audrey/src/mpv.rs

mod ffi;

use std::ffi::{c_int, c_void, CStr, CString};

#[link(name = "mpv")]
extern "C" {}

pub struct Error(c_int);

impl Error {
    fn from_return_code(rc: c_int) -> Result<(), Self> {
        if rc == 0 {
            Ok(())
        } else {
            Err(Self(rc))
        }
    }
}

impl std::fmt::Debug for Error {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
        f.debug_tuple("Error")
            .field(unsafe { &CStr::from_ptr(ffi::mpv_error_string(self.0 as c_int)) })
            .finish()
    }
}

use std::pin::Pin;
use std::ptr::NonNull;

pub struct Handle {
    inner: NonNull<ffi::mpv_handle>,
    _wakeup_send: Pin<Box<async_channel::Sender<()>>>, // the wakeup callback controls this one
    wakeup_recv: async_channel::Receiver<()>,

    observed_property_callbacks:
        Vec<Pin<Box<Box<dyn FnMut(ffi::mpv_format, *mut c_void) + 'static>>>>,
}

// The client API is generally fully thread-safe, unless otherwise noted.
unsafe impl Send for Handle {}
unsafe impl Sync for Handle {}

impl Default for Handle {
    fn default() -> Self {
        Self::create()
    }
}

impl Handle {
    pub fn create() -> Self {
        let inner =
            NonNull::new(unsafe { ffi::mpv_create() }).expect("could not create mpv handle");

        let (wakeup_send, wakeup_recv) = async_channel::bounded(1);
        let wakeup_send = Box::pin(wakeup_send);

        extern "C" fn wakeup_callback(d: *mut c_void) {
            let d = d as *const async_channel::Sender<()>;
            let wakeup_send = unsafe { &*d };
            match wakeup_send.try_send(()) {
                Ok(()) => {}
                Err(async_channel::TrySendError::Full(())) => {
                    // assume the main thread has already been notified
                }
                Err(async_channel::TrySendError::Closed(())) => {
                    panic!("wakeup channgel was closed before mpv handle was finalized");
                }
            }
        }
        unsafe {
            ffi::mpv_set_wakeup_callback(
                inner.as_ptr(),
                Some(wakeup_callback),
                std::ptr::from_ref::<async_channel::Sender<()>>(&wakeup_send) as *mut c_void,
            );
        }

        Self {
            inner: inner,
            _wakeup_send: wakeup_send,
            wakeup_recv: wakeup_recv,

            observed_property_callbacks: vec![],
        }
    }

    pub fn initialize(&self) -> Result<(), Error> {
        Error::from_return_code(unsafe { ffi::mpv_initialize(self.inner.as_ptr()) })
    }

    pub fn set_property<'a>(&self, name: &str, value: impl FormatValue) -> Result<(), Error> {
        // need to add zero terminator
        let name = CString::new(name).expect("null bytes in property name");
        value.into_data(|format, data| {
            Error::from_return_code(unsafe {
                ffi::mpv_set_property(self.inner.as_ptr(), name.as_ptr(), format, data)
            })
        })
    }

    // TODO: some way to deregister these maybe??
    pub fn observe_property<T>(
        &mut self,
        name: &str,
        mut cb: impl FnMut(Option<T>) + 'static,
    ) -> Result<(), Error>
    where
        T: FormatValue,
    {
        let name = CString::new(name).unwrap();
        let cb = Box::new(move |format, data| T::from_data(format, data, |x| cb(x)));
        let cb = Box::<dyn FnMut(ffi::mpv_format, *mut c_void)>::from(cb);
        let cb = Box::pin(cb);
        let userdata =
            std::ptr::from_ref::<Box<dyn FnMut(ffi::mpv_format, *mut c_void)>>(&cb) as usize as u64;

        Error::from_return_code(unsafe {
            ffi::mpv_observe_property(self.inner.as_ptr(), userdata, name.as_ptr(), T::FORMAT)
        })?;

        self.observed_property_callbacks.push(cb);
        Ok(())
    }

    pub async fn wait(&self) {
        match self.wakeup_recv.recv().await {
            Ok(()) => {}
            Err(async_channel::RecvError) => unreachable!(),
        }
    }

    pub fn tick(&mut self) {
        loop {
            let event = unsafe { &*ffi::mpv_wait_event(self.inner.as_ptr(), 0.0) };
            match event.event_id {
                ffi::mpv_event_id_MPV_EVENT_NONE => break,

                ffi::mpv_event_id_MPV_EVENT_PROPERTY_CHANGE => {
                    let cb = unsafe {
                        &mut *(event.reply_userdata
                            as *mut Box<dyn FnMut(ffi::mpv_format, *mut c_void)>)
                    };
                    let data = unsafe { &*(event.data as *mut ffi::mpv_event_property) };
                    cb(data.format, data.data);
                }

                11 => { /* deprecated, ignore */ }

                _ => todo!("event {}", event.event_id),
            }
        }
    }
}

impl Drop for Handle {
    fn drop(&mut self) {
        // destroy? terminate_destroy??
        todo!()
    }
}

pub trait FormatValue: Sized {
    const FORMAT: ffi::mpv_format;
    fn into_data<T>(self, f: impl FnOnce(ffi::mpv_format, *mut c_void) -> T) -> T;
    fn from_data<T>(
        format: ffi::mpv_format,
        data: *mut c_void,
        f: impl FnOnce(Option<Self>) -> T,
    ) -> T;
}

impl<'a> FormatValue for &'a str {
    const FORMAT: ffi::mpv_format = ffi::mpv_format_MPV_FORMAT_STRING;

    fn into_data<T>(self, f: impl FnOnce(ffi::mpv_format, *mut c_void) -> T) -> T {
        let str = CString::new(self).expect("null bytes in string");
        let str_ptr = str.as_ptr();
        f(Self::FORMAT, (&str_ptr) as *const _ as *mut c_void)
    }

    fn from_data<T>(
        _format: ffi::mpv_format,
        _data: *mut c_void,
        _f: impl FnOnce(Option<Self>) -> T,
    ) -> T {
        todo!()
    }
}

impl FormatValue for bool {
    const FORMAT: ffi::mpv_format = ffi::mpv_format_MPV_FORMAT_FLAG;

    fn into_data<T>(self, f: impl FnOnce(ffi::mpv_format, *mut c_void) -> T) -> T {
        let flag: c_int = if self { 1 } else { 0 };
        f(Self::FORMAT, (&flag) as *const c_int as *mut c_void)
    }

    fn from_data<T>(
        _format: ffi::mpv_format,
        _data: *mut c_void,
        _f: impl FnOnce(Option<Self>) -> T,
    ) -> T {
        todo!()
    }
}

impl FormatValue for f64 {
    const FORMAT: ffi::mpv_format = ffi::mpv_format_MPV_FORMAT_DOUBLE;

    fn into_data<T>(self, f: impl FnOnce(ffi::mpv_format, *mut c_void) -> T) -> T {
        f(Self::FORMAT, (&self) as *const f64 as *mut c_void)
    }

    fn from_data<T>(
        format: ffi::mpv_format,
        data: *mut c_void,
        f: impl FnOnce(Option<Self>) -> T,
    ) -> T {
        match format {
            ffi::mpv_format_MPV_FORMAT_NONE => f(None),
            ffi::mpv_format_MPV_FORMAT_DOUBLE => f(Some(unsafe { *(data as *mut f64) })),
            _ => panic!(),
        }
    }
}