use std::borrow::Borrow;
use std::num::NonZeroU32;
use std::ptr::NonNull;
use std::sync::Arc;

use anyhow::{Context, Result};
use crossbeam::sync::Parker;
use jack::{
    AsyncClient, AudioIn, AudioOut, Client, ClientOptions, ClosureProcessHandler, Control, MidiIn,
    MidiOut, Port,
};
use parking_lot::Mutex;

use super::super::config::WrapperConfig;
use super::Backend;
use crate::midi::MidiResult;
use crate::prelude::{
    AudioIOLayout, AuxiliaryBuffers, Buffer, MidiConfig, NoteEvent, Plugin, PluginNoteEvent,
    Transport,
};
use crate::wrapper::util::buffer_management::{BufferManager, ChannelPointers};
use crate::wrapper::util::{clamp_input_event_timing, clamp_output_event_timing};

/// Uses JACK audio and MIDI.
pub struct Jack {
    audio_io_layout: AudioIOLayout,
    config: WrapperConfig,
    /// The JACK client, wrapped in an option since it needs to be transformed into an `AsyncClient`
    /// and then back into a regular `Client`.
    client: Option<Client>,

    main_inputs: Arc<Vec<Port<AudioIn>>>,
    main_outputs: Arc<Mutex<Vec<Port<AudioOut>>>>,
    aux_input_ports: Arc<Mutex<Vec<Vec<Port<AudioIn>>>>>,
    aux_output_ports: Arc<Mutex<Vec<Vec<Port<AudioOut>>>>>,
    midi_input: Option<Arc<Port<MidiIn>>>,
    midi_output: Option<Arc<Mutex<Port<MidiOut>>>>,
}

/// Send+Sync wrapper for `Vec<*mut f32>` so we can preallocate channel pointer vectors for use with
/// the `BufferManager` API.
struct ChannelPointerVec(Vec<*mut f32>);

unsafe impl Send for ChannelPointerVec {}
unsafe impl Sync for ChannelPointerVec {}

impl ChannelPointerVec {
    // If you directly access the `.0` field then it will try to move it out of the struct which
    // undoes the Send+Sync impl.
    pub fn get(&mut self) -> &mut Vec<*mut f32> {
        &mut self.0
    }
}

impl<P: Plugin> Backend<P> for Jack {
    fn run(
        &mut self,
        mut cb: impl FnMut(
                &mut Buffer,
                &mut AuxiliaryBuffers,
                Transport,
                &[PluginNoteEvent<P>],
                &mut Vec<PluginNoteEvent<P>>,
            ) -> bool
            + 'static
            + Send,
    ) {
        let client = self.client.take().unwrap();
        let buffer_size = client.buffer_size();

        // We'll preallocate the buffers here, and then assign them to the slices belonging to the
        // JACK ports later. For consistency with the other backends we'll reuse the
        // `BufferManager`, which means we'll need to collect pointers to individual channel slices
        // into vectors so we can provide the needed `*mut *mut f32` pointers.
        let mut buffer_manager =
            BufferManager::for_audio_io_layout(buffer_size as usize, self.audio_io_layout);
        let mut main_output_channel_pointers = ChannelPointerVec(Vec::with_capacity(
            self.audio_io_layout
                .main_output_channels
                .map(NonZeroU32::get)
                .unwrap_or(0) as usize,
        ));
        let mut main_input_channel_pointers = ChannelPointerVec(Vec::with_capacity(
            self.audio_io_layout
                .main_input_channels
                .map(NonZeroU32::get)
                .unwrap_or(0) as usize,
        ));
        let mut aux_input_channel_pointers =
            Vec::with_capacity(self.audio_io_layout.aux_input_ports.len());
        for channel_count in self.audio_io_layout.aux_input_ports {
            aux_input_channel_pointers.push(ChannelPointerVec(Vec::with_capacity(
                channel_count.get() as usize,
            )));
        }
        let mut aux_output_channel_pointers =
            Vec::with_capacity(self.audio_io_layout.aux_output_ports.len());
        for channel_count in self.audio_io_layout.aux_output_ports {
            aux_output_channel_pointers.push(ChannelPointerVec(Vec::with_capacity(
                channel_count.get() as usize,
            )));
        }

        let mut input_events: Vec<PluginNoteEvent<P>> = Vec::with_capacity(2048);
        let mut output_events: Vec<PluginNoteEvent<P>> = Vec::with_capacity(2048);

