/* 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 rusqlite::{params, Connection};
use serde::Deserialize;
use std::collections::{BTreeSet, HashMap, HashSet};
use std::env;
use std::fs;
use std::io::Write;
use std::os::unix::fs::MetadataExt;
use std::path::{Path, PathBuf};
use std::process::{Command, Stdio};
use walkdir::WalkDir;
use std::io::ErrorKind;

#[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>,

    #[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 },
    Umount { target: PathBuf },
    Delete { #[arg(short = 's')] s: usize },
}

#[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>,
}

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()),
        }
    }
}

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));
        }
    }
    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); }
    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); }
    Ok(cfg)
}

fn default_config_paths() -> Vec<PathBuf> {
    let mut v = Vec::new();
    if let Ok(xdg) = env::var("XDG_CONFIG_HOME") {
        v.push(PathBuf::from(xdg).join("squashr/squashr.conf"));
    }
    if let Ok(home) = env::var("HOME") {
        v.push(PathBuf::from(home).join(".config/squashr/squashr.conf"));
    }
    v.push(PathBuf::from("/etc/squashr.conf"));
    v
}

#[derive(Clone)]
struct Ctx {
    state_dir: PathBuf,
    mounts_dir: PathBuf,
    work_dir: PathBuf,
    index_db: PathBuf,
    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>,
}

impl Ctx {
    fn new(cfg: Config) -> 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 index_db = state_dir.join("index.sqlite");
        let max_raw = cfg.SQUASHR_N_SNAPSHOTS_MAX.unwrap_or(0);
        let max_keep = if max_raw == 0 { None } else { Some(max_raw) };
        Ok(Self {
            state_dir,
            mounts_dir,
            work_dir,
            index_db,
            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,
        })
    }

    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)
            })
            .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 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_path = match &cli.config {
        Some(p) => Some(p.clone()),
        None => default_config_paths().into_iter().find(|p| p.exists()),
    };
    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)?;

    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::Umount { target } => cmd_umount(&mut ctx, &target),
        Cmd::Delete { s } => cmd_delete(&mut ctx, s),
    }
}

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_stem().and_then(|s| s.to_str()).ok_or_else(||anyhow!("Invalid filename: {}", p.display()))?;
    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_interactive(cmd:&mut Command, desc:&str)->Result<()>{
    cmd.stdin(Stdio::inherit()).stdout(Stdio::inherit()).stderr(Stdio::inherit());
    run(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 is_excluded(ctx:&Ctx, p:&Path) -> bool {
    let Ok(cp) = fs::canonicalize(p) else { return false; };
    for ex in &ctx.exclude {
        if let Ok(cex) = fs::canonicalize(ex) {
            if cp.starts_with(&cex) { return true; }
        }
    }
    false
}

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 db_open_init(ctx:&Ctx) -> Result<Connection> {
    let must_init = !ctx.index_db.exists();
    let conn = Connection::open(&ctx.index_db)
        .with_context(|| format!("Opening index.sqlite: {}", ctx.index_db.display()))?;
    conn.pragma_update(None, "journal_mode", "WAL")?;
    conn.pragma_update(None, "synchronous", "NORMAL")?;
    conn.execute_batch("PRAGMA foreign_keys=ON;")?;

    if must_init {
        conn.execute_batch(r#"
        CREATE TABLE IF NOT EXISTS snapshots(
            id INTEGER PRIMARY KEY,
            created_at TEXT NOT NULL
        );
        CREATE TABLE IF NOT EXISTS roots(
            id INTEGER PRIMARY KEY,
            top_name TEXT UNIQUE NOT NULL,
            abs_path TEXT NOT NULL
        );
        CREATE TABLE IF NOT EXISTS files(
            id INTEGER PRIMARY KEY,
            root_id INTEGER NOT NULL,
            rel_path TEXT NOT NULL,
            kind TEXT NOT NULL,
            UNIQUE(root_id, rel_path),
            FOREIGN KEY(root_id) REFERENCES roots(id) ON DELETE CASCADE
        );
        CREATE TABLE IF NOT EXISTS events(
            snapshot_id INTEGER NOT NULL,
            file_id INTEGER NOT NULL,
            change CHAR NOT NULL CHECK(change IN ('c','m','d')),
            size INTEGER,
            mtime INTEGER,
            checksum TEXT,
            PRIMARY KEY(snapshot_id, file_id),
            FOREIGN KEY(snapshot_id) REFERENCES snapshots(id) ON DELETE CASCADE,
            FOREIGN KEY(file_id) REFERENCES files(id) ON DELETE CASCADE
        );
        "#)?;
    }
    Ok(conn)
}

