use crate::transcoder::Transcoder;
use async_std::sync::{Arc, Receiver, RecvError, RwLock, RwLockReadGuard, Sender, TryRecvError};
use async_std::task;
use std::collections::{HashMap, HashSet};
use std::option::Option::Some;
use std::thread::Builder;
use std::thread::JoinHandle;
use uuid::Uuid;

#[derive(Debug)]
pub struct TranscoderInstance {
    id: Uuid,
    channel: Channel<Message>,
    state: RwLock<TranscoderInstanceState>,
    command: TranscoderCommand,
}

impl TranscoderInstance {
    pub async fn state<T>(&self, block: fn(RwLockReadGuard<TranscoderInstanceState>) -> T) -> T {
        block(self.state.read().await)
    }
}

#[derive(Debug, Default)]
pub struct TranscoderInstanceState {
    thread: Option<JoinHandle<()>>,
    duration_secs: f64,
    segments: HashSet<u32>,
    init_written: bool,
}

impl TranscoderInstanceState {
    #[inline]
    pub fn duration(&self) -> f64 {
        self.duration_secs
    }

    #[inline]
    pub fn segments(&self) -> &HashSet<u32> {
        &self.segments
    }

    #[inline]
    pub fn init_written(&self) -> bool {
        self.init_written
    }
}

#[derive(Debug, Default)]
pub struct TranscoderManager {
    instances: HashMap<Uuid, Arc<TranscoderInstance>>,
}

#[derive(Debug, Clone)]
pub struct Channel<T> {
    receiver: Receiver<T>,
    sender: Sender<T>,
}

impl<T> Channel<T> {
    async fn send(&self, msg: T) {
        self.sender.send(msg).await
    }

    fn send_blocking(&self, msg: T) {
        task::block_on(self.sender.send(msg))
    }

    async fn recv(&self) -> Result<T, RecvError> {
        self.receiver.recv().await
    }

    fn recv_blocking(&self) -> Result<T, RecvError> {
        task::block_on(self.receiver.recv())
    }

    fn try_recv(&self) -> Result<T, TryRecvError> {
        self.receiver.try_recv()
    }
}

fn new_channel() -> (Channel<Message>, Channel<Message>) {
    let (sender_a, receiver_a) = async_std::sync::channel(25);
    let (sender_b, receiver_b) = async_std::sync::channel(25);

    (
        Channel {
            sender: sender_a,
            receiver: receiver_b,
        },
        Channel {
            sender: sender_b,
            receiver: receiver_a,
        },
    )
}

#[derive(Debug, Clone)]
pub struct TranscoderCommand {
    input: String,
    output: String,
    audio: Option<i32>,
    video: Option<i32>,
}

#[derive(Debug)]
pub enum Message {
    Info { duration_secs: f64 },
    SegmentReady(u32),
    Seek(u32),
    Failure(String),
    Stop,
    Finished,
}

fn transcoder_thread_main(command: TranscoderCommand, channel: Channel<Message>) {
    if let Err(err) = transcoder_thread(command, &channel) {
        channel.send_blocking(Message::Failure(err));
        return;
    }
}

fn transcoder_thread(command: TranscoderCommand, channel: &Channel<Message>) -> Result<(), String> {
    let transcoder = Transcoder::create(
        &command.input,
        &command.output,
        command.video,
        command.audio,
    );

    let mut transcoder = match transcoder {
        Ok(t) => t,
        Err(e) => {
            channel.send_blocking(Message::Failure(e));
            return Ok(());
        }
    };

    transcoder.open()?;

    channel.send_blocking(Message::Info {
        duration_secs: transcoder.duration_secs(),
    });

    let mut last_segment = transcoder.segment();
    while transcoder.transcode()? {
        while let Ok(msg) = channel.try_recv() {
            match msg {
                Message::Seek(segment) => {
                    transcoder.seek(segment, Some(transcoder.video_stream()))?;
                }
                Message::Stop => {
                    transcoder.stop();
                    return Ok(());
                }

                _ => {}
            };
        }

        if last_segment < transcoder.segment() {
            channel.send_blocking(Message::SegmentReady(last_segment));
            last_segment = transcoder.segment();
        }
    }

    transcoder.finish()?;
    channel.send_blocking(Message::SegmentReady(transcoder.segment()));
    transcoder.stop();
    channel.send_blocking(Message::Finished);

    Ok(())
}

impl TranscoderManager {
    pub fn start(
        &mut self,
        input: String,
        audio: Option<i32>,
        video: Option<i32>,
    ) -> Result<Uuid, std::io::Error> {
        let uuid = Uuid::new_v4();
        let command = TranscoderCommand {
            input: input.clone(),
            output: format!("/tmp/transotf/{}/", uuid),
            audio,
            video,
        };
        let (thread_channel, own_channel) = new_channel();
        let thread = {
            let command = command.clone();
            Builder::new()
                .name(format!("t#{}", uuid))
                .spawn(|| transcoder_thread_main(command, thread_channel))?
        };

        let instance = TranscoderInstance {
            id: uuid,
            command,
            state: RwLock::new(TranscoderInstanceState {
                thread: Some(thread),
                init_written: false,
                segments: HashSet::new(),
                duration_secs: 0.0,
            }),
            channel: own_channel,
        };

        let instance = Arc::new(instance);
        self.instances.insert(uuid, instance.clone());

        task::spawn(async move {
            loop {
                let fut = instance.channel.recv();
                if let Ok(x) = fut.await {
                    match x {
                        Message::Finished => {
                            let mut state = instance.state.write().await;
                            if let Some(join_handle) = std::mem::replace(&mut state.thread, None) {
                                join_handle.join().unwrap();
                            }

                            break;
                        }

                        Message::Info { duration_secs } => {
                            let mut state = instance.state.write().await;
                            state.duration_secs = duration_secs
                        }

                        Message::SegmentReady(segment) => {
                            let mut state = instance.state.write().await;
                            if segment == 0 {
                                state.init_written = true
                            }

                            state.segments.insert(segment);
                        }

                        _ => {}
                    }

                    println!("> {:?}", x);
                } else {
                    return;
                }
            }
        });

        Ok(uuid)
    }

    pub fn get(&self, id: Uuid) -> Option<Arc<TranscoderInstance>> {
        self.instances.get(&id).cloned()
    }
}