        // This thread needs to be blocked until processing is finished
        let parker = Parker::new();
        let unparker = parker.unparker().clone();

        let config = self.config.clone();
        let main_inputs = self.main_inputs.clone();
        let main_outputs = self.main_outputs.clone();
        let aux_input_ports = self.aux_input_ports.clone();
        let aux_output_ports = self.aux_output_ports.clone();
        let midi_input = self.midi_input.clone();
        let midi_output = self.midi_output.clone();
        let process_handler = ClosureProcessHandler::new(move |client, ps| {
            // In theory we could handle `num_frames <= buffer_size`, but JACK will never chop up
            // buffers like that so we'll just make it easier for ourselves by not supporting that
            let num_frames = ps.n_frames();
            if num_frames != buffer_size {
                nih_error!(
                    "Buffer size changed from {buffer_size} to {num_frames}. Buffer size changes \
                     are currently not supported, aborting..."
                );
                unparker.unpark();
                return Control::Quit;
            }

            let mut transport = Transport::new(client.sample_rate() as f32);
            transport.tempo = Some(config.tempo as f64);
            transport.time_sig_numerator = Some(config.timesig_num as i32);
            transport.time_sig_denominator = Some(config.timesig_denom as i32);

            if let Ok(jack_transport) = client.transport().query() {
                transport.pos_samples = Some(jack_transport.pos.frame() as i64);
                transport.playing = jack_transport.state == jack::TransportState::Rolling;

                if let Some(bbt) = jack_transport.pos.bbt() {
                    transport.tempo = Some(bbt.bpm);
                    transport.time_sig_numerator = Some(bbt.sig_num as i32);
                    transport.time_sig_denominator = Some(bbt.sig_denom as i32);

                    transport.pos_beats = Some(
                        (bbt.bar as f64 * 4.0)
                            + (bbt.beat as f64 / bbt.sig_denom as f64 * 4.0)
                            + (bbt.tick as f64 / bbt.ticks_per_beat),
                    );
                    transport.bar_number = Some(bbt.bar as i32);
                }
            }

            // Just like all of the plugin backends, we need to grab the output slices and copy the
            // inputs to the outputs. To do that we need to first create the same kind of `*mut *mut
            // f32` pointers we would receive from a plugin API.
            let mut main_outputs = main_outputs.lock();
            main_output_channel_pointers.get().clear();
            for port in main_outputs.iter_mut() {
                let slice = port.as_mut_slice(ps);
                assert!(slice.len() == num_frames as usize);

                main_output_channel_pointers.get().push(slice.as_mut_ptr());
            }

            main_input_channel_pointers.get().clear();
            for port in main_inputs.iter() {
                let slice = port.as_slice(ps);
                assert!(slice.len() == num_frames as usize);

                main_input_channel_pointers
                    .get()
                    .push(slice.as_ptr() as *mut f32);
            }

            let aux_input_ports = aux_input_ports.lock();
            for (input_channel_pointers, input_ports) in aux_input_channel_pointers
                .iter_mut()
                .zip(aux_input_ports.iter())
            {
                input_channel_pointers.get().clear();
                for port in input_ports.iter() {
                    let slice = port.as_slice(ps);
                    assert!(slice.len() == num_frames as usize);

                    input_channel_pointers
                        .get()
                        .push(slice.as_ptr() as *mut f32);
                }
            }

            let mut aux_output_ports = aux_output_ports.lock();
            for (output_channel_pointers, output_ports) in aux_output_channel_pointers
                .iter_mut()
                .zip(aux_output_ports.iter_mut())
            {
                output_channel_pointers.get().clear();
                for port in output_ports.iter_mut() {
                    let slice = port.as_mut_slice(ps);
                    assert!(slice.len() == num_frames as usize);

                    output_channel_pointers.get().push(slice.as_mut_ptr());
                }
            }

            let buffers = unsafe {
                buffer_manager.create_buffers(0, num_frames as usize, |buffer_sources| {
                    *buffer_sources.main_output_channel_pointers = Some(ChannelPointers {
                        ptrs: NonNull::new(main_output_channel_pointers.get().as_mut_ptr())
                            .unwrap(),
                        num_channels: main_output_channel_pointers.get().len(),
                    });
                    *buffer_sources.main_input_channel_pointers = Some(ChannelPointers {
                        ptrs: NonNull::new(main_input_channel_pointers.get().as_mut_ptr()).unwrap(),
                        num_channels: main_input_channel_pointers.get().len(),
                    });

                    for (input_source_channel_pointers, input_channel_pointers) in buffer_sources
                        .aux_input_channel_pointers
                        .iter_mut()
                        .zip(aux_input_channel_pointers.iter_mut())
                    {
                        *input_source_channel_pointers = Some(ChannelPointers {
                            ptrs: NonNull::new(input_channel_pointers.get().as_mut_ptr()).unwrap(),
                            num_channels: input_channel_pointers.get().len(),
                        });
                    }

