use std::fmt::Debug;
use std::io::SeekFrom;
use std::sync::atomic::{AtomicU64, Ordering};
use std::sync::Arc;
use std::time::{Duration, SystemTime, UNIX_EPOCH};

use bytes::{Buf, Bytes, BytesMut};
use dav_server::{
    davpath::DavPath,
    fs::{
        DavDirEntry, DavFile, DavFileSystem, DavMetaData, FsError, FsFuture, FsResult, FsStream,
        OpenOptions, ReadDirMeta,
    },
};
use futures_util::stream;
use tracing::{debug, error, warn};
use zeroize::Zeroizing;

use crate::carrier::CarrierFs;
use crate::crypto::{decrypt_chunk, encrypt_chunk, CHUNK_SIZE};
use crate::storage::{Database, NodeRecord};

/// Prüft, ob ein Dateiname zu den typischen Windows Explorer Metadaten-, Cache-
/// oder Thumbnail-Dateien gehört (z. B. Thumbs.db, desktop.ini), die standardmäßig
/// im Container blockiert und verborgen werden (Anti-Leak Shield).
pub fn is_leak_file(filename: &str) -> bool {
    let lower = filename.trim().to_ascii_lowercase();
    match lower.as_str() {
        "thumbs.db"
        | "ehthumbs.db"
        | "ehthumbs_vista.db"
        | "desktop.ini"
        | "folder.jpg"
        | "albumartsmall.jpg"
        | "autorun.inf"
        | ".ds_store" => true,
        _ => {
            if lower.starts_with("albumart") && (lower.ends_with(".jpg") || lower.ends_with(".ini"))
            {
                true
            } else {
                false
            }
        }
    }
}

// ---------------------------------------------------------------------------
// Metadaten
// ---------------------------------------------------------------------------

#[derive(Debug, Clone)]
pub struct SanctumMetaData {
    pub is_dir: bool,
    pub size: u64,
    pub modified_at: SystemTime,
    pub created_at: SystemTime,
}

impl DavMetaData for SanctumMetaData {
    fn len(&self) -> u64 {
        self.size
    }

    fn modified(&self) -> FsResult<SystemTime> {
        Ok(self.modified_at)
    }

    fn is_dir(&self) -> bool {
        self.is_dir
    }

    fn created(&self) -> FsResult<SystemTime> {
        Ok(self.created_at)
    }

    fn is_file(&self) -> bool {
        !self.is_dir
    }
}

// ---------------------------------------------------------------------------
// Verzeichniseintrag
// ---------------------------------------------------------------------------

#[derive(Debug, Clone)]
pub struct SanctumDirEntry {
    pub name: String,
    pub meta: SanctumMetaData,
}

impl DavDirEntry for SanctumDirEntry {
    fn name(&self) -> Vec<u8> {
        self.name.as_bytes().to_vec()
    }

    fn metadata(&self) -> FsFuture<'_, Box<dyn DavMetaData>> {
        let meta = self.meta.clone();
        Box::pin(async move { Ok(Box::new(meta) as Box<dyn DavMetaData>) })
    }
}

// ---------------------------------------------------------------------------
// Datei-Handle mit Streaming & Chunk-Pufferung
// ---------------------------------------------------------------------------

pub struct SanctumFile {
    node_id: i64,
    file_size: u64,
    cursor: u64,
    db: Database,
    dek: Arc<Zeroizing<[u8; 32]>>,
    meta: SanctumMetaData,
    // (chunk_index, decrypted_payload, is_dirty)
    cached_chunk: Option<(u32, Vec<u8>, bool)>,
    format_version: u32,
    last_activity: Arc<AtomicU64>,
}

impl Debug for SanctumFile {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("SanctumFile")
            .field("node_id", &self.node_id)
            .field("file_size", &self.file_size)
            .field("cursor", &self.cursor)
            .field("format_version", &self.format_version)
            .finish()
    }
}

impl SanctumFile {
    pub fn new(
        node: NodeRecord,
        db: Database,
        dek: Arc<Zeroizing<[u8; 32]>>,
        format_version: u32,
        last_activity: Arc<AtomicU64>,
    ) -> Self {
        let meta = SanctumMetaData {
            is_dir: node.is_dir,
            size: node.size,
            created_at: UNIX_EPOCH + Duration::from_secs(node.created_at),
            modified_at: UNIX_EPOCH + Duration::from_secs(node.modified_at),
        };

