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

use futures_channel::mpsc::{self, UnboundedReceiver};
use futures_core::Stream;
use futures_util::StreamExt;
use glib::ffi::{gboolean, gpointer};
use glib::prelude::*;
use glib::source::{Continue, Priority, SourceId};
use glib::translate::*;
use std::cell::RefCell;
use std::future;
use std::mem::transmute;
use std::pin::Pin;
use std::task::{Context, Poll};

use crate::Bus;
use crate::BusSyncReply;
use crate::Message;
use crate::MessageType;

unsafe extern "C" fn trampoline_watch<F: FnMut(&Bus, &Message) -> Continue + 'static>(
    bus: *mut ffi::GstBus,
    msg: *mut ffi::GstMessage,
    func: gpointer,
) -> gboolean {
    let func: &RefCell<F> = &*(func as *const RefCell<F>);
    (&mut *func.borrow_mut())(&from_glib_borrow(bus), &Message::from_glib_borrow(msg)).into_glib()
}

unsafe extern "C" fn destroy_closure_watch<F: FnMut(&Bus, &Message) -> Continue + 'static>(
    ptr: gpointer,
) {
    Box::<RefCell<F>>::from_raw(ptr as *mut _);
}

fn into_raw_watch<F: FnMut(&Bus, &Message) -> Continue + 'static>(func: F) -> gpointer {
    #[allow(clippy::type_complexity)]
    let func: Box<RefCell<F>> = Box::new(RefCell::new(func));
    Box::into_raw(func) as gpointer
}

unsafe extern "C" fn trampoline_sync<
    F: Fn(&Bus, &Message) -> BusSyncReply + Send + Sync + 'static,
>(
    bus: *mut ffi::GstBus,
    msg: *mut ffi::GstMessage,
    func: gpointer,
) -> ffi::GstBusSyncReply {
    let f: &F = &*(func as *const F);
    let res = f(&from_glib_borrow(bus), &Message::from_glib_borrow(msg)).into_glib();

    if res == ffi::GST_BUS_DROP {
        ffi::gst_mini_object_unref(msg as *mut _);
    }

    res
}

unsafe extern "C" fn destroy_closure_sync<
    F: Fn(&Bus, &Message) -> BusSyncReply + Send + Sync + 'static,
>(
    ptr: gpointer,
) {
    Box::<F>::from_raw(ptr as *mut _);
}

fn into_raw_sync<F: Fn(&Bus, &Message) -> BusSyncReply + Send + Sync + 'static>(
    func: F,
) -> gpointer {
    let func: Box<F> = Box::new(func);
    Box::into_raw(func) as gpointer
}

impl Bus {
    /// Adds a bus signal watch to the default main context with the given `priority`
    /// (e.g. `G_PRIORITY_DEFAULT`). It is also possible to use a non-default main
    /// context set up using [`crate::glib::MainContext::push_thread_default()`]
    /// (before one had to create a bus watch source and attach it to the desired
    /// main context 'manually').
    ///
    /// After calling this statement, the bus will emit the "message" signal for each
    /// message posted on the bus when the main loop is running.
    ///
    /// This function may be called multiple times. To clean up, the caller is
    /// responsible for calling [`Self::remove_signal_watch()`] as many times as this
    /// function is called.
    ///
    /// There can only be a single bus watch per bus, you must remove any signal
    /// watch before you can set another type of watch.
    ///
    /// MT safe.
    /// ## `priority`
    /// The priority of the watch.
    pub fn add_signal_watch_full(&self, priority: Priority) {
        unsafe {
            ffi::gst_bus_add_signal_watch_full(self.to_glib_none().0, priority.into_glib());
        }
    }

    /// Create watch for this bus. The GSource will be dispatched whenever
    /// a message is on the bus. After the GSource is dispatched, the
    /// message is popped off the bus and unreffed.
    ///
    /// # Returns
    ///
    /// a [`crate::glib::Source`] that can be added to a mainloop.
    pub fn create_watch<F>(&self, name: Option<&str>, priority: Priority, func: F) -> glib::Source
    where
        F: FnMut(&Bus, &Message) -> Continue + Send + 'static,
    {
        skip_assert_initialized!();
        unsafe {
            let source = ffi::gst_bus_create_watch(self.to_glib_none().0);
            glib::ffi::g_source_set_callback(
                source,
                Some(transmute::<
                    _,
                    unsafe extern "C" fn(glib::ffi::gpointer) -> i32,
                >(trampoline_watch::<F> as *const ())),
                into_raw_watch(func),
                Some(destroy_closure_watch::<F>),
            );
            glib::ffi::g_source_set_priority(source, priority.into_glib());

            if let Some(name) = name {
                glib::ffi::g_source_set_name(source, name.to_glib_none().0);
            }

