// Copyright 2015-2020 Parity Technologies (UK) Ltd.
// This file is part of OpenEthereum.

// OpenEthereum is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// OpenEthereum is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with OpenEthereum.  If not, see <http://www.gnu.org/licenses/>.

use std::collections::BTreeMap;

use super::oneshot;
use ethereum_types::U256;
use parking_lot::{Mutex, RwLock};
use v1::{
    helpers::{
        errors,
        requests::{ConfirmationPayload, ConfirmationRequest},
    },
    types::{ConfirmationResponse, Origin},
};

use jsonrpc_core::Error;

/// Result that can be returned from JSON RPC.
pub type ConfirmationResult = Result<ConfirmationResponse, Error>;

/// Possible events happening in the queue that can be listened to.
#[derive(Debug, PartialEq, Clone)]
pub enum QueueEvent {
    /// Receiver should stop work upon receiving `Finish` message.
    Finish,
    /// Informs about new request.
    NewRequest(U256),
    /// Request rejected.
    RequestRejected(U256),
    /// Request resolved.
    RequestConfirmed(U256),
}

/// Defines possible errors when inserting to queue
#[derive(Debug, PartialEq)]
pub enum QueueAddError {
    LimitReached,
}

// TODO [todr] to consider: timeout instead of limit?
pub const QUEUE_LIMIT: usize = 50;

/// A queue of transactions awaiting to be confirmed and signed.
pub trait SigningQueue: Send + Sync {
    /// Add new request to the queue.
    /// Returns a `Result` wrapping  `ConfirmationReceiver` together with it's unique id in the queue.
    /// `ConfirmationReceiver` is a `Future` awaiting for resolution of the given request.
    fn add_request(
        &self,
        request: ConfirmationPayload,
        origin: Origin,
    ) -> Result<(U256, ConfirmationReceiver), QueueAddError>;

    /// Notifies possible token holders that request was rejected.
    fn request_rejected(&self, sender: ConfirmationSender) -> Option<ConfirmationRequest>;

    /// Notifies possible token holders that request was confirmed and given hash was assigned.
    fn request_confirmed(
        &self,
        sender: ConfirmationSender,
        result: ConfirmationResult,
    ) -> Option<ConfirmationRequest>;

    /// Put a request taken from `SigningQueue::take` back to the queue.
    fn request_untouched(&self, sender: ConfirmationSender);

    /// Returns and removes a request if it is contained in the queue.
    fn take(&self, id: &U256) -> Option<ConfirmationSender>;

    /// Return copy of all the requests in the queue.
    fn requests(&self) -> Vec<ConfirmationRequest>;

    /// Returns number of requests awaiting confirmation.
    fn len(&self) -> usize;

    /// Returns true if there are no requests awaiting confirmation.
    fn is_empty(&self) -> bool;
}

/// Confirmation request information with result notifier.
pub struct ConfirmationSender {
    /// Confirmation request information.
    pub request: ConfirmationRequest,

    sender: oneshot::Sender<ConfirmationResult>,
}

/// Receiving end of the Confirmation channel; can be used as a `Future` to await for `ConfirmationRequest`
/// being processed and turned into `ConfirmationOutcome`
pub type ConfirmationReceiver = oneshot::Receiver<ConfirmationResult>;

/// Queue for all unconfirmed requests.
#[derive(Default)]
pub struct ConfirmationsQueue {
    id: Mutex<U256>,
    queue: RwLock<BTreeMap<U256, ConfirmationSender>>,
    on_event: RwLock<Vec<Box<dyn Fn(QueueEvent) -> () + Send + Sync>>>,
}

impl ConfirmationsQueue {
    /// Adds a queue listener. For each event, `listener` callback will be invoked.
    pub fn on_event<F: Fn(QueueEvent) -> () + Send + Sync + 'static>(&self, listener: F) {
        self.on_event.write().push(Box::new(listener));
    }

    /// Notifies consumer that the communcation is over.
    /// No more events will be sent after this function is invoked.
    pub fn finish(&self) {
        self.notify_message(QueueEvent::Finish);
        self.on_event.write().clear();
    }

    /// Notifies `ConfirmationReceiver` holder about the result given a request.
    fn notify_result(
        &self,
        sender: ConfirmationSender,
        result: Option<ConfirmationResult>,
    ) -> Option<ConfirmationRequest> {
        // notify receiver about the event
        self.notify_message(result.clone().map_or_else(
            || QueueEvent::RequestRejected(sender.request.id),
            |_| QueueEvent::RequestConfirmed(sender.request.id),
        ));

        // notify confirmation receiver about resolution
        let result = result.ok_or_else(errors::request_rejected);
        sender.sender.send(result);

        Some(sender.request)
    }

    /// Notifies receiver about the event happening in this queue.
    fn notify_message(&self, message: QueueEvent) {
        for listener in &*self.on_event.read() {
            listener(message.clone())
        }
    }
}

impl Drop for ConfirmationsQueue {
    fn drop(&mut self) {
        self.finish();
    }
}

impl SigningQueue for ConfirmationsQueue {
    fn add_request(
        &self,
        request: ConfirmationPayload,
        origin: Origin,
    ) -> Result<(U256, ConfirmationReceiver), QueueAddError> {
        if self.len() > QUEUE_LIMIT {
            return Err(QueueAddError::LimitReached);
        }

