// SPDX-License-Identifier: AGPL-3.0-or-later
//! Definitions of messages passed between filesystem clients and servers.
use super::{Handle, Inode};

use btlib::{
    bterr, crypto::ConcretePub, BlockMetaSecrets, DirEntry, DirEntryKind, Epoch, IssuedProcRec,
};
use bttp::CallMsg;
use core::time::Duration;
use paste::paste;
use serde::{Deserialize, Serialize};
use std::{
    fmt::Display,
    io,
    ops::{BitOr, BitOrAssign},
};

/// Top-level message type for the filesystem protocol.
/// All messages passed from clients to servers are of this type.
#[derive(Serialize, Deserialize)]
pub enum FsMsg<'a> {
    #[serde(borrow)]
    Lookup(Lookup<'a>),
    #[serde(borrow)]
    Create(Create<'a>),
    Open(Open),
    Read(Read),
    #[serde(borrow)]
    Write(Write<&'a [u8]>),
    Flush(Flush),
    ReadDir(ReadDir),
    #[serde(borrow)]
    Link(Link<'a>),
    #[serde(borrow)]
    Unlink(Unlink<'a>),
    ReadMeta(ReadMeta),
    WriteMeta(WriteMeta),
    Allocate(Allocate),
    Close(Close),
    Forget(Forget),
    Lock(Lock),
    Unlock(Unlock),
    AddReadcap(AddReadcap),
    GrantAccess(GrantAccess),
}

/// The type for every reply sent from servers to clients.
#[derive(Serialize, Deserialize)]
pub enum FsReply<'a> {
    /// Indicates a message was received successfully but does not provide any additional data.
    Ack(()),
    Lookup(LookupReply),
    Create(CreateReply),
    Open(OpenReply),
    #[serde(borrow)]
    Read(ReadReply<'a>),
    Write(WriteReply),
    ReadDir(ReadDirReply),
    Link(LinkReply),
    ReadMeta(ReadMetaReply),
    WriteMeta(WriteMetaReply),
}

impl<'a> CallMsg<'a> for FsMsg<'a> {
    type Reply<'b> = FsReply<'b>;
}

#[repr(u64)]
/// An enumeration of special Inodes.
pub enum SpecInodes {
    RootDir = 1,
    Sb = 2,
    FirstFree = 11,
}

impl SpecInodes {
    pub fn value(self) -> Inode {
        self as Inode
    }
}

impl From<SpecInodes> for Inode {
    fn from(special: SpecInodes) -> Self {
        special.value()
    }
}

#[derive(Debug, Clone, Hash, PartialEq, Eq, Serialize, Deserialize)]
#[repr(u32)] // This type needs to match `libc::mode_t`.
/// The type of a file (regular, directory, etc).
pub enum FileType {
    /// Directory.
    Dir = libc::S_IFDIR,
    /// Regular file.
    Reg = libc::S_IFREG,
}

impl FileType {
    /// Returns the underlying mode bits for this file type.
    pub fn value(self) -> libc::mode_t {
        self as libc::mode_t
    }

    /// Attempts to convert the given mode bits into a `FileType` enum value.
    pub fn from_value(value: libc::mode_t) -> btlib::Result<Self> {
        if (value & libc::S_IFDIR) != 0 {
            return Ok(FileType::Dir);
        }
        if (value & libc::S_IFREG) != 0 {
            return Ok(FileType::Reg);
        }
        Err(bterr!("unknown file type: 0o{value:0o}"))
    }

    pub fn dir_entry_kind(self) -> DirEntryKind {
        match self {
            Self::Dir => DirEntryKind::Directory,
            Self::Reg => DirEntryKind::File,
        }
    }
}

impl From<FileType> for libc::mode_t {
    fn from(file_type: FileType) -> Self {
        file_type.value()
    }
}

impl TryFrom<libc::mode_t> for FileType {
    type Error = btlib::Error;
    fn try_from(value: libc::mode_t) -> btlib::Result<Self> {
        Self::from_value(value)
    }
}

impl From<FileType> for DirEntryKind {
    fn from(value: FileType) -> Self {
        value.dir_entry_kind()
    }
}

impl BitOr<libc::mode_t> for FileType {
    type Output = libc::mode_t;
    fn bitor(self, rhs: libc::mode_t) -> Self::Output {
        self.value() | rhs
    }
}