        Self {
            node_id: node.id,
            file_size: node.size,
            cursor: 0,
            db,
            dek,
            meta,
            cached_chunk: None,
            format_version,
            last_activity,
        }
    }

    fn touch(&self) {
        let now = SystemTime::now()
            .duration_since(UNIX_EPOCH)
            .map(|d| d.as_secs())
            .unwrap_or(0);
        self.last_activity.store(now, Ordering::Relaxed);
    }


    /// Schreibt den aktuell im RAM gehaltenen Chunk verschlüsselt in die SQLite-Datenbank zurück.
    fn flush_cached_chunk(&mut self) -> Result<(), FsError> {
        if let Some((idx, ref data, true)) = self.cached_chunk {
            let (ciphertext, nonce, tag) =
                encrypt_chunk(&self.dek, self.node_id, idx, data, self.format_version).map_err(|e| {
                    error!("Verschlüsselungsfehler beim Chunk-Flush: {e}");
                    FsError::GeneralFailure
                })?;

            self.db
                .write_chunk(self.node_id, idx, &nonce, &tag, &ciphertext)
                .map_err(|e| {
                    error!("DB-Fehler beim Schreiben des Chunks: {e}");
                    FsError::GeneralFailure
                })?;

            if let Some((_, _, ref mut dirty)) = self.cached_chunk {
                *dirty = false;
            }
        }
        Ok(())
    }

    /// Stellt sicher, dass der angeforderte Chunk im Cache geladen und entschlüsselt ist.
    fn ensure_chunk_loaded(&mut self, chunk_index: u32) -> Result<&mut Vec<u8>, FsError> {
        let is_current = match &self.cached_chunk {
            Some((idx, _, _)) => *idx == chunk_index,
            None => false,
        };

        if !is_current {
            self.flush_cached_chunk()?;

            let payload = match self.db.read_chunk(self.node_id, chunk_index).map_err(|e| {
                error!("Fehler beim Lesen des Chunks #{chunk_index}: {e}");
                FsError::GeneralFailure
            })? {
                Some(record) => decrypt_chunk(
                    &self.dek,
                    self.node_id,
                    chunk_index,
                    &record.ciphertext,
                    &record.nonce,
                    &record.tag,
                    self.format_version,
                )
                .map_err(|e| {
                    error!("AEAD-Entschlüsselungsfehler bei Chunk #{chunk_index}: {e}");
                    FsError::GeneralFailure
                })?,
                None => Vec::new(),
            };

            self.cached_chunk = Some((chunk_index, payload, false));
        }

        match &mut self.cached_chunk {
            Some((_, ref mut data, _)) => Ok(data),
            None => unreachable!(),
        }
    }
}

impl Drop for SanctumFile {
    fn drop(&mut self) {
        if let Err(e) = self.flush_cached_chunk() {
            warn!("Fehler beim automatischen Flush im SanctumFile::drop: {:?}", e);
        }
        let now = SystemTime::now()
            .duration_since(UNIX_EPOCH)
            .map(|d| d.as_secs())
            .unwrap_or(0);
        let _ = self.db.update_node_size_and_time(self.node_id, self.file_size, now);
    }
}

impl DavFile for SanctumFile {
    fn metadata(&mut self) -> FsFuture<'_, Box<dyn DavMetaData>> {
        self.meta.size = self.file_size;
        let meta = self.meta.clone();
        Box::pin(async move { Ok(Box::new(meta) as Box<dyn DavMetaData>) })
    }

    fn read_bytes(&mut self, mut count: usize) -> FsFuture<'_, Bytes> {
        self.touch();
        Box::pin(async move {
            if self.cursor >= self.file_size || count == 0 {
                return Ok(Bytes::new());
            }

            let remaining_file = (self.file_size - self.cursor) as usize;
            if count > remaining_file {
                count = remaining_file;
            }

            let mut result = BytesMut::with_capacity(count);

            while count > 0 && self.cursor < self.file_size {
                let chunk_idx = (self.cursor / CHUNK_SIZE as u64) as u32;
                let offset_in_chunk = (self.cursor % CHUNK_SIZE as u64) as usize;
                let bytes_in_chunk_left = CHUNK_SIZE - offset_in_chunk;

                let to_read = count
                    .min(bytes_in_chunk_left)
                    .min((self.file_size - self.cursor) as usize);

                let chunk_data = self.ensure_chunk_loaded(chunk_idx)?;
                if offset_in_chunk >= chunk_data.len() {
                    break;
                }

                let available = (chunk_data.len() - offset_in_chunk).min(to_read);
                result.extend_from_slice(&chunk_data[offset_in_chunk..offset_in_chunk + available]);

                self.cursor += available as u64;
                count -= available;

                if available < to_read {
                    break;
                }
            }

