lamco-data-control 1.0.1

//! The public clipboard handle.

use std::{
    collections::HashMap,
    io::{Read, Write},
    os::{
        fd::OwnedFd,
        unix::{io::AsFd, net::UnixStream},
    },
    sync::{
        Arc, Mutex, MutexGuard,
        atomic::{AtomicBool, Ordering},
        mpsc,
    },
    thread::JoinHandle,
    time::Duration,
};

use nix::poll::{PollFd, PollFlags, PollTimeout, poll};

use crate::{
    error::{Error, Result},
    mime::find_mime_match,
    options::{Options, Protocol},
    state::{Command, Shared},
    worker,
};

/// How long a read waits for the source to deliver more data.
const READ_IDLE_TIMEOUT: Duration = Duration::from_secs(5);

/// What to offer as the clipboard selection.
///
/// Each MIME type is either given data up front with [`data`](Self::data), or
/// only advertised with [`advertise`](Self::advertise). A paste of an
/// advertised type with no data raises a [`TransferRequest`], which the owner
/// answers later. That is delayed rendering: the data is produced only if
/// something pastes it.
#[derive(Debug, Clone, Default)]
pub struct Content {
    mime_types: Vec<String>,
    data: HashMap<String, Vec<u8>>,
}

impl Content {
    /// Empty content.
    #[must_use]
    pub fn new() -> Self {
        Self::default()
    }

    /// Offer `mime_type` with its data.
    #[must_use]
    pub fn data(mut self, mime_type: impl Into<String>, data: impl Into<Vec<u8>>) -> Self {
        let mime_type = mime_type.into();
        self.push_type(&mime_type);
        self.data.insert(mime_type, data.into());
        self
    }

    /// Offer `mime_type` without data; pastes of it raise a [`TransferRequest`].
    #[must_use]
    pub fn advertise(mut self, mime_type: impl Into<String>) -> Self {
        self.push_type(&mime_type.into());
        self
    }

    fn push_type(&mut self, mime_type: &str) {
        if !self.mime_types.iter().any(|m| m == mime_type) {
            self.mime_types.push(mime_type.to_owned());
        }
    }
}

/// Channel to the worker thread: a command queue and a socket that wakes its
/// poll loop.
struct Link {
    commands: mpsc::Sender<Command>,
    wake: UnixStream,
}

impl Link {
    fn send(&self, command: Command) -> Result<()> {
        self.commands.send(command).map_err(|_| Error::Stopped)?;
        self.notify();
        Ok(())
    }

    fn notify(&self) {
        // A full socket buffer means a wake-up is already pending.
        let _ = (&self.wake).write(&[1]);
    }
}

/// A paste waiting for data that was advertised without any.
///
/// Answer it with [`complete`](Self::complete), or [`fail`](Self::fail) if the
/// data cannot be produced. Dropping it without answering leaves the paste
/// waiting until the selection is replaced.
#[derive(Debug)]
#[must_use = "a paste stays open until the request is answered"]
pub struct TransferRequest {
    serial: u32,
    mime_type: String,
    link: Arc<Link>,
}

impl std::fmt::Debug for Link {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("Link").finish_non_exhaustive()
    }
}

impl TransferRequest {
    /// The MIME type being pasted.
    #[must_use]
    pub fn mime_type(&self) -> &str {
        &self.mime_type
    }

    /// Supply the data. It is written to every paste of this type that is
    /// waiting, and cached for later pastes.
    ///
    /// # Errors
    ///
    /// [`Error::Stopped`] if the clipboard worker has shut down.
    pub fn complete(self, data: impl Into<Vec<u8>>) -> Result<()> {
        self.link.send(Command::CompleteTransfer {
            serial: self.serial,
            data: Some(data.into()),
        })
    }

    /// Close the waiting pastes with no data.
    ///
    /// # Errors
    ///
    /// [`Error::Stopped`] if the clipboard worker has shut down.
    pub fn fail(self) -> Result<()> {
        self.link.send(Command::CompleteTransfer {
            serial: self.serial,
            data: None,
        })
    }
}

