
    }

    fn meta_plain_path(&self) -> PathBuf { self.state_dir.join("meta.squashfs") }
    fn meta_luks_path(&self) -> PathBuf { self.state_dir.join("meta.squashfs.luks") }

    fn temp_path(&self, stem: &str) -> PathBuf {
        let ts = chrono::Local::now().format("%Y%m%d-%H%M%S");
        self.work_dir.join(format!("{}_{}", stem, ts))
    }
}

fn main() -> Result<()> {
    let cli = Cli::parse();
    let cfg = load_config(cli.config.as_deref())?;
    let cfg = apply_env_overrides(cfg)?;
    let cfg = apply_cli_overrides(cfg, &cli)?;
    let mut ctx = Ctx::new(cfg, cli.verbose)?;

    match cli.cmd {
        Cmd::Backup => cmd_backup(&mut ctx),
        Cmd::Minimize { n } => cmd_minimize(&mut ctx, n),
        Cmd::New => cmd_new(&mut ctx),
        Cmd::Mount { s, target } => cmd_mount(&mut ctx, s, &target),
        Cmd::Delete { s } => cmd_delete(&mut ctx, s),
        Cmd::Umount { target } => cmd_umount(&mut ctx, target.as_deref()),
    }
}

fn abspath(p: &Path) -> PathBuf {
    fs::canonicalize(p).unwrap_or_else(|_| p.to_path_buf())
}

fn abs_key(p: &Path) -> Result<String> {
    let abs = fs::canonicalize(p)?;
    let s = abs.to_string_lossy();
    Ok(s.trim_start_matches('/').to_string())
}

fn parse_snap_index(p:&Path)->Result<usize>{
    let fname = p.file_name().and_then(|s| s.to_str()).ok_or_else(||anyhow!("Invalid filename: {}", p.display()))?;
    // robust: nur führende 4 Ziffern extrahieren
    let re = Regex::new(r"^(\d{4})").unwrap();
    let caps = re.captures(fname).ok_or_else(|| anyhow!("No index found: {}", p.display()))?;
    Ok(caps.get(1).unwrap().as_str().parse::<usize>().unwrap())
}

fn shell_split(s:&str)->Vec<String>{
    s.split_whitespace().map(|x| x.to_string()).collect()
}

fn run(cmd:&mut Command, desc:&str)->Result<()>{
    let status = cmd.status().with_context(|| format!("Unable to start {}", desc))?;
    if !status.success(){ bail!("Command failed: {}", desc); }
    Ok(())
}

fn run_ok_status(cmd:&mut Command)->std::io::Result<std::process::ExitStatus>{
    cmd.status()
}

fn run_interactive(cmd:&mut Command, desc:&str)->Result<()>{
    cmd.stdin(Stdio::inherit()).stdout(Stdio::inherit()).stderr(Stdio::inherit());
    run(cmd, desc)
}

fn run_with_stdin(cmd:&mut Command, input:&[u8], desc:&str)->Result<()>{
    cmd.stdin(Stdio::piped()).stdout(Stdio::inherit()).stderr(Stdio::inherit());
    let mut child = cmd.spawn().with_context(|| format!("Unable to start {}", desc))?;
    {
        let mut stdin = child.stdin.take().ok_or_else(|| anyhow!("Cannot open stdin for {}", desc))?;
        stdin.write_all(input)?;
    }
    let status = child.wait()?;
    if !status.success(){ bail!("Command failed: {}", desc); }
    Ok(())
}

fn cryptsetup_run(cmd:&mut Command, pass: Option<&[u8]>, desc:&str)->Result<()>{
    if pass.is_some() {
        cmd.arg("--key-file").arg("-");
        cmd.arg("--batch-mode");
        run_with_stdin(cmd, pass.unwrap(), desc)
    } else {
        run_interactive(cmd, desc)
    }
}

fn require_root(op: &str) -> Result<()> {
    if unsafe { libc::geteuid() } != 0 {
        bail!("{op} requires root privileges.");
    }
    Ok(())
}

fn ensure_includes_nonempty(ctx:&Ctx)->Result<()>{
    if ctx.include.is_empty(){ bail!("SQUASHR_INCLUDE is empty."); }
    Ok(())
}

fn canonicalize_or_same(p: &Path) -> PathBuf {
    fs::canonicalize(p).unwrap_or_else(|_| p.to_path_buf())
}

fn build_prune_set_for_root(abs_root: &Path, ctx: &Ctx) -> Vec<PathBuf> {
    let mut v = Vec::new();
    for ex in &ctx.exclude {
        let ex_abs = canonicalize_or_same(ex);
        if ex_abs.starts_with(abs_root) {
            v.push(ex_abs);
        }
    }
    // stets interne Verzeichnisse ausschließen
    for auto in [&ctx.state_dir, &ctx.mounts_dir, &ctx.work_dir] {
        let ex_abs = canonicalize_or_same(auto);
        if ex_abs.starts_with(abs_root) { v.push(ex_abs); }
    }
    v
}

/// Liefert (top_namespace->abs_root) und Manifest (alle Dateien/Symlinks) relativ zum Archiv-Root: "top/relpath".
fn collect_manifest(ctx: &Ctx) -> Result<(HashMap<String, PathBuf>, BTreeSet<String>)> {
    let mut manifest: BTreeSet<String> = BTreeSet::new();
    let mut roots: HashMap<String, PathBuf> = HashMap::new();

    for inc in &ctx.include {
        let abs_root = fs::canonicalize(inc)?;
        let top = abs_key(&abs_root)?;
        roots.insert(top.clone(), abs_root.clone());

        let prune_set = build_prune_set_for_root(&abs_root, ctx);

        let iter = WalkDir::new(&abs_root)
            .follow_links(false)
            .into_iter()
            .filter_entry(|e| {
                let p = e.path();
                let skip = prune_set.iter().any(|ex| p.starts_with(ex));
                !skip
            })
            .filter_map(|e| e.ok());

        for entry in iter {
            let p = entry.path();
            let ft = entry.file_type();
            if ft.is_dir() { continue; }

            let md = fs::symlink_metadata(p)?;
            if !(md.file_type().is_symlink() || md.is_file()) { continue; }

            let rel = p
                .strip_prefix(&abs_root)
                .unwrap_or(Path::new(""))
                .to_string_lossy()
                .to_string();

            let name = if rel.is_empty() { top.clone() } else { format!("{}/{}", top, rel) };
            manifest.insert(name);
        }
    }