            Ok(result.freeze())
        })
    }

    fn write_bytes(&mut self, buf: Bytes) -> FsFuture<'_, ()> {
        self.touch();
        Box::pin(async move {
            let mut src = &buf[..];

            while !src.is_empty() {
                let chunk_idx = (self.cursor / CHUNK_SIZE as u64) as u32;
                let offset_in_chunk = (self.cursor % CHUNK_SIZE as u64) as usize;
                let space_in_chunk = CHUNK_SIZE - offset_in_chunk;
                let to_write = src.len().min(space_in_chunk);

                let chunk_data = self.ensure_chunk_loaded(chunk_idx)?;

                if chunk_data.len() < offset_in_chunk {
                    chunk_data.resize(offset_in_chunk, 0);
                }
                if chunk_data.len() < offset_in_chunk + to_write {
                    chunk_data.resize(offset_in_chunk + to_write, 0);
                }

                chunk_data[offset_in_chunk..offset_in_chunk + to_write]
                    .copy_from_slice(&src[..to_write]);

                if let Some((_, _, ref mut dirty)) = self.cached_chunk {
                    *dirty = true;
                }

                self.cursor += to_write as u64;
                if self.cursor > self.file_size {
                    self.file_size = self.cursor;
                }

                // Wenn der Chunk exakt 1 MB erreicht hat, sofort flushen, um RAM zu schonen
                if self.cached_chunk.as_ref().map(|(_, d, _)| d.len() >= CHUNK_SIZE).unwrap_or(false) {
                    self.flush_cached_chunk()?;
                }

                src = &src[to_write..];
            }

            Ok(())
        })
    }

    fn write_buf(&mut self, mut buf: Box<dyn Buf + Send>) -> FsFuture<'_, ()> {
        let bytes = buf.copy_to_bytes(buf.remaining());
        self.write_bytes(bytes)
    }

    fn seek(&mut self, pos: SeekFrom) -> FsFuture<'_, u64> {
        self.touch();
        Box::pin(async move {
            let new_cursor = match pos {
                SeekFrom::Start(offset) => offset as i64,
                SeekFrom::End(offset) => self.file_size as i64 + offset,
                SeekFrom::Current(offset) => self.cursor as i64 + offset,
            };

            if new_cursor < 0 {
                return Err(FsError::GeneralFailure);
            }

            self.cursor = new_cursor as u64;
            Ok(self.cursor)
        })
    }

    fn flush(&mut self) -> FsFuture<'_, ()> {
        self.touch();
        Box::pin(async move {
            self.flush_cached_chunk()?;
            let now = SystemTime::now()
                .duration_since(UNIX_EPOCH)
                .map(|d| d.as_secs())
                .unwrap_or(0);
            self.db
                .update_node_size_and_time(self.node_id, self.file_size, now)
                .map_err(|e| {
                    error!("Fehler beim Aktualisieren der Knotengröße: {e}");
                    FsError::GeneralFailure
                })?;
            self.meta.size = self.file_size;
            self.meta.modified_at = UNIX_EPOCH + Duration::from_secs(now);
            Ok(())
        })
    }
}

// ---------------------------------------------------------------------------
// DavFileSystem Implementierung
// ---------------------------------------------------------------------------

#[derive(Clone)]
pub struct SanctumFs {
    db: Database,
    dek: Arc<Zeroizing<[u8; 32]>>,
    #[allow(dead_code)]
    carrier_dek: Option<Arc<Zeroizing<[u8; 32]>>>,
    carrier_node_id: Option<i64>,
    carrier_fs: Option<CarrierFs>,
    format_version: u32,
    anti_leak: bool,
    vault_id: u32,
    last_activity: Arc<AtomicU64>,
}

impl SanctumFs {
    pub fn new(db: Database, dek: Zeroizing<[u8; 32]>, format_version: u32) -> Self {
        Self::with_vault(db, dek, format_version, true, 0)
    }

    pub fn with_options(
        db: Database,
        dek: Zeroizing<[u8; 32]>,
        format_version: u32,
        anti_leak: bool,
    ) -> Self {
        Self::with_vault(db, dek, format_version, anti_leak, 0)
    }

    pub fn with_vault(
        db: Database,
        dek: Zeroizing<[u8; 32]>,
        format_version: u32,
        anti_leak: bool,
        vault_id: u32,
    ) -> Self {
        Self::with_carrier(db, dek, None, None, format_version, anti_leak, vault_id)
    }