fn ensure_root(conn:&Connection, include_abs:&Path) -> Result<(i64,String,PathBuf)> {
    let top = abs_key(include_abs)?;
    conn.execute("INSERT OR IGNORE INTO roots(top_name,abs_path) VALUES(?,?)",
        params![&top, include_abs.to_string_lossy()])?;
    let id = conn.query_row("SELECT id FROM roots WHERE top_name=?", params![&top], |r| r.get(0))?;
    Ok((id, top, include_abs.to_path_buf()))
}

fn ensure_file_row(conn:&Connection, root_id:i64, rel:&str, kind:char) -> Result<i64> {
    conn.execute("INSERT OR IGNORE INTO files(root_id,rel_path,kind) VALUES(?,?,?)",
        params![root_id, rel, kind.to_string()])?;
    Ok(conn.query_row("SELECT id FROM files WHERE root_id=? AND rel_path=?",
        params![root_id, rel], |r| r.get(0))?)
}

fn prev_last_events(conn:&Connection) -> Result<HashMap<(String,String),(String,i64,i64)>> {
    let mut map = HashMap::new();
    let sql = r#"
    SELECT r.top_name, f.rel_path, e.change, e.size, e.mtime
    FROM files f
    JOIN roots r ON r.id=f.root_id
    JOIN events e ON e.file_id=f.id
    WHERE e.snapshot_id = (SELECT MAX(e2.snapshot_id) FROM events e2 WHERE e2.file_id=f.id)
    "#;
    let mut stmt = conn.prepare(sql)?;
    let rows = stmt.query_map([], |row| {
        Ok((
            row.get::<_,String>(0)?,
            row.get::<_,String>(1)?,
            row.get::<_,String>(2)?,
            row.get::<_,i64>(3)?,
            row.get::<_,i64>(4)?,
        ))
    })?;
    for r in rows {
        let (top, rel, ch, sz, mt) = r?;
        map.insert((top, rel), (ch, sz, mt));
    }
    Ok(map)
}

fn deletions_up_to(conn:&Connection, upto:i64) -> Result<Vec<(String,String)>> {
    let mut out = vec![];
    let sql = r#"
    SELECT r.top_name, f.rel_path
    FROM files f
    JOIN roots r ON r.id=f.root_id
    JOIN events e ON e.file_id=f.id
    WHERE e.snapshot_id = (
        SELECT MAX(e2.snapshot_id) FROM events e2 WHERE e2.file_id=f.id AND e2.snapshot_id <= ?
    )
    AND e.change='d'
    "#;
    let mut stmt = conn.prepare(sql)?;
    let rows = stmt.query_map(params![upto], |row| Ok((row.get::<_,String>(0)?, row.get::<_,String>(1)?)))?;
    for r in rows { out.push(r?); }
    Ok(out)
}

