#![recursion_limit = "2048"]
#![allow(clippy::should_implement_trait, clippy::unnecessary_to_owned)]
use cpal::{
    traits::{HostTrait, StreamTrait},
    BuildStreamError, Stream, StreamConfig,
};
use gonk_database::{Index, Song};
use std::{
    fs::File,
    io::ErrorKind,
    sync::{Arc, RwLock},
    time::Duration,
    vec::IntoIter,
};
use symphonia::{
    core::{
        audio::SampleBuffer,
        codecs::{Decoder, DecoderOptions},
        errors::{Error, SeekErrorKind},
        formats::{FormatOptions, SeekMode, SeekTo},
        io::MediaSourceStream,
        meta::MetadataOptions,
        probe::{Hint, ProbeResult},
        units::{Time, TimeBase},
    },
    default::get_probe,
};

pub use cpal::{traits::DeviceTrait, Device};

mod cpal;

#[inline]
const fn gcd(a: usize, b: usize) -> usize {
    if b == 0 {
        a
    } else {
        gcd(b, a % b)
    }
}

#[inline]
fn lerp(a: f32, b: f32, t: f32) -> f32 {
    a + t * (b - a)
}

const VOLUME_STEP: u8 = 5;
const VOLUME_REDUCTION: f32 = 500.0;
const MAX_DECODE_ERRORS: usize = 3;

pub struct Resampler {
    probed: ProbeResult,
    decoder: Box<dyn Decoder>,

    input_real: usize,
    input: usize,
    output: usize,

    buffer: IntoIter<f32>,

    current_frame: Vec<f32>,
    current_frame_pos: usize,

    next_frame: Vec<f32>,
    next_frame_pos: usize,

    output_buffer: Option<f32>,

    time_base: TimeBase,

    gain: f32,

    pub volume: f32,
    pub duration: Duration,
    pub finished: bool,
    pub elapsed: Duration,
}

impl Resampler {
    pub fn new(output: usize, file: File, volume: u8, gain: f32) -> Self {
        let mss = MediaSourceStream::new(Box::new(file), Default::default());

        let mut probed = get_probe()
            .format(
                &Hint::default(),
                mss,
                &FormatOptions {
                    prebuild_seek_index: true,
                    seek_index_fill_rate: 1,
                    enable_gapless: false,
                },
                &MetadataOptions::default(),
            )
            .unwrap();

        let track = probed.format.default_track().unwrap();
        let input = track.codec_params.sample_rate.unwrap() as usize;
        let time_base = track.codec_params.time_base.unwrap();

        let n_frames = track.codec_params.n_frames.unwrap();
        let time = track.codec_params.time_base.unwrap().calc_time(n_frames);
        let duration = Duration::from_secs(time.seconds) + Duration::from_secs_f64(time.frac);

        let mut decoder = symphonia::default::get_codecs()
            .make(&track.codec_params, &DecoderOptions::default())
            .unwrap();

        let next_packet = probed.format.next_packet().unwrap();
        let decoded = decoder.decode(&next_packet).unwrap();
        let mut buffer = SampleBuffer::<f32>::new(decoded.capacity() as u64, *decoded.spec());
        buffer.copy_interleaved_ref(decoded);
        let mut buffer = buffer.samples().to_vec().into_iter();

        let ts = next_packet.ts();
        let t = time_base.calc_time(ts);
        let elapsed = Duration::from_secs(t.seconds) + Duration::from_secs_f64(t.frac);

        let gcd = gcd(input, output);

        let (current_frame, next_frame) = if input == output {
            (Vec::new(), Vec::new())
        } else {
            (
                vec![buffer.next().unwrap(), buffer.next().unwrap()],
                vec![buffer.next().unwrap(), buffer.next().unwrap()],
            )
        };

        Self {
            probed,
            decoder,
            buffer,
            input_real: input,
            input: input / gcd,
            output: output / gcd,
            current_frame_pos: 0,
            next_frame_pos: 0,
            current_frame,
            next_frame,
            output_buffer: None,
            volume: volume as f32 / VOLUME_REDUCTION,
            duration,
            elapsed,
            time_base,
            finished: false,
            gain,
        }
    }

    pub fn update_sample_rate(&mut self, output: usize) {
        let gcd = gcd(self.input_real, output);
        self.input = self.input_real / gcd;
        self.output = output / gcd;

