bevy_dlc/

pack_format.rs

/// .dlcpack container magic header (4 bytes) used to identify encrypted pack containers.
pub const DLC_PACK_MAGIC: &[u8; 4] = b"BDLP";

/// Current supported .dlcpack format version. This is stored in the container header and used to determine how to parse the contents.
pub const DLC_PACK_VERSION_LATEST: u8 = 4;

/// Default block size for v4 hybrid format (10 MB). Blocks are individually encrypted tar.gz chunks.
pub const DEFAULT_BLOCK_SIZE: usize = 10 * 1024 * 1024;

/// List of file extensions that are never allowed to be packed.  These are
/// taken from the same array that used to live in [lib.rs]; we keep the
/// array for deterministic build and the hash set for fast membership tests.
pub const FORBIDDEN_EXTENSIONS: &[&str] = &[
    "dlcpack", "pubkey", "slicense", // these are the expected extensions for keys/licenses; they should be packed with the dedicated macros rather than as raw files
    // these are generated by a script that pulls a list of extensions that can be used maliciously
    "7z", "accda", "accdb", "accde", "accdr", "ace", "ade", "adp", "app", "appinstaller", "application", "appref", "appx", "appxbundle", "arj", "asax", "asd", "ashx", "asp", "aspx", "b64", "bas", "bat", "bgi", "bin", "btm", "bz", "bz2", "bzip", "bzip2", "cab", "cer", "cfg", "chi", "chm", "cla", "class", "cmd", "com", "cpi", "cpio", "cpl", "crt", "crx", "csh", "der", "desktopthemefile", "diagcab", "diagcfg", "diagpkg", "dll", "dmg", "doc", "docm", "docx", "dotm", "drv", "eml", "exe", "fon", "fxp", "gadget", "grp", "gz", "gzip", "hlp", "hta", "htc", "htm", "html", "htt", "ics", "img", "ini", "ins", "inx", "iqy", "iso", "isp", "isu", "jar", "jnlp", "job", "js", "jse", "ksh", "lha", "lnk", "local", "lz", "lzh", "lzma", "mad", "maf", "mag", "mam", "manifest", "maq", "mar", "mas", "mat", "mav", "maw", "mda", "mdb", "mde", "mdt", "mdw", "mdz", "mht", "mhtml", "mmc", "msc", "msg", "msh", "msh1", "msh1xml", "msh2", "msh2xml", "mshxml", "msi", "msix", "msixbundle", "msm", "msp", "mst", "msu", "ocx", "odt", "one", "onepkg", "onetoc", "onetoc2", "ops", "oxps", "oxt", "paf", "partial", "pcd", "pdf", "pif", "pl", "plg", "pol", "potm", "ppam", "ppkg", "ppsm", "ppt", "pptm", "pptx", "prf", "prg", "ps1", "ps1xml", "ps2", "ps2xml", "psc1", "psc2", "psm1", "pst", "r00", "r01", "r02", "r03", "rar", "reg", "rels", "rev", "rgs", "rpm", "rtf", "scf", "scr", "sct", "search", "settingcontent", "settingscontent", "sh", "shb", "sldm", "slk", "svg", "swf", "sys", "tar", "tbz", "tbz2", "tgz", "tlb", "url", "uue", "vb", "vbe", "vbs", "vbscript", "vdx", "vhd", "vhdx", "vsmacros", "vss", "vssm", "vssx", "vst", "vstm", "vstx", "vsw", "vsx", "vtx", "wbk", "webarchive", "website", "wml", "ws", "wsc", "wsf", "wsh", "xar", "xbap", "xdp", "xlam", "xll", "xlm", "xls", "xlsb", "xlsm", "xlsx", "xltm", "xlw", "xml", "xnk", "xps", "xrm", "xsd", "xsl", "xxe", "xz", "z", "zip",
];

/// Lazy hash set used by [`is_forbidden_extension`].
// static FORBIDDEN_SET: LazyLock<HashSet<&'static str>> = LazyLock::new(|| {
//     FORBIDDEN_EXTENSIONS.iter().copied().collect()
// });