            from_glib_full(source)
        }
    }

    /// Adds a bus watch to the default main context with the default priority
    /// (`G_PRIORITY_DEFAULT`). It is also possible to use a non-default main
    /// context set up using [`crate::glib::MainContext::push_thread_default()`] (before
    /// one had to create a bus watch source and attach it to the desired main
    /// context 'manually').
    ///
    /// This function is used to receive asynchronous messages in the main loop.
    /// There can only be a single bus watch per bus, you must remove it before you
    /// can set a new one.
    ///
    /// The bus watch will only work if a GLib main loop is being run.
    ///
    /// The watch can be removed using [`Self::remove_watch()`] or by returning [`false`]
    /// from `func`. If the watch was added to the default main context it is also
    /// possible to remove the watch using [`crate::glib::Source::remove()`].
    ///
    /// The bus watch will take its own reference to the `self`, so it is safe to unref
    /// `self` using [`crate::prelude::GstObjectExt::unref()`] after setting the bus watch.
    ///
    /// MT safe.
    /// ## `func`
    /// A function to call when a message is received.
    /// ## `user_data`
    /// user data passed to `func`.
    ///
    /// # Returns
    ///
    /// The event source id or 0 if `self` already got an event source.
    pub fn add_watch<F>(&self, func: F) -> Result<SourceId, glib::BoolError>
    where
        F: FnMut(&Bus, &Message) -> Continue + Send + 'static,
    {
        unsafe {
            let res = ffi::gst_bus_add_watch_full(
                self.to_glib_none().0,
                glib::ffi::G_PRIORITY_DEFAULT,
                Some(trampoline_watch::<F>),
                into_raw_watch(func),
                Some(destroy_closure_watch::<F>),
            );

            if res == 0 {
                Err(glib::bool_error!("Bus already has a watch"))
            } else {
                Ok(from_glib(res))
            }
        }
    }

    pub fn add_watch_local<F>(&self, func: F) -> Result<SourceId, glib::BoolError>
    where
        F: FnMut(&Bus, &Message) -> Continue + 'static,
    {
        unsafe {
            assert!(glib::MainContext::ref_thread_default().is_owner());

            let res = ffi::gst_bus_add_watch_full(
                self.to_glib_none().0,
                glib::ffi::G_PRIORITY_DEFAULT,
                Some(trampoline_watch::<F>),
                into_raw_watch(func),
                Some(destroy_closure_watch::<F>),
            );

            if res == 0 {
                Err(glib::bool_error!("Bus already has a watch"))
            } else {
                Ok(from_glib(res))
            }
        }
    }

    /// Sets the synchronous handler on the bus. The function will be called
    /// every time a new message is posted on the bus. Note that the function
    /// will be called in the same thread context as the posting object. This
    /// function is usually only called by the creator of the bus. Applications
    /// should handle messages asynchronously using the gst_bus watch and poll
    /// functions.
    ///
    /// Before 1.16.3 it was not possible to replace an existing handler and
    /// clearing an existing handler with [`None`] was not thread-safe.
    /// ## `func`
    /// The handler function to install
    /// ## `user_data`
    /// User data that will be sent to the handler function.
    /// ## `notify`
    /// called when `user_data` becomes unused
    pub fn set_sync_handler<F>(&self, func: F)
    where
        F: Fn(&Bus, &Message) -> BusSyncReply + Send + Sync + 'static,
    {
        use once_cell::sync::Lazy;
        static SET_ONCE_QUARK: Lazy<glib::Quark> =
            Lazy::new(|| glib::Quark::from_string("gstreamer-rs-sync-handler"));

        unsafe {
            let bus = self.to_glib_none().0;

            // This is not thread-safe before 1.16.3, see
            // https://gitlab.freedesktop.org/gstreamer/gstreamer-rs/merge_requests/416
            if crate::version() < (1, 16, 3, 0) {
                if !glib::gobject_ffi::g_object_get_qdata(bus as *mut _, SET_ONCE_QUARK.into_glib())
                    .is_null()
                {
                    panic!("Bus sync handler can only be set once");
                }

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

            ffi::gst_bus_set_sync_handler(
                bus,
                Some(trampoline_sync::<F>),
                into_raw_sync(func),
                Some(destroy_closure_sync::<F>),
            )
        }
    }

    pub fn unset_sync_handler(&self) {
        // This is not thread-safe before 1.16.3, see
        // https://gitlab.freedesktop.org/gstreamer/gstreamer-rs/merge_requests/416
        if crate::version() < (1, 16, 3, 0) {
            return;
        }

        unsafe {
            use std::ptr;

            ffi::gst_bus_set_sync_handler(self.to_glib_none().0, None, ptr::null_mut(), None)
        }
    }

    pub fn iter(&self) -> Iter {
        self.iter_timed(0.into())
    }

    pub fn iter_timed(&self, timeout: crate::ClockTime) -> Iter {
        Iter { bus: self, timeout }
    }

    pub fn iter_filtered<'a>(
        &'a self,
        msg_types: &'a [MessageType],
    ) -> impl Iterator<Item = Message> + 'a {
        self.iter_timed_filtered(0.into(), msg_types)
    }

    pub fn iter_timed_filtered<'a>(
        &'a self,
        timeout: crate::ClockTime,
        msg_types: &'a [MessageType],
    ) -> impl Iterator<Item = Message> + 'a {
        self.iter_timed(timeout)
            .filter(move |msg| msg_types.contains(&msg.type_()))
    }

