use std::sync::Once;

use gstreamer as gst;
use gst::prelude::*;
use gstreamer_app::{AppSink, AppSinkCallbacks};
use gstreamer_audio::{StreamVolume, StreamVolumeFormat};
use gst::{GhostPad};

use log::{info, debug, warn, error};
use std::sync::mpsc::Sender;
use std::sync::{Mutex, Arc};
use crate::{State, ApplicationMessage};
use glib::BoolError;

static GST_INIT: Once = Once::new();

#[derive(Debug)]
pub enum AudioPlayerError {
    GStreamerError(glib::error::BoolError),
    StateChangeFailed,
}

impl From<glib::error::BoolError> for AudioPlayerError {
    fn from(err: BoolError) -> Self {
        AudioPlayerError::GStreamerError(err)
    }
}

impl From<gst::StateChangeError> for AudioPlayerError {
    fn from(_err: gst::StateChangeError) -> Self {
        AudioPlayerError::StateChangeFailed
    }
}

pub struct AudioPlayer {
    pipeline: gst::Pipeline,
    bus: gst::Bus,
    http_src: gst::Element,

    volume: gst::Element,
    sender: Arc<Mutex<Sender<ApplicationMessage>>>,
}

fn make_element(factoryname: &str, display_name: &str) -> Result<gst::Element, AudioPlayerError> {
    Ok(gst::ElementFactory::make(
        factoryname,
        Some(display_name)
    )?)
}

fn link_elements(a: &gst::Element, b: &gst::Element) -> Result<(), AudioPlayerError> {
    a.link(b)?;

    Ok(())
}

fn add_decode_bin_new_pad_callback(
    decode_bin: &gst::Element,
    audio_bin: gst::Bin,
    ghost_pad: gst::GhostPad,
) {
    decode_bin.connect_pad_added(move |_, new_pad| {
        debug!("New pad received on decode bin");
        let name = if let Some(caps) = new_pad.get_current_caps() {
            debug!("Pad caps: {}", caps.to_string());
            if let Some(structure) = caps.get_structure(0) {
                Some(structure.get_name().to_string())
            } else {
                None
            }
        } else {
            None
        };

        match name.as_deref() {
            Some("audio/x-raw") => {
                if let Some(peer) = ghost_pad.get_peer() {
                    peer.unlink(&ghost_pad).unwrap();
                }

                info!("Found raw audio, linking audio bin");
                new_pad.link(&ghost_pad).unwrap();

                audio_bin.sync_state_with_parent().unwrap();
            }
            _ => {}
        }
    });
}

impl AudioPlayer {
    pub fn new(sender: Arc<Mutex<Sender<ApplicationMessage>>>, callback: Option<Box<dyn FnMut(&[u8]) + Send>>) -> Result<Self, AudioPlayerError> {
        GST_INIT.call_once(|| gst::init().unwrap());

        info!("Creating audio player");

        let pipeline = gst::Pipeline::new(Some("TeamSpeak Audio Player"));
        let bus = pipeline.get_bus().unwrap();
        let http_src = make_element("souphttpsrc", "http source")?;
        let decode_bin = make_element("decodebin", "decode bin")?;
        pipeline.add_many(&[&http_src, &decode_bin])?;

        link_elements(&http_src, &decode_bin)?;

        let (audio_bin, volume, ghost_pad) = Self::create_audio_bin(callback)?;

        add_decode_bin_new_pad_callback(
            &decode_bin,
            audio_bin.clone(),
            ghost_pad);

        pipeline.add(&audio_bin)?;

        pipeline.set_state(gst::State::Ready)?;

        Ok(AudioPlayer {
            pipeline,
            bus,
            http_src,

            volume,
            sender,
        })
    }

    fn create_audio_bin(callback: Option<Box<dyn FnMut(&[u8]) + Send>>) -> Result<(gst::Bin, gst::Element, gst::GhostPad), AudioPlayerError> {
        let audio_bin = gst::Bin::new(Some("audio bin"));
        let queue = make_element("queue", "audio queue")?;
        let convert = make_element("audioconvert", "audio converter")?;
        let volume = make_element("volume", "volume")?;
        let resample = make_element("audioresample", "audio resampler")?;
        let pads = queue.get_sink_pads();
        let queue_sink_pad = pads
            .first()
            .unwrap();

        audio_bin.add_many(&[
            &queue,
            &convert,
            &volume,
            &resample,
        ])?;

        if let Some(mut callback) = callback {
            let opus_enc = make_element("opusenc", "opus encoder")?;
            let sink = make_element("appsink", "app sink")?;

            let appsink = sink
                .clone()
                .dynamic_cast::<AppSink>()
                .expect("Sink element is expected to be an appsink!");
            appsink.set_caps(Some(&gst::Caps::new_simple("audio/x-opus", &[
                ("channels", &(2i32)),
                ("rate", &(48_000i32)),
            ])));
            let callbacks = AppSinkCallbacks::new()
                .new_sample(move |sink| {
                    let sample = sink.pull_sample().map_err(|_| gst::FlowError::Eos)?;
                    let buffer = sample.get_buffer().ok_or(gst::FlowError::Error)?;
                    let map = buffer.map_readable().map_err(|_| gst::FlowError::Error)?;
                    let samples = map.as_slice();

                    callback(samples);