        //TODO: There might be more buffers that should be cleared
        //when changing the sample rate. It's hard to test.
        self.output_buffer = None;
    }

    pub fn next(&mut self) -> f32 {
        if self.finished {
            0.0
        } else if let Some(smp) = self.next_sample() {
            if self.gain == 0.0 {
                //Reduce the volume a little to match
                //songs with replay gain information.
                smp * self.volume * 0.75
            } else {
                smp * self.volume * self.gain
            }
        } else {
            let mut decode_errors: usize = 0;
            loop {
                if self.finished {
                    return 0.0;
                }

                match self.probed.format.next_packet() {
                    Ok(next_packet) => {
                        let decoded = self.decoder.decode(&next_packet).unwrap();
                        let mut buffer =
                            SampleBuffer::<f32>::new(decoded.capacity() as u64, *decoded.spec());
                        buffer.copy_interleaved_ref(decoded);
                        self.buffer = buffer.samples().to_vec().into_iter();

                        let ts = next_packet.ts();
                        let t = self.time_base.calc_time(ts);
                        self.elapsed =
                            Duration::from_secs(t.seconds) + Duration::from_secs_f64(t.frac);

                        if self.input == self.output {
                            self.current_frame = Vec::new();
                            self.next_frame = Vec::new();
                        } else {
                            self.current_frame =
                                vec![self.buffer.next().unwrap(), self.buffer.next().unwrap()];
                            self.next_frame =
                                vec![self.buffer.next().unwrap(), self.buffer.next().unwrap()];
                        }

                        self.current_frame_pos = 0;
                        self.next_frame_pos = 0;

                        debug_assert!(self.output_buffer.is_none());

                        return self.next();
                    }
                    Err(err) => match err {
                        Error::IoError(err) => match err.kind() {
                            ErrorKind::UnexpectedEof => {
                                self.finished = true;
                                return 0.0;
                            }
                            _ => continue,
                        },
                        Error::DecodeError(_) => {
                            decode_errors += 1;
                            if decode_errors > MAX_DECODE_ERRORS {
                                panic!("{:?}", err);
                            }
                            continue;
                        }
                        _ => panic!("{}", err),
                    },
                }
            }
        }
    }

    fn next_input_frame(&mut self) {
        self.current_frame = std::mem::take(&mut self.next_frame);

        if let Some(sample) = self.buffer.next() {
            self.next_frame.push(sample);
        }

        if let Some(sample) = self.buffer.next() {
            self.next_frame.push(sample);
        }

        self.current_frame_pos += 1;
    }

    fn next_sample(&mut self) -> Option<f32> {
        if self.input == self.output {
            return self.buffer.next();
        } else if let Some(sample) = self.output_buffer.take() {
            return Some(sample);
        }

        if self.next_frame_pos == self.output {
            self.next_frame_pos = 0;

            self.next_input_frame();
            while self.current_frame_pos != self.input {
                self.next_input_frame();
            }
            self.current_frame_pos = 0;
        } else {
            let req_left_sample = (self.input * self.next_frame_pos / self.output) % self.input;

            while self.current_frame_pos != req_left_sample {
                self.next_input_frame();
                debug_assert!(self.current_frame_pos < self.input);
            }
        }

        let numerator = (self.input * self.next_frame_pos) % self.output;

        self.next_frame_pos += 1;

        if self.current_frame.is_empty() && self.next_frame.is_empty() {
            return None;
        }

        if self.next_frame.is_empty() {
            let r = self.current_frame.remove(0);
            self.output_buffer = self.current_frame.first().cloned();
            self.current_frame.clear();
            Some(r)
        } else {
            let ratio = numerator as f32 / self.output as f32;
            self.output_buffer = Some(lerp(self.current_frame[1], self.next_frame[1], ratio));
            Some(lerp(self.current_frame[0], self.next_frame[0], ratio))
        }
    }

    pub fn set_volume(&mut self, volume: u8) {
        self.volume = volume as f32 / VOLUME_REDUCTION;
    }
    pub fn seek(&mut self, time: Duration) -> Result<(), String> {
        match self.probed.format.seek(
            SeekMode::Coarse,
            SeekTo::Time {
                time: Time::new(time.as_secs(), time.subsec_nanos() as f64 / 1_000_000_000.0),
                track_id: None,
            },
        ) {
            Ok(_) => Ok(()),
            Err(e) => match e {
                Error::SeekError(e) => match e {
                    SeekErrorKind::OutOfRange => Err(String::from("Seek out of range!")),
                    _ => panic!("{:?}", e),
                },
                _ => panic!("{}", e),
            },
        }
    }
}