    Ok((roots, manifest))
}

/* ---------- TAR Streaming Filter: GNU 'D' dumpdir strip ---------- */

fn is_zero_block(b: &[u8]) -> bool {
    b.iter().all(|&x| x == 0)
}

fn parse_tar_size_octal(field: &[u8]) -> u64 {
    let mut s = 0u64;
    for &c in field {
        if c >= b'0' && c <= b'7' {
            s = (s << 3) + (c - b'0') as u64;
        }
    }
    s
}

fn forward_tar_strip_gnu_dumpdirs<R: Read, W: Write>(mut r: R, mut w: W) -> Result<()> {
    let mut header = [0u8; 512];
    let mut buf = vec![0u8; 1024 * 1024];

    loop {
        r.read_exact(&mut header).with_context(|| "read tar header")?;

        if is_zero_block(&header) {
            w.write_all(&header)?;
            r.read_exact(&mut header).with_context(|| "read tar trailing zero")?;
            w.write_all(&header)?;
            w.flush()?;
            break;
        }

        let typeflag = header[156] as char;
        let size = parse_tar_size_octal(&header[124..124+12]);
        let padded = ((size + 511) / 512) * 512;

        if typeflag == 'D' {
            let mut to_skip = padded;
            while to_skip > 0 {
                let take = to_skip.min(buf.len() as u64) as usize;
                r.read_exact(&mut buf[..take])?;
                to_skip -= take as u64;
            }
            continue;
        }

        w.write_all(&header)?;
        let mut remaining = padded as i64;
        while remaining > 0 {
            let take = remaining.min(buf.len() as i64) as usize;
            r.read_exact(&mut buf[..take])?;
            w.write_all(&buf[..take])?;
            remaining -= take as i64;
        }
    }

    Ok(())
}

/* ---------- Meta-Container (Manifeste + tar.snapshot) ---------- */

fn meta_existing(ctx: &Ctx) -> Option<PathBuf> {
    let luks = ctx.meta_luks_path();
    let plain = ctx.meta_plain_path();
    if luks.exists() { Some(luks) }
    else if plain.exists() { Some(plain) }
    else { None }
}

fn open_meta_read(ctx:&Ctx) -> Result<Option<(PathBuf /*src*/, Option<String> /*mapper*/)>> {
    if let Some(img) = meta_existing(ctx) {
        if img.extension().and_then(|e| e.to_str()) == Some("luks") {
            require_root("open meta LUKS")?;
            let mapper = "squashr_meta".to_string();
            let mut o = Command::new("cryptsetup");
            if let Some(args)=ctx.luks_open_args.as_ref(){ for t in shell_split(args){ o.arg(t);} }
            o.arg("open").arg(&img).arg(&mapper);
            cryptsetup_run(&mut o, ctx.luks_pass.as_deref(), "cryptsetup open (meta)")?;
            Ok(Some((PathBuf::from(format!("/dev/mapper/{mapper}")), Some(mapper))))
        } else {
            Ok(Some((img, None)))
        }
    } else {
        Ok(None)
    }
}

fn close_meta_mapper(mapper: Option<String>) {
    if let Some(m) = mapper {
        let _ = Command::new("cryptsetup").arg("close").arg(&m).status();
    }
}

fn extract_all_meta_to(ctx:&Ctx, dest:&Path) -> Result<()> {
    if let Some((src, mapper)) = open_meta_read(ctx)? {
        fs::create_dir_all(dest)?;
        let mut cmd = Command::new("unsquashfs");
        cmd.arg("-d").arg(dest).arg(&src);
        run(&mut cmd, "unsquashfs meta")?;
        close_meta_mapper(mapper);
    } else {
        fs::create_dir_all(dest)?;
    }
    Ok(())
}

fn extract_file_from_meta(ctx:&Ctx, filename:&str, dest_path:&Path) -> Result<bool> {
    if let Some((src, mapper)) = open_meta_read(ctx)? {
        let tmp = ctx.temp_path("meta.extract");
        fs::create_dir_all(&tmp)?;
        // nur die gewünschte Datei extrahieren
        let mut cmd = Command::new("unsquashfs");
        cmd.arg("-d").arg(&tmp).arg(&src).arg(filename);
        let st = run_ok_status(&mut cmd).with_context(|| "run unsquashfs")?;
        let ok = st.success();
        let srcf = tmp.join(filename);
        let mut present = false;
        if ok && srcf.exists() {
            fs::create_dir_all(dest_path.parent().unwrap_or_else(|| Path::new(".")))?;
            fs::rename(&srcf, dest_path)?;
            present = true;
        }
        // aufräumen
        let _ = fs::remove_dir_all(&tmp);
        close_meta_mapper(mapper);
        Ok(present)
    } else {
        Ok(false)
    }
}

fn cleanup_plain_meta_files(ctx:&Ctx) {
    // tar.snapshot + alle manifest_* im state_dir entfernen, falls vorhanden
    let _ = fs::remove_file(&ctx.tar_snapshot);
    if let Ok(rd) = fs::read_dir(&ctx.state_dir) {
        for e in rd.flatten() {
            if let Some(name) = e.file_name().to_str() {
                if name.starts_with("manifest_") && name.ends_with(".txt") {
                    let _ = fs::remove_file(e.path());
                }
            }
        }
    }
}

fn rebuild_meta_from_staging(ctx:&Ctx, staging:&Path) -> Result<()> {
    // meta tmp plain
    let tmp_plain = ctx.temp_path("meta.plain.squashfs");
    if tmp_plain.exists() { let _ = fs::remove_file(&tmp_plain); }
    let mut cmd = Command::new("mksquashfs");
    cmd.arg(staging).arg(&tmp_plain).arg("-no-progress").arg("-no-recovery");
    if ctx.comp_enable {
        cmd.arg("-comp").arg(&ctx.comp_algo);
        if let Some(extra)=ctx.comp_args.as_ref(){ for tok in shell_split(extra){ cmd.arg(tok);} }
    }
    run(&mut cmd, "mksquashfs (meta)")?;

