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#![cfg(target_os = "linux")]

//! # tokio-udev
//!
//! This library implements an stream of device events from `udev`
//! asynchronously.
//!
//! # Usage
//!
//! First put the dependency on your crate's `Cargo.toml`. For example:
//!
//! ```toml
//! [dependencies]
//! tokio-udev = "0.1"
//! ```
//!
//! Then import it in your crate root as:
//!
//! ```rust
//! extern crate tokio_udev;
//! ```

extern crate libc;

extern crate mio;
extern crate mio_udev;

extern crate futures;
extern crate tokio_reactor;

pub use mio_udev::{Attribute, Attributes, Context, Device, Event, EventType,
                   Property, Properties, UdevError};

use std::io;
use std::ffi::OsStr;
use std::sync::Mutex;

use tokio_reactor::PollEvented;
use futures::{Async, Poll, stream::Stream};

/// Monitors for device events.
///
/// A monitor communicates with the kernel over a socket. Filtering events is
/// performed efficiently in the kernel, and only events that match the filters
/// are received by the socket. Filters must be setup before listening for
/// events.
pub struct MonitorBuilder {
    builder: mio_udev::MonitorBuilder,
}

impl MonitorBuilder {
    /// Creates a new `MonitorSocket`.
    #[inline(always)]
    pub fn new(context: &mio_udev::Context) -> io::Result<Self> {
        Ok(MonitorBuilder { builder: mio_udev::MonitorBuilder::new(context)? })
    }

    /// Adds a filter that matches events for devices with the given subsystem.
    #[inline(always)]
    pub fn match_subsystem<T>(&mut self, subsystem: T) -> io::Result<()>
        where T: AsRef<OsStr>,
    {
        Ok(self.builder.match_subsystem::<T>(subsystem)?)
    }

    /// Adds a filter that matches events for devices with the given subsystem
    /// and device type.
    #[inline(always)]
    pub fn match_subsystem_devtype<T, U>(&mut self,
                                         subsystem: T,
                                         devtype: U) -> io::Result<()>
        where T: AsRef<OsStr>,
              U: AsRef<OsStr>,
    {
        Ok(self.builder.match_subsystem_devtype::<T, U>(subsystem, devtype)?)
    }

    /// Adds a filter that matches events for devices with the given tag.
    #[inline(always)]
    pub fn match_tag<T>(&mut self, tag: T) -> io::Result<()>
        where T: AsRef<OsStr>,
    {
        Ok(self.builder.match_tag::<T>(tag)?)
    }

    /// Removes all filters currently set on the monitor.
    #[inline(always)]
    pub fn clear_filters(&mut self) -> io::Result<()> {
        Ok(self.builder.clear_filters()?)
    }

    /// Listens for events matching the current filters.
    ///
    /// This method consumes the `MonitorBuilder`.
    pub fn listen(self) -> io::Result<MonitorSocket> {
        Ok(MonitorSocket::new(self.builder.listen()?))
    }
}

/// Asynchronous stream of device events.
pub struct MonitorSocket {
    inner: Mutex<Inner>,
}

impl MonitorSocket {
    fn new(monitor: mio_udev::MonitorSocket) -> MonitorSocket {
        MonitorSocket { inner: Mutex::new(Inner::new(monitor)), }
    }
}

unsafe impl Send for MonitorSocket {}
unsafe impl Sync for MonitorSocket {}

impl Stream for MonitorSocket {
    type Item = mio_udev::Event;
    type Error = io::Error;

    fn poll(&mut self) -> Poll<Option<Self::Item>, Self::Error> {
        self.inner.lock().unwrap().poll_receive()
    }
}

struct Inner {
    io: PollEvented<mio_udev::MonitorSocket>,
}

impl Inner {
    fn new(monitor: mio_udev::MonitorSocket) -> Inner {
        Inner { io: PollEvented::new(monitor), }
    }

    fn poll_receive(&mut self) -> Poll<Option<mio_udev::Event>, io::Error> {
        if let Async::NotReady = self.io.poll_read_ready(mio::Ready::readable())? {
            return Ok(Async::NotReady);
        }

        match self.io.get_mut().next() {
            Some(device) => Ok(Async::Ready(Some(device))),
            None => {
                self.io.clear_read_ready(mio::Ready::readable())?;
                Ok(Async::NotReady)
            },
        }

    }
}