#[derive(Debug, PartialEq, Eq)]
pub enum State {
    Playing,
    Paused,
    Stopped,
}

pub struct Player {
    pub stream: Stream,
    pub resampler: Arc<RwLock<Option<Resampler>>>,
    pub sample_rate: usize,
    pub state: State,
    pub songs: Index<Song>,
    pub volume: u8,
}

impl Player {
    pub fn new(wanted_device: &str, volume: u8, songs: Index<Song>, elapsed: f32) -> Self {
        #[cfg(unix)]
        let _gag = gag::Gag::stderr().unwrap();

        let mut device = None;

        for d in audio_devices() {
            if d.name().unwrap() == wanted_device {
                device = Some(d);
            }
        }

        let device = if let Some(device) = device {
            device
        } else {
            default_device()
        };

        let config = device.default_output_config().unwrap().config();
        if config.channels != 2 {
            panic!("TODO: Support downmixing multiple channels")
        }

        let resampler = Arc::new(RwLock::new(None));
        let stream = create_output_stream(&device, &config, resampler.clone()).unwrap();

        let mut state = State::Stopped;
        let sample_rate = config.sample_rate.0 as usize;

        //Force update the playback position when restoring the queue.
        if let Some(song) = songs.selected() {
            let file = match File::open(&song.path) {
                Ok(file) => file,
                Err(_) => {
                    return Self {
                        stream,
                        resampler,
                        sample_rate,
                        state,
                        songs,
                        volume,
                    }
                }
            };
            let elapsed = Duration::from_secs_f32(elapsed);
            let mut r = Resampler::new(sample_rate, file, volume, song.gain as f32);
            //Elapsed will not update while paused so force update it.
            r.elapsed = elapsed;
            r.seek(elapsed).unwrap();
            state = State::Paused;
            *resampler.write().unwrap() = Some(r);
        };

        Self {
            resampler,
            sample_rate: config.sample_rate.0 as usize,
            stream,
            volume,
            state,
            songs,
        }
    }

    pub fn set_output_device(&mut self, device: &Device) -> Result<(), String> {
        //TODO: Pausing the stream and hanging the thread for 500ms
        //gives the device enough time to release it's lock.
        //My interface has two outputs on the same device and
        //is unable to grab handles for each other while
        //in use.

        match device.default_output_config() {
            Ok(supported_stream) => {
                match create_output_stream(
                    device,
                    &supported_stream.config(),
                    self.resampler.clone(),
                ) {
                    Ok(stream) => {
                        self.stream = stream;
                        self.sample_rate = supported_stream.sample_rate().0 as usize;

                        if let Some(resampler) = self.resampler.write().unwrap().as_mut() {
                            resampler.update_sample_rate(self.sample_rate);
                        }

                        self.stream.play().unwrap();
                        Ok(())
                    }
                    Err(e) => match e {
                        BuildStreamError::BackendSpecific { err } => Err(err.description),
                        _ => Err(format!("{}", e)),
                    },
                }
            }
            Err(e) => Err(format!("{}", e)),
        }
    }

    pub fn update(&mut self) -> Result<(), String> {
        let mut next = false;
        if let Some(resampler) = self.resampler.read().unwrap().as_ref() {
            if resampler.finished {
                next = true;
            }
        }

        if next {
            self.next()?;
        }

        Ok(())
    }

    pub fn add_songs(&mut self, songs: &[Song]) -> Result<(), String> {
        self.songs.data.extend(songs.to_vec());
        if self.songs.selected().is_none() {
            self.songs.select(Some(0));
            self.play_selected()
        } else {
            Ok(())
        }
    }

    pub fn previous(&mut self) -> Result<(), String> {
        self.songs.up();
        self.play_selected()
    }

    pub fn next(&mut self) -> Result<(), String> {
        self.songs.down();
        self.play_selected()
    }

    fn play_selected(&mut self) -> Result<(), String> {
        if let Some(song) = self.songs.selected() {
            let file = match File::open(&song.path) {
                Ok(file) => file,
                //TODO: Error might be too vague.
                Err(_) => return Err(format!("Could not open file: {:?}", song.path)),
            };
            if let Some(resampler) = self.resampler.write().unwrap().as_mut() {
                resampler.finished = true;
            }
            *self.resampler.write().unwrap() = Some(Resampler::new(
                self.sample_rate,
                file,
                self.volume,
                song.gain as f32,
            ));
            self.play();
        }
        Ok(())
    }

    pub fn play_index(&mut self, i: usize) -> Result<(), String> {
        self.songs.select(Some(i));
        self.play_selected()
    }

