use anyhow::{anyhow, Result};
use api::{Event, Message, MemeResponse};
use bytes::Bytes;
use pin_project_lite::pin_project;
use reqwest::Client;
use std::{
    pin::Pin,
    string::FromUtf8Error,
    task::{Context, Poll},
};
use structopt::StructOpt;
use thiserror::Error;
use tokio::stream::{Stream, StreamExt};

pub mod api;
pub mod config;

#[derive(StructOpt)]
#[structopt(about = "The next generation uffbot for matterbridge!")]
pub struct Opt {
    #[structopt(
        long,
        short,
        help = "Use the given config file instead of the default. (located at \
                .config/ruff/config.toml)"
    )]
    config: Option<String>,
}

#[tokio::main]
async fn main() -> Result<()> {
    fern::Dispatch::new()
        .format(|out, message, record| {
            out.finish(format_args!(
                "{}[{}][{}] {}",
                chrono::Local::now().format("[%Y-%m-%d][%H:%M:%S]"),
                record.target(),
                record.level(),
                message
            ))
        })
        .level(log::LevelFilter::Debug)
        // hyper is quite spammy
        .level_for("hyper", log::LevelFilter::Info)
        .chain(std::io::stdout())
        .apply()?;

    let client = Client::new();
    let opt = Opt::from_args_safe()?;

    if let Some(c) = opt.config {
        let _ = config::CONFIG_PATH.set(c.into());
    }

    loop {
        let mut stream = stream(&client).await?;

        while let Some(msg) = stream.next().await {
            if let Err(e) = next_message(&client, msg).await {
                log::error!("Got error processing message: {}", e);
            }
        }

        log::error!("Stream to server closed. restarting.");
    }
}

#[derive(Debug, Error)]
enum MessageProcessError {
    #[error("Got error `{error}` trying to deserialize message:\n{data}")]
    Deserialize {
        error: serde_json::Error,
        data: String,
    },

    #[error("Got Error `{error}` try to deserialize invalid UTF-8 data:\n{data:X?}")]
    InvalidUtf8 { error: FromUtf8Error, data: Vec<u8> },
}

async fn next_message(client: &Client, raw_msg: Vec<u8>) -> Result<()> {
    let s_data =
        String::from_utf8(raw_msg.clone()).map_err(|error| MessageProcessError::InvalidUtf8 {
            error,
            data: raw_msg,
        })?;
    let message =
        serde_json::from_str(&s_data).map_err(|error| MessageProcessError::Deserialize {
            error,
            data: s_data,
        })?;

    log::info!("Processing message {:?}", &message);
    process_message(client, message).await
}

async fn process_message(client: &Client, message: Message) -> Result<()> {
    let config = config::try_get_config().await?;
    match message {
        Message {
            event: Some(Event::ApiConnected),
            ..
        } => log::info!("got api connected event"),
        Message { text, gateway, .. } if config.gateways.contains(&gateway) && !text.is_empty() => {
            if let Some(start) = text.split(" ").next() {
                let lower = start.to_lowercase();
                if lower == "uff" {
                    // TODO this is temporary, once JM3.0 is out, we will request uff memes at
                    // startup and take a random one when needed, so we don't make a request each
                    // time (which slows the bot down significantly)
                    let res = client.get("https://data.tilera.xyz/api/jensmemes/random?category=uff").send().await?.text().await?;
                    let MemeResponse { link } = serde_json::from_str(&res)?;

                    let message = Message {
                        text: link,
                        gateway,
                        username: config.nickname.clone(),
                        event: None,
                    };

                    send_message(client, &message).await?;

                    return Ok(());
                }
                
                if let Some(meme) = config.memes.map.get(&lower) {
                    log::info!(
                        r#"found meme matching message "{}". responding with "{}""#,
                        text,
                        &meme
                    );

                    let message = Message {
                        text: meme.clone(),
                        gateway,
                        username: config.nickname.clone(),
                        event: None,
                    };

                    send_message(client, &message).await?;
                }
            }
        },
        msg => log::warn!("Got unknown message: {:?}", msg),
    }

    Ok(())
}

async fn send_message(client: &Client, msg: &Message) -> Result<()> {
    let config = config::try_get_config().await?;
    log::info!("Sending message: {:?}", msg);
    let res: Result<()> = {
        let response = client
            .post(&format!("{}/message", config.api))
            .header("Content-Type", "application/json")
            .body(serde_json::to_vec(&msg)?)
            .send()
            .await?;

        log::info!(
            "sent message. server responded with `{}`",
            response.text().await?
        );

        Ok(())
    };

    res.map_err(|e| anyhow!("Error sending message:\n{}", e))
}

async fn stream(client: &Client) -> Result<impl Stream<Item = Vec<u8>>> {
    let conf = config::try_get_config().await?;
    let stream = client
        .get(&format!("{}/stream", conf.api))
        .send()
        .await?
        .bytes_stream();
    Ok(NewlineStream::new(stream.filter_map(Result::ok)))
}

pin_project! {
    struct NewlineStream<T: Stream<Item = Bytes>> {
        #[pin]
        inner: T,
        buf: Vec<u8>,
    }
}

impl<T: Stream<Item = Bytes>> Stream for NewlineStream<T> {
    type Item = Vec<u8>;

    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
        loop {
            let poll = self.as_mut().project().inner.poll_next(cx);
            // if the inner stream is not done yet, we are not either
            let poll = match poll {
                Poll::Ready(x) => x,
                Poll::Pending => return Poll::Pending,
            };

            match poll {
                Some(i) => {
                    let buf = &mut self.as_mut().project().buf;
                    buf.extend(i.into_iter());

                    let pos = match buf.iter().position(|&e| e == b'\n') {
                        Some(n) => n,
                        // if there is no newline yet, try again
                        None => continue,
                    };

                    let result = Vec::from(&buf[0..pos]);
                    **buf = Vec::from(&buf[1 + pos..]);

                    return Poll::Ready(Some(result));
                },
                // if the inner stream had nothing, we return the buffer and are done
                // in order to avoid an inifite loop when the inner stream is done, we clear the
                // buffer and return None once the buffer has been output once
                None => {
                    if !self.buf.is_empty() {
                        let buf = self.buf.clone();
                        *self.as_mut().project().buf = vec![];
                        return Poll::Ready(Some(buf));
                    } else {
                        return Poll::Ready(None);
                    }
                },
            }
        }
    }
}

impl<T: Stream<Item = Bytes>> NewlineStream<T> {
    pub fn new(stream: T) -> Self {
        Self {
            inner: stream,
            buf: vec![],
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use bytes::Bytes;
    use tokio::stream::StreamExt;

    #[tokio::test]
    async fn newline_stream() {
        let stream = tokio::stream::iter(
            vec![
                Bytes::from("hello "),
                Bytes::from("world"),
                Bytes::from("\nfoobar"),
            ]
            .into_iter(),
        );

        let mut newline_stream = NewlineStream::new(stream);

        assert_eq!(newline_stream.next().await, Some(b"hello world".to_vec()));
        assert_eq!(newline_stream.next().await, Some(b"foobar".to_vec()));
        assert_eq!(newline_stream.next().await, None);
    }
}