// Take a look at the license at the top of the repository in the LICENSE file.

use futures_sink::Sink;
use glib::ffi::{gboolean, gpointer};
use glib::prelude::*;
use glib::translate::*;

use crate::AppSrc;
use std::cell::RefCell;
use std::mem;
use std::panic;
use std::pin::Pin;
use std::ptr;
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::{Arc, Mutex};
use std::task::{Context, Poll, Waker};

#[allow(clippy::type_complexity)]
pub struct AppSrcCallbacks {
    need_data: Option<RefCell<Box<dyn FnMut(&AppSrc, u32) + Send + 'static>>>,
    enough_data: Option<Box<dyn Fn(&AppSrc) + Send + Sync + 'static>>,
    seek_data: Option<Box<dyn Fn(&AppSrc, u64) -> bool + Send + Sync + 'static>>,
    panicked: AtomicBool,
    callbacks: ffi::GstAppSrcCallbacks,
}

unsafe impl Send for AppSrcCallbacks {}
unsafe impl Sync for AppSrcCallbacks {}

impl AppSrcCallbacks {
    pub fn builder() -> AppSrcCallbacksBuilder {
        skip_assert_initialized!();

        AppSrcCallbacksBuilder {
            need_data: None,
            enough_data: None,
            seek_data: None,
        }
    }
}

#[allow(clippy::type_complexity)]
pub struct AppSrcCallbacksBuilder {
    need_data: Option<RefCell<Box<dyn FnMut(&AppSrc, u32) + Send + 'static>>>,
    enough_data: Option<Box<dyn Fn(&AppSrc) + Send + Sync + 'static>>,
    seek_data: Option<Box<dyn Fn(&AppSrc, u64) -> bool + Send + Sync + 'static>>,
}

impl AppSrcCallbacksBuilder {
    pub fn need_data<F: FnMut(&AppSrc, u32) + Send + 'static>(self, need_data: F) -> Self {
        Self {
            need_data: Some(RefCell::new(Box::new(need_data))),
            ..self
        }
    }

    pub fn enough_data<F: Fn(&AppSrc) + Send + Sync + 'static>(self, enough_data: F) -> Self {
        Self {
            enough_data: Some(Box::new(enough_data)),
            ..self
        }
    }

    pub fn seek_data<F: Fn(&AppSrc, u64) -> bool + Send + Sync + 'static>(
        self,
        seek_data: F,
    ) -> Self {
        Self {
            seek_data: Some(Box::new(seek_data)),
            ..self
        }
    }

    pub fn build(self) -> AppSrcCallbacks {
        let have_need_data = self.need_data.is_some();
        let have_enough_data = self.enough_data.is_some();
        let have_seek_data = self.seek_data.is_some();

        AppSrcCallbacks {
            need_data: self.need_data,
            enough_data: self.enough_data,
            seek_data: self.seek_data,
            panicked: AtomicBool::new(false),
            callbacks: ffi::GstAppSrcCallbacks {
                need_data: if have_need_data {
                    Some(trampoline_need_data)
                } else {
                    None
                },
                enough_data: if have_enough_data {
                    Some(trampoline_enough_data)
                } else {
                    None
                },
                seek_data: if have_seek_data {
                    Some(trampoline_seek_data)
                } else {
                    None
                },
                _gst_reserved: [
                    ptr::null_mut(),
                    ptr::null_mut(),
                    ptr::null_mut(),
                    ptr::null_mut(),
                ],
            },
        }
    }
}

fn post_panic_error_message(element: &AppSrc, err: &dyn std::any::Any) {
    skip_assert_initialized!();
    if let Some(cause) = err.downcast_ref::<&str>() {
        gst::element_error!(&element, gst::LibraryError::Failed, ["Panicked: {}", cause]);
    } else if let Some(cause) = err.downcast_ref::<String>() {
        gst::element_error!(&element, gst::LibraryError::Failed, ["Panicked: {}", cause]);
    } else {
        gst::element_error!(&element, gst::LibraryError::Failed, ["Panicked"]);
    }
}

unsafe extern "C" fn trampoline_need_data(
    appsrc: *mut ffi::GstAppSrc,
    length: u32,
    callbacks: gpointer,
) {
    let callbacks = &*(callbacks as *const AppSrcCallbacks);
    let element: Borrowed<AppSrc> = from_glib_borrow(appsrc);