    pub fn delete_index(&mut self, i: usize) -> Result<(), String> {
        if self.songs.is_empty() {
            return Ok(());
        }
        self.songs.data.remove(i);

        if let Some(playing) = self.songs.index() {
            let len = self.songs.len();

            if len == 0 {
                self.clear();
            } else if i == playing && i == 0 {
                if i == 0 {
                    self.songs.select(Some(0));
                }
                return self.play_selected();
            } else if i == playing && i == len {
                self.songs.select(Some(len - 1));
            } else if i < playing {
                self.songs.select(Some(playing - 1));
            }
        };
        Ok(())
    }

    pub fn clear(&mut self) {
        self.songs = Index::default();
        self.state = State::Stopped;
        *self.resampler.write().unwrap() = None;
    }

    pub fn clear_except_playing(&mut self) {
        if let Some(index) = self.songs.index() {
            let playing = self.songs.data.remove(index);
            self.songs = Index::new(vec![playing], Some(0));
        }
    }

    pub fn volume_up(&mut self) {
        self.volume += VOLUME_STEP;
        if self.volume > 100 {
            self.volume = 100;
        }

        if let Some(resampler) = self.resampler.write().unwrap().as_mut() {
            resampler.set_volume(self.volume);
        }
    }

    pub fn volume_down(&mut self) {
        if self.volume != 0 {
            self.volume -= VOLUME_STEP;
        }

        if let Some(resampler) = self.resampler.write().unwrap().as_mut() {
            resampler.set_volume(self.volume);
        }
    }

    pub fn duration(&self) -> Duration {
        if let Some(resampler) = self.resampler.read().unwrap().as_ref() {
            resampler.duration
        } else {
            Duration::default()
        }
    }

    pub fn elapsed(&self) -> Duration {
        if let Some(resampler) = self.resampler.read().unwrap().as_ref() {
            resampler.elapsed
        } else {
            Duration::default()
        }
    }

    pub fn toggle_playback(&mut self) -> Result<(), String> {
        if self.resampler.read().unwrap().is_none() {
            self.play_selected()
        } else {
            match self.state {
                State::Playing => self.pause(),
                State::Paused => self.play(),
                State::Stopped => (),
            };
            Ok(())
        }
    }

    pub fn play(&mut self) {
        self.stream.play().unwrap();
        self.state = State::Playing;
    }

    pub fn pause(&mut self) {
        self.stream.pause().unwrap();
        self.state = State::Paused;
    }

    pub fn seek_by(&mut self, time: f32) -> Result<(), String> {
        let time = if let Some(resampler) = self.resampler.read().unwrap().as_ref() {
            resampler.elapsed.as_secs_f32() + time
        } else {
            return Ok(());
        };

        if time > self.duration().as_secs_f32() {
            self.next()?;
        } else {
            self.seek_to(time)?;
            self.play();
        }

        Ok(())
    }

    pub fn seek_to(&mut self, time: f32) -> Result<(), String> {
        //Seeking at under 0.5 seconds causes an unexpected EOF.
        //Could be because of the coarse seek.
        let time = Duration::from_secs_f32(time.clamp(0.5, f32::MAX));
        if time > self.duration() {
            self.next()?;
        } else {
            if let Some(resampler) = self.resampler.write().unwrap().as_mut() {
                resampler.seek(time)?;
            }
            self.play();
        }
        Ok(())
    }

    pub fn is_playing(&self) -> bool {
        State::Playing == self.state
    }
}

unsafe impl Send for Player {}

fn create_output_stream(
    device: &Device,
    config: &StreamConfig,
    resampler: Arc<RwLock<Option<Resampler>>>,
) -> Result<Stream, BuildStreamError> {
    device.build_output_stream(
        config,
        move |data: &mut [f32], _: &cpal::OutputCallbackInfo| {
            for frame in data.chunks_mut(2) {
                for sample in frame.iter_mut() {
                    let smp = if let Some(resampler) = resampler.write().unwrap().as_mut() {
                        resampler.next()
                    } else {
                        0.0
                    };
                    *sample = smp;
                }
            }
        },
        |err| panic!("{}", err),
    )
}

pub fn audio_devices() -> Vec<Device> {
    let host_id = cpal::default_host().id();
    let host = cpal::host_from_id(host_id).unwrap();

    //FIXME: Getting just the output devies was too slow(150ms).
    //Collecting every device is still slow but it's not as bad.
    host.devices().unwrap().collect()
}

pub fn default_device() -> Device {
    cpal::default_host().default_output_device().unwrap()
}