vahanafs/src/fs/permission.rs

use char_enum::{char_enum_derive::FromChar, AsIter, FromChar, FromStrError, ToChar};
use enumflags2::{bitflags, BitFlag, BitFlags, FromBitsError};
use std::{error::Error, fmt::Display, num::ParseIntError, ops::BitOr, str::FromStr};

use crate::utils::MapWhileRefExt;

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct ParseModeError(String);

impl ParseModeError {
    pub fn from_bits(bits: &str) -> Self {
        Self(format!("invalid mode: `{bits}`"))
    }
}

impl Display for ParseModeError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.0)
    }
}

impl Error for ParseModeError {}

impl From<ParseIntError> for ParseModeError {
    fn from(value: ParseIntError) -> Self {
        Self(value.to_string())
    }
}

impl From<FromBitsError<Mode>> for ParseModeError {
    fn from(value: FromBitsError<Mode>) -> Self {
        Self::from_bits(&value.invalid_bits().to_string())
    }
}

#[bitflags]
#[repr(u16)]
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum Mode {
    IXOTH = 0x0001,
    IWOTH = 0x0002,
    IROTH = 0x0004,
    IXGRP = 0x0010,
    IWGRP = 0x0020,
    IRGRP = 0x0040,
    IXUSR = 0x0100,
    IWUSR = 0x0200,
    IRUSR = 0x0400,
    ISVTX = 0x1000,
    ISGID = 0x2000,
    ISUID = 0x4000,
}

impl Display for Mode {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self)
    }
}

#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
pub struct ModeFlags(BitFlags<Mode>);

impl FromStr for ModeFlags {
    type Err = ParseModeError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let bits = u16::from_str_radix(s, 16)?;

        Ok(Self(BitFlags::from_bits(bits)?))
    }
}

impl Display for ModeFlags {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{:X}", self.0)
    }
}

impl TryFrom<u16> for ModeFlags {
    type Error = FromBitsError<Mode>;

    fn try_from(value: u16) -> Result<Self, Self::Error> {
        Ok(Self(BitFlags::from_bits(value)?))
    }
}

impl From<BitFlags<Mode>> for ModeFlags {
    fn from(value: BitFlags<Mode>) -> Self {
        Self(value)
    }
}

#[derive(Clone, Copy, Debug, FromChar, PartialEq, Eq)]
pub enum Operator {
    #[value = "-"]
    Sub,
    #[value = "+"]
    Add,
    #[value = "="]
    Eq,
}

impl Operator {
    pub fn split(s: &str) -> Option<(&str, char, &str)> {
        let mut result = None;

        for d in Operator::iter() {
            if let Some((a, b)) = s.split_once(d) {
                result = Some((a, d, b));
                break;
            }
        }

        result
    }
}

#[bitflags]
#[repr(u8)]
#[derive(Clone, Copy, Debug, FromChar, PartialEq, Eq)]
pub enum SymbolicMode {
    #[value = 'r']
    Read,
    #[value = 'w']
    Write,
    #[value = 'x']
    Execute,
    #[value = 'X']
    Search,
    #[value = 's']
    SetId,
    #[value = 't']
    Sticky,
}

#[bitflags]
#[repr(u8)]
#[derive(Clone, Copy, Debug, FromChar, PartialEq, Eq)]
pub enum GroupId {
    #[value = 'u']
    User,
    #[value = 'g']
    Group,
    #[value = 'o']
    Other,
}

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct Modes<T: BitFlag>(BitFlags<T>);

impl<T: BitFlag> Default for Modes<T> {
    fn default() -> Self {
        Modes(BitFlags::<T>::default())
    }
}

impl<T: BitFlag + FromChar> FromStr for Modes<T> {
    type Err = FromStrError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let flags = s
            .chars()
            .map_while_ref(|c: &char| T::from_char(*c))
            .fold(BitFlags::default(), BitOr::bitor);

        Ok(Self(flags))
    }
}

impl<T: BitFlag + Display> Display for Modes<T> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let mut iter = self.0.iter();
        if let Some(head) = iter.next() {
            write!(f, "{head}")?;

            for item in iter {
                write!(f, "{item}")?;
            }
        }

        Ok(())
    }
}

#[derive(Clone, Debug, PartialEq)]
pub struct ParseSymbolicArgsError(FromStrError);

impl Display for ParseSymbolicArgsError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.0)
    }
}

impl Error for ParseSymbolicArgsError {}

impl From<ParseSymbolicArgsError> for FromStrError {
    fn from(value: ParseSymbolicArgsError) -> Self {
        value.0
    }
}

impl From<FromStrError> for ParseSymbolicArgsError {
    fn from(value: FromStrError) -> Self {
        Self(value)
    }
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub enum SymbolicArgs {
    Group(Modes<GroupId>),
    Mode(Modes<SymbolicMode>),
}

impl FromStr for SymbolicArgs {
    type Err = ParseSymbolicArgsError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        match Modes::<SymbolicMode>::from_str(s) {
            Ok(perms) => Ok(Self::Mode(perms)),
            Err(_) => match Modes::<GroupId>::from_str(s) {
                Ok(perms) => Ok(Self::Group(perms)),
                Err(_) => Err(FromStrError::new(format!("{} is not a valid argument", s)).into()),
            },
        }
    }
}

