//! *catar* binary format definition
//!
//! Please note the all values are stored in little endian ordering.
//!
//! The Archive contains a list of items. Each item starts with a
//! `CaFormatHeader`, followed by the item data.

use failure::*;
use endian_trait::Endian;

use siphasher::sip::SipHasher24;

pub const CA_FORMAT_ENTRY: u64 = 0x1396fabcea5bbb51;
pub const CA_FORMAT_FILENAME: u64 = 0x6dbb6ebcb3161f0b;
pub const CA_FORMAT_SYMLINK: u64 = 0x664a6fb6830e0d6c;
pub const CA_FORMAT_PAYLOAD: u64 = 0x8b9e1d93d6dcffc9;

pub const CA_FORMAT_GOODBYE: u64 = 0xdfd35c5e8327c403;
/* The end marker used in the GOODBYE object */
pub const CA_FORMAT_GOODBYE_TAIL_MARKER: u64 = 0x57446fa533702943;


// Feature flags

// DOS file flags
pub const CA_FORMAT_WITH_FLAG_HIDDEN: u64      = 0x2000;
pub const CA_FORMAT_WITH_FLAG_SYSTEM: u64      = 0x4000;
pub const CA_FORMAT_WITH_FLAG_ARCHIVE: u64     = 0x8000;

// chattr() flags
pub const CA_FORMAT_WITH_FLAG_APPEND: u64      = 0x10000;
pub const CA_FORMAT_WITH_FLAG_NOATIME: u64     = 0x20000;
pub const CA_FORMAT_WITH_FLAG_COMPR: u64       = 0x40000;
pub const CA_FORMAT_WITH_FLAG_NOCOW: u64       = 0x80000;
pub const CA_FORMAT_WITH_FLAG_NODUMP: u64      = 0x100000;
pub const CA_FORMAT_WITH_FLAG_DIRSYNC: u64     = 0x200000;
pub const CA_FORMAT_WITH_FLAG_IMMUTABLE: u64   = 0x400000;
pub const CA_FORMAT_WITH_FLAG_SYNC: u64        = 0x800000;
pub const CA_FORMAT_WITH_FLAG_NOCOMP: u64      = 0x1000000;
pub const CA_FORMAT_WITH_FLAG_PROJINHERIT: u64 = 0x2000000;

pub const CA_FORMAT_FEATURE_FLAGS_MAX: u64 = 0xb000_0001_ffef_fe26; // fixme: ?

#[derive(Endian,Clone)]
#[repr(C)]
pub struct CaFormatHeader {
    /// The size of the item, including the size of `CaFormatHeader`.
    pub size: u64,
    /// The item type (see `CA_FORMAT_` constants).
    pub htype: u64,
}

#[derive(Endian,Clone)]
#[repr(C)]
pub struct CaFormatEntry {
    pub feature_flags: u64,
    pub mode: u64,
    pub flags: u64,
    pub uid: u64,
    pub gid: u64,
    pub mtime: u64,
}

#[derive(Endian)]
#[repr(C)]
pub struct CaFormatGoodbyeItem {
    /// The offset from the start of the GOODBYE object to the start
    /// of the matching directory item (point to a FILENAME). The last
    /// GOODBYE item points to the start of the matching ENTRY
    /// object.
    pub offset: u64,
    /// The overall size of the directory item. The last GOODBYE item
    /// repeats the size of the GOODBYE item.
    pub size: u64,
    /// SipHash24 of the directory item name. The last GOODBYE item
    /// uses the special hash value `CA_FORMAT_GOODBYE_TAIL_MARKER`.
    pub hash: u64,
}


/// Helper function to extract file names from binary archive.
pub fn read_os_string(buffer: &[u8]) -> std::ffi::OsString {
    let len = buffer.len();

    use std::os::unix::ffi::OsStrExt;

    let name = if len > 0 && buffer[len-1] == 0 {
        std::ffi::OsStr::from_bytes(&buffer[0..len-1])
    } else {
        std::ffi::OsStr::from_bytes(&buffer)
    };

    name.into()
}

/// Create SipHash values for goodby tables.
//pub fn compute_goodbye_hash(name: &std::ffi::CStr) -> u64 {
pub fn compute_goodbye_hash(name: &[u8]) -> u64 {

    use std::hash::Hasher;
    let mut hasher = SipHasher24::new_with_keys(0x8574442b0f1d84b3, 0x2736ed30d1c22ec1);
    hasher.write(name);
    hasher.finish()
}

pub fn check_ca_header<T>(head: &CaFormatHeader, htype: u64) -> Result<(), Error> {
    if head.htype != htype {
        bail!("got wrong header type ({:016x} != {:016x}", head.htype, htype);
    }
    if head.size != (std::mem::size_of::<T>() + std::mem::size_of::<CaFormatHeader>()) as u64 {
        bail!("got wrong header size for type {:016x}", htype);
    }

    Ok(())
}

// form /usr/include/linux/fs.h
const FS_APPEND_FL: u32 =      0x00000020;
const FS_NOATIME_FL: u32 =     0x00000080;
const FS_COMPR_FL: u32 =       0x00000004;
const FS_NOCOW_FL: u32 =       0x00800000;
const FS_NODUMP_FL: u32 =      0x00000040;
const FS_DIRSYNC_FL: u32 =     0x00010000;
const FS_IMMUTABLE_FL: u32 =   0x00000010;
const FS_SYNC_FL: u32 =        0x00000008;
const FS_NOCOMP_FL: u32 =      0x00000400;
const FS_PROJINHERIT_FL: u32 = 0x20000000;

static CHATTR_MAP: [(u64, u32); 10] = [
    ( CA_FORMAT_WITH_FLAG_APPEND,      FS_APPEND_FL      ),
    ( CA_FORMAT_WITH_FLAG_NOATIME,     FS_NOATIME_FL     ),
    ( CA_FORMAT_WITH_FLAG_COMPR,       FS_COMPR_FL       ),
    ( CA_FORMAT_WITH_FLAG_NOCOW,       FS_NOCOW_FL       ),
    ( CA_FORMAT_WITH_FLAG_NODUMP,      FS_NODUMP_FL      ),
    ( CA_FORMAT_WITH_FLAG_DIRSYNC,     FS_DIRSYNC_FL     ),
    ( CA_FORMAT_WITH_FLAG_IMMUTABLE,   FS_IMMUTABLE_FL   ),
    ( CA_FORMAT_WITH_FLAG_SYNC,        FS_SYNC_FL        ),
    ( CA_FORMAT_WITH_FLAG_NOCOMP,      FS_NOCOMP_FL      ),
    ( CA_FORMAT_WITH_FLAG_PROJINHERIT, FS_PROJINHERIT_FL ),
];

pub fn ca_feature_flags_from_chattr(attr: u32) -> u64 {

    let mut flags = 0u64;

    for (ca_flag, fs_flag) in &CHATTR_MAP {
        if (attr & fs_flag) != 0 { flags = flags | ca_flag; }
    }


    flags
}