                    for (output_source_channel_pointers, output_channel_pointers) in buffer_sources
                        .aux_output_channel_pointers
                        .iter_mut()
                        .zip(aux_output_channel_pointers.iter_mut())
                    {
                        *output_source_channel_pointers = Some(ChannelPointers {
                            ptrs: NonNull::new(output_channel_pointers.get().as_mut_ptr()).unwrap(),
                            num_channels: output_channel_pointers.get().len(),
                        });
                    }
                })
            };

            input_events.clear();
            if let Some(midi_input) = &midi_input {
                input_events.extend(midi_input.iter(ps).filter_map(|midi| {
                    let timing = clamp_input_event_timing(midi.time, num_frames);

                    NoteEvent::from_midi(timing, midi.bytes).ok()
                }));
            }

            output_events.clear();
            let mut aux = AuxiliaryBuffers {
                inputs: buffers.aux_inputs,
                outputs: buffers.aux_outputs,
            };
            if cb(
                buffers.main_buffer,
                &mut aux,
                transport,
                &input_events,
                &mut output_events,
            ) {
                if let Some(midi_output) = &midi_output {
                    let mut midi_output = midi_output.lock();
                    let mut midi_writer = midi_output.writer(ps);
                    for event in output_events.drain(..) {
                        // Out of bounds events are clamped to the buffer's size
                        let timing = clamp_output_event_timing(event.timing(), num_frames);

                        match event.as_midi() {
                            Some(MidiResult::Basic(midi_data)) => {
                                let write_result = midi_writer.write(&jack::RawMidi {
                                    time: timing,
                                    bytes: &midi_data,
                                });

                                nih_debug_assert!(write_result.is_ok(), "The MIDI buffer is full");
                            }
                            Some(MidiResult::SysEx(padded_sysex_buffer, length)) => {
                                // The SysEx buffer may contain padding
                                let padded_sysex_buffer = padded_sysex_buffer.borrow();
                                nih_debug_assert!(length <= padded_sysex_buffer.len());
                                let write_result = midi_writer.write(&jack::RawMidi {
                                    time: timing,
                                    bytes: &padded_sysex_buffer[..length],
                                });

                                nih_debug_assert!(write_result.is_ok(), "The MIDI buffer is full");
                            }
                            None => (),
                        }
                    }
                }

                Control::Continue
            } else {
                unparker.unpark();
                Control::Quit
            }
        });

        // PipeWire lets us connect the ports whenever we want, but JACK2 is very strict and only
        // allows us to connect the ports when the client is active. And the connections will
        // disappear when the client is deactivated. Fun.
        let async_client = client.activate_async((), process_handler).unwrap();
        if let Err(err) = self.connect_ports(&async_client) {
            nih_error!("Error connecting JACK ports: {err}")
        }

        // The process callback happens on another thread, so we need to block this thread until we
        // get the request to shut down or until the process callback runs into an error
        parker.park();

        // And put the client back where it belongs in case this function is called a second time
        let (client, _, _) = async_client.deactivate().unwrap();
        self.client = Some(client);
    }
}

impl Jack {
    /// Initialize the JACK backend. Returns an error if this failed for whatever reason. The plugin
    /// generic argument is to get the name for the client, and to know whether or not the
    /// standalone should expose JACK MIDI ports.
    pub fn new<P: Plugin>(config: WrapperConfig) -> Result<Self> {
        let audio_io_layout = config.audio_io_layout_or_exit::<P>();
        let plugin_name = P::NAME.to_lowercase().replace(' ', "_");
        let (client, status) = Client::new(&plugin_name, ClientOptions::NO_START_SERVER)
            .context("Error while initializing the JACK client")?;
        if !status.is_empty() {
            anyhow::bail!("The JACK server returned an error: {status:?}");
        }

        if config.connect_jack_inputs.is_none() && audio_io_layout.main_input_channels.is_some() {
            nih_log!(
                "Audio inputs are not connected automatically to prevent feedback. Use the \
                 '--connect-jack-inputs' option to connect the input ports."
            )
        }

        let mut main_inputs = Vec::new();
        let num_input_channels = audio_io_layout
            .main_input_channels
            .map(NonZeroU32::get)
            .unwrap_or_default() as usize;
        let main_input_name = audio_io_layout
            .main_input_name()
            .to_lowercase()
            .replace(' ', "_");
        for port_no in 1..num_input_channels + 1 {
            main_inputs
                .push(client.register_port(&format!("{main_input_name}_{port_no}"), AudioIn)?);
        }