    pub fn with_carrier(
        db: Database,
        dek: Zeroizing<[u8; 32]>,
        carrier_dek: Option<Zeroizing<[u8; 32]>>,
        carrier_node_id: Option<i64>,
        format_version: u32,
        anti_leak: bool,
        vault_id: u32,
    ) -> Self {
        let now = SystemTime::now()
            .duration_since(UNIX_EPOCH)
            .map(|d| d.as_secs())
            .unwrap_or(0);
        let dek_arc = Arc::new(dek);
        let carrier_dek_arc = carrier_dek.map(Arc::new);

        let carrier_fs = if vault_id == 1 {
            if let (Some(ref c_dek), Some(c_nid)) = (&carrier_dek_arc, carrier_node_id) {
                match CarrierFs::load(
                    db.clone(),
                    c_nid,
                    c_dek.clone(),
                    dek_arc.clone(),
                    format_version,
                    anti_leak,
                ) {
                    Ok(cfs) => Some(cfs),
                    Err(e) => {
                        warn!("CarrierFs konnte nicht initialisiert werden: {e}");
                        None
                    }
                }
            } else {
                None
            }
        } else {
            None
        };

        Self {
            db,
            dek: dek_arc,
            carrier_dek: carrier_dek_arc,
            carrier_node_id,
            carrier_fs,
            format_version,
            anti_leak,
            vault_id,
            last_activity: Arc::new(AtomicU64::new(now)),
        }
    }

    pub fn vault_id(&self) -> u32 {
        self.vault_id
    }

    pub fn last_activity(&self) -> Arc<AtomicU64> {
        if let Some(ref cfs) = self.carrier_fs {
            cfs.last_activity()
        } else {
            self.last_activity.clone()
        }
    }

    pub fn is_anti_leak_enabled(&self) -> bool {
        self.anti_leak
    }

    pub fn touch(&self) {
        if let Some(ref cfs) = self.carrier_fs {
            cfs.touch();
        } else {
            let now = SystemTime::now()
                .duration_since(UNIX_EPOCH)
                .map(|d| d.as_secs())
                .unwrap_or(0);
            self.last_activity.store(now, Ordering::Relaxed);
        }
    }

    fn path_to_str(path: &DavPath) -> String {
        String::from_utf8_lossy(path.as_bytes()).to_string()
    }

    fn split_parent_and_name<'a>(&self, path: &'a str) -> (&'a str, &'a str) {
        let trimmed = path.trim_matches('/');
        match trimmed.rfind('/') {
            Some(pos) => (&trimmed[..pos], &trimmed[pos + 1..]),
            None => ("", trimmed),
        }
    }

    fn resolve_path(&self, path: &str) -> Result<Option<NodeRecord>, FsError> {
        self.db
            .resolve_path_in_vault(path, self.vault_id, &self.dek)
            .map_err(|_| FsError::GeneralFailure)
    }

    fn list_children(&self, parent_id: i64) -> Result<Vec<NodeRecord>, FsError> {
        self.db
            .list_children_in_vault(parent_id, self.vault_id, &self.dek)
            .map_err(|_| FsError::GeneralFailure)
    }

    fn create_node(&self, parent_id: i64, name: &str, is_dir: bool) -> Result<NodeRecord, FsError> {
        self.db
            .create_node_in_vault(self.vault_id, parent_id, name, is_dir, &self.dek)
            .map_err(|e| {
                error!("Fehler beim Erstellen des Knotens '{}': {e}", name);
                FsError::GeneralFailure
            })
    }

    fn rename_node(&self, id: i64, new_parent_id: i64, new_name: &str) -> Result<(), FsError> {
        self.db
            .rename_node_in_vault(id, new_parent_id, new_name, self.vault_id, &self.dek)
            .map_err(|_| FsError::GeneralFailure)
    }
}

impl DavFileSystem for SanctumFs {
    fn open<'a>(
        &'a self,
        path: &'a DavPath,
        options: OpenOptions,
    ) -> FsFuture<'a, Box<dyn DavFile>> {
        if let Some(ref cfs) = self.carrier_fs {
            return cfs.open(path, options);
        }

        Box::pin(async move {
            let path_str = Self::path_to_str(path);
            let (parent_path, file_name) = self.split_parent_and_name(&path_str);