// NOTE: if additional heuristics are required in the future they can be
// reintroduced or re‑exported from the CLI/generation layer rather than the
// core format library.
/// Simple heuristic used by the packer to detect executable payloads.  It is
/// intentionally forgiving; the goal is merely to catch obvious binaries when
/// a user accidentally tries to pack them.
pub fn is_data_executable(data: &[u8]) -> bool {
    if infer::is_app(data) {
        return true;
    }
    
    for ext in FORBIDDEN_EXTENSIONS {
        if infer::is(data, *ext) {
            return true;
        }
    }

    if data.starts_with(b"#!") {
        return true;
    }
    false
}

/// Representation of a single manifest entry inside a v2+ `.dlcpack`.
#[derive(serde::Serialize, serde::Deserialize, Debug, Clone)]
pub struct ManifestEntry {
    pub path: String,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub original_extension: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")]
    pub type_path: Option<String>,
}

impl ManifestEntry {
    pub fn from_pack_item(item: &crate::PackItem) -> Self {
        ManifestEntry {
            path: item.path.clone(),
            original_extension: item
                .original_extension
                .clone()
                .filter(|s| !s.is_empty()),
            type_path: item.type_path.clone(),
        }
    }
}

/// V4 manifest entry: binary-serializable format for faster parsing.
/// Format: path_len(u32) + path(utf8) + ext_len(u8) + ext(utf8) + type_len(u16) + type(utf8) + block_id(u32) + block_offset(u32) + size(u32)
#[derive(Clone, Debug)]
pub struct V4ManifestEntry {
    pub path: String,
    pub original_extension: String,
    pub type_path: Option<String>,
    /// Which block contains this asset
    pub block_id: u32,
    /// Offset within the decompressed block's tar archive
    pub block_offset: u32,
    /// Uncompressed size (for progress/buffer allocation)
    pub size: u32,
}

impl V4ManifestEntry {
    pub fn from_pack_item(item: &crate::PackItem, block_id: u32, block_offset: u32) -> Self {
        V4ManifestEntry {
            path: item.path.clone(),
            original_extension: item.original_extension.clone().unwrap_or_default(),
            type_path: item.type_path.clone(),
            block_id,
            block_offset,
            size: item.plaintext.len() as u32,
        }
    }

    /// Write this entry in binary format (used by v4 format conversion)
    #[allow(dead_code)]
    fn write_binary<W: std::io::Write>(&self, writer: &mut PackWriter<W>) -> std::io::Result<()> {
        writer.write_u32(self.path.len() as u32)?;
        writer.write_bytes(self.path.as_bytes())?;

        writer.write_u8(self.original_extension.len() as u8)?;
        writer.write_bytes(self.original_extension.as_bytes())?;

        if let Some(ref tp) = self.type_path {
            writer.write_u16(tp.len() as u16)?;
            writer.write_bytes(tp.as_bytes())?;
        } else {
            writer.write_u16(0)?;
        }

        writer.write_u32(self.block_id)?;
        writer.write_u32(self.block_offset)?;
        writer.write_u32(self.size)
    }

    /// Read binary format from reader (used by v4 format parsing)
    #[allow(dead_code)]
    fn read_binary<R: std::io::Read>(reader: &mut PackReader<R>) -> std::io::Result<Self> {
        let path_len = reader.read_u32()? as usize;
        let path = String::from_utf8(reader.read_bytes(path_len)?)
            .map_err(|e| std::io::Error::new(std::io::ErrorKind::InvalidData, e))?;

        let ext_len = reader.read_u8()? as usize;
        let original_extension = if ext_len > 0 {
            String::from_utf8(reader.read_bytes(ext_len)?)
                .map_err(|e| std::io::Error::new(std::io::ErrorKind::InvalidData, e))?
        } else {
            String::new()
        };

        let type_len = reader.read_u16()? as usize;
        let type_path = if type_len > 0 {
            let tp = String::from_utf8(reader.read_bytes(type_len)?)
                .map_err(|e| std::io::Error::new(std::io::ErrorKind::InvalidData, e))?;
            Some(tp)
        } else {
            None
        };

        let block_id = reader.read_u32()?;
        let block_offset = reader.read_u32()?;
        let size = reader.read_u32()?;