    // Ziel festlegen (verschlüsselt/unkryptiert)
    let plain = ctx.meta_plain_path();
    let luks  = ctx.meta_luks_path();

    // vorhandene Varianten löschen, um Inkonsistenzen zu vermeiden
    let _ = fs::remove_file(&plain);
    let _ = fs::remove_file(&luks);

    if ctx.luks_enable {
        encrypt_into_luks(ctx, &tmp_plain, &luks)?;
        let _ = fs::remove_file(&tmp_plain);
    } else {
        fs::rename(&tmp_plain, &plain)?;
    }

    // Klartextreste entfernen
    cleanup_plain_meta_files(ctx);
    Ok(())
}

fn save_manifest_to_dir(dest_dir:&Path, idx: usize, manifest: &BTreeSet<String>) -> Result<()> {
    fs::create_dir_all(dest_dir)?;
    let path = dest_dir.join(Ctx::manifest_name(idx));
    let mut f = fs::File::create(&path).with_context(|| format!("manifest schreiben: {}", path.display()))?;
    for line in manifest {
        writeln!(f, "{line}")?;
    }
    Ok(())
}

fn load_manifest(ctx:&Ctx, idx: usize) -> Result<BTreeSet<String>> {
    // Primär aus Meta-Container lesen
    let fname = Ctx::manifest_name(idx);
    let tmp = ctx.temp_path("manifest.read");
    fs::create_dir_all(&tmp)?;
    let out = tmp.join(&fname);
    if extract_file_from_meta(ctx, &fname, &out)? {
        let text = fs::read_to_string(&out)
            .with_context(|| format!("manifest lesen: {}", out.display()))?;
        let _ = fs::remove_dir_all(&tmp);
        return Ok(text.lines().map(|s| s.trim().to_string()).filter(|s| !s.is_empty()).collect());
    }
    // Fallback (falls sehr früher Zustand): Klartextdatei
    let legacy = ctx.state_dir.join(&fname);
    if legacy.exists() {
        let text = fs::read_to_string(&legacy)
            .with_context(|| format!("manifest lesen: {}", legacy.display()))?;
        let _ = fs::remove_dir_all(&tmp);
        return Ok(text.lines().map(|s| s.trim().to_string()).filter(|s| !s.is_empty()).collect());
    }
    let _ = fs::remove_dir_all(&tmp);
    bail!("manifest {} not found", fname);
}

/* ---------- TAR → SQFSTAR ---------- */

/// Erzeugt inkrementellen *tar* und streamt ihn (mit Filter) in `sqfstar`.
/// Rückgabewert: true, falls tar mit Non-Zero beendet wurde (Warnung).
fn build_squash_image_tar_sqfstar(
    ctx: &Ctx,
    out: &Path,
    roots: &HashMap<String, PathBuf>,
) -> Result<bool /* tar_nonzero */> {
    if out.exists() {
        fs::remove_file(out).with_context(|| format!("remove old output: {}", out.display()))?;
    }

    // sqfstar: Tar von stdin → SquashFS out
    let mut sq = Command::new("sqfstar");
    if ctx.comp_enable {
        sq.arg("-comp").arg(&ctx.comp_algo);
    }
    sq.arg(out).arg("-");
    sq.stdin(Stdio::piped());
    sq.stdout(Stdio::inherit());
    sq.stderr(Stdio::inherit());

    vlog!(ctx, "[backup] sqfstar ← tar (incremental stream, dumpdir-filtered) → {}", out.display());
    let mut sq_child = sq.spawn().with_context(|| "Unable to start sqfstar")?;
    let sq_stdin = sq_child.stdin.take().ok_or_else(|| anyhow!("cannot open sqfstar stdin"))?;

    // tar: POSIX/PAX + GNU listed-incremental; Pfade relativ zu /
    let mut tar = Command::new("tar");
    tar.arg("--format=posix")
        .arg("-C").arg("/")
        .arg("--null")
        .arg("--files-from=-")
        .arg("--listed-incremental").arg(&ctx.tar_snapshot)
        .arg("-cf").arg("-")
        .arg("--numeric-owner")
        .arg("--ignore-failed-read");

    // Excludes (relativ zu /)
    let mut all_excludes: Vec<PathBuf> = ctx.exclude.clone();
    for auto in [&ctx.state_dir, &ctx.mounts_dir, &ctx.work_dir] {
        all_excludes.push(auto.clone());
    }
    for ex in all_excludes {
        let ex_rel = ex.to_string_lossy().trim_start_matches('/').to_string();
        if !ex_rel.is_empty() {
            tar.arg(format!("--exclude={}", ex_rel));
        }
    }

    tar.stdin(Stdio::piped());
    tar.stdout(Stdio::piped());
    tar.stderr(Stdio::inherit());
    let mut tar_child = tar.spawn().with_context(|| "Unable to start tar")?;

    // Pfadliste: Roots *relativ* zu / (z.B. "usr", "var", "home/lk")
    {
        let mut w = std::io::BufWriter::new(
            tar_child.stdin.take().ok_or_else(|| anyhow!("cannot open tar stdin"))?
        );
        for (_top, abs_root) in roots.iter() {
            let rel = abs_root.to_string_lossy().trim_start_matches('/').to_string();
            let item = if rel.is_empty() { ".".to_string() } else { rel };
            w.write_all(item.as_bytes())?;
            w.write_all(&[0])?; // NUL
        }
        w.flush()?;
        drop(w);
    }

    // tar stdout → (Filter: strip dumpdir) → sqfstar stdin
    {
        let tar_stdout = tar_child.stdout.take().ok_or_else(|| anyhow!("cannot open tar stdout"))?;
        forward_tar_strip_gnu_dumpdirs(tar_stdout, sq_stdin)?;
    }

    let tar_status = tar_child.wait().with_context(|| "waiting for tar failed")?;
    let tar_code = tar_status.code().unwrap_or(-1);
    let tar_nonzero = tar_code != 0;
    if tar_nonzero {
        eprintln!("[warn] tar exited with code {tar_code}; continuing (image may be partial).");
    }

    let sq_status = sq_child.wait().with_context(|| "waiting for sqfstar failed")?;
    if !sq_status.success() {
        bail!("sqfstar failed with status {}", sq_status);
    }