            // Anti-Leak Shield: Blockiere Schreib- oder Neuerstellungsversuche für Explorer-Metadaten
            if self.anti_leak && is_leak_file(file_name) {
                if options.create
                    || options.create_new
                    || options.write
                    || options.append
                    || options.truncate
                {
                    debug!(
                        "Anti-Leak: Blockiere Erstellung/Schreibzugriff für '{}'",
                        file_name
                    );
                    return Err(FsError::Forbidden);
                }
            }

            self.touch();
            debug!("VFS open aufgerufen: path='{}', options={:?}", path_str, options);

            let existing_node = self.resolve_path(&path_str)?;

            let node = match existing_node {
                Some(n) => {
                    // Schutz der Trägerdatei im Decoy Vault: Keine Schreib- oder Truncate-Operationen erlaubt!
                    if self.carrier_node_id == Some(n.id) && (options.write || options.truncate || options.append) {
                        return Err(FsError::Forbidden);
                    }

                    if n.is_dir && (options.write || options.append) {
                        return Err(FsError::Forbidden);
                    }
                    if options.create_new {
                        return Err(FsError::Exists);
                    }

                    if options.truncate {
                        self.db
                            .truncate_chunks_after(n.id, 0)
                            .map_err(|_| FsError::GeneralFailure)?;
                        let now = SystemTime::now()
                            .duration_since(UNIX_EPOCH)
                            .map(|d| d.as_secs())
                            .unwrap_or(0);
                        self.db
                            .update_node_size_and_time(n.id, 0, now)
                            .map_err(|_| FsError::GeneralFailure)?;

                        NodeRecord {
                            size: 0,
                            modified_at: now,
                            ..n
                        }
                    } else {
                        n
                    }
                }
                None => {
                    if options.create || options.create_new {
                        let parent = self
                            .resolve_path(parent_path)?
                            .ok_or(FsError::NotFound)?;

                        if !parent.is_dir {
                            return Err(FsError::Forbidden);
                        }

                        self.create_node(parent.id, file_name, false)?
                    } else {
                        return Err(FsError::NotFound);
                    }
                }
            };

            let file = SanctumFile::new(
                node,
                self.db.clone(),
                self.dek.clone(),
                self.format_version,
                self.last_activity.clone(),
            );
            Ok(Box::new(file) as Box<dyn DavFile>)
        })
    }

    fn read_dir<'a>(
        &'a self,
        path: &'a DavPath,
        meta: ReadDirMeta,
    ) -> FsFuture<'a, FsStream<Box<dyn DavDirEntry>>> {
        if let Some(ref cfs) = self.carrier_fs {
            return cfs.read_dir(path, meta);
        }

        Box::pin(async move {
            self.touch();
            let path_str = Self::path_to_str(path);
            let node = self
                .resolve_path(&path_str)?
                .ok_or(FsError::NotFound)?;

            if !node.is_dir {
                return Err(FsError::Forbidden);
            }

            let children = self.list_children(node.id)?;

            let entries: Vec<Result<Box<dyn DavDirEntry>, FsError>> = children
                .into_iter()
                .filter(|child| !self.anti_leak || !is_leak_file(&child.name))
                .map(|child| {
                    Ok(Box::new(SanctumDirEntry {
                        name: child.name,
                        meta: SanctumMetaData {
                            is_dir: child.is_dir,
                            size: child.size,
                            created_at: UNIX_EPOCH + Duration::from_secs(child.created_at),
                            modified_at: UNIX_EPOCH + Duration::from_secs(child.modified_at),
                        },
                    }) as Box<dyn DavDirEntry>)
                })
                .collect();

            Ok(Box::pin(stream::iter(entries)) as FsStream<Box<dyn DavDirEntry>>)
        })
    }

    fn metadata<'a>(&'a self, path: &'a DavPath) -> FsFuture<'a, Box<dyn DavMetaData>> {
        if let Some(ref cfs) = self.carrier_fs {
            return cfs.metadata(path);
        }

        Box::pin(async move {
            let path_str = Self::path_to_str(path);
            if path_str != "/" && !path_str.is_empty() {
                self.touch();
            }
            let node = self
                .resolve_path(&path_str)?
                .ok_or(FsError::NotFound)?;

            let meta = SanctumMetaData {
                is_dir: node.is_dir,
                size: node.size,
                created_at: UNIX_EPOCH + Duration::from_secs(node.created_at),
                modified_at: UNIX_EPOCH + Duration::from_secs(node.modified_at),
            };