#[derive(Debug, Clone, Hash, PartialEq, Eq, Serialize, Deserialize)]
#[repr(i32)]
/// The generators for the group of [Flags].
/// 
/// These are mostly values from libc, save for several custom values. Note that the presence of a
/// flag in this enum does not guarantee it's supported.
/// The standard libc `O_*` value which corresponds to each variant is given in the variant's
/// comment.
/// Consult your libc documentation for an explanation of what these means.
pub enum FlagValue {
    // Standard flags.
    /// `O_RDONLY`
    ReadOnly = libc::O_RDONLY,
    /// `O_WRONLY`
    WriteOnly = libc::O_WRONLY,
    /// `O_RDWR`
    ReadWrite = libc::O_RDWR,
    /// `O_ACCMODE`
    AccMode = libc::O_ACCMODE,
    /// `O_CREAT`
    Create = libc::O_CREAT,
    /// `O_EXCL`
    Exclusive = libc::O_EXCL,
    /// `O_NOCTTY`
    NoCtty = libc::O_NOCTTY,
    /// `O_TRUNC`
    Truncate = libc::O_TRUNC,
    /// `O_APPEND`
    Append = libc::O_APPEND,
    /// `O_NONBLOCK`
    NonBlock = libc::O_NONBLOCK,
    /// `O_DSYNC`
    Dsync = libc::O_DSYNC,
    /// `O_ASYNC`
    Async = libc::O_ASYNC,
    /// `O_DIRECT`
    Direct = libc::O_DIRECT,
    /// `O_DIRECTORY`
    Directory = libc::O_DIRECTORY,
    /// `O_NOFOLLOW`
    NoFollow = libc::O_NOFOLLOW,
    /// `O_NOATIME`
    NoAtime = libc::O_NOATIME,
    /// `O_CLOEXEC`
    CloseExec = libc::O_CLOEXEC,
    /// `O_RSYNC`
    Rsync = libc::O_RSYNC,
    /// `O_PATH`
    Path = libc::O_PATH,
    /// `O_TMPFILE`
    TmpFile = libc::O_TMPFILE,
    // Custom flags.
    /// Indicates that a process block should be created.
    Process = 0x01000000,
    /// Indicates that a server block should be created.
    Server = 0x02000000,
}

impl FlagValue {
    /// Returns the underlying [i32] value.
    pub const fn value(self) -> i32 {
        self as i32
    }
}

impl Copy for FlagValue {}

impl From<FlagValue> for i32 {
    fn from(flag_value: FlagValue) -> Self {
        flag_value.value()
    }
}

impl BitOr for FlagValue {
    type Output = Flags;
    fn bitor(self, rhs: Self) -> Self::Output {
        Flags::new(self.value() | rhs.value())
    }
}

#[derive(Debug, Clone, Hash, PartialEq, Eq, Serialize, Deserialize)]
/// A wrapper type around [i32] with convenience methods for checking if `libc::O_*`
/// flags have been set.
pub struct Flags(i32);

impl Copy for Flags {}

impl Flags {
    /// Wraps the given [i32] value.
    pub const fn new(value: i32) -> Self {
        Self(value)
    }

    /// Returns the inner [i32] value.
    pub const fn value(self) -> i32 {
        self.0
    }

    /// Returns true if these flags allow the file to be written to.
    pub const fn writeable(self) -> bool {
        const MASK: i32 = FlagValue::ReadWrite.value() | FlagValue::WriteOnly.value();
        self.0 & MASK != 0
    }

    /// Returns true if these flags allow the file to be read from.
    pub const fn readable(self) -> bool {
        !self.write_only()
    }

    /// Returns true if the file was opened readonly.
    pub const fn read_only(self) -> bool {
        self.0 == FlagValue::ReadOnly.value()
    }

    /// Returns true if the file was opened writeonly
    pub const fn write_only(self) -> bool {
        self.0 & FlagValue::WriteOnly.value() != 0
    }

    /// Returns true if these flags are for a directory.
    pub const fn directory(self) -> bool {
        self.0 & FlagValue::Directory.value() != 0
    }

    /// Returns true if these flags are for a process.
    pub const fn process(self) -> bool {
        self.0 & FlagValue::Process.value() != 0
    }

    /// Returns true if these flags are for a server.
    pub const fn server(self) -> bool {
        self.0 & FlagValue::Server.value() != 0
    }

    /// Asserts that these flags allow a file to be read.
    /// 
    /// If the assertion fails then an [io::Error] with the errno [libc::EACCES] is returned.
    pub fn assert_readable(self) -> Result<(), io::Error> {
        if !self.readable() {
            Err(io::Error::from_raw_os_error(libc::EACCES))
        } else {
            Ok(())
        }
    }