    if callbacks.panicked.load(Ordering::Relaxed) {
        let element: Borrowed<AppSrc> = from_glib_borrow(appsrc);
        gst::element_error!(&element, gst::LibraryError::Failed, ["Panicked"]);
        return;
    }

    if let Some(ref need_data) = callbacks.need_data {
        let result = panic::catch_unwind(panic::AssertUnwindSafe(|| {
            (&mut *need_data.borrow_mut())(&element, length)
        }));
        match result {
            Ok(result) => result,
            Err(err) => {
                callbacks.panicked.store(true, Ordering::Relaxed);
                post_panic_error_message(&element, &err);
            }
        }
    }
}

unsafe extern "C" fn trampoline_enough_data(appsrc: *mut ffi::GstAppSrc, callbacks: gpointer) {
    let callbacks = &*(callbacks as *const AppSrcCallbacks);
    let element: Borrowed<AppSrc> = from_glib_borrow(appsrc);

    if callbacks.panicked.load(Ordering::Relaxed) {
        let element: Borrowed<AppSrc> = from_glib_borrow(appsrc);
        gst::element_error!(&element, gst::LibraryError::Failed, ["Panicked"]);
        return;
    }

    if let Some(ref enough_data) = callbacks.enough_data {
        let result = panic::catch_unwind(panic::AssertUnwindSafe(|| (*enough_data)(&element)));
        match result {
            Ok(result) => result,
            Err(err) => {
                callbacks.panicked.store(true, Ordering::Relaxed);
                post_panic_error_message(&element, &err);
            }
        }
    }
}

unsafe extern "C" fn trampoline_seek_data(
    appsrc: *mut ffi::GstAppSrc,
    offset: u64,
    callbacks: gpointer,
) -> gboolean {
    let callbacks = &*(callbacks as *const AppSrcCallbacks);
    let element: Borrowed<AppSrc> = from_glib_borrow(appsrc);

    if callbacks.panicked.load(Ordering::Relaxed) {
        let element: Borrowed<AppSrc> = from_glib_borrow(appsrc);
        gst::element_error!(&element, gst::LibraryError::Failed, ["Panicked"]);
        return false.into_glib();
    }

    let ret = if let Some(ref seek_data) = callbacks.seek_data {
        let result =
            panic::catch_unwind(panic::AssertUnwindSafe(|| (*seek_data)(&element, offset)));
        match result {
            Ok(result) => result,
            Err(err) => {
                callbacks.panicked.store(true, Ordering::Relaxed);
                post_panic_error_message(&element, &err);

                false
            }
        }
    } else {
        false
    };

    ret.into_glib()
}

unsafe extern "C" fn destroy_callbacks(ptr: gpointer) {
    Box::<AppSrcCallbacks>::from_raw(ptr as *mut _);
}

impl AppSrc {
    /// Adds a buffer to the queue of buffers that the appsrc element will
    /// push to its source pad. This function takes ownership of the buffer.
    ///
    /// When the block property is TRUE, this function can block until free
    /// space becomes available in the queue.
    /// ## `buffer`
    /// a [`crate::gst::Buffer`] to push
    ///
    /// # Returns
    ///
    /// [`crate::gst::FlowReturn::Ok`] when the buffer was successfully queued.
    /// [`crate::gst::FlowReturn::Flushing`] when `self` is not PAUSED or PLAYING.
    /// [`crate::gst::FlowReturn::Eos`] when EOS occurred.
    pub fn push_buffer(&self, buffer: gst::Buffer) -> Result<gst::FlowSuccess, gst::FlowError> {
        unsafe {
            gst::FlowSuccess::try_from_glib(ffi::gst_app_src_push_buffer(
                self.to_glib_none().0,
                buffer.into_ptr(),
            ))
        }
    }