        Ok(V4ManifestEntry {
            path,
            original_extension,
            type_path,
            block_id,
            block_offset,
            size,
        })
    }
}

/// V4 block metadata: stores information about a tar-gz block within the pack file
#[derive(Clone, Debug)]
pub struct BlockMetadata {
    pub block_id: u32,
    pub file_offset: u64,      // Where this block starts in the file
    pub encrypted_size: u32,   // Size of encrypted ciphertext
    pub uncompressed_size: u32, // Size after decompression (for buffer allocation)
    pub nonce: [u8; 12],       // Per-block nonce
    pub crc32: u32,            // CRC32 checksum for integrity
}

impl BlockMetadata {
    #[allow(dead_code)]
    fn write_binary<W: std::io::Write>(&self, writer: &mut PackWriter<W>) -> std::io::Result<()> {
        writer.write_u32(self.block_id)?;
        writer.write_u64(self.file_offset)?;
        writer.write_u32(self.encrypted_size)?;
        writer.write_u32(self.uncompressed_size)?;
        writer.write_bytes(&self.nonce)?;
        writer.write_u32(self.crc32)
    }

    #[allow(dead_code)]
    fn read_binary<R: std::io::Read>(reader: &mut PackReader<R>) -> std::io::Result<Self> {
        let block_id = reader.read_u32()?;
        let file_offset = reader.read_u64()?;
        let encrypted_size = reader.read_u32()?;
        let uncompressed_size = reader.read_u32()?;
        let nonce = reader.read_nonce()?;
        let crc32 = reader.read_u32()?;

        Ok(BlockMetadata {
            block_id,
            file_offset,
            encrypted_size,
            uncompressed_size,
            nonce,
            crc32,
        })
    }
}

// converters and migration helpers have been removed – the crate
// now only supports v4 packs.  The old `PackConverter` trait, the
// `V3toV4Converter` implementation and the `PackConverterRegistry` type
// were used to upgrade on‑disk packs to the latest format; they are
// retained in history if needed but no longer compiled.

/// Internal helper for binary parsing with offset management.
pub(crate) struct PackReader<R: std::io::Read> {
    inner: R,
}

impl<R: std::io::Read> PackReader<R> {
    pub fn new(inner: R) -> Self {
        Self { inner }
    }

    /// Read a byte.
    pub fn read_u8(&mut self) -> std::io::Result<u8> {
        let mut buf = [0u8; 1];
        self.inner.read_exact(&mut buf)?;
        Ok(buf[0])
    }

    /// Convenience method: read `len` bytes and immediately decrypt them with
    /// the provided AES-GCM key/nonce.
    #[allow(dead_code)]
    pub fn read_and_decrypt(
        &mut self,
        key: &crate::EncryptionKey,
        len: usize,
        nonce: &[u8],
    ) -> Result<Vec<u8>, DlcError> {
        let ciphertext = self.read_bytes(len)?;

        let cursor = std::io::Cursor::new(ciphertext);
        crate::pack_format::decrypt_with_key(key, cursor, nonce)
    }

    pub fn read_u16(&mut self) -> std::io::Result<u16> {
        let mut buf = [0u8; 2];
        self.inner.read_exact(&mut buf)?;
        Ok(u16::from_be_bytes(buf))
    }

    pub fn read_u32(&mut self) -> std::io::Result<u32> {
        let mut buf = [0u8; 4];
        self.inner.read_exact(&mut buf)?;
        Ok(u32::from_be_bytes(buf))
    }