#[derive(Debug, Clone)]
struct FsMeta { size:u64, mtime:i64 }

fn scan_current(ctx:&Ctx, conn:&Connection) -> Result<(HashMap<(String,String),FsMeta>, HashMap<String,(i64,PathBuf)>)> {
    let mut now_map = HashMap::new();
    let mut roots = HashMap::new();
    for inc in &ctx.include {
        let inc_abs = fs::canonicalize(inc)?;
        let (root_id, top_name, abs_root) = ensure_root(conn, &inc_abs)?;
        roots.insert(top_name.clone(), (root_id, abs_root.clone()));
        for e in WalkDir::new(&abs_root).follow_links(false).into_iter().filter_map(|e| e.ok()) {
            let p = e.path();
            if is_excluded(ctx, p) { continue; }
            let md = fs::symlink_metadata(p)?;
            if md.is_dir() { continue; }
            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();
            now_map.insert((top_name.clone(), rel), FsMeta{ size: md.len(), mtime: md.mtime() });
        }
    }
    Ok((now_map, roots))
}

fn build_squash_image_pf(
    ctx: &Ctx,
    out: &Path,
    changed: &[(String, String)],
    roots: &HashMap<String, (i64, PathBuf)>,
) -> Result<()> {
    use std::collections::BTreeSet;

    let mut dirset: BTreeSet<String> = BTreeSet::new();
    for (top_ns, rel) in changed {
        let img_path = if rel.is_empty() {
            top_ns.clone()
        } else {
            format!("{}/{}", top_ns, rel)
        };
        let mut cur = Path::new(&img_path);
        while let Some(p) = cur.parent() {
            let s = p.to_string_lossy();
            if !s.is_empty() {
                dirset.insert(s.to_string());
            }
            if p.as_os_str().is_empty() { break; }
            cur = p;
        }
    }

    let pf = ctx.temp_path("filelist.pf");
    {
        let mut f = fs::File::create(&pf)?;
        writeln!(f, "/ d 0755 0 0")?;

        let mut dirs: Vec<String> = dirset.into_iter().collect();
        dirs.sort_by_key(|d| Path::new(d).components().count());
        for d in &dirs {
            writeln!(f, "{} d 0755 0 0", d)?;
        }
    }

    {
        let mut f = fs::OpenOptions::new().append(true).open(&pf)?;
        for (top_ns, rel) in changed {
            let (_id, abs_root) = roots.get(top_ns)
                .ok_or_else(|| anyhow!("unknown root {}", top_ns))?;
            let src = if rel.is_empty() { abs_root.clone() } else { abs_root.join(rel) };
            let md  = fs::symlink_metadata(&src)?;

            let img_path = if rel.is_empty() { top_ns.clone() } else { format!("{}/{}", top_ns, rel) };

            if md.file_type().is_symlink() {
                // Symlink: Ziel lesen und als 's' schreiben
                let target = fs::read_link(&src)?.to_string_lossy().to_string();
                writeln!(f, "{} s 0777 0 0 {}", img_path, escape_pf(&target))?;
            } else if md.is_file() {
                writeln!(f, "{} l {}", img_path, escape_pf(&src.to_string_lossy()))?;
            }
        }
    }

    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(out)
       .arg("-no-progress")
       .arg("-no-recovery")
       .arg("-always-use-fragments")
       .arg("-pf").arg(&pf);

    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); }
        }
    } else {
        cmd.arg("-noI").arg("-noD").arg("-noF");
    }

    run(&mut cmd, "mksquashfs (-pf)")?;
    Ok(())
}

fn escape_pf<S: AsRef<str>>(s: S) -> String {
    let s = s.as_ref();
    if s.chars().any(|c| c.is_whitespace() || c == '"') {
        let escaped = s.replace('\\', "\\\\").replace('"', "\\\"");
        format!("\"{}\"", escaped)
    } else {
        s.to_string()
    }
}

fn encrypt_into_luks(ctx:&Ctx, plain:&Path, out_luks:&Path)->Result<()>{
    require_root("Creatintg 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)?;
    }
    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);
    run_interactive(&mut c, "cryptsetup luksFormat")?;

    let mapper = format!("squashr_{}", parse_snap_index(out_luks).unwrap_or(0));
    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);
    run_interactive(&mut o, "cryptsetup open")?;

    let dev = format!("/dev/mapper/{}", mapper);
    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")?;

    let mut close = Command::new("cryptsetup");
    close.arg("close").arg(&mapper);
    run(&mut close, "cryptsetup close")?;

