/// 文件打开标志（映射 SSH_FXF_* 和 POSIX open flags）
#[derive(Debug, Clone, Default)]
pub struct OpenFlags {
    pub read: bool,
    pub write: bool,
    pub append: bool,
    pub create: bool,
    pub truncate: bool,
    pub exclusive: bool,
    pub mode: u32,
}

impl OpenFlags {
    pub fn new() -> Self {
        Self::default()
    }

    pub fn read(mut self) -> Self {
        self.read = true;
        self
    }

    pub fn write(mut self) -> Self {
        self.write = true;
        self
    }

    pub fn append(mut self) -> Self {
        self.append = true;
        self.write = true;
        self
    }

    pub fn create(mut self) -> Self {
        self.create = true;
        self.write = true;
        self
    }

    pub fn truncate(mut self) -> Self {
        self.truncate = true;
        self.write = true;
        self
    }

    pub fn exclusive(mut self) -> Self {
        self.exclusive = true;
        self
    }

    pub fn mode(mut self, mode: u32) -> Self {
        self.mode = mode;
        self
    }

    /// 从 SFTP 的 pflags（SSH_FXF_*）构建 OpenFlags
    pub fn from_sftp_pflags(pflags: u32) -> Self {
        let read = pflags & 0x00000001 != 0;
        let write = pflags & 0x00000002 != 0;
        let append = pflags & 0x00000004 != 0;
        let create = pflags & 0x00000008 != 0;
        let truncate = pflags & 0x00000010 != 0;
        let exclusive = pflags & 0x00000020 != 0;

        Self {
            read,
            write,
            append,
            create,
            truncate,
            exclusive,
            mode: 0o644,
        }
    }
}