                    Ok(gst::FlowSuccess::Ok)
                })
                .build();
            appsink.set_callbacks(callbacks);

            audio_bin.add_many(&[
                &opus_enc,
                &sink
            ])?;

            gst::Element::link_many(&[
                &queue,
                &convert,
                &volume,
                &resample,
                &opus_enc,
                &sink
            ])?;
        } else {
            let sink = make_element("autoaudiosink", "auto audio sink")?;

            audio_bin.add_many(&[
                &sink
            ])?;

            gst::Element::link_many(&[
                &queue,
                &convert,
                &volume,
                &resample,
                &sink
            ])?;
        };

        let ghost_pad = GhostPad::new(Some("audio bin sink"), queue_sink_pad).unwrap();
        ghost_pad.set_active(true)?;
        audio_bin.add_pad(&ghost_pad)?;

        Ok((audio_bin, volume, ghost_pad))
    }

    pub fn set_source_url(&self, location: String) -> Result<(), AudioPlayerError> {
        info!("Setting location URI: {}", location);
        self.http_src.set_property("location", &location)?;

        Ok(())
    }

    pub fn set_volume(&self, volume: f64) -> Result<(), AudioPlayerError> {
        let db = 50.0 * volume.log10();
        info!("Setting volume: {} -> {} dB", volume, db);

        let linear = StreamVolume::convert_volume(
            StreamVolumeFormat::Db,
            StreamVolumeFormat::Linear,
            db,
        );

        self.volume.set_property("volume", &linear)?;

        Ok(())
    }

    pub fn is_started(&self) -> bool {
        let (_, current, pending) = self.pipeline.get_state(gst::ClockTime(None));

        match (current, pending) {
            (gst::State::Null, gst::State::VoidPending) => false,
            (_, gst::State::Null) => false,
            (gst::State::Ready, gst::State::VoidPending) => false,
            _ => true
        }
    }

    pub fn reset(&self) -> Result<(), AudioPlayerError> {
        info!("Setting pipeline state to null");

        self.pipeline.set_state(gst::State::Null)?;

        Ok(())
    }

    pub fn play(&self) -> Result<(), AudioPlayerError> {
        info!("Setting pipeline state to playing");

        self.pipeline.set_state(gst::State::Playing)?;

        Ok(())
    }

    pub fn pause(&self) -> Result<(), AudioPlayerError> {
        info!("Setting pipeline state to paused");

        self.pipeline.set_state(gst::State::Paused)?;

        Ok(())
    }

    pub fn stop_current(&self) {
        info!("Stopping pipeline, sending EOS");

        let handled =  self.http_src.send_event(gst::Event::new_eos().build());
        if !handled {
            warn!("EOS event was not handled");
        }
    }

    fn send_state(&self, state: State) {
        info!("Sending state {:?} to application", state);
        let sender = self.sender.lock().unwrap();
        sender.send(ApplicationMessage::StateChange(state)).unwrap();
    }

    pub fn poll(&self) {
        debug!("Polling GStreamer");
        'outer: loop {
            while let Some(msg) = self.bus.timed_pop(gst::ClockTime(None)) {
                use gst::MessageView;

                match msg.view() {
                    MessageView::StateChanged(state) => {
                        if let Some(src) = state.get_src() {
                            if src.get_name() != self.pipeline.get_name() {
                                continue;
                            }
                        }

                        let old = state.get_old();
                        let current = state.get_current();
                        let pending = state.get_pending();

                        match (old, current, pending) {
                            (gst::State::Paused, gst::State::Playing, gst::State::VoidPending) => self.send_state(State::Playing),
                            (gst::State::Playing, gst::State::Paused, gst::State::VoidPending) => self.send_state(State::Paused),
                            (_, gst::State::Ready, gst::State::Null) => self.send_state(State::Stopped),
                            (_, gst::State::Null, gst::State::VoidPending) => self.send_state(State::Stopped),
                            _ => {
                                debug!("Pipeline transitioned from {:?} to {:?}, with {:?} pending", old, current, pending);
                            }
                        }
                    }
                    MessageView::Eos(..) => {
                        info!("End of stream reached");
                        self.reset().unwrap();

                        break 'outer;
                    },
                    MessageView::Warning(warn) => {
                        warn!(
                            "Warning from {:?}: {} ({:?})",
                            warn.get_src().map(|s| s.get_path_string()),
                            warn.get_error(),
                            warn.get_debug()
                        );
                        break 'outer;
                    }
                    MessageView::Error(err) => {
                        error!(
                            "Error from {:?}: {} ({:?})",
                            err.get_src().map(|s| s.get_path_string()),
                            err.get_error(),
                            err.get_debug()
                        );
                        break 'outer;
                    }
                    _ => {
                        // debug!("{:?}", msg)
                    },
                };
            }
        }
        debug!("Left GStreamer message loop");
    }
}