    Ok(tar_nonzero)
}

fn truncate_logs(ctx:&Ctx)->Result<()>{
    if ctx.truncate.is_empty(){ return Ok(()); }
    for base in &ctx.truncate {
        if !base.exists(){ continue; }
        for entry in WalkDir::new(base).follow_links(false).into_iter().filter_map(|e| e.ok()) {
            let p = entry.path();
            if p.is_file() {
                let name = p.file_name().and_then(|s| s.to_str()).unwrap_or("");
                if name.ends_with(".gz") || name.ends_with(".xz") || name.ends_with(".zst") || name.ends_with(".bz2") {
                    let _ = fs::remove_file(p);
                    continue;
                }
                let _ = fs::OpenOptions::new().write(true).open(p).and_then(|f| { f.set_len(0)?; Ok(()) });
            }
        }
    }
    Ok(())
}

fn encrypt_into_luks(ctx:&Ctx, plain:&Path, out_luks:&Path)->Result<()>{
    require_root("Creating LUKS container")?;

    let plain_size = fs::metadata(plain)?.len();
    let size = plain_size + 16 * 1024 * 1024;
    {
        let f = fs::File::create(out_luks)?;
        f.set_len(size)?;
    }

    vlog!(ctx, "[luks] luksFormat {}", out_luks.display());
    let mut c = Command::new("cryptsetup");
    if let Some(args)=ctx.luks_create_args.as_ref(){ for t in shell_split(args){ c.arg(t);} }
    c.arg("luksFormat").arg(out_luks);
    cryptsetup_run(&mut c, ctx.luks_pass.as_deref(), "cryptsetup luksFormat")?;

    let mapper = format!("squashr_{}", parse_snap_index(out_luks).unwrap_or(0));
    vlog!(ctx, "[luks] open {} as {}", out_luks.display(), mapper);
    let mut o = Command::new("cryptsetup");
    if let Some(args)=ctx.luks_open_args.as_ref(){ for t in shell_split(args){ o.arg(t);} }
    o.arg("open").arg(out_luks).arg(&mapper);
    cryptsetup_run(&mut o, ctx.luks_pass.as_deref(), "cryptsetup open")?;

    let dev = format!("/dev/mapper/{}", mapper);
    vlog!(ctx, "[luks] dd {} → {}", plain.display(), dev);
    let mut dd = Command::new("dd");
    dd.arg(format!("if={}", plain.display()))
      .arg(format!("of={}", dev))
      .arg("bs=4M").arg("status=none").arg("conv=fsync");
    run(&mut dd, "dd")?;

    vlog!(ctx, "[luks] close {}", mapper);
    let mut close = Command::new("cryptsetup");
    close.arg("close").arg(&mapper);
    run(&mut close, "cryptsetup close")?;

    Ok(())
}

/* ---------- Mount Helfer / FUSE Fallback ---------- */

fn try_mount_kernel_squashfs(source:&Path, mnt:&Path, use_loop:bool) -> Result<bool> {
    let mut cmd = Command::new("mount");
    cmd.arg("-t").arg("squashfs");
    if use_loop { cmd.arg("-o").arg("loop,ro"); } else { cmd.arg("-o").arg("ro"); }
    cmd.arg(source).arg(mnt);
    let status = cmd.status().with_context(|| "start mount squashfs (kernel)")?;
    Ok(status.success())
}

fn try_mount_fuse_squashfs(source:&Path, mnt:&Path) -> Result<bool> {
    let status = Command::new("squashfuse")
        .arg("-o").arg("ro")
        .arg(source)
        .arg(mnt)
        .status();

    match status {
        Ok(s) => Ok(s.success()),
        Err(e) => Err(anyhow!("squashfuse nicht startbar: {e}")),
    }
}

/* ---------- Mount-Info Utilities ---------- */

#[derive(Debug)]
struct MountEntry { src:String, tgt:PathBuf, fstype:String, opts:String }

fn read_proc_mounts() -> Result<Vec<MountEntry>> {
    let text = fs::read_to_string("/proc/mounts").context("read /proc/mounts")?;
    let mut out = Vec::new();
    for line in text.lines() {
        // /proc/mounts: src tgt fstype opts 0 0
        let mut it = line.split_whitespace();
        let (Some(src), Some(tgt), Some(fstype), Some(opts)) = (it.next(), it.next(), it.next(), it.next()) else { continue };
        out.push(MountEntry{
            src: src.to_string(),
            tgt: PathBuf::from(tgt),
            fstype: fstype.to_string(),
            opts: opts.to_string(),
        });
    }
    Ok(out)
}

fn is_target_mounted(tgt: &Path) -> bool {
    if let Ok(ms) = read_proc_mounts() {
        let at = abspath(tgt);
        ms.into_iter().any(|m| abspath(&m.tgt) == at)
    } else {
        false
    }
}

fn sort_paths_deep_first(mut v: Vec<PathBuf>) -> Vec<PathBuf> {
    v.sort_by_key(|p| std::cmp::Reverse(p.components().count()));
    v.dedup();
    v
}

fn loop_backing_file(dev: &str) -> Option<PathBuf> {
    // Erwartet "/dev/loopX"
    let name = Path::new(dev).file_name()?.to_string_lossy().to_string();
    let candidates = [
        format!("/sys/block/{}/loop/backing_file", name),
        format!("/sys/devices/virtual/block/{}/loop/backing_file", name),
    ];
    for p in candidates {
        if let Ok(s) = fs::read_to_string(&p) {
            let t = s.trim();
            if !t.is_empty() { return Some(PathBuf::from(t)); }
        }
    }
    None
}

/* ---------- Backup ---------- */

fn ensure_tar_snapshot_materialized(ctx:&Ctx) -> Result<()> {
    // Falls in Meta enthalten → herausziehen, sonst tar lässt neu schreiben
    let _ = extract_file_from_meta(ctx, "tar.snapshot", &ctx.tar_snapshot)?;
    Ok(())
}

fn cmd_backup(ctx:&mut Ctx)->Result<()>{
    ensure_includes_nonempty(ctx)?;
    truncate_logs(ctx)?;

