pub const PermissionsUnix = struct {
    mode: Mode,

    const Self = @This();

    /// Returns `true` if permissions represent an unwritable file.
    /// `true` is returned only if no class has write permissions.
    pub fn readOnly(self: Self) bool {
        return self.mode & 0o222 == 0;
    }

    /// Sets whether write permissions are provided.
    /// This affects *all* classes. If this is undesired, use `unixSet`.
    /// This method *DOES NOT* set permissions on the filesystem: use `File.setPermissions(permissions)`
    pub fn setReadOnly(self: *Self, read_only: bool) void {
        if (read_only) {
            self.mode &= ~@as(Mode, 0o222);
        } else {
            self.mode |= @as(Mode, 0o222);
        }
    }

    pub const Class = enum(u2) {
        user = 2,
        group = 1,
        other = 0,
    };

    pub const Permission = enum(u3) {
        read = 0o4,
        write = 0o2,
        execute = 0o1,
    };

    /// Returns `true` if the chosen class has the selected permission.
    /// This method is only available on Unix platforms.
    pub fn unixHas(self: Self, class: Class, permission: Permission) bool {
        const mask = @as(Mode, @intFromEnum(permission)) << @as(u3, @intFromEnum(class)) * 3;
        return self.mode & mask != 0;
    }

    /// Sets the permissions for the chosen class. Any permissions set to `null` are left unchanged.
    /// This method *DOES NOT* set permissions on the filesystem: use `File.setPermissions(permissions)`
    pub fn unixSet(self: *Self, class: Class, permissions: struct {
        read: ?bool = null,
        write: ?bool = null,
        execute: ?bool = null,
    }) void {
        const shift = @as(u3, @intFromEnum(class)) * 3;
        if (permissions.read) |r| {
            if (r) {
                self.mode |= @as(Mode, 0o4) << shift;
            } else {
                self.mode &= ~(@as(Mode, 0o4) << shift);
            }
        }
        if (permissions.write) |w| {
            if (w) {
                self.mode |= @as(Mode, 0o2) << shift;
            } else {
                self.mode &= ~(@as(Mode, 0o2) << shift);
            }
        }
        if (permissions.execute) |x| {
            if (x) {
                self.mode |= @as(Mode, 0o1) << shift;
            } else {
                self.mode &= ~(@as(Mode, 0o1) << shift);
            }
        }
    }

    /// Returns a `Permissions` struct representing the permissions from the passed mode.
    pub fn unixNew(new_mode: Mode) Self {
        return Self{
            .mode = new_mode,
        };
    }
}