impl Display for SymbolicArgs {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            SymbolicArgs::Group(modes) => write!(f, "{modes}"),
            SymbolicArgs::Mode(modes) => write!(f, "{modes}"),
        }
    }
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub enum ParseSymbolicError {
    Group(String),
    Operator(String),
    Mode(String),
}

impl Display for ParseSymbolicError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(
            f,
            "{}",
            match self {
                Self::Group(e) => e,
                Self::Operator(e) => e,
                Self::Mode(e) => e,
            }
        )
    }
}

impl Error for ParseSymbolicError {}

impl From<ParseSymbolicArgsError> for ParseSymbolicError {
    fn from(value: ParseSymbolicArgsError) -> Self {
        Self::Mode(value.to_string())
    }
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct SymbolicPermissions {
    groups: Modes<GroupId>,
    operator: Operator,
    mode: SymbolicArgs,
}

impl SymbolicPermissions {
    pub fn new(groups: Modes<GroupId>, operator: Operator, mode: SymbolicArgs) -> Self {
        Self {
            groups,
            operator,
            mode,
        }
    }
}

impl FromStr for SymbolicPermissions {
    type Err = ParseSymbolicError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        match Operator::split(s) {
            Some((groups, operator, mode)) => {
                let groups =
                    Modes::from_str(groups).map_err(|e| ParseSymbolicError::Group(e.to_string()));

                let operator = Operator::from_char(operator)
                    .map_err(|o| ParseSymbolicError::Operator(o.to_string()));

                let mode = SymbolicArgs::from_str(mode)?;

                Ok(Self::new(groups?, operator?, mode))
            }
            None => Err(ParseSymbolicError::Operator(format!(
                "received invalid permission syntax: {s}"
            ))),
        }
    }
}

impl Display for SymbolicPermissions {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}{}{}", self.groups, self.operator, self.mode)
    }
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct ParseOctalError(String);

impl Display for ParseOctalError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.0)
    }
}

impl Error for ParseOctalError {}

impl From<ParseModeError> for ParseOctalError {
    fn from(value: ParseModeError) -> Self {
        Self(value.0)
    }
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub struct OctalPermissions(ModeFlags);

impl Display for OctalPermissions {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.0)
    }
}

impl FromStr for OctalPermissions {
    type Err = ParseOctalError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        Ok(Self(ModeFlags::from_str(s)?))
    }
}

impl TryFrom<u16> for OctalPermissions {
    type Error = FromBitsError<Mode>;

    fn try_from(value: u16) -> Result<Self, Self::Error> {
        Ok(Self(ModeFlags::try_from(value)?))
    }
}

impl From<BitFlags<Mode>> for OctalPermissions {
    fn from(value: BitFlags<Mode>) -> Self {
        Self(value.into())
    }
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub enum ParsePermissionsError {
    Symbolic(ParseSymbolicError),
    Octal(ParseOctalError),
}

impl Display for ParsePermissionsError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            ParsePermissionsError::Symbolic(e) => write!(f, "{e}"),
            ParsePermissionsError::Octal(e) => write!(f, "{e}"),
        }
    }
}

impl Error for ParsePermissionsError {}

impl From<ParseSymbolicError> for ParsePermissionsError {
    fn from(value: ParseSymbolicError) -> Self {
        Self::Symbolic(value)
    }
}

impl From<ParseOctalError> for ParsePermissionsError {
    fn from(value: ParseOctalError) -> Self {
        Self::Octal(value)
    }
}

#[derive(Clone, Debug, PartialEq, Eq)]
pub enum Permissions {
    Symbolic(SymbolicPermissions),
    Octal(OctalPermissions),
}

impl FromStr for Permissions {
    type Err = ParsePermissionsError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        Ok(SymbolicPermissions::from_str(s)
            .map(Self::Symbolic)
            .or_else(|_| OctalPermissions::from_str(s).map(Self::Octal))?)
    }
}

impl Display for Permissions {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Permissions::Symbolic(v) => write!(f, "{v}"),
            Permissions::Octal(v) => write!(f, "{v}"),
        }
    }
}

#[cfg(test)]
mod tests {
    use std::str::FromStr;

    use enumflags2::BitFlags;

    use crate::fs::permission::{
        GroupId, Modes, Operator, SymbolicArgs, SymbolicMode, SymbolicPermissions,
    };

    use super::{ModeFlags, Permissions};

    #[test]
    fn mode_flags() {
        let flags = ModeFlags(BitFlags::all());
        assert_eq!(flags.to_string(), "7777");
    }

    #[test]
    fn symbolic_permissions() {
        let sym = Permissions::from_str("ug+w").unwrap();
        let group_sym = Permissions::from_str("g=u").unwrap();

        assert_eq!(
            sym,
            Permissions::Symbolic(SymbolicPermissions::new(
                Modes(GroupId::User | GroupId::Group),
                Operator::Add,
                SymbolicArgs::Mode(Modes(BitFlags::from(SymbolicMode::Write)))
            ))
        );

        assert_eq!(
            group_sym,
            Permissions::Symbolic(SymbolicPermissions::new(
                Modes(GroupId::Group.into()),
                Operator::Eq,
                SymbolicArgs::Group(Modes(BitFlags::from(GroupId::User)))
            ))
        );
    }
}