    /// Asserts that these flags allow a file to be written.
    /// 
    /// If the assertion fails then an [io::Error] with the errno [libc::EACCES] is returned.
    pub fn assert_writeable(self) -> Result<(), io::Error> {
        if !self.writeable() {
            Err(io::Error::from_raw_os_error(libc::EACCES))
        } else {
            Ok(())
        }
    }
}

impl From<i32> for Flags {
    fn from(value: i32) -> Self {
        Self::new(value)
    }
}

impl From<Flags> for i32 {
    fn from(flags: Flags) -> Self {
        flags.value()
    }
}

impl From<FlagValue> for Flags {
    fn from(flag_value: FlagValue) -> Self {
        Self::new(flag_value.value())
    }
}

impl BitOr<Flags> for Flags {
    type Output = Flags;
    fn bitor(self, rhs: Flags) -> Self::Output {
        Self::new(self.value() | rhs.value())
    }
}

impl BitOr<FlagValue> for Flags {
    type Output = Flags;
    fn bitor(self, rhs: FlagValue) -> Self::Output {
        Self::new(self.value() | rhs.value())
    }
}

impl Display for Flags {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        self.value().fmt(f)
    }
}

impl Default for Flags {
    fn default() -> Self {
        Self::new(0)
    }
}

/// Attributes of a file.
#[derive(Serialize, Deserialize, PartialEq, Eq, Clone, Hash, Default)]
pub struct Attrs {
    pub mode: u32,
    pub uid: u32,
    pub gid: u32,
    pub atime: Epoch,
    pub mtime: Epoch,
    pub ctime: Epoch,
    pub tags: Vec<(String, Vec<u8>)>,
}

#[derive(Serialize, Deserialize, PartialEq, Eq, Clone, Hash)]
/// A type for indicating which fields in [Attrs] have been set and which should be ignored.
/// 
/// This method was chosen over using [Option] for greater efficiency on the wire.
pub struct AttrsSet(u16);

macro_rules! field {
    ($index:expr, $name:ident) => {
        pub const $name: AttrsSet = AttrsSet::new(1 << $index);

        paste! {
            pub fn [<$name:lower>](self) -> bool {
                const MASK: u16 = 1 << $index;
                self.0 & MASK != 0
            }
        }
    };
}

impl AttrsSet {
    field!(0, MODE);
    field!(1, UID);
    field!(2, GID);
    field!(3, ATIME);
    field!(4, MTIME);
    field!(5, CTIME);

    pub const ALL: Self = Self::new(
        Self::MODE.0 | Self::UID.0 | Self::GID.0 | Self::ATIME.0 | Self::MTIME.0 | Self::CTIME.0,
    );

    pub const fn new(value: u16) -> Self {
        Self(value)
    }

    pub const fn none() -> Self {
        Self(0)
    }

    pub const fn value(self) -> u16 {
        self.0
    }
}

impl Copy for AttrsSet {}

impl From<u16> for AttrsSet {
    fn from(value: u16) -> Self {
        Self::new(value)
    }
}

impl From<AttrsSet> for u16 {
    fn from(attr: AttrsSet) -> Self {
        attr.value()
    }
}

impl BitOr<Self> for AttrsSet {
    type Output = Self;
    fn bitor(self, rhs: Self) -> Self::Output {
        AttrsSet::new(self.value() | rhs.value())
    }
}

impl BitOrAssign<Self> for AttrsSet {
    fn bitor_assign(&mut self, rhs: Self) {
        self.0 |= rhs.0
    }
}

/// A filesystem entry.
/// 
/// This struct includes attributes of a file as well as cache control
/// information for how long it may be cached.
#[derive(Debug, Serialize, Deserialize)]
pub struct Entry {
    pub attr: BlockMetaSecrets,
    pub attr_timeout: Duration,
    pub entry_timeout: Duration,
}

/// A request to lookup a name in a directory.
#[derive(Serialize, Deserialize)]
pub struct Lookup<'a> {
    pub parent: Inode,
    pub name: &'a str,
}

/// A reply containing the [Entry] stored under a name in a directory.
#[derive(Debug, Serialize, Deserialize)]
pub struct LookupReply {
    pub inode: Inode,
    pub generation: u64,
    pub entry: Entry,
}

/// A request to create a file in a directory under a given name.
#[derive(Serialize, Deserialize)]
pub struct Create<'a> {
    pub parent: Inode,
    pub name: &'a str,
    pub flags: Flags,
    pub mode: u32,
    pub umask: u32,
}

/// A reply containing information about a newly created file.
#[derive(Serialize, Deserialize)]
pub struct CreateReply {
    pub inode: Inode,
    pub handle: Handle,
    pub entry: Entry,
}

/// A request to hope a file.
#[derive(Serialize, Deserialize)]
pub struct Open {
    pub inode: Inode,
    pub flags: Flags,
}

/// A reply which contains a handle to an open file.
#[derive(Serialize, Deserialize)]
pub struct OpenReply {
    pub handle: Handle,
}

/// A request to read data at a particular offset from an open file.
#[derive(Serialize, Deserialize)]
pub struct Read {
    pub inode: Inode,
    pub handle: Handle,
    pub offset: u64,
    pub size: u64,
}

/// A reply containing data read from a file.
#[derive(Serialize, Deserialize)]
pub struct ReadReply<'a> {
    pub data: &'a [u8],
}