    #[allow(dead_code)]
    pub fn read_u64(&mut self) -> std::io::Result<u64> {
        let mut buf = [0u8; 8];
        self.inner.read_exact(&mut buf)?;
        Ok(u64::from_be_bytes(buf))
    }

    pub fn read_bytes(&mut self, len: usize) -> std::io::Result<Vec<u8>> {
        let mut buf = vec![0u8; len];
        self.inner.read_exact(&mut buf)?;
        Ok(buf)
    }

    pub fn read_string_u16(&mut self) -> std::io::Result<String> {
        let len = self.read_u16()? as usize;
        self.read_string(len)
    }

    pub fn read_string(&mut self, len: usize) -> std::io::Result<String> {
        let bytes = self.read_bytes(len)?;
        // Avoid allocation for UTF-8 validation by using from_utf8_lossy internally,
        // but preserve error semantics for actual validation
        String::from_utf8(bytes)
            .map_err(|e| std::io::Error::new(std::io::ErrorKind::InvalidData, e))
    }

    pub fn read_nonce(&mut self) -> std::io::Result<[u8; 12]> {
        let mut nonce = [0u8; 12];
        self.inner.read_exact(&mut nonce)?;
        Ok(nonce)
    }
}

// additional helpers available when the inner reader also implements `Seek`
#[allow(unused)]
impl<R: std::io::Read + std::io::Seek> PackReader<R> {
    /// Seek the underlying reader to `pos` and return the new position.
    pub fn seek(&mut self, pos: std::io::SeekFrom) -> std::io::Result<u64> {
        self.inner.seek(pos)
    }
}

/// Internal helper for binary packing.
pub(crate) struct PackWriter<W: std::io::Write> {
    inner: W,
}

impl<W: std::io::Write> PackWriter<W> {
    pub fn new(inner: W) -> Self {
        Self { inner }
    }

    /// Encrypt `plaintext` with the provided key/nonce and write the
    /// resulting ciphertext to the underlying writer.
    #[allow(dead_code)]
    pub fn write_encrypted(
        &mut self,
        key: &crate::EncryptionKey,
        nonce: &[u8],
        plaintext: &[u8],
    ) -> Result<(), DlcError> {
        use aes_gcm::{Aes256Gcm, KeyInit, Nonce, aead::Aead};
        let cipher = key.with_secret(|kb| {
            Aes256Gcm::new_from_slice(kb).map_err(|e| DlcError::CryptoError(e.to_string()))
        })?;
        let ct = cipher
            .encrypt(Nonce::from_slice(nonce), plaintext)
            .map_err(|_| DlcError::EncryptionFailed("block encryption failed".into()))?;
        self.write_bytes(&ct).map_err(|e| DlcError::Other(e.to_string()))
    }

    pub fn write_u8(&mut self, val: u8) -> std::io::Result<()> {
        self.inner.write_all(&[val])
    }

    pub fn write_u16(&mut self, val: u16) -> std::io::Result<()> {
        self.inner.write_all(&val.to_be_bytes())
    }

    pub fn write_u32(&mut self, val: u32) -> std::io::Result<()> {
        self.inner.write_all(&val.to_be_bytes())
    }

    pub fn write_u64(&mut self, val: u64) -> std::io::Result<()> {
        self.inner.write_all(&val.to_be_bytes())
    }

    pub fn write_bytes(&mut self, bytes: &[u8]) -> std::io::Result<()> {
        self.inner.write_all(bytes)
    }

    pub fn write_string_u16(&mut self, s: &str) -> std::io::Result<()> {
        let bytes = s.as_bytes();
        self.write_u16(bytes.len() as u16)?;
        self.write_bytes(bytes)
    }

    pub fn finish(mut self) -> std::io::Result<W> {
        self.inner.flush()?;
        Ok(self.inner)
    }
}

/// Represents the header of any version of a `.dlcpack`.
struct PackHeader {
    version: u8,
    product: String,
    dlc_id: String,
}

impl PackHeader {
    fn read<R: std::io::Read>(reader: &mut PackReader<R>) -> std::io::Result<Self> {
        let magic = reader.read_bytes(4)?;
        if magic != DLC_PACK_MAGIC {
            return Err(std::io::Error::new(
                std::io::ErrorKind::InvalidData,
                "invalid dlcpack magic",
            ));
        }

        let version = reader.read_u8()?;
        let mut product = String::new();

        if version == 3 || version == 4 {
            product = reader.read_string_u16()?;
        } else if version > 4 {
            return Err(std::io::Error::new(
                std::io::ErrorKind::InvalidData,
                format!("unsupported pack version: {}", version),
            ));
        }

        let dlc_id = reader.read_string_u16()?;