        // We can't immediately connect the outputs. Or well we can with PipeWire, but JACK2 says
        // no. So the connections are made just after activating the client in the `run()` function
        // above.
        let mut main_outputs = Vec::new();
        let num_output_channels = audio_io_layout
            .main_output_channels
            .map(NonZeroU32::get)
            .unwrap_or_default() as usize;
        let main_output_name = audio_io_layout
            .main_output_name()
            .to_lowercase()
            .replace(' ', "_");
        for port_no in 1..num_output_channels + 1 {
            main_outputs
                .push(client.register_port(&format!("{main_output_name}_{port_no}"), AudioOut)?);
        }

        // The JACK backend also exposes ports for auxiliary inputs and outputs
        let mut aux_input_ports = Vec::new();
        for (aux_input_idx, channel_count) in audio_io_layout.aux_input_ports.iter().enumerate() {
            let aux_input_name = audio_io_layout
                .aux_input_name(aux_input_idx)
                .expect("Out of range aux input port")
                .to_lowercase()
                .replace(' ', "_");

            let mut ports = Vec::new();
            for port_no in 1..channel_count.get() + 1 {
                ports.push(client.register_port(&format!("{aux_input_name}_{port_no}"), AudioIn)?);
            }

            aux_input_ports.push(ports);
        }

        let mut aux_output_ports = Vec::new();
        for (aux_output_idx, channel_count) in audio_io_layout.aux_output_ports.iter().enumerate() {
            let aux_output_name = audio_io_layout
                .aux_output_name(aux_output_idx)
                .expect("Out of range aux output port")
                .to_lowercase()
                .replace(' ', "_");

            let mut ports = Vec::new();
            for port_no in 1..channel_count.get() + 1 {
                ports
                    .push(client.register_port(&format!("{aux_output_name}_{port_no}"), AudioOut)?);
            }

            aux_output_ports.push(ports);
        }

        let midi_input = if P::MIDI_INPUT >= MidiConfig::Basic {
            Some(Arc::new(client.register_port("midi_input", MidiIn)?))
        } else {
            None
        };

        let midi_output = if P::MIDI_OUTPUT >= MidiConfig::Basic {
            Some(Arc::new(Mutex::new(
                client.register_port("midi_output", MidiOut)?,
            )))
        } else {
            None
        };

        Ok(Self {
            audio_io_layout,
            config,
            client: Some(client),

            main_inputs: Arc::new(main_inputs),
            main_outputs: Arc::new(Mutex::new(main_outputs)),
            aux_input_ports: Arc::new(Mutex::new(aux_input_ports)),
            aux_output_ports: Arc::new(Mutex::new(aux_output_ports)),
            midi_input,
            midi_output,
        })
    }

    /// With JACK2 ports can only be connected while the client is active, and they'll be
    /// disconnected automatically on deactivation. So we need to call this as part of the `run()`
    /// function above.
    fn connect_ports<N, P>(&self, async_client: &AsyncClient<N, P>) -> Result<()> {
        let client = async_client.as_client();

        // We don't connect the inputs automatically to avoid feedback loops, but this should be
        // safe. And if this fails, then that's fine.
        for (i, output) in self.main_outputs.lock().iter().enumerate() {
            // The system ports are 1-indexed
            let port_no = i + 1;

            let system_playback_port_name = &format!("system:playback_{port_no}");
            let _ = client.connect_ports_by_name(&output.name()?, system_playback_port_name);
        }

        // This option can either be set to a single port all inputs should be connected to, or a
        // comma separated list of ports
        if let Some(port_name) = &self.config.connect_jack_inputs {
            if port_name.contains(',') {
                for (port_name, input) in port_name.split(',').zip(self.main_inputs.iter()) {
                    if let Err(err) = client.connect_ports_by_name(port_name, &input.name()?) {
                        nih_error!("Could not connect to '{port_name}': {err}");
                    }
                }
            } else {
                for input in self.main_inputs.iter() {
                    if let Err(err) = client.connect_ports_by_name(port_name, &input.name()?) {
                        nih_error!("Could not connect to '{port_name}': {err}");
                        break;
                    }
                }
            }
        }

        if let (Some(port), Some(port_name)) =
            (&self.midi_input, &self.config.connect_jack_midi_input)
        {
            if let Err(err) = client.connect_ports_by_name(port_name, &port.name()?) {
                nih_error!("Could not connect to '{port_name}': {err}");
            }
        }
        if let (Some(port), Some(port_name)) =
            (&self.midi_output, &self.config.connect_jack_midi_output)
        {
            if let Err(err) = client.connect_ports_by_name(&port.lock().name()?, port_name) {
                nih_error!("Could not connect to '{port_name}': {err}");
            }
        }

        Ok(())
    }
}