/// A request to write data to a particular offset in an open file.
#[derive(Serialize, Deserialize)]
pub struct Write<R> {
    pub inode: Inode,
    pub handle: Handle,
    pub offset: u64,
    pub data: R,
}

/// A reply containing the number of bytes written to a file.
#[derive(Serialize, Deserialize)]
pub struct WriteReply {
    pub written: u64,
}

/// A request to flush all data cached for an open file to durable storage.
#[derive(Serialize, Deserialize)]
pub struct Flush {
    pub inode: Inode,
    pub handle: Handle,
}

/// A request to read the contents of a directory.
#[derive(Serialize, Deserialize)]
pub struct ReadDir {
    pub inode: Inode,
    pub handle: Handle,
    /// The maximum number of directory entries to return in a single response. A value of 0
    /// indicates there is no limit. Note that the server may impose it's own limit.
    pub limit: u32,
    /// An opaque value which the server uses to keep track of the client's position in reading
    /// the directory. A value of 0 indicates the directory is to be iterated from the beginning.
    pub state: u64,
}

/// A reply containing the contents of a directory.
#[derive(Serialize, Deserialize)]
pub struct ReadDirReply {
    pub entries: Vec<(String, DirEntry)>,
    /// This is the value to pass in a subsequent [ReadDir] message to continue reading this
    /// directory. A value of 0 indicates that all entries have been returned.
    pub new_state: u64,
}

/// A request to create a new hard link to a file.
#[derive(Serialize, Deserialize)]
pub struct Link<'a> {
    pub inode: Inode,
    pub new_parent: Inode,
    pub name: &'a str,
}

/// A reply containing the [Entry] of the newly created hard link.
#[derive(Serialize, Deserialize)]
pub struct LinkReply {
    pub entry: Entry,
}

/// A request to remove a name referring to an inode.
/// 
/// If the inode becomes orphaned, it is removed from durable storage.
#[derive(Serialize, Deserialize)]
pub struct Unlink<'a> {
    pub parent: Inode,
    pub name: &'a str,
}

/// A request to read a file's metadata.
#[derive(Serialize, Deserialize)]
pub struct ReadMeta {
    pub inode: Inode,
    pub handle: Option<Handle>,
}

/// A reply containing the metadata of a file.
#[derive(Serialize, Deserialize)]
pub struct ReadMetaReply {
    pub attrs: BlockMetaSecrets,
    pub valid_for: Duration,
}

/// A request to write the metadata of a file.
#[derive(Serialize, Deserialize)]
pub struct WriteMeta {
    pub inode: Inode,
    pub handle: Option<Handle>,
    pub attrs: Attrs,
    /// The bits in this value indicate which fields in `attrs` have been initialized.
    pub attrs_set: AttrsSet,
}

/// A reply containing the newly written file metadata.
#[derive(Serialize, Deserialize)]
pub struct WriteMetaReply {
    pub attrs: BlockMetaSecrets,
    pub valid_for: Duration,
}

/// A request to pre-allocate a given amount of space from durable storage for a file.
#[derive(Serialize, Deserialize)]
pub struct Allocate {
    pub inode: Inode,
    pub handle: Handle,
    pub offset: Option<u64>,
    pub size: u64,
}

/// A request to close an open file.
#[derive(Serialize, Deserialize)]
pub struct Close {
    pub inode: Inode,
    pub handle: Handle,
}

/// A request to forget about an inode which was previously referenced.
/// 
/// This message must be sent
/// so the server knows when it can free resources associated with the inode.
/// If `N` [Entry] structs are sent in a reply to [Lookup] messages, then the caller must send one
/// or more [Forget] messages such that their `count` fields add up to `N`.
#[derive(Serialize, Deserialize)]
pub struct Forget {
    pub inode: Inode,
    pub count: u64,
}

/// The description of a region in a file to lock.
#[derive(Serialize, Deserialize)]
pub struct LockDesc {
    pub offset: u64,
    pub size: u64,
    pub exclusive: bool,
}

/// A request to lock a region of a file.
#[derive(Serialize, Deserialize)]
pub struct Lock {
    pub inode: Inode,
    pub handle: Handle,
    pub desc: LockDesc,
}

/// A request to unlock a region of a file.
#[derive(Serialize, Deserialize)]
pub struct Unlock {
    pub inode: Inode,
    pub handle: Handle,
}

/// A request to add a [btlib::Readcap] to a file.
#[derive(Serialize, Deserialize)]
pub struct AddReadcap {
    pub inode: Inode,
    pub handle: Handle,
    pub pub_creds: ConcretePub,
}

/// A request to give a process access to an inode.
#[derive(Serialize, Deserialize)]
pub struct GrantAccess {
    pub inode: Inode,
    pub record: IssuedProcRec,
}