        Ok(PackHeader {
            version,
            product,
            dlc_id,
        })
    }

    fn write<W: std::io::Write>(&self, writer: &mut PackWriter<W>) -> std::io::Result<()> {
        writer.write_bytes(DLC_PACK_MAGIC)?;
        writer.write_u8(self.version)?;

        if self.version == 3 || self.version == 4 {
            writer.write_string_u16(&self.product)?;
        }

        writer.write_string_u16(&self.dlc_id)
    }
}

/// Decrypt with a 32-byte AES key using AES-GCM.  This is the same logic that
/// used to live in `lib.rs`; moving it here allows crates that only depend on
/// the pack format helpers to perform decryption without pulling in the
/// higher-level API.

use aes_gcm::{Aes256Gcm, KeyInit, Nonce, aead::AeadInPlace};
use secure_gate::ExposeSecret;

use crate::{DlcError, DlcId, EncryptionKey, PackItem, Product};

pub(crate) fn decrypt_with_key<R: std::io::Read>(
    key: &crate::EncryptionKey,
    mut reader: R,
    nonce: &[u8],
) -> Result<Vec<u8>, DlcError> {
    // read ciphertext into a single buffer; decrypt it in-place to avoid
    // allocating a second plaintext buffer.
    let mut buf = Vec::new();
    reader
        .read_to_end(&mut buf)
        .map_err(|e| DlcError::Other(e.to_string()))?;

    key.with_secret(|key_bytes| {
        if key_bytes.len() != 32 {
            return Err(DlcError::InvalidEncryptKey(
                "encrypt key must be 32 bytes (AES-256)".into(),
            ));
        }
        if nonce.len() != 12 {
            return Err(DlcError::InvalidNonce(
                "nonce must be 12 bytes (AES-GCM)".into(),
            ));
        }
        let cipher = Aes256Gcm::new_from_slice(key_bytes)
            .map_err(|e| DlcError::CryptoError(e.to_string()))?;
        let nonce = Nonce::from_slice(nonce);
        // decrypt in-place; `buf` will be overwritten with plaintext
        cipher
            .decrypt_in_place(nonce, &[], &mut buf)
            .map_err(|_|
                DlcError::DecryptionFailed(
                    "authentication failed (incorrect key or corrupted ciphertext)".to_string(),
                )
            )
    })?;
    Ok(buf)
}

/// Compression level for packing. Controls the trade-off between pack size and packing time.
/// Higher levels produce smaller files but take longer to create.
#[derive(Debug, Clone, Copy)]
pub enum CompressionLevel {
    /// Fast compression (level 1), suitable for rapid iterations
    Fast,
    /// Balanced compression (level 6, default), good trade-off
    Default,
    /// Best compression (level 9), smallest file size for distribution
    Best,
}

impl From<CompressionLevel> for flate2::Compression {
    fn from(level: CompressionLevel) -> Self {
        match level {
            CompressionLevel::Fast => flate2::Compression::fast(),
            CompressionLevel::Default => flate2::Compression::default(),
            CompressionLevel::Best => flate2::Compression::best(),
        }
    }
}

/// Pack multiple entries into a single encrypted `.dlcpack` binary using the latest version format.  This is the main entry point for pack creation and is used by the CLI tool; it can also be used by other tools that want to generate packs programmatically.
pub fn pack_encrypted_pack(
    dlc_id: &DlcId,
    items: &[PackItem],
    product: &Product,
    key: &EncryptionKey,
    block_size: usize,
) -> Result<Vec<u8>, DlcError> {
    use aes_gcm::{Aes256Gcm, KeyInit, Nonce, aead::Aead};
    use flate2::Compression;
    use flate2::write::GzEncoder;
    use tar::Builder;

    let cipher = key.with_secret(|kb| {
        Aes256Gcm::new_from_slice(kb.as_slice()).map_err(|e| DlcError::CryptoError(e.to_string()))
    })?;