    Ok(())
}

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

    let mut conn = db_open_init(ctx)?;
    let tx = conn.transaction()?;
    let last_id: i64 = tx.query_row("SELECT IFNULL(MAX(id),0) FROM snapshots", [], |r| r.get(0))?;
    let snap_id = last_id + 1;
    tx.execute("INSERT INTO snapshots(id,created_at) VALUES(?,datetime('now'))", params![snap_id])?;

    let (now_map, roots) = scan_current(ctx, &tx)?;
    let prev_map = prev_last_events(&tx)?;

    let mut changed: Vec<(String,String)> = vec![];
    for ((top, rel), meta) in &now_map {
        match prev_map.get(&(top.clone(), rel.clone())) {
            None => changed.push((top.clone(), rel.clone())),
            Some((ch, psz, pmt)) => {
                if ch == "d" || *psz as u64 != meta.size || *pmt as i64 != meta.mtime {
                    changed.push((top.clone(), rel.clone()));
                }
            }
        }
    }

    let prev_present: HashSet<(String,String)> = prev_map.iter()
        .filter(|(_k,(ch,_,_))| ch != "d")
        .map(|(k,_v)| k.clone()).collect();
    let now_keys: HashSet<(String,String)> = now_map.keys().cloned().collect();
    let deleted: Vec<(String,String)> = prev_present.difference(&now_keys).cloned().collect();

    // SquashFS deterministisch via -pf erzeugen
    let idx = snap_id as usize;
    let plain_img = ctx.temp_path("snapshot.plain.squashfs");

    if changed.is_empty() {
        // Leeres Delta → minimales Image
        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 {
        build_squash_image_pf(ctx, &plain_img, &changed, &roots)?;
    }

    let final_path = if ctx.luks_enable {
        let out = ctx.snapshot_path(idx, true);
        encrypt_into_luks(ctx, &plain_img, &out)?;
        fs::remove_file(&plain_img).ok();
        out
    } else {
        let out = ctx.snapshot_path(idx, false);
        fs::rename(&plain_img, &out)?;
        out
    };

    for (top, rel) in &changed {
        let (root_id, abs_root) = roots.get(top).unwrap();
        let real = if rel.is_empty(){ abs_root.clone() } else { abs_root.join(rel) };
        let md = fs::symlink_metadata(&real)?;
        let kind = if md.file_type().is_symlink() { 'l' } else { 'f' };
        let fid = ensure_file_row(&tx, *root_id, rel, kind)?;
        let ev = match prev_map.get(&(top.clone(), rel.clone())) {
            None => "c",
            Some((ch,_,_)) if ch == "d" => "c",
            _ =>"m" 
        };
        tx.execute("INSERT OR REPLACE INTO events(snapshot_id,file_id,change,size,mtime,checksum) VALUES(?,?,?,?,?,NULL)",
            params![snap_id, fid, ev, md.len() as i64, md.mtime()])?;
    }
    for (top, rel) in &deleted {
        let (root_id, _abs) = roots.get(top).unwrap();
        let fid = ensure_file_row(&tx, *root_id, rel, 'f')?;
        tx.execute("INSERT OR REPLACE INTO events(snapshot_id,file_id,change,size,mtime,checksum) VALUES(?,?,?,?,?,NULL)",
            params![snap_id, fid, "d", 0i64, 0i64])?;
    }

    tx.commit()?;
    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(())
}

fn present_state_up_to(conn:&Connection, upto:i64) -> Result<Vec<(String,String,i64,i64,String)>> {
    let present_sql = r#"
      SELECT r.top_name, f.rel_path, e.size, e.mtime, f.kind
      FROM files f
      JOIN roots r ON r.id=f.root_id
      JOIN events e ON e.file_id=f.id
      WHERE e.snapshot_id = (
        SELECT MAX(e2.snapshot_id) FROM events e2 WHERE e2.file_id=f.id AND e2.snapshot_id <= ?
      ) AND e.change!='d'
    "#;
    let mut stmt = conn.prepare(present_sql)?;
    let rows = stmt.query_map(params![upto], |r| Ok((r.get(0)?, r.get(1)?, r.get(2)?, r.get(3)?, r.get(4)?)))?;
    let mut v = vec![];
    for r in rows { v.push(r?); }
    Ok(v)
}