            Ok(Box::new(meta) as Box<dyn DavMetaData>)
        })
    }

    fn symlink_metadata<'a>(&'a self, path: &'a DavPath) -> FsFuture<'a, Box<dyn DavMetaData>> {
        if let Some(ref cfs) = self.carrier_fs {
            return cfs.symlink_metadata(path);
        }
        self.metadata(path)
    }

    fn create_dir<'a>(&'a self, path: &'a DavPath) -> FsFuture<'a, ()> {
        if let Some(ref cfs) = self.carrier_fs {
            return cfs.create_dir(path);
        }

        Box::pin(async move {
            self.touch();
            let path_str = Self::path_to_str(path);
            let (parent_path, dir_name) = self.split_parent_and_name(&path_str);

            if self.anti_leak && is_leak_file(dir_name) {
                return Err(FsError::Forbidden);
            }

            if self.resolve_path(&path_str)?.is_some() {
                return Err(FsError::Exists);
            }

            let parent = self
                .resolve_path(parent_path)?
                .ok_or(FsError::NotFound)?;

            if !parent.is_dir {
                return Err(FsError::Forbidden);
            }

            self.create_node(parent.id, dir_name, true)?;

            Ok(())
        })
    }

    fn remove_dir<'a>(&'a self, path: &'a DavPath) -> FsFuture<'a, ()> {
        if let Some(ref cfs) = self.carrier_fs {
            return cfs.remove_dir(path);
        }

        Box::pin(async move {
            self.touch();
            let path_str = Self::path_to_str(path);
            let node = self
                .resolve_path(&path_str)?
                .ok_or(FsError::NotFound)?;

            if !node.is_dir {
                return Err(FsError::Forbidden);
            }
            let root_id = Database::get_root_node_id_for_vault(self.vault_id);
            if node.id == root_id {
                // Root-Verzeichnis darf nicht gelöscht werden
                return Err(FsError::Forbidden);
            }

            self.db
                .delete_node(node.id)
                .map_err(|_| FsError::GeneralFailure)?;

            Ok(())
        })
    }

    fn remove_file<'a>(&'a self, path: &'a DavPath) -> FsFuture<'a, ()> {
        if let Some(ref cfs) = self.carrier_fs {
            return cfs.remove_file(path);
        }

        Box::pin(async move {
            self.touch();
            let path_str = Self::path_to_str(path);
            let node = self
                .resolve_path(&path_str)?
                .ok_or(FsError::NotFound)?;

            if node.is_dir {
                return Err(FsError::Forbidden);
            }

            // Schutz der Trägerdatei im Decoy Vault: Löschen verboten!
            if self.carrier_node_id == Some(node.id) {
                return Err(FsError::Forbidden);
            }

            self.db
                .delete_node(node.id)
                .map_err(|_| FsError::GeneralFailure)?;

            Ok(())
        })
    }

    fn rename<'a>(
        &'a self,
        from: &'a DavPath,
        to: &'a DavPath,
    ) -> FsFuture<'a, ()> {
        if let Some(ref cfs) = self.carrier_fs {
            return cfs.rename(from, to);
        }

        Box::pin(async move {
            self.touch();
            let from_str = Self::path_to_str(from);
            let to_str = Self::path_to_str(to);

            let node = self
                .resolve_path(&from_str)?
                .ok_or(FsError::NotFound)?;

            // Schutz der Trägerdatei im Decoy Vault: Umbenennen verboten!
            if self.carrier_node_id == Some(node.id) {
                return Err(FsError::Forbidden);
            }

            let (to_parent_path, to_name) = self.split_parent_and_name(&to_str);

            if self.anti_leak && is_leak_file(to_name) {
                return Err(FsError::Forbidden);
            }

            let to_parent = self
                .resolve_path(to_parent_path)?
                .ok_or(FsError::NotFound)?;

            if !to_parent.is_dir {
                return Err(FsError::Forbidden);
            }

            // Falls Zieldatei bereits existiert und Datei ist: überschreiben / löschen
            if let Some(dest) = self.resolve_path(&to_str)? {
                if dest.is_dir {
                    return Err(FsError::Forbidden);
                }
                self.db
                    .delete_node(dest.id)
                    .map_err(|_| FsError::GeneralFailure)?;
            }

            self.rename_node(node.id, to_parent.id, to_name)?;