    // Vorbereitungen: tar.snapshot bereitstellen
    ensure_tar_snapshot_materialized(ctx)?;

    let snaps = ctx.list_snapshots()?;
    let next_idx = snaps.len() + 1;

    // 1) Manifest aufnehmen (inkl. Excludes & interne Verzeichnisse)
    let (roots, manifest_now) = collect_manifest(ctx)?;
    let manifest_prev = if next_idx > 1 {
        load_manifest(ctx, next_idx - 1).ok()
    } else { None };

    // 2) Falls keine Änderung: minimalistisches Image erstellen (wie bisher)
    let no_changes = manifest_prev.as_ref().map_or(false, |m| m == &manifest_now);
    let plain_img = ctx.temp_path("snapshot.plain.squashfs");

    let mut tar_warn = false;
    if no_changes {
        vlog!(ctx, "[backup] no changes → creating minimal image {}", plain_img.display());
        let empty_src = ctx.temp_path("empty.src");
        fs::create_dir_all(&empty_src)?;
        let mut cmd = Command::new("mksquashfs");
        cmd.arg(&empty_src).arg(&plain_img).arg("-no-progress").arg("-no-recovery");
        if ctx.comp_enable {
            cmd.arg("-comp").arg(&ctx.comp_algo);
            if let Some(extra)=ctx.comp_args.as_ref() { for tok in shell_split(extra){ cmd.arg(tok); } }
        }
        run(&mut cmd, "mksquashfs (empty)")?;
    } else {
        // 3) tar (listed-incremental) → Filter (strip 'D') → sqfstar
        tar_warn = build_squash_image_tar_sqfstar(ctx, &plain_img, &roots)?;
    }

    // 4) Optional: LUKS-Container schreiben
    let final_path = if ctx.luks_enable {
        let out = ctx.snapshot_path(next_idx, true);
        encrypt_into_luks(ctx, &plain_img, &out)?;
        fs::remove_file(&plain_img).ok();
        out
    } else {
        let out = ctx.snapshot_path(next_idx, false);
        fs::rename(&plain_img, &out)?;
        out
    };

    // 5) Meta-Container neu bauen (alle Manifeste + tar.snapshot)
    let staging = ctx.temp_path("meta.staging");
    extract_all_meta_to(ctx, &staging)?;
    // neues Manifest hinein
    save_manifest_to_dir(&staging, next_idx, &manifest_now)?;
    // aktualisierte tar.snapshot hinein (falls vorhanden)
    if ctx.tar_snapshot.exists() {
        let dst = staging.join("tar.snapshot");
        if dst.exists() { let _ = fs::remove_file(&dst); }
        fs::copy(&ctx.tar_snapshot, &dst)?;
    }
    rebuild_meta_from_staging(ctx, &staging)?;
    let _ = fs::remove_dir_all(&staging);

    if tar_warn {
        eprintln!("[warn] Snapshot {:04} created, but tar reported non-zero exit. Some files may be missing or changed during read.", next_idx);
    }

    println!("Created new snapshot: {:04}", final_path.display());

    rotate_if_needed(ctx)?;
    Ok(())
}

fn rotate_if_needed(ctx:&mut Ctx)->Result<()>{
    if let Some(max)=ctx.max_keep {
        loop {
            let snaps = ctx.list_snapshots()?;
            if snaps.len() <= max { break; }
            merge_first_two(ctx)?;
        }
    }
    Ok(())
}

/* ---------- Whiteouts / Mount / Overlay ---------- */

fn create_whiteouts_unlink_list(ctx:&Ctx, upto:usize)->Result<Vec<String>>{
    if upto == 0 { return Ok(vec![]); }
    let present = load_manifest(ctx, upto).unwrap_or_default();
    let mut union_past: BTreeSet<String> = BTreeSet::new();
    for i in 1..upto {
        let m = load_manifest(ctx, i).unwrap_or_default();
        for s in m { union_past.insert(s); }
    }
    let deletions: Vec<String> = union_past.difference(&present).cloned().collect();
    Ok(deletions)
}

fn apply_whiteouts_via_unlink(view_root:&Path, deletes:&[String]) -> Result<()> {
    for rel in deletes {
        let p = view_root.join(rel);
        match fs::remove_file(&p) {
            Ok(_) => {},
            Err(e) if e.kind() == ErrorKind::IsADirectory => {
                let _ = fs::remove_dir(&p);
            }
            Err(e) if e.kind() == ErrorKind::NotFound => { /* okay */ }
            Err(e) => return Err(anyhow!("Unlink failed for {}: {}", p.display(), e)),
        }
    }
    Ok(())
}

fn mount_image_ro(ctx:&Ctx, img:&Path, mnt:&Path)->Result<()>{
    require_root("Mount SquashFS")?;
    let mnt_abs = abspath(mnt);

    if img.extension().and_then(|e| e.to_str()) == Some("luks") {
        // LUKS → /dev/mapper/<mapper>
        let mapper = format!(
            "squashr_mount_{}",
            img.file_stem().and_then(|s| s.to_str()).unwrap_or("img")
        );
        let dev = format!("/dev/mapper/{}", mapper);

        // evtl. Alt-Mapping schließen
        let _ = Command::new("cryptsetup").arg("close").arg(&mapper).status();

        let mut o = Command::new("cryptsetup");
        if let Some(args)=ctx.luks_open_args.as_ref(){ for t in shell_split(args){ o.arg(t);} }
        o.arg("open").arg(img).arg(&mapper);
        cryptsetup_run(&mut o, ctx.luks_pass.as_deref(), "cryptsetup open (mount)")?;

        // 1) Kernel-Mount versuchen
        match try_mount_kernel_squashfs(Path::new(&dev), &mnt_abs, false) {
            Ok(true) => return Ok(()),
            Ok(false) => {
                eprintln!("[warn] Kernel-SquashFS-Mount fehlgeschlagen – versuche FUSE (squashfuse).");
            }
            Err(e) => {
                eprintln!("[warn] Kernel-SquashFS-Mount Fehler: {e} – versuche FUSE (squashfuse).");
            }
        }

