/// An actual current process may expose a bounded, owner-checked user range
/// to a kernel-owned buffer. No external output is part of this operation.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum GuestCopyError {
    Fault,
    Context,
    Owner,
}

pub trait GuestCopyBackend: GuestLaunchBackend {
    fn copy_current_user_data(
        &self,
        bag: &Self::Bag,
        id: ProcessId,
        address: u64,
        output: &mut [u8],
    ) -> Result<(), GuestCopyError>;
}

impl<B: GuestCopyBackend, const N: usize> Table<B, N> {
    pub fn copy_current_user_data(
        &self,
        id: ProcessId,
        address: u64,
        output: &mut [u8],
    ) -> Result<(), GuestCopyError> {
        let before = self.gate().map_err(|_| GuestCopyError::Context)?;
        if before.current != Some(id) || before.kernel_bootstrap {
            return Err(GuestCopyError::Context);
        }
        self.current_launch(id)
            .map_err(|_| GuestCopyError::Context)?;
        let index = self.public_index(id).map_err(|_| GuestCopyError::Owner)?;
        let entry = &self.entries[index];
        if entry.phase != Phase::Published {
            return Err(GuestCopyError::Owner);
        }
        let bag = entry.bag.as_ref().ok_or(GuestCopyError::Owner)?;
        self.backend()
            .copy_current_user_data(bag, id, address, output)?;
        if self.gate() != Ok(before) {
            return Err(GuestCopyError::Context);
        }
        Ok(())
    }
}