            Ok(())
        })
    }

    fn copy<'a>(
        &'a self,
        from: &'a DavPath,
        to: &'a DavPath,
    ) -> FsFuture<'a, ()> {
        Box::pin(async move {
            self.touch();
            let from_str = Self::path_to_str(from);
            let to_str = Self::path_to_str(to);

            let node = self
                .resolve_path(&from_str)?
                .ok_or(FsError::NotFound)?;

            if node.is_dir {
                return Err(FsError::NotImplemented);
            }

            let (to_parent_path, to_name) = self.split_parent_and_name(&to_str);

            if self.anti_leak && is_leak_file(to_name) {
                return Err(FsError::Forbidden);
            }

            let to_parent = self
                .resolve_path(to_parent_path)?
                .ok_or(FsError::NotFound)?;

            let dest_node = self.create_node(to_parent.id, to_name, false)?;

            // Kopiere alle Chunks und re-verschlüssele mit neuer node_id (wegen AAD-Bindung!)
            let total_chunks = if node.size == 0 {
                0
            } else {
                ((node.size - 1) / CHUNK_SIZE as u64 + 1) as u32
            };

            for idx in 0..total_chunks {
                if let Some(record) = self
                    .db
                    .read_chunk(node.id, idx)
                    .map_err(|_| FsError::GeneralFailure)?
                {
                    let plaintext = decrypt_chunk(
                        &self.dek,
                        node.id,
                        idx,
                        &record.ciphertext,
                        &record.nonce,
                        &record.tag,
                        self.format_version,
                    )
                    .map_err(|_| FsError::GeneralFailure)?;

                    let (new_ct, new_nonce, new_tag) =
                        encrypt_chunk(&self.dek, dest_node.id, idx, &plaintext, self.format_version)
                            .map_err(|_| FsError::GeneralFailure)?;

                    self.db
                        .write_chunk(dest_node.id, idx, &new_nonce, &new_tag, &new_ct)
                        .map_err(|_| FsError::GeneralFailure)?;
                }
            }

            let now = SystemTime::now()
                .duration_since(UNIX_EPOCH)
                .map(|d| d.as_secs())
                .unwrap_or(0);
            self.db
                .update_node_size_and_time(dest_node.id, node.size, now)
                .map_err(|_| FsError::GeneralFailure)?;

            Ok(())
        })
    }

    fn get_quota(&self) -> FsFuture<'_, (u64, Option<u64>)> {
        Box::pin(async move {
            // Virtueller Speicherplatz für Explorer: 1 TB
            let total_capacity: u64 = 1024 * 1024 * 1024 * 1024;
            Ok((0, Some(total_capacity)))
        })
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::crypto::{derive_kek, generate_dek, generate_salt, wrap_dek, KdfParams, FORMAT_VERSION};
    use dav_server::fs::OpenOptions;
    use futures_util::StreamExt;

    #[test]
    fn test_is_leak_file() {
        assert!(is_leak_file("Thumbs.db"));
        assert!(is_leak_file("thumbs.db"));
        assert!(is_leak_file("THUMBS.DB"));
        assert!(is_leak_file("ehthumbs.db"));
        assert!(is_leak_file("ehthumbs_vista.db"));
        assert!(is_leak_file("desktop.ini"));
        assert!(is_leak_file("Desktop.ini"));
        assert!(is_leak_file("Folder.jpg"));
        assert!(is_leak_file("albumartsmall.jpg"));
        assert!(is_leak_file("AlbumArt_{12345}_Large.jpg"));
        assert!(is_leak_file("AlbumArt_{12345}_Small.jpg"));
        assert!(is_leak_file("autorun.inf"));
        assert!(is_leak_file(".ds_store"));

        // Harmlos:
        assert!(!is_leak_file("secret.txt"));
        assert!(!is_leak_file("passwords.kdbx"));
        assert!(!is_leak_file("my_folder.jpg.txt"));
        assert!(!is_leak_file("desktop_notes.ini.bak"));
    }

    fn create_test_fs(anti_leak: bool) -> (SanctumFs, tempfile_placeholder::TempDir) {
        let temp_dir = tempfile_placeholder::TempDir::new();
        let db_path = temp_dir.path().join("test_vfs.sanctum");
        let db = Database::open(&db_path).unwrap();

        let salt = generate_salt();
        let kdf_params = KdfParams {
            memory_cost: 1024,
            time_cost: 1,
            parallelism: 1,
        };
        let kek = derive_kek("testpwd", &salt, &kdf_params).unwrap();
        let dek = generate_dek();
        let (wrapped_dek, header_nonce, header_tag) = wrap_dek(&kek, &dek).unwrap();
        db.init_schema(&salt, &kdf_params, &wrapped_dek, &header_nonce, &header_tag)
            .unwrap();