/// A connection to the Wayland compositor's clipboard.
///
/// Connecting spawns one thread that owns the Wayland connection. Dropping the
/// handle stops and joins it.
///
/// ```no_run
/// use lamco_data_control::{Content, DataControl};
///
/// # fn main() -> lamco_data_control::Result<()> {
/// let clipboard = DataControl::connect()?;
/// clipboard.set_selection(Content::new().data("text/plain;charset=utf-8", "hello"))?;
/// # Ok(())
/// # }
/// ```
pub struct DataControl {
    link: Arc<Link>,
    shared: Arc<Mutex<Shared>>,
    protocol: Protocol,
    max_read_bytes: usize,
    stop: Arc<AtomicBool>,
    thread: Option<JoinHandle<()>>,
}

impl std::fmt::Debug for DataControl {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("DataControl")
            .field("protocol", &self.protocol)
            .finish_non_exhaustive()
    }
}

impl DataControl {
    /// Connect with the default [`Options`].
    ///
    /// # Errors
    ///
    /// See [`Error`]: no compositor, no data-control protocol, or no seat.
    pub fn connect() -> Result<Self> {
        Self::connect_with(&Options::new())
    }

    /// Connect with explicit options.
    ///
    /// # Errors
    ///
    /// See [`Error`]: no compositor, no data-control protocol, or no seat.
    pub fn connect_with(options: &Options) -> Result<Self> {
        let (command_tx, command_rx) = mpsc::channel();
        let (wake_tx, wake_rx) = UnixStream::pair()?;
        wake_tx.set_nonblocking(true)?;
        wake_rx.set_nonblocking(true)?;
        let stop = Arc::new(AtomicBool::new(false));
        let (ready_tx, ready_rx) = mpsc::sync_channel(1);

        let thread_options = options.clone();
        let thread_stop = Arc::clone(&stop);
        let thread = std::thread::Builder::new()
            .name("lamco-data-control".into())
            .spawn(move || {
                match worker::connect(&thread_options, command_rx, wake_rx, thread_stop) {
                    Ok((worker, connected)) => {
                        if ready_tx.send(Ok(connected)).is_ok() {
                            worker.run();
                        }
                    }
                    Err(error) => {
                        let _ = ready_tx.send(Err(error));
                    }
                }
            })?;

        let connected = match ready_rx.recv() {
            Ok(Ok(connected)) => connected,
            Ok(Err(error)) => {
                let _ = thread.join();
                return Err(error);
            }
            Err(_) => {
                let _ = thread.join();
                return Err(Error::Stopped);
            }
        };

        Ok(Self {
            link: Arc::new(Link {
                commands: command_tx,
                wake: wake_tx,
            }),
            shared: connected.shared,
            protocol: connected.protocol,
            max_read_bytes: options.max_read_bytes,
            stop,
            thread: Some(thread),
        })
    }

    /// The protocol the compositor is speaking.
    #[must_use]
    pub fn protocol(&self) -> Protocol {
        self.protocol
    }

    fn shared(&self) -> MutexGuard<'_, Shared> {
        self.shared
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner)
    }

    /// MIME types the current selection offers; empty if there is none.
    #[must_use]
    pub fn selection_mime_types(&self) -> Vec<String> {
        self.shared().mime_types.clone()
    }

    /// A counter that increases on every selection change.
    #[must_use]
    pub fn serial(&self) -> u32 {
        self.shared().serial
    }

    /// Call `callback` with the offered MIME types whenever another client
    /// changes the selection.
    ///
    /// A selection this handle set itself is not reported; it still advances
    /// [`serial`](Self::serial) and updates
    /// [`selection_mime_types`](Self::selection_mime_types).
    ///
    /// The callback runs on the worker thread and must not block.
    pub fn on_change(&self, callback: impl Fn(Vec<String>) + Send + Sync + 'static) {
        self.shared().on_change = Some(Arc::new(callback));
    }