    /// Adds a buffer list to the queue of buffers and buffer lists that the
    /// appsrc element will push to its source pad. This function takes ownership
    /// of `buffer_list`.
    ///
    /// When the block property is TRUE, this function can block until free
    /// space becomes available in the queue.
    /// ## `buffer_list`
    /// a [`crate::gst::BufferList`] to push
    ///
    /// # Returns
    ///
    /// [`crate::gst::FlowReturn::Ok`] when the buffer list was successfully queued.
    /// [`crate::gst::FlowReturn::Flushing`] when `self` is not PAUSED or PLAYING.
    /// [`crate::gst::FlowReturn::Eos`] when EOS occurred.
    #[cfg(any(feature = "v1_14", feature = "dox"))]
    #[cfg_attr(feature = "dox", doc(cfg(feature = "v1_14")))]
    pub fn push_buffer_list(
        &self,
        list: gst::BufferList,
    ) -> Result<gst::FlowSuccess, gst::FlowError> {
        unsafe {
            gst::FlowSuccess::try_from_glib(ffi::gst_app_src_push_buffer_list(
                self.to_glib_none().0,
                list.into_ptr(),
            ))
        }
    }

    /// Set callbacks which will be executed when data is needed, enough data has
    /// been collected or when a seek should be performed.
    /// This is an alternative to using the signals, it has lower overhead and is thus
    /// less expensive, but also less flexible.
    ///
    /// If callbacks are installed, no signals will be emitted for performance
    /// reasons.
    ///
    /// Before 1.16.3 it was not possible to change the callbacks in a thread-safe
    /// way.
    /// ## `callbacks`
    /// the callbacks
    /// ## `user_data`
    /// a user_data argument for the callbacks
    /// ## `notify`
    /// a destroy notify function
    pub fn set_callbacks(&self, callbacks: AppSrcCallbacks) {
        use once_cell::sync::Lazy;
        static SET_ONCE_QUARK: Lazy<glib::Quark> =
            Lazy::new(|| glib::Quark::from_string("gstreamer-rs-app-src-callbacks"));

        unsafe {
            let src = self.to_glib_none().0;
            // This is not thread-safe before 1.16.3, see
            // https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/merge_requests/570
            if gst::version() < (1, 16, 3, 0) {
                if !glib::gobject_ffi::g_object_get_qdata(src as *mut _, SET_ONCE_QUARK.into_glib())
                    .is_null()
                {
                    panic!("AppSrc callbacks can only be set once");
                }

                glib::gobject_ffi::g_object_set_qdata(
                    src as *mut _,
                    SET_ONCE_QUARK.into_glib(),
                    1 as *mut _,
                );
            }

            ffi::gst_app_src_set_callbacks(
                src,
                mut_override(&callbacks.callbacks),
                Box::into_raw(Box::new(callbacks)) as *mut _,
                Some(destroy_callbacks),
            );
        }
    }

    /// Configure the `min` and `max` latency in `src`. If `min` is set to -1, the
    /// default latency calculations for pseudo-live sources will be used.
    /// ## `min`
    /// the min latency
    /// ## `max`
    /// the max latency
    pub fn set_latency(&self, min: gst::ClockTime, max: gst::ClockTime) {
        unsafe {
            ffi::gst_app_src_set_latency(self.to_glib_none().0, min.into_glib(), max.into_glib());
        }
    }

    /// Retrieve the min and max latencies in `min` and `max` respectively.
    /// ## `min`
    /// the min latency
    /// ## `max`
    /// the max latency
    #[doc(alias = "get_latency")]
    pub fn latency(&self) -> (gst::ClockTime, gst::ClockTime) {
        unsafe {
            let mut min = mem::MaybeUninit::uninit();
            let mut max = mem::MaybeUninit::uninit();
            ffi::gst_app_src_get_latency(self.to_glib_none().0, min.as_mut_ptr(), max.as_mut_ptr());
            (from_glib(min.assume_init()), from_glib(max.assume_init()))
        }
    }

    pub fn sink(&self) -> AppSrcSink {
        AppSrcSink::new(self)
    }
}

#[derive(Debug)]
pub struct AppSrcSink {
    app_src: glib::WeakRef<AppSrc>,
    waker_reference: Arc<Mutex<Option<Waker>>>,
}

impl AppSrcSink {
    fn new(app_src: &AppSrc) -> Self {
        skip_assert_initialized!();

        let waker_reference = Arc::new(Mutex::new(None as Option<Waker>));

        app_src.set_callbacks(
            AppSrcCallbacks::builder()
                .need_data({
                    let waker_reference = Arc::clone(&waker_reference);

                    move |_, _| {
                        if let Some(waker) = waker_reference.lock().unwrap().take() {
                            waker.wake();
                        }
                    }
                })
                .build(),
        );