        // 2) FUSE-Fallback versuchen
        match try_mount_fuse_squashfs(Path::new(&dev), &mnt_abs) {
            Ok(true) => return Ok(()),
            Ok(false) => {
                // Mapping sauber schließen
                let _ = Command::new("cryptsetup").arg("close").arg(&mapper).status();
                bail!("FUSE-Mount (squashfuse) fehlgeschlagen. Prüfe Kernelmodul 'squashfs' oder installiere 'squashfuse'.");
            }
            Err(e) => {
                let _ = Command::new("cryptsetup").arg("close").arg(&mapper).status();
                bail!("{e}. Prüfe Kernelmodul 'squashfs' oder installiere 'squashfuse'.");
            }
        }
    } else {
        // Plain SquashFS-Datei
        match try_mount_kernel_squashfs(img, &mnt_abs, true) {
            Ok(true) => return Ok(()),
            Ok(false) => {
                eprintln!("[warn] Kernel-SquashFS-Mount fehlgeschlagen – versuche FUSE (squashfuse).");
            }
            Err(e) => {
                eprintln!("[warn] Kernel-SquashFS-Mount Fehler: {e} – versuche FUSE (squashfuse).");
            }
        }
        match try_mount_fuse_squashfs(img, &mnt_abs) {
            Ok(true) => Ok(()),
            Ok(false) => bail!("FUSE-Mount (squashfuse) fehlgeschlagen. Prüfe Kernelmodul 'squashfs' oder installiere 'squashfuse'."),
            Err(e) => bail!("{e}. Prüfe Kernelmodul 'squashfs' oder installiere 'squashfuse'."),
        }
    }
}

fn mount_overlay(lowerdirs:&str, upper:&Path, work:&Path, target:&Path)->Result<()>{
    require_root("Mount OverlayFS")?;
    let opt = format!(
        "lowerdir={},upperdir={},workdir={}",
        lowerdirs,
        abspath(upper).display(),
        abspath(work).display()
    );
    let mut cmd = Command::new("mount");
    cmd.arg("-t").arg("overlay").arg("overlay")
       .arg("-o").arg(opt)
       .arg(abspath(target));
    run(&mut cmd, "mount overlay")?;
    Ok(())
}

/* ---------- Umount (robust, idempotent) ---------- */

fn umount(path:&Path)->Result<()>{
    require_root("umount")?;
    // Wenn nicht gemountet → OK (idempotent)
    if !is_target_mounted(path) {
        return Ok(());
    }
    // Erst normal versuchen
    let mut cmd = Command::new("umount");
    cmd.arg(path);
    let status = cmd.status().with_context(|| "umount aufrufen")?;
    if status.success() {
        return Ok(());
    }
    // FUSE-Fälle: fusermount3/fusermount
    let _ = Command::new("fusermount3").arg("-u").arg(path).status();
    let status2 = Command::new("fusermount").arg("-u").arg(path).status();
    if let Ok(s) = status2 {
        if s.success() { return Ok(()); }
    }
    // Letzter Versuch: lazy
    let _ = Command::new("umount").arg("-l").arg(path).status();
    if !is_target_mounted(path) { return Ok(()); }

    bail!("umount/fusermount fehlgeschlagen für {}", path.display());
}

fn find_snapshot_file(ctx:&Ctx, idx:usize)->Result<PathBuf>{
    let p1 = ctx.snapshot_path(idx, false);
    let p2 = ctx.snapshot_path(idx, true);
    if p1.exists(){ Ok(p1) }
    else if p2.exists(){ Ok(p2) }
    else { bail!("Snapshot not found: {}.", idx); }
}

fn cmd_mount(ctx:&mut Ctx, s:Option<usize>, target:&Path)->Result<()>{
    require_root("mount")?;
    fs::create_dir_all(target)?;
    let snaps = ctx.list_snapshots()?;
    if snaps.is_empty(){ bail!("No snapshots found."); }

    let upto = if let Some(n)=s {
        let max = snaps.len();
        if n==0 || n>max { bail!("Snapshot -s {} is invalid (1..={}).", n, max); }
        n
    } else { snaps.len() };

    if upto == 1 {
        let img = find_snapshot_file(ctx, 1)?;
        mount_image_ro(ctx, &img, &abspath(target))?;
        println!("Mounted to {}.", abspath(target).display());
        return Ok(());
    }

    // MULTI-LAYER
    let mut lowers: Vec<PathBuf> = vec![];
    for i in 1..=upto {
        let img = find_snapshot_file(ctx, i)?;
        let mnt = ctx.mounts_dir.join(format!("snap_{:04}", i));
        fs::create_dir_all(&mnt)?;
        mount_image_ro(ctx, &img, &mnt)?;
        lowers.push(abspath(&mnt));
    }

    let upper = abspath(&ctx.temp_path("overlay.upper"));
    let work  = abspath(&ctx.temp_path("overlay.work"));
    fs::create_dir_all(&upper)?;
    fs::create_dir_all(&work)?;

    let loweropt = lowers.iter().rev().map(|p| p.display().to_string()).join(":"); // neuester zuerst
    mount_overlay(&loweropt, &upper, &work, &abspath(target))?;

    // Whiteouts/Unlinks anhand der Manifeste bis 'upto'
    let deletes = create_whiteouts_unlink_list(ctx, upto)?;
    if !deletes.is_empty() {
        apply_whiteouts_via_unlink(&abspath(target), &deletes)?;
    }

    println!("Mounted to {} up to snapshot {:04}.", target.display(), upto);
    println!("Unmount with: umount {} ; und die snap-Mounts unter {}", target.display(), ctx.mounts_dir.display());
    Ok(())
}

/* ---------- Delete / New ---------- */

fn cmd_delete(ctx:&mut Ctx, s:usize)->Result<()>{
    let path_plain = ctx.snapshot_path(s, false);
    let path_luks  = ctx.snapshot_path(s, true);
    if !path_plain.exists() && !path_luks.exists() { bail!("Snapshot {} does not exist.", s); }
    if path_plain.exists(){ fs::remove_file(&path_plain)?; }
    if path_luks.exists(){ fs::remove_file(&path_luks)?; }