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)?;

    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)?; }
    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)?;
        }
    }

    let mut conn = db_open_init(ctx)?;
    let tx = conn.transaction()?;

    let present = present_state_up_to(&tx, 2)?;
    tx.execute("DELETE FROM events WHERE snapshot_id IN (1,2)", [])?;
    tx.execute("DELETE FROM snapshots WHERE id IN (1,2)", [])?;
    tx.execute("INSERT INTO snapshots(id,created_at) VALUES(1,datetime('now'))", [])?;
    for (top, rel, sz, mt, kind) in present {
        let root_id: i64 = tx.query_row("SELECT id FROM roots WHERE top_name=?", params![top], |r| r.get(0))?;
        let fid = ensure_file_row(&tx, root_id, &rel, kind.chars().next().unwrap_or('f'))?;
        tx.execute("INSERT OR REPLACE INTO events(snapshot_id,file_id,change,size,mtime,checksum) VALUES(?,?,?,?,?,NULL)",
            params![1i64, fid, "c", sz, mt])?;
    }
    tx.execute("UPDATE events SET snapshot_id = snapshot_id - 1 WHERE snapshot_id > 2", [])?;
    tx.execute("UPDATE snapshots SET id = id - 1 WHERE id > 2", [])?;
    tx.commit()?;

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

fn create_whiteouts(upper:&Path, deletes:&[(String,String)]) -> Result<()> {
    for (top_ns, rel) in deletes {
        let p = Path::new(rel);
        let parent = upper.join(top_ns).join(p.parent().unwrap_or(Path::new("")));
        fs::create_dir_all(&parent)?;
        let base = p.file_name().ok_or_else(|| anyhow!("Empty filename: {}", rel))?
            .to_string_lossy().to_string();
        let wh = parent.join(format!(".wh.{}", base));
        if wh.exists() { continue; }
        let mut cmd = Command::new("mknod");
        cmd.arg(&wh).arg("c").arg("0").arg("0");
        run(&mut cmd, "mknod whiteout")?;
    }
    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") {
        let mapper = format!(
            "squashr_mount_{}",
            img.file_stem().and_then(|s| s.to_str()).unwrap_or("img")
        );
        let dev = format!("/dev/mapper/{}", mapper);

        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);
        run_interactive(&mut o, "cryptsetup open (mount)")?;

        let mut cmd = Command::new("mount");
        cmd.arg("-t").arg("squashfs").arg("-o").arg("ro").arg(&dev).arg(&mnt_abs);
        run(&mut cmd, "mount squashfs (luks)")?;
    } else {
        let mut cmd = Command::new("mount");
        cmd.arg("-t").arg("squashfs").arg("-o").arg("loop,ro").arg(img).arg(&mnt_abs);
        run(&mut cmd, "mount squashfs")?;
    }
    Ok(())
}

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(())
}

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

fn umount(path:&Path)->Result<()>{
    require_root("umount")?;
    let mut cmd = Command::new("umount");
    cmd.arg(path);
    run(&mut cmd, "umount")?;
    Ok(())
}

// --- NEU: robustes Umount, ignoriert "not mounted" (Exit-Code 32)
fn umount_ignore_not_mounted(path:&Path)->Result<()>{
    require_root("umount")?;
    let status = Command::new("umount")
        .arg(path)
        .status()
        .with_context(|| format!("umount {}", path.display()))?;
    if !status.success() {
        if let Some(32) = status.code() {
            // EX_NOTMNT – war kein Mountpoint; passt.
            return Ok(());
        }
        bail!("umount failed for {}", path.display());
    }
    Ok(())
}

fn crypt_close_ignore(name:&str){
    let _ = Command::new("cryptsetup").arg("close").arg(name).status();
}

