// nrepl.rs
// Copyright 2022 Matti Hänninen
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.

use std::io::ErrorKind;

use serde::{Deserialize, Serialize};

use super::socket::Socket;
use crate::{bencode, error::Error};

#[derive(Debug)]
pub struct Session {
  // The session can own the connection as We do not support multiple sessions
  // even though the nREPL protocol would permit it.
  connection: Connection,
  session_id: Box<str>,
  request_count: usize,
}

impl Session {
  pub fn close(mut self) -> Result<Connection, Error> {
    let id = format!("{}:close", self.session_id);
    self.connection.send(WireRequest {
      op: Op::Close,
      id: &id,
      session: Some(&self.session_id),
      ns: None,
      code: None,
      line: None,
      column: None,
      file: None,
    })?;
    #[allow(clippy::blocks_in_if_conditions)]
    while self
      .connection
      .recv(|r| Ok(!(r.matches(&id) && r.has_status("session-closed"))))?
    {}
    Ok(self.connection)
  }

  pub fn eval<F>(
    &mut self,
    code: &str,
    file_name: Option<&str>,
    line: Option<usize>,
    column: Option<usize>,
    mut handler: F,
  ) -> Result<(), Error>
  where
    F: FnMut(Response) -> Result<(), Error>,
  {
    self.request_count += 1;
    let id = format!("{}:{}", self.session_id, self.request_count);
    self.connection.send(WireRequest {
      id: &id,
      op: Op::Eval,
      session: Some(&self.session_id),
      ns: None,
      code: Some(code),
      line: line.map(|n| n.try_into().unwrap_or_default()),
      column: column.map(|n| n.try_into().unwrap_or_default()),
      file: file_name,
    })?;
    #[allow(clippy::blocks_in_if_conditions)]
    while self.connection.recv(|r| {
      if !r.matches(&id) {
        return Ok(true);
      }
      handler(Response {
        value: r.value.as_deref(),
        out: r.out.as_deref(),
        err: r.err.as_deref(),
        ex: r.ex.as_deref(),
        root_ex: r.root_ex.as_deref(),
      })?;
      Ok(!r.has_status("done"))
    })? {}
    Ok(())
  }
}

#[derive(Debug)]
pub struct Response<'a> {
  pub value: Option<&'a str>,
  pub ex: Option<&'a str>,
  pub root_ex: Option<&'a str>,
  pub out: Option<&'a str>,
  pub err: Option<&'a str>,
}

#[derive(Debug)]
pub enum Op {
  Clone,
  Close,
  Eval,
}

impl Op {
  pub fn as_str(&self) -> &'static str {
    match *self {
      Op::Clone => "clone",
      Op::Close => "close",
      Op::Eval => "eval",
    }
  }
}

fn serialize_op<S: serde::Serializer>(
  op: &Op,
  serializer: S,
) -> Result<S::Ok, S::Error> {
  serializer.serialize_str(op.as_str())
}

#[derive(Debug, Serialize)]
#[serde(rename_all = "kebab-case")]
pub struct WireRequest<'a> {
  #[serde(serialize_with = "serialize_op")]
  pub op: Op,
  pub id: &'a str,
  pub session: Option<&'a str>,
  pub ns: Option<&'a str>,
  pub code: Option<&'a str>,
  pub line: Option<i32>,
  pub column: Option<i32>,
  pub file: Option<&'a str>,
}

#[derive(Debug, Deserialize)]
#[serde(rename_all = "kebab-case")]
pub struct WireResponse {
  pub session: String,
  pub id: Option<String>,
  pub status: Option<Vec<String>>,
  pub new_session: Option<String>,
  pub value: Option<String>,
  pub ex: Option<String>,
  pub root_ex: Option<String>,
  pub out: Option<String>,
  pub err: Option<String>,
}

impl WireResponse {
  pub fn matches(&self, id: &str) -> bool {
    self.id.as_ref().map(|our| our == id).unwrap_or(false)
  }

  pub fn has_status(&self, label: &str) -> bool {
    self
      .status
      .as_ref()
      .map(|labels| labels.iter().any(|our| our == label))
      .unwrap_or(false)
  }
}

#[derive(Debug)]
pub struct Connection {
  socket: Socket,
  buffer: Vec<u8>,
}

impl Connection {
  pub fn new(socket: Socket) -> Self {
    Self {
      socket,
      buffer: Default::default(),
    }
  }

  pub fn session(mut self) -> Result<Session, Error> {
    self.send(WireRequest {
      op: Op::Clone,
      id: "",
      session: None,
      ns: None,
      code: None,
      line: None,
      column: None,
      file: None,
    })?;
    let session_id = self.recv(|response| {
      if let Some(session) = response.new_session.as_deref() {
        Ok(session.to_owned().into_boxed_str())
      } else {
        Err(Error::UnexptectedResponse)
      }
    })?;
    Ok(Session {
      connection: self,
      session_id,
      request_count: 0,
    })
  }

  fn send(&mut self, request: WireRequest) -> Result<(), Error> {
    let payload = serde_bencode::to_bytes(&request).unwrap();
    let w = self.socket.borrow_mut_write();
    w.write_all(&payload).map_err(Error::CannotSendToHost)?;
    w.flush().map_err(Error::CannotSendToHost)
  }

  fn recv<F, V>(&mut self, mut handler: F) -> Result<V, Error>
  where
    F: FnMut(&WireResponse) -> Result<V, Error>,
  {
    let mut buffer = [0_u8; 4096];
    loop {
      match bencode::scan_next(&self.buffer) {
        Ok((_, len)) => {
          let result = serde_bencode::from_bytes(&self.buffer[0..len])
            .map_err(|_| Error::CorruptedResponse);
          self.buffer.copy_within(len.., 0);
          self.buffer.truncate(self.buffer.len() - len);
          return handler(&result?);
        }
        Err(bencode::Error::BadInput) => {
          return Err(Error::CorruptedResponse);
        }
        Err(bencode::Error::UnexpectedEnd) => {}
      }
      match self.socket.borrow_mut_read().read(&mut buffer) {
        Ok(0) => return Err(Error::HostDisconnected),
        Ok(len) => self.buffer.extend_from_slice(&buffer[0..len]),
        Err(e) if e.kind() == ErrorKind::Interrupted => {}
        Err(e) => return Err(Error::CannotReceiveFromHost(e)),
      }
    }
  }
}