    // Alle nachfolgenden Snapshots umnummerieren
    let snaps = ctx.list_snapshots()?;
    for p in snaps {
        let n = parse_snap_index(&p)?;
        if n > s {
            let is_luks = p.extension().and_then(|e| e.to_str()).unwrap_or("") == "luks";
            let newp = ctx.snapshot_path(n-1, is_luks);
            fs::rename(&p, &newp)?;
        }
    }

    // Meta-Container anpassen: manifest_s löschen, >s dekrementieren
    let staging = ctx.temp_path("meta.staging");
    extract_all_meta_to(ctx, &staging)?;
    let to_del = staging.join(Ctx::manifest_name(s));
    let _ = fs::remove_file(&to_del);
    // renumber
    let mut k = s + 1;
    loop {
        let from = staging.join(Ctx::manifest_name(k));
        if !from.exists() { break; }
        let to = staging.join(Ctx::manifest_name(k - 1));
        if to.exists() { let _ = fs::remove_file(&to); }
        fs::rename(&from, &to)?;
        k += 1;
    }
    rebuild_meta_from_staging(ctx, &staging)?;
    let _ = fs::remove_dir_all(&staging);

    println!("Deleted snapshot {}, decrementing children.", s);
    Ok(())
}

fn cmd_new(ctx:&mut Ctx)->Result<()>{
    for s in ctx.list_snapshots()? { fs::remove_file(s)?; }
    // Meta-Container & Klartextreste löschen
    let _ = fs::remove_file(ctx.meta_plain_path());
    let _ = fs::remove_file(ctx.meta_luks_path());
    cleanup_plain_meta_files(ctx);

    println!("State cleared. Creating new initial snapshot.");
    cmd_backup(ctx)
}

/* ---------- Umount Command ---------- */

fn cmd_umount(ctx:&mut Ctx, target: Option<&Path>) -> Result<()> {
    require_root("umount")?;

    let mounts_before = read_proc_mounts()?;
    let mut todo: Vec<PathBuf> = Vec::new();
    let mut mappers_in_use: HashSet<String> = HashSet::new();
    let mut loops_in_use: HashSet<String> = HashSet::new();

    if let Some(t) = target {
        if is_target_mounted(t) {
            todo.push(abspath(t));
        }
        if let Some(m) = mounts_before.iter().find(|m| abspath(&m.tgt) == abspath(t)) {
            if m.src.starts_with("/dev/mapper/squashr_") {
                mappers_in_use.insert(Path::new(&m.src).file_name().unwrap_or_default().to_string_lossy().to_string());
            } else if m.src.starts_with("/dev/loop") {
                loops_in_use.insert(m.src.clone());
            }
        }
    } else {
        // 1) Alle Mounts unter mounts_dir
        for m in &mounts_before {
            if m.tgt.starts_with(&ctx.mounts_dir) {
                todo.push(m.tgt.clone());
            }
        }
        // 2) Overlay-Ziele mit upperdir in work_dir
        for m in &mounts_before {
            if m.fstype == "overlay" && m.opts.contains("upperdir=") {
                if let Some(start) = m.opts.find("upperdir=") {
                    let rest = &m.opts[start + "upperdir=".len()..];
                    let upper = rest.split(',').next().unwrap_or("");
                    if upper.starts_with(ctx.work_dir.to_string_lossy().as_ref()) {
                        todo.push(m.tgt.clone());
                    }
                }
            }
        }
        // 3) Mapper-SquashFS
        for m in &mounts_before {
            if m.fstype == "squashfs" && m.src.starts_with("/dev/mapper/squashr_") {
                todo.push(m.tgt.clone());
                let mapper = Path::new(&m.src).file_name().unwrap_or_default().to_string_lossy().to_string();
                mappers_in_use.insert(mapper);
            }
        }
        // 4) Loop-SquashFS aus state_dir
        for m in &mounts_before {
            if m.fstype == "squashfs" && m.src.starts_with("/dev/loop") {
                if let Some(back) = loop_backing_file(&m.src) {
                    if back.starts_with(&ctx.state_dir) {
                        todo.push(m.tgt.clone());
                        loops_in_use.insert(m.src.clone());
                    }
                }
            }
        }
        // 5) FUSE mounts auf state_dir-Quellen oder Mapper
        for m in &mounts_before {
            if m.fstype.starts_with("fuse") {
                let src_path = PathBuf::from(&m.src);
                if src_path.starts_with(&ctx.state_dir) && src_path.extension().and_then(|e| e.to_str()) == Some("squashfs") {
                    todo.push(m.tgt.clone());
                }
                if m.src.starts_with("/dev/mapper/squashr_") {
                    todo.push(m.tgt.clone());
                    let mapper = Path::new(&m.src).file_name().unwrap_or_default().to_string_lossy().to_string();
                    mappers_in_use.insert(mapper);
                }
            }
        }
    }

    // Nur aktuell gemountete Ziele behalten
    let mounted_now: HashSet<PathBuf> = read_proc_mounts()?
        .into_iter()
        .map(|m| abspath(&m.tgt))
        .collect();

    todo = todo.into_iter()
        .map(|p| abspath(&p))
        .filter(|p| mounted_now.contains(p))
        .collect();

    let mut did_something = !todo.is_empty();
    let todo = sort_paths_deep_first(todo);

    // Aushängen
    let mut errors = Vec::new();
    for mpt in &todo {
        match umount(mpt) {
            Ok(_) => vlog!(ctx, "[umount] {}", mpt.display()),
            Err(e) => {
                eprintln!("[warn] umount {}: {}", mpt.display(), e);
                errors.push((mpt.clone(), e.to_string()));
            }
        }
    }

    // Nach dem Aushängen erneut Mounts einlesen
    let mounts_after = read_proc_mounts().unwrap_or_default();

    // LUKS-Mapper schließen (nur, wenn nicht mehr gemountet)
    for mapper in mappers_in_use {
        let devpath = format!("/dev/mapper/{mapper}");
        let still_mounted = mounts_after.iter().any(|m| m.src == devpath);
        if !still_mounted {
            let _ = Command::new("cryptsetup").arg("close").arg(&mapper).status();
            vlog!(ctx, "[cryptsetup] close {}", mapper);
            did_something = true;
        } else {
            eprintln!("[warn] Device {mapper} is still in use.");
            errors.push((PathBuf::from(devpath), "still in use".into()));
        }
    }