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))?;

    // <<<<<< NEU: Whiteouts NACH dem Mount via unlink erzeugen
    let mut conn = db_open_init(ctx)?;
    let deletes = deletions_up_to(&conn, upto as i64)?;
    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(())
}

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

    // 1) Overlay-Ziel aushängen (falls gemountet)
    match umount_ignore_not_mounted(&abspath(target)) {
        Ok(_) => println!("Umounted {} (overlay/target, falls vorhanden).", abspath(target).display()),
        Err(e) => println!("Hinweis: {} (fahre fort)", e),
    }

    // 2) Alle per-snapshot Mounts unter mounts_dir aushängen
    let mut entries: Vec<_> = fs::read_dir(&ctx.mounts_dir)?
        .filter_map(|e| e.ok())
        .map(|e| e.path())
        .filter(|p| p.is_dir())
        .collect();
    // in umgekehrter Reihenfolge, damit höhere Indizes zuerst fallen
    entries.sort();
    entries.reverse();

    for mnt in &entries {
        let _ = umount_ignore_not_mounted(mnt);
    }

    // 3) LUKS-Mapper schließen, wenn vorhanden
    for mnt in &entries {
        if let Some(name) = mnt.file_name().and_then(|s| s.to_str()) {
            // Verzeichnisnamen sind "snap_0001" / "merge_0001"
            if let Some(idx_str) = name.split('_').nth(1) {
                // Versuche beide möglichen Mapper-Namen (je nach file_stem):
                // "squashr_mount_0001" und "squashr_mount_0001.squashfs"
                let mapper_a = format!("squashr_mount_{}", idx_str);
                let mapper_b = format!("squashr_mount_{}.squashfs", idx_str);
                crypt_close_ignore(&mapper_a);
                crypt_close_ignore(&mapper_b);
            }
        }
    }

    // 4) Leere Mount-Verzeichnisse wegräumen (optional & best effort)
    for mnt in entries {
        let _ = fs::remove_dir(mnt);
    }

    // 5) Verwaiste temporäre Upper/Work-Verzeichnisse aus der letzten Mount-Session aufräumen
    if let Ok(ws) = fs::read_dir(&ctx.work_dir) {
        for e in ws.filter_map(|e| e.ok()) {
            if let Some(n) = e.file_name().to_str() {
                if n.starts_with("overlay.upper_") || n.starts_with("overlay.work_") {
                    let _ = fs::remove_dir_all(e.path());
                }
            }
        }
    }
    println!("Umount abgeschlossen.");
    Ok(())
}

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)?; }

    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)?;
        }
    }

    // DB anpassen
    let mut conn = db_open_init(ctx)?;
    let tx = conn.transaction()?;
    tx.execute("DELETE FROM events WHERE snapshot_id=?", params![s as i64])?;
    tx.execute("DELETE FROM snapshots WHERE id=?", params![s as i64])?;
    tx.execute("UPDATE events SET snapshot_id = snapshot_id - 1 WHERE snapshot_id > ?", params![s as i64])?;
    tx.execute("UPDATE snapshots SET id = id - 1 WHERE id > ?", params![s as i64])?;
    tx.commit()?;
    println!("Deleted snapshot {}, decrementing children.", s);
    Ok(())
}

fn cmd_new(ctx:&mut Ctx)->Result<()>{
    for s in ctx.list_snapshots()? { fs::remove_file(s)?; }
    let mut conn = db_open_init(ctx)?;
    conn.execute("DELETE FROM events", [])?;
    conn.execute("DELETE FROM snapshots", [])?;
    println!("Database cleared. Creating new initial snapshot.");
    cmd_backup(ctx)
}

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!("Database minimized. New snapshot count: {}", ctx.list_snapshots()?.len());
    Ok(())
}