    // 1. Group items into blocks
    let mut blocks: Vec<Vec<&PackItem>> = Vec::new();
    let mut current_block = Vec::new();
    let mut current_size = 0;

    for item in items {
        if !current_block.is_empty() && current_size + item.plaintext.len() > block_size {
            blocks.push(std::mem::take(&mut current_block));
            current_size = 0;
        }
        current_size += item.plaintext.len();
        current_block.push(item);
    }
    if !current_block.is_empty() {
        blocks.push(current_block);
    }

    // 2. Build blocks and track offsets
    let mut encrypted_blocks = Vec::new();
    let mut manifest_entries = Vec::new();
    let mut block_metadatas = Vec::new();

    for (block_id, block_items) in blocks.into_iter().enumerate() {
        let block_id = block_id as u32;
        let mut tar_gz = Vec::new();
        let mut uncompressed_size = 0;
        {
            let mut gz = GzEncoder::new(&mut tar_gz, Compression::default());
            {
                let mut tar = Builder::new(&mut gz);
                let mut offset = 0;

                for item in block_items {
                    let mut header = tar::Header::new_gnu();
                    header.set_size(item.plaintext.len() as u64);
                    header.set_mode(0o644);
                    header.set_cksum();

                    let path_str = item.path.clone();
                    manifest_entries.push(V4ManifestEntry {
                        path: path_str,
                        original_extension: item.original_extension.clone().unwrap_or_default(),
                        type_path: item.type_path.clone(),
                        block_id,
                        block_offset: offset,
                        size: item.plaintext.len() as u32,
                    });

                    tar.append_data(&mut header, &item.path, &item.plaintext[..])
                        .map_err(|e| DlcError::Other(e.to_string()))?;

                    // tar header is 512, plus data (padded to 512)
                    let data_len = item.plaintext.len() as u32;
                    let padded_len = (data_len + 511) & !511;
                    offset += 512 + padded_len;
                    uncompressed_size += data_len;
                }
                tar.finish().map_err(|e| DlcError::Other(e.to_string()))?;
            }
            gz.finish().map_err(|e| DlcError::Other(e.to_string()))?;
        }

        // Encrypt block
        let nonce_bytes: [u8; 12] = rand::random();
        let nonce = Nonce::from_slice(&nonce_bytes);
        let ciphertext = cipher
            .encrypt(nonce, tar_gz.as_slice())
            .map_err(|_| DlcError::EncryptionFailed("block encryption failed".into()))?;

        let crc32 = crc32fast::hash(&ciphertext);

        block_metadatas.push(BlockMetadata {
            block_id,
            file_offset: 0, // Fill later
            encrypted_size: ciphertext.len() as u32,
            uncompressed_size,
            nonce: nonce_bytes,
            crc32,
        });

        encrypted_blocks.push(ciphertext);
    }

    // 3. Assemble final binary
    let product_str = product.as_ref();
    let dlc_id_str = dlc_id.to_string();

    let mut out = Vec::new();
    {
        let mut writer = PackWriter::new(&mut out);

        let header = PackHeader {
            version: 4,
            product: product_str.to_string(),
            dlc_id: dlc_id_str.clone(),
        };
        header.write(&mut writer).map_err(|e| DlcError::Other(e.to_string()))?;

        // Manifest
        writer.write_u32(manifest_entries.len() as u32).map_err(|e| DlcError::Other(e.to_string()))?;
        for entry in &manifest_entries {
            entry.write_binary(&mut writer).map_err(|e| DlcError::Other(e.to_string()))?;
        }

        // Block Metadata placeholder
        writer.write_u32(block_metadatas.len() as u32).map_err(|e| DlcError::Other(e.to_string()))?;
        writer.finish().map_err(|e| DlcError::Other(e.to_string()))?;
    }
    let metadata_start_pos = out.len();
    {
        let mut writer = PackWriter::new(&mut out);
        for meta in &block_metadatas {
            meta.write_binary(&mut writer).map_err(|e| DlcError::Other(e.to_string()))?;
        }
        writer.finish().map_err(|e| DlcError::Other(e.to_string()))?;
    }

    // Encrypted Blocks
    for (i, block) in encrypted_blocks.into_iter().enumerate() {
        let pos = out.len() as u64;
        block_metadatas[i].file_offset = pos;
        out.extend_from_slice(&block);
    }

