use similar::{TextDiff, ChangeTag};
use tokio::sync::{watch, mpsc};
use tonic::transport::Channel;
use tonic::{async_trait, Streaming};
use woot::crdt::{Op, CRDT, TextEditor};
use woot::woot::Woot;

use crate::proto::{OperationRequest, RawOp};
use crate::proto::buffer_client::BufferClient;
use crate::api::controller::ControllerWorker;

use super::TextChange;
use super::controller::BufferController;


pub(crate) struct BufferControllerWorker {
	uid: String,
	content: watch::Sender<String>,
	operations: mpsc::UnboundedReceiver<TextChange>,
	receiver: watch::Receiver<String>,
	sender: mpsc::UnboundedSender<TextChange>,
	buffer: Woot,
	path: String,
	stop: mpsc::UnboundedReceiver<()>,
	stop_control: mpsc::UnboundedSender<()>,
}

impl BufferControllerWorker {
	pub fn new(uid: String, buffer: &str, path: &str) -> Self {
		let (txt_tx, txt_rx) = watch::channel(buffer.to_string());
		let (op_tx, op_rx) = mpsc::unbounded_channel();
		let (end_tx, end_rx) = mpsc::unbounded_channel();
		BufferControllerWorker {
			uid,
			content: txt_tx,
			operations: op_rx,
			receiver: txt_rx,
			sender: op_tx,
			buffer: Woot::new(42069), // TODO initialize with buffer!
			path: path.to_string(),
			stop: end_rx,
			stop_control: end_tx,
		}
	}

	async fn send_op(&self, tx: &mut BufferClient<Channel>, outbound: &Op) -> crate::Result<()> {
		let opseq = serde_json::to_string(outbound).expect("could not serialize opseq");
		let req = OperationRequest {
			path: self.path.clone(),
			hash: format!("{:x}", md5::compute(self.buffer.view())),
			op: Some(RawOp {
				opseq, user: self.uid.clone(),
			}),
		};
		let _ = tx.edit(req).await?;
		Ok(())
	}
}

#[async_trait]
impl ControllerWorker<String> for BufferControllerWorker {
	type Controller = BufferController;
	type Tx = BufferClient<Channel>;
	type Rx = Streaming<RawOp>;

	fn subscribe(&self) -> BufferController {
		BufferController::new(
			self.receiver.clone(),
			self.sender.clone(),
			self.stop_control.clone(),
		)
	}

	async fn work(mut self, mut tx: Self::Tx, mut rx: Self::Rx) {
		loop {
			// block until one of these is ready
			tokio::select! {
				biased;

				// received stop signal
				_ = self.stop.recv() => break,

				// received a text change from editor
				res = self.operations.recv() => match res {
					None => break,
					Some(change) => {
						let span = &self.buffer.view()[change.span.clone()];
						let diff = TextDiff::from_chars(span, &change.content);

						let mut i = 0;
						let mut ops = Vec::new();
						for diff in diff.iter_all_changes() {
							match diff.tag() {
								ChangeTag::Equal => i += 1,
								ChangeTag::Delete => ops.push(self.buffer.delete(change.span.start + i).unwrap()),
								ChangeTag::Insert => {
									for c in diff.value().chars() {
										ops.push(self.buffer.insert(change.span.start + i, c).unwrap());
										i += 1;
									}
								},
							}
						}

						for op in ops {
							match self.send_op(&mut tx, &op).await {
								Ok(()) => self.buffer.enqueue(op),
								Err(e) => tracing::error!("server refused to broadcast {}: {}", op, e),
							}
						}
					}
				},

				// received a stop request (or channel got closed)
				res = rx.message() => match res {
					Err(_e) => break,
					Ok(None) => break,
					Ok(Some(change)) => {
						let op : Op = serde_json::from_str(&change.opseq).unwrap();
						self.buffer.enqueue(op);
						self.content.send(self.buffer.view()).unwrap();
					},
				},
			}

		}
	}
}