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// Copyright 2015-2016 Benjamin Fry <benjaminfry@me.com>
//
// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
// http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
// http://opensource.org/licenses/MIT>, at your option. This file may not be
// copied, modified, or distributed except according to those terms.
use std::cell::RefCell;
use std::rc::Rc;
use std::collections::HashMap;

use futures::Future;

use ::client::ClientHandle;
use ::client::rc_future::{rc_future, RcFuture};
use ::error::*;
use ::op::{Message, Query};

/// Will return memoized (cached) responses to queries
///
/// This wraps a ClientHandle, changing the implementation `send()` to store the response against
///  the Message.Query that was sent. This should reduce network traffic especially during things
///  like DNSSec validation. *Warning* this will currently cache for the life of the Client.
#[derive(Clone)]
#[must_use = "queries can only be sent through a ClientHandle"]
pub struct MemoizeClientHandle<H: ClientHandle> {
  client: H,
  active_queries: Rc<RefCell<HashMap<Query, RcFuture<Box<Future<Item=Message, Error=ClientError>>>>>>,
}

impl<H> MemoizeClientHandle<H> where H: ClientHandle {
  /// Returns a new handle wrapping the specified client
  pub fn new(client: H) -> MemoizeClientHandle<H> {
    MemoizeClientHandle { client: client, active_queries: Rc::new(RefCell::new(HashMap::new())) }
  }

}

impl<H> ClientHandle for MemoizeClientHandle<H> where H: ClientHandle {
  // TODO: should send be &mut so that we don't need RefCell here?
  fn send(&self, message: Message) -> Box<Future<Item=Message, Error=ClientError>> {
    let query = message.get_queries().first().expect("no query!").clone();

    if let Some(rc_future) = self.active_queries.borrow().get(&query) {
      // TODO check TTLs?
      return Box::new(rc_future.clone());
    }

    // TODO: it should be safe to loop here until the entry.or_insert_with returns...
    // check if there are active queries
    let mut map = self.active_queries.borrow_mut();
    let rc_future = map.entry(query).or_insert_with(move ||{
      rc_future(self.client.send(message))
    });

    return Box::new(rc_future.clone());
  }
}

#[cfg(test)]
mod test {
  use std::cell::Cell;
  use ::client::*;
  use ::error::*;
  use ::op::*;
  use ::rr::*;
  use futures::*;

  #[derive(Clone)]
  struct TestClient { i: Cell<u16> }

  impl ClientHandle for TestClient {
    fn send(&self, _: Message) -> Box<Future<Item=Message, Error=ClientError>> {
      let mut message = Message::new();
      let i = self.i.get();

      message.id(i);
      self.i.set(i + 1);

      Box::new(finished(message))
    }
  }

  #[test]
  fn test_memoized() {
    let client = MemoizeClientHandle::new(TestClient{i: Cell::new(0)});

    let mut test1 = Message::new();
    test1.add_query(Query::new().query_type(RecordType::A).clone());

    let mut test2 = Message::new();
    test2.add_query(Query::new().query_type(RecordType::AAAA).clone());

    let result = client.send(test1.clone()).wait().ok().unwrap();
    assert_eq!(result.get_id(), 0);

    let result = client.send(test2.clone()).wait().ok().unwrap();
    assert_eq!(result.get_id(), 1);

    // should get the same result for each...
    let result = client.send(test1).wait().ok().unwrap();
    assert_eq!(result.get_id(), 0);

    let result = client.send(test2).wait().ok().unwrap();
    assert_eq!(result.get_id(), 1);
  }

}