    /// Get a message from the bus whose type matches the message type mask `types`,
    /// waiting up to the specified timeout (and discarding any messages that do not
    /// match the mask provided).
    ///
    /// If `timeout` is 0, this function behaves like [`Self::pop_filtered()`]. If
    /// `timeout` is `GST_CLOCK_TIME_NONE`, this function will block forever until a
    /// matching message was posted on the bus.
    /// ## `timeout`
    /// a timeout in nanoseconds, or GST_CLOCK_TIME_NONE to wait forever
    /// ## `types`
    /// message types to take into account, GST_MESSAGE_ANY for any type
    ///
    /// # Returns
    ///
    /// a [`crate::Message`] matching the
    ///  filter in `types`, or [`None`] if no matching message was found on
    ///  the bus until the timeout expired. The message is taken from
    ///  the bus and needs to be unreffed with `gst_message_unref()` after
    ///  usage.
    ///
    /// MT safe.
    pub fn timed_pop_filtered(
        &self,
        timeout: crate::ClockTime,
        msg_types: &[MessageType],
    ) -> Option<Message> {
        loop {
            let msg = self.timed_pop(timeout)?;
            if msg_types.contains(&msg.type_()) {
                return Some(msg);
            }
        }
    }

    /// Get a message matching `type_` from the bus. Will discard all messages on
    /// the bus that do not match `type_` and that have been posted before the first
    /// message that does match `type_`. If there is no message matching `type_` on
    /// the bus, all messages will be discarded. It is not possible to use message
    /// enums beyond [`crate::MessageType::Extended`] in the `events` mask.
    /// ## `types`
    /// message types to take into account
    ///
    /// # Returns
    ///
    /// the next [`crate::Message`] matching
    ///  `type_` that is on the bus, or [`None`] if the bus is empty or there
    ///  is no message matching `type_`. The message is taken from the bus
    ///  and needs to be unreffed with `gst_message_unref()` after usage.
    ///
    /// MT safe.
    pub fn pop_filtered(&self, msg_types: &[MessageType]) -> Option<Message> {
        loop {
            let msg = self.pop()?;
            if msg_types.contains(&msg.type_()) {
                return Some(msg);
            }
        }
    }

    pub fn stream(&self) -> BusStream {
        BusStream::new(self)
    }

    pub fn stream_filtered<'a>(
        &self,
        message_types: &'a [MessageType],
    ) -> impl Stream<Item = Message> + Unpin + Send + 'a {
        self.stream().filter(move |message| {
            let message_type = message.type_();

            future::ready(message_types.contains(&message_type))
        })
    }
}

#[derive(Debug)]
pub struct Iter<'a> {
    bus: &'a Bus,
    timeout: crate::ClockTime,
}

impl<'a> Iterator for Iter<'a> {
    type Item = Message;

    fn next(&mut self) -> Option<Message> {
        self.bus.timed_pop(self.timeout)
    }
}

#[derive(Debug)]
pub struct BusStream {
    bus: glib::WeakRef<Bus>,
    receiver: UnboundedReceiver<Message>,
}

impl BusStream {
    fn new(bus: &Bus) -> Self {
        skip_assert_initialized!();

        let (sender, receiver) = mpsc::unbounded();

        bus.set_sync_handler(move |_, message| {
            let _ = sender.unbounded_send(message.to_owned());

            BusSyncReply::Drop
        });

        Self {
            bus: bus.downgrade(),
            receiver,
        }
    }
}

impl Drop for BusStream {
    fn drop(&mut self) {
        if let Some(bus) = self.bus.upgrade() {
            bus.unset_sync_handler();
        }
    }
}

impl Stream for BusStream {
    type Item = Message;

    fn poll_next(mut self: Pin<&mut Self>, context: &mut Context) -> Poll<Option<Self::Item>> {
        self.receiver.poll_next_unpin(context)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::sync::{Arc, Mutex};

    #[test]
    fn test_sync_handler() {
        crate::init().unwrap();

        let bus = Bus::new();
        let msgs = Arc::new(Mutex::new(Vec::new()));
        let msgs_clone = msgs.clone();
        bus.set_sync_handler(move |_, msg| {
            msgs_clone.lock().unwrap().push(msg.clone());
            BusSyncReply::Pass
        });

        bus.post(&crate::message::Eos::new()).unwrap();

        let msgs = msgs.lock().unwrap();
        assert_eq!(msgs.len(), 1);
        match msgs[0].view() {
            crate::MessageView::Eos(_) => (),
            _ => unreachable!(),
        }
    }

    #[test]
    fn test_bus_stream() {
        crate::init().unwrap();

        let bus = Bus::new();
        let bus_stream = bus.stream();

        let eos_message = crate::message::Eos::new();
        bus.post(&eos_message).unwrap();

        let bus_future = bus_stream.into_future();
        let (message, _) = futures_executor::block_on(bus_future);

        match message.unwrap().view() {
            crate::MessageView::Eos(_) => (),
            _ => unreachable!(),
        }
    }
}