    // Rewrite block metadatas with correct file_offsets
    {
        let mut writer_fixed = PackWriter::new(&mut out[metadata_start_pos..]);
        for meta in &block_metadatas {
            meta.write_binary(&mut writer_fixed).map_err(|e| DlcError::Other(e.to_string()))?;
        }
        writer_fixed.finish().map_err(|e| DlcError::Other(e.to_string()))?;
    }

    Ok(out)
}

pub type Version = usize;

/// Returns: (product, dlc_id, version, entries)
pub fn parse_encrypted_pack<R: std::io::Read>(
    reader: R,
) -> Result<
    (
        Product,
        DlcId,
        Version,
        Vec<(String, crate::asset_loader::EncryptedAsset)>,
        Vec<BlockMetadata>,
    ),
    std::io::Error,
> {
    use std::io::ErrorKind;

    let mut reader = PackReader::new(reader);
    let header = PackHeader::read(&mut reader)?;
    let mut block_metadatas = Vec::new();

    let entries = if header.version < DLC_PACK_VERSION_LATEST {
        return Err(std::io::Error::new(
            ErrorKind::InvalidData,
            format!("unsupported pack version: {}", header.version),
        ));
    } else if header.version == 4 {
        // version 4: hybrid multi-block format
        let manifest_count = reader.read_u32()? as usize;
        let mut manifest: Vec<V4ManifestEntry> = Vec::with_capacity(manifest_count);
        for _ in 0..manifest_count {
            manifest.push(V4ManifestEntry::read_binary(&mut reader)?);
        }

        let block_count = reader.read_u32()? as usize;
        block_metadatas = Vec::with_capacity(block_count);
        for _ in 0..block_count {
            block_metadatas.push(BlockMetadata::read_binary(&mut reader)?);
        }

        let mut out = Vec::with_capacity(manifest.len());
        for entry in manifest {
            out.push((
                entry.path,
                crate::asset_loader::EncryptedAsset {
                    dlc_id: header.dlc_id.clone(),
                    original_extension: entry.original_extension,
                    type_path: entry.type_path,
                    nonce: [0u8; 12],
                    ciphertext: std::sync::Arc::new([]),
                    block_id: entry.block_id,
                    block_offset: entry.block_offset,
                    size: entry.size,
                },
            ));
        }
        out
    } else {
        // version 2/3: manifest JSON followed by shared nonce and ciphertext
        let manifest_len = reader.read_u32()? as usize;
        let manifest_bytes = reader.read_bytes(manifest_len)?;
        let manifest: Vec<ManifestEntry> = serde_json::from_slice(&manifest_bytes)
            .map_err(|e| std::io::Error::new(ErrorKind::InvalidData, e))?;

        let mut out = Vec::with_capacity(manifest.len());

        let shared_nonce = reader.read_nonce()?;
        let shared_ciphertext_len = reader.read_u32()? as usize;
        let shared_ciphertext: std::sync::Arc<[u8]> = reader.read_bytes(shared_ciphertext_len)?.into();

        for entry in manifest {
            out.push((
                entry.path,
                crate::asset_loader::EncryptedAsset {
                    dlc_id: header.dlc_id.clone(),
                    original_extension: entry.original_extension.unwrap_or_default(),
                    type_path: entry.type_path,
                    nonce: shared_nonce,
                    ciphertext: shared_ciphertext.clone(),
                    block_id: 0,
                    block_offset: 0,
                    size: shared_ciphertext.len() as u32,
                },
            ));
        }
        out
    };

    Ok((
        Product::from(header.product),
        DlcId::from(header.dlc_id),
        header.version as usize,
        entries,
        block_metadatas,
    ))
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn manifest_roundtrip() {
        let item = crate::PackItem::new("foo.txt", b"hello" as &[u8]).unwrap();
        let entry = ManifestEntry::from_pack_item(&item);
        let bytes = serde_json::to_vec(&entry).unwrap();
        let back: ManifestEntry = serde_json::from_slice(&bytes).unwrap();
        assert_eq!(entry.path, back.path);
    }
}