    // Loop-Devices lösen
    for loopdev in loops_in_use {
        let still_mounted = mounts_after.iter().any(|m| m.src == loopdev);
        if !still_mounted {
            if Path::new(&loopdev).exists() {
                let _ = Command::new("losetup").arg("-d").arg(&loopdev).status();
                vlog!(ctx, "[losetup] detach {}", loopdev);
                did_something = true;
            }
        } else {
            eprintln!("[warn] Loop device {} still in use.", loopdev);
            errors.push((PathBuf::from(loopdev), "still in use".into()));
        }
    }

    if !did_something && target.is_none() {
        println!("No SquashR mounts found.");
    }

    if errors.is_empty() {
        println!("All requested mounts unmounted and SquashR devices closed.");
        Ok(())
    } else {
        bail!(
            "Some mounts/devices could not be released: {:?}",
            errors.iter().map(|(p,_)| p.display().to_string()).collect::<Vec<_>>()
        )
    }
}

/* ---------- Minimize ---------- */

fn cmd_minimize(ctx:&mut Ctx, n_opt:Option<usize>)->Result<()>{
    let target = n_opt.unwrap_or(ctx.min_keep);
    if target < ctx.min_keep {
        bail!("n ({}) < SQUASHR_N_SNAPSHOTS_MIN ({}) not allowed.", target, ctx.min_keep);
    }
    loop {
        let snaps = ctx.list_snapshots()?;
        if snaps.len() <= target { break; }
        merge_first_two(ctx)?;
    }
    println!("Minimized. New snapshot count: {}", ctx.list_snapshots()?.len());
    Ok(())
}

/* ---------- Merge ---------- */

fn merge_first_two(ctx:&mut Ctx)->Result<()>{
    require_root("merge (mounts / overlay)")?;
    let snaps = ctx.list_snapshots()?;
    if snaps.len() < 2 { return Ok(()); }
    let s1 = &snaps[0];
    let s2 = &snaps[1];
    let idx1 = parse_snap_index(s1)?;
    let idx2 = parse_snap_index(s2)?;
    if idx2 != idx1+1 { bail!("Unexpected indices: {:04} + {:04}", idx1, idx2); }

    let m1 = ctx.mounts_dir.join(format!("merge_{:04}", idx1));
    let m2 = ctx.mounts_dir.join(format!("merge_{:04}", idx2));
    fs::create_dir_all(&m1)?;
    fs::create_dir_all(&m2)?;
    mount_image_ro(ctx, s1, &m1)?;
    mount_image_ro(ctx, s2, &m2)?;

    let upper = ctx.temp_path("merge.upper");
    let work  = ctx.temp_path("merge.work");
    let view  = ctx.temp_path("merge.view");
    fs::create_dir_all(&upper)?;
    fs::create_dir_all(&work)?;
    fs::create_dir_all(&view)?;
    let loweropt = format!("{}:{}", abspath(&m1).display(), abspath(&m2).display()); // s2 über s1
    mount_overlay(&loweropt, &upper, &work, &view)?;

    // Unlinks gemäß manifest_2 (Zielzustand) gegenüber manifest_1
    let present = load_manifest(ctx, idx2).unwrap_or_default();
    let past = load_manifest(ctx, idx1).unwrap_or_default();
    let deletes: Vec<String> = past.difference(&present).cloned().collect();
    if !deletes.is_empty() {
        apply_whiteouts_via_unlink(&abspath(&view), &deletes)?;
    }

    // neues SquashFS aus dem View
    let tmp_plain = ctx.temp_path("merge.plain.sqsh");
    let mut cmd = Command::new("mksquashfs");
    cmd.arg(&view).arg(&tmp_plain).arg("-no-progress").arg("-no-recovery");
    if ctx.comp_enable {
        cmd.arg("-comp").arg(&ctx.comp_algo);
        if let Some(extra)=ctx.comp_args.as_ref(){ for tok in shell_split(extra){ cmd.arg(tok);} }
    }
    run(&mut cmd, "mksquashfs (merge)")?;

    let _ = umount(&view);
    let _ = umount(&m2);
    let _ = umount(&m1);

    let is_luks = s1.extension().and_then(|e| e.to_str()).unwrap_or("") == "luks";
    let out_path = ctx.snapshot_path(idx1, is_luks);
    if s1.exists(){ fs::remove_file(s1)?; }
    if is_luks {
        encrypt_into_luks(ctx, &tmp_plain, &out_path)?;
        fs::remove_file(&tmp_plain).ok();
    } else {
        fs::rename(&tmp_plain, &out_path)?;
    }
    if s2.exists(){ fs::remove_file(s2)?; }

    // Indizes > idx2 runterzählen (Dateien)
    let rest = ctx.list_snapshots()?;
    for p in rest {
        let n = parse_snap_index(&p)?;
        if n > idx2 {
            let is_luks = p.extension().and_then(|e| e.to_str()).unwrap_or("") == "luks";
            let newp = ctx.snapshot_path(n-1, is_luks);
            fs::rename(&p, &newp)?;
        }
    }

    // Meta-Container anpassen: manifest_1 := manifest_2; danach alle >2 dekrementieren
    let staging = ctx.temp_path("meta.staging");
    extract_all_meta_to(ctx, &staging)?;
    // manifest_2 -> manifest_1 (overwrite)
    let m1p = staging.join(Ctx::manifest_name(1));
    let m2p = staging.join(Ctx::manifest_name(2));
    if m1p.exists(){ let _ = fs::remove_file(&m1p); }
    if m2p.exists(){ fs::rename(&m2p, &m1p).ok(); }
    // ab 3 dekrementieren
    let mut k = 3usize;
    loop {
        let from = staging.join(Ctx::manifest_name(k));
        if !from.exists() { break; }
        let to = staging.join(Ctx::manifest_name(k-1));
        if to.exists() { let _ = fs::remove_file(&to); }
        fs::rename(&from, &to)?;
        k += 1;
    }
    rebuild_meta_from_staging(ctx, &staging)?;
    let _ = fs::remove_dir_all(&staging);

    println!("Merged snapshots {:04} + {:04} → {:04}.", idx1, idx2, idx1);
    Ok(())
}