        Self {
            app_src: app_src.downgrade(),
            waker_reference,
        }
    }
}

impl Drop for AppSrcSink {
    fn drop(&mut self) {
        // This is not thread-safe before 1.16.3, see
        // https://gitlab.freedesktop.org/gstreamer/gst-plugins-base/merge_requests/570
        if gst::version() >= (1, 16, 3, 0) {
            if let Some(app_src) = self.app_src.upgrade() {
                app_src.set_callbacks(AppSrcCallbacks::builder().build());
            }
        }
    }
}

impl Sink<gst::Sample> for AppSrcSink {
    type Error = gst::FlowError;

    fn poll_ready(self: Pin<&mut Self>, context: &mut Context) -> Poll<Result<(), Self::Error>> {
        let mut waker = self.waker_reference.lock().unwrap();

        let app_src = match self.app_src.upgrade() {
            Some(app_src) => app_src,
            None => return Poll::Ready(Err(gst::FlowError::Eos)),
        };

        let current_level_bytes = app_src.current_level_bytes();
        let max_bytes = app_src.max_bytes();

        if current_level_bytes >= max_bytes && max_bytes != 0 {
            waker.replace(context.waker().to_owned());

            Poll::Pending
        } else {
            Poll::Ready(Ok(()))
        }
    }

    fn start_send(self: Pin<&mut Self>, sample: gst::Sample) -> Result<(), Self::Error> {
        let app_src = match self.app_src.upgrade() {
            Some(app_src) => app_src,
            None => return Err(gst::FlowError::Eos),
        };

        app_src.push_sample(&sample)?;

        Ok(())
    }

    fn poll_flush(self: Pin<&mut Self>, _: &mut Context) -> Poll<Result<(), Self::Error>> {
        Poll::Ready(Ok(()))
    }

    fn poll_close(self: Pin<&mut Self>, _: &mut Context) -> Poll<Result<(), Self::Error>> {
        let app_src = match self.app_src.upgrade() {
            Some(app_src) => app_src,
            None => return Poll::Ready(Ok(())),
        };

        app_src.end_of_stream()?;

        Poll::Ready(Ok(()))
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use futures_util::{sink::SinkExt, stream::StreamExt};
    use gst::prelude::*;
    use std::sync::atomic::{AtomicUsize, Ordering};

    #[test]
    fn test_app_src_sink() {
        gst::init().unwrap();

        let appsrc = gst::ElementFactory::make("appsrc", None).unwrap();
        let fakesink = gst::ElementFactory::make("fakesink", None).unwrap();

        fakesink.set_property("signal-handoffs", &true).unwrap();

        let pipeline = gst::Pipeline::new(None);
        pipeline.add(&appsrc).unwrap();
        pipeline.add(&fakesink).unwrap();

        appsrc.link(&fakesink).unwrap();

        let mut bus_stream = pipeline.bus().unwrap().stream();
        let mut app_src_sink = appsrc.dynamic_cast::<AppSrc>().unwrap().sink();

        let sample_quantity = 5;

        let samples = (0..sample_quantity)
            .map(|_| gst::Sample::builder().buffer(&gst::Buffer::new()).build())
            .collect::<Vec<gst::Sample>>();

        let mut sample_stream = futures_util::stream::iter(samples).map(Ok);

        let handoff_count_reference = Arc::new(AtomicUsize::new(0));

        fakesink
            .connect("handoff", false, {
                let handoff_count_reference = Arc::clone(&handoff_count_reference);

                move |_| {
                    handoff_count_reference.fetch_add(1, Ordering::AcqRel);

                    None
                }
            })
            .unwrap();

        pipeline.set_state(gst::State::Playing).unwrap();

        futures_executor::block_on(app_src_sink.send_all(&mut sample_stream)).unwrap();
        futures_executor::block_on(app_src_sink.close()).unwrap();

        while let Some(message) = futures_executor::block_on(bus_stream.next()) {
            match message.view() {
                gst::MessageView::Eos(_) => break,
                gst::MessageView::Error(_) => unreachable!(),
                _ => continue,
            }
        }

        pipeline.set_state(gst::State::Null).unwrap();

        assert_eq!(
            handoff_count_reference.load(Ordering::Acquire),
            sample_quantity
        );
    }
}