        // Increment id
        let id = {
            let mut last_id = self.id.lock();
            *last_id += U256::from(1);
            *last_id
        };
        // Add request to queue
        let res = {
            debug!(target: "own_tx", "Signer: New entry ({:?}) in confirmation queue.", id);
            trace!(target: "own_tx", "Signer: ({:?}) : {:?}", id, request);

            let mut queue = self.queue.write();
            let (sender, receiver) = oneshot::oneshot::<ConfirmationResult>();

            queue.insert(
                id,
                ConfirmationSender {
                    sender,
                    request: ConfirmationRequest {
                        id,
                        payload: request,
                        origin,
                    },
                },
            );
            (id, receiver)
        };
        // Notify listeners
        self.notify_message(QueueEvent::NewRequest(id));
        Ok(res)
    }

    fn take(&self, id: &U256) -> Option<ConfirmationSender> {
        self.queue.write().remove(id)
    }

    fn request_rejected(&self, sender: ConfirmationSender) -> Option<ConfirmationRequest> {
        debug!(target: "own_tx", "Signer: Request rejected ({:?}).", sender.request.id);
        self.notify_result(sender, None)
    }

    fn request_confirmed(
        &self,
        sender: ConfirmationSender,
        result: ConfirmationResult,
    ) -> Option<ConfirmationRequest> {
        debug!(target: "own_tx", "Signer: Request confirmed ({:?}).", sender.request.id);
        self.notify_result(sender, Some(result))
    }

    fn request_untouched(&self, sender: ConfirmationSender) {
        self.queue.write().insert(sender.request.id, sender);
    }

    fn requests(&self) -> Vec<ConfirmationRequest> {
        let queue = self.queue.read();
        queue
            .values()
            .map(|sender| sender.request.clone())
            .collect()
    }

    fn len(&self) -> usize {
        let queue = self.queue.read();
        queue.len()
    }

    fn is_empty(&self) -> bool {
        let queue = self.queue.read();
        queue.is_empty()
    }
}

#[cfg(test)]
mod test {
    use ethereum_types::{Address, H256, U256};
    use jsonrpc_core::futures::Future;
    use parking_lot::Mutex;
    use std::sync::Arc;
    use v1::{
        helpers::{
            external_signer::{ConfirmationsQueue, QueueEvent, SigningQueue},
            ConfirmationPayload, FilledTransactionRequest,
        },
        types::ConfirmationResponse,
    };

    fn request() -> ConfirmationPayload {
        ConfirmationPayload::SendTransaction(FilledTransactionRequest {
            transaction_type: Default::default(),
            from: Address::from_low_u64_be(1),
            used_default_from: false,
            to: Some(Address::from_low_u64_be(2)),
            gas_price: Some(U256::from(0)),
            max_fee_per_gas: None,
            gas: 10_000.into(),
            value: 10_000_000.into(),
            data: vec![],
            nonce: None,
            condition: None,
            access_list: None,
            max_priority_fee_per_gas: None,
        })
    }

    #[test]
    fn should_wait_for_hash() {
        // given
        let queue = Arc::new(ConfirmationsQueue::default());
        let request = request();

        // when
        let (id, future) = queue.add_request(request, Default::default()).unwrap();
        let sender = queue.take(&id).unwrap();
        queue.request_confirmed(
            sender,
            Ok(ConfirmationResponse::SendTransaction(
                H256::from_low_u64_be(1),
            )),
        );

        // then
        let confirmation = future.wait().unwrap();
        assert_eq!(
            confirmation,
            Ok(ConfirmationResponse::SendTransaction(
                H256::from_low_u64_be(1)
            ))
        );
    }

    #[test]
    fn should_receive_notification() {
        // given
        let received = Arc::new(Mutex::new(vec![]));
        let queue = Arc::new(ConfirmationsQueue::default());
        let request = request();

        // when
        let r = received.clone();
        queue.on_event(move |notification| {
            r.lock().push(notification);
        });
        let _future = queue.add_request(request, Default::default()).unwrap();
        queue.finish();

        // then
        let r = received.lock();
        assert_eq!(r[0], QueueEvent::NewRequest(U256::from(1)));
        assert_eq!(r[1], QueueEvent::Finish);
        assert_eq!(r.len(), 2);
    }

    #[test]
    fn should_add_transactions() {
        // given
        let queue = ConfirmationsQueue::default();
        let request = request();

        // when
        let _future = queue
            .add_request(request.clone(), Default::default())
            .unwrap();
        let all = queue.requests();

        // then
        assert_eq!(all.len(), 1);
        let el = all.get(0).unwrap();
        assert_eq!(el.id, U256::from(1));
        assert_eq!(el.payload, request);
    }
}