use std::{
    collections::HashMap,
    sync::{
        Arc,
        RwLock,
    },
};
use futures::{Stream, StreamExt};
use tokio::{
    io::AsyncWriteExt,
    net::TcpListener,
    sync::mpsc::{channel, Receiver, Sender},
};
use cave::{
    config::LoadConfig,
    feed::Post,
    firehose::FirehoseFactory,
};

mod config;

fn html_to_text(html: &str) -> String {
    let mut result = String::with_capacity(html.len());
    let mut in_tag = false;
    let mut entity = None;
    for c in html.chars() {
        if c == '<' {
            // tag open
            in_tag = true;
        } else if in_tag && c == '>' {
            // tag close
            in_tag = false;
        } else if in_tag {
            // ignore
        } else if c == '&' {
            entity = Some(String::with_capacity(5));
        } else if entity.is_some() && c == ';' {
            let r = match entity.take().unwrap().as_str() {
                "amp" => "&",
                "lt" => "<",
                "gt" => ">",
                "quot" => "\"",
                "apos" => "\'",
                _ => "",
            };
            result.push_str(r);
        } else if let Some(entity) = entity.as_mut() {
            entity.push(c);
        } else {
            result.push(c);
        }
    }
    result
}

fn format_message(post: Post) -> Option<String> {
    let language = &post.language?;
    let time = &post.created_at;
    let display_name = &post.account.display_name;
    let username = &post.account.username;
    let host = post.account.host()?;
    let text = html_to_text(&post.content);
    Some(format!(
        "[{}] {} {} <@{}@{}>\r\n{}\r\n\r\n",
        language,
        time,
        display_name,
        username,
        host,
        text,
    ))
}

#[derive(Clone)]
struct State {
    next_id: Arc<RwLock<usize>>,
    consumers: Arc<RwLock<HashMap<usize, Sender<Arc<Vec<u8>>>>>>,
}

impl State {
    pub fn new() -> Self {
        State {
            next_id: Arc::new(RwLock::new(0)),
            consumers: Arc::new(RwLock::new(HashMap::new())),
        }
    }

    pub fn get_next_id(&self) -> usize {
        let mut next_id = self.next_id.write().unwrap();
        let result = *next_id;
        *next_id += 1;
        result
    }

    pub fn pipe(&self) -> Pipe {
        let (tx, rx) = channel(1);

        let id = self.get_next_id();
        let mut consumers = self.consumers.write().unwrap();
        consumers.insert(id, tx);

        Pipe {
            id, rx,
            consumers: self.consumers.clone(),
        }
    }

    pub async fn broadcast(&self, msg: Arc<Vec<u8>>) {
        let txs = {
            let consumers = self.consumers.read().unwrap();
            consumers.values()
                .cloned()
                .collect::<Vec<_>>()
        };
        for tx in txs {
            let _ = tx.send(msg.clone()).await;
        }
    }
}

struct Pipe {
    id: usize,
    pub rx: Receiver<Arc<Vec<u8>>>,
    consumers: Arc<RwLock<HashMap<usize, Sender<Arc<Vec<u8>>>>>>,
}

impl Drop for Pipe {
    fn drop(&mut self) {
        log::trace!("drop pipe");
        let mut consumers = self.consumers.write().unwrap();
        consumers.remove(&self.id);
    }
}

async fn publisher(state: State, firehose: impl Stream<Item = Vec<u8>>) {
    firehose.for_each(move |data| {
        let state = state.clone();
        async move {
            let post = serde_json::from_slice(&data)
                .ok();
            let msg = post.and_then(format_message);
            if let Some(msg) = msg {
                state.broadcast(Arc::new(msg.into_bytes())).await;
            }
        }
    }).await;
}

#[tokio::main]
async fn main() {
    cave::init::exit_on_panic();
    cave::init::init_logger();

    let config = config::Config::load();

    let state = State::new();

    let firehose_factory = FirehoseFactory::new(config.redis);
    let firehose = firehose_factory.produce()
        .await
        .expect("firehose")
        .filter_map(|item| async move { item.ok() });
    tokio::spawn(
        publisher(state.clone(), firehose)
    );

    let listener = TcpListener::bind(
        format!("[::]:{}", config.listen_port)
    ).await.expect("TcpListener::bind");

    cave::systemd::ready();

    while let Ok((mut socket, addr)) = listener.accept().await {
        log::info!("Accepted connection from {:?}", addr);
        let mut pipe = state.pipe();

        tokio::spawn(async move {
            log::trace!("while...");
            while let Some(msg) = pipe.rx.recv().await {
                match socket.write_all(&msg[..]).await {
                    Ok(_) => {}
                    Err(_) => break,
                }
            }
        });
    }
}