    /// Call `callback` when something pastes a type that was advertised
    /// without data.
    ///
    /// The callback runs on the worker thread and must not block; hand the
    /// request to another thread and answer it there.
    pub fn on_transfer(&self, callback: impl Fn(TransferRequest) + Send + Sync + 'static) {
        let link = Arc::clone(&self.link);
        self.shared().on_transfer = Some(Arc::new(move |serial, mime_type| {
            callback(TransferRequest {
                serial,
                mime_type,
                link: Arc::clone(&link),
            });
        }));
    }

    /// Become the clipboard owner and offer `content`.
    ///
    /// # Errors
    ///
    /// [`Error::Stopped`] if the worker has shut down.
    pub fn set_selection(&self, content: Content) -> Result<()> {
        self.link.send(Command::SetSelection {
            mime_types: content.mime_types,
            data: content.data,
        })
    }

    /// Add data for a type after [`set_selection`](Self::set_selection),
    /// without replacing the selection.
    ///
    /// # Errors
    ///
    /// [`Error::Stopped`] if the worker has shut down.
    pub fn update_data(
        &self,
        mime_type: impl Into<String>,
        data: impl Into<Vec<u8>>,
    ) -> Result<()> {
        self.link.send(Command::UpdateSourceData {
            mime_type: mime_type.into(),
            data: data.into(),
        })
    }

    /// Give up the selection if this handle still owns it.
    ///
    /// # Errors
    ///
    /// [`Error::Stopped`] if the worker has shut down.
    pub fn clear_selection(&self) -> Result<()> {
        self.link.send(Command::ClearSelection)
    }

    /// Read the current selection as `mime_type`.
    ///
    /// Charset differences are tolerated, see [`find_mime_match`]. Returns
    /// `Ok(None)` when there is no selection or it does not offer the type.
    ///
    /// # Errors
    ///
    /// [`Error::TooLarge`] past the size limit, [`Error::Timeout`] if the
    /// source stalls for five seconds, [`Error::Stopped`] if the worker has
    /// shut down, [`Error::Io`] for pipe failures.
    pub fn read(&self, mime_type: &str) -> Result<Option<Vec<u8>>> {
        let available = self.selection_mime_types();
        let Some(matched) = find_mime_match(mime_type, &available) else {
            return Ok(None);
        };

        let (mut reader, writer) = std::io::pipe()?;
        self.link.send(Command::ReceiveFromOffer {
            mime_type: matched.to_owned(),
            fd: OwnedFd::from(writer),
        })?;

        let mut data = Vec::new();
        let mut chunk = vec![0u8; 64 * 1024];
        loop {
            let mut fds = [PollFd::new(reader.as_fd(), PollFlags::POLLIN)];
            let timeout = PollTimeout::try_from(READ_IDLE_TIMEOUT).unwrap_or(PollTimeout::NONE);
            match poll(&mut fds, timeout) {
                Ok(0) => return Err(Error::Timeout),
                Ok(_) => {}
                Err(nix::errno::Errno::EINTR) => continue,
                Err(errno) => return Err(std::io::Error::from(errno).into()),
            }
            match reader.read(&mut chunk) {
                // The writer closed: the source has sent everything.
                Ok(0) => return Ok(Some(data)),
                Ok(n) => {
                    if data.len() + n > self.max_read_bytes {
                        return Err(Error::TooLarge {
                            size: data.len() + n,
                            limit: self.max_read_bytes,
                        });
                    }
                    data.extend_from_slice(&chunk[..n]);
                }
                Err(error) if error.kind() == std::io::ErrorKind::Interrupted => {}
                Err(error) => return Err(error.into()),
            }
        }
    }
}

impl Drop for DataControl {
    fn drop(&mut self) {
        self.stop.store(true, Ordering::Relaxed);
        self.link.notify();
        if let Some(thread) = self.thread.take() {
            let _ = thread.join();
        }
    }
}