        let fs = SanctumFs::with_options(db, dek, FORMAT_VERSION, anti_leak);
        (fs, temp_dir)
    }

    mod tempfile_placeholder {
        use std::path::{Path, PathBuf};
        pub struct TempDir(PathBuf);
        impl TempDir {
            pub fn new() -> Self {
                let p = std::env::temp_dir().join(format!("sanctum_test_{}", rand::random::<u64>()));
                std::fs::create_dir_all(&p).unwrap();
                Self(p)
            }
            pub fn path(&self) -> &Path {
                &self.0
            }
        }
        impl Drop for TempDir {
            fn drop(&mut self) {
                let _ = std::fs::remove_dir_all(&self.0);
            }
        }
    }

    #[tokio::test]
    async fn test_anti_leak_blocks_creation() {
        let (fs, _dir) = create_test_fs(true);

        let path = DavPath::new("/desktop.ini").unwrap();
        let mut opts = OpenOptions::default();
        opts.write = true;
        opts.create_new = true;

        // desktop.ini muss blockiert werden mit Forbidden
        let res = fs.open(&path, opts).await;
        assert!(matches!(res, Err(FsError::Forbidden)));

        // create_dir mit Thumbs.db muss auch blockiert werden
        let dir_path = DavPath::new("/Thumbs.db").unwrap();
        let res_dir = fs.create_dir(&dir_path).await;
        assert!(matches!(res_dir, Err(FsError::Forbidden)));

        // Normale Datei muss erlaubt sein
        let valid_path = DavPath::new("/notes.txt").unwrap();
        let mut valid_opts = OpenOptions::default();
        valid_opts.write = true;
        valid_opts.create_new = true;
        let res_valid = fs.open(&valid_path, valid_opts).await;
        assert!(res_valid.is_ok());
    }

    #[tokio::test]
    async fn test_anti_leak_filters_read_dir() {
        let (fs_shielded, _dir) = create_test_fs(true);

        // Erstelle eine normale Datei
        let normal_path = DavPath::new("/legit.txt").unwrap();
        let mut opts = OpenOptions::default();
        opts.write = true;
        opts.create_new = true;
        let res = fs_shielded.open(&normal_path, opts).await;
        assert!(res.is_ok());

        // Erzwinge direkt in die DB eine Thumbs.db Datei
        fs_shielded.db.create_node(1, "Thumbs.db", false).unwrap();

        // read_dir mit anti_leak = true darf Thumbs.db NICHT anzeigen
        let root_path = DavPath::new("/").unwrap();
        let mut stream = fs_shielded.read_dir(&root_path, ReadDirMeta::None).await.unwrap();
        let mut names = Vec::new();
        while let Some(entry) = stream.next().await {
            let entry = entry.unwrap();
            names.push(String::from_utf8_lossy(&entry.name()).to_string());
        }

        assert!(names.contains(&"legit.txt".to_string()));
        assert!(!names.contains(&"Thumbs.db".to_string()));

        // Mit unshielded FS (anti_leak = false) muss Thumbs.db sichtbar sein
        let fs_unshielded = SanctumFs::with_options(
            fs_shielded.db.clone(),
            zeroize::Zeroizing::new([0u8; 32]),
            FORMAT_VERSION,
            false,
        );
        let mut stream_unshielded = fs_unshielded.read_dir(&root_path, ReadDirMeta::None).await.unwrap();
        let mut names_unshielded = Vec::new();
        while let Some(entry) = stream_unshielded.next().await {
            let entry = entry.unwrap();
            names_unshielded.push(String::from_utf8_lossy(&entry.name()).to_string());
        }
        assert!(names_unshielded.contains(&"Thumbs.db".to_string()));
    }

    #[tokio::test]
    async fn test_vfs_activity_tracking() {
        let (fs, _dir) = create_test_fs(true);
        let act_arc = fs.last_activity();
        let initial_time = act_arc.load(Ordering::Relaxed);
        assert!(initial_time > 0);

        // Manuell zurückdatieren
        act_arc.store(1000, Ordering::Relaxed);
        assert_eq!(act_arc.load(Ordering::Relaxed), 1000);

        // Nach einem VFS-Zugriff muss die Zeit aktualisiert sein
        let path = DavPath::new("/test_activity.txt").unwrap();
        let mut opts = OpenOptions::default();
        opts.write = true;
        opts.create_new = true;
        let _ = fs.open(&path, opts).await;

        let new_time = act_arc.load(Ordering::Relaxed);
        assert!(new_time > 1000);
    }
}