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// 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 deque;
use futures::future::{self, Loop};
use service_mio::{HandlerId, IoChannel, IoContext};
use std::{
    sync::{
        atomic::{AtomicBool, Ordering as AtomicOrdering},
        Arc,
    },
    thread::{self, JoinHandle},
};
use tokio::{self};
use IoHandler;
use LOCAL_STACK_SIZE;

use parking_lot::{Condvar, Mutex};

const STACK_SIZE: usize = 16 * 1024 * 1024;

pub enum WorkType<Message> {
    Readable,
    Writable,
    Hup,
    Timeout,
    Message(Arc<Message>),
}

pub struct Work<Message> {
    pub work_type: WorkType<Message>,
    pub token: usize,
    pub handler_id: HandlerId,
    pub handler: Arc<dyn IoHandler<Message>>,
}

/// An IO worker thread
/// Sorts them ready for blockchain insertion.
pub struct Worker {
    thread: Option<JoinHandle<()>>,
    wait: Arc<Condvar>,
    deleting: Arc<AtomicBool>,
    wait_mutex: Arc<Mutex<()>>,
}

impl Worker {
    /// Creates a new worker instance.
    pub fn new<Message>(
        name: &str,
        stealer: deque::Stealer<Work<Message>>,
        channel: IoChannel<Message>,
        wait: Arc<Condvar>,
        wait_mutex: Arc<Mutex<()>>,
    ) -> Worker
    where
        Message: Send + Sync + 'static,
    {
        let deleting = Arc::new(AtomicBool::new(false));
        let mut worker = Worker {
            thread: None,
            wait: wait.clone(),
            deleting: deleting.clone(),
            wait_mutex: wait_mutex.clone(),
        };
        worker.thread = Some(
            thread::Builder::new()
                .stack_size(STACK_SIZE)
                .name(format!("Worker {}", name))
                .spawn(move || {
                    LOCAL_STACK_SIZE.with(|val| val.set(STACK_SIZE));
                    let ini = (stealer, channel.clone(), wait, wait_mutex.clone(), deleting);
                    let future =
                        future::loop_fn(ini, |(stealer, channel, wait, wait_mutex, deleting)| {
                            {
                                let mut lock = wait_mutex.lock();
                                if deleting.load(AtomicOrdering::SeqCst) {
                                    return Ok(Loop::Break(()));
                                }
                                wait.wait(&mut lock);
                            }

                            while !deleting.load(AtomicOrdering::SeqCst) {
                                match stealer.steal() {
                                    deque::Steal::Data(work) => {
                                        Worker::do_work(work, channel.clone())
                                    }
                                    deque::Steal::Retry => {}
                                    deque::Steal::Empty => break,
                                }
                            }
                            Ok(Loop::Continue((
                                stealer, channel, wait, wait_mutex, deleting,
                            )))
                        });
                    if let Err(()) = tokio::runtime::current_thread::block_on_all(future) {
                        error!(target: "ioworker", "error while executing future")
                    }
                })
                .expect("Error creating worker thread"),
        );
        worker
    }

    fn do_work<Message>(work: Work<Message>, channel: IoChannel<Message>)
    where
        Message: Send + Sync + 'static,
    {
        match work.work_type {
            WorkType::Readable => {
                work.handler
                    .stream_readable(&IoContext::new(channel, work.handler_id), work.token);
            }
            WorkType::Writable => {
                work.handler
                    .stream_writable(&IoContext::new(channel, work.handler_id), work.token);
            }
            WorkType::Hup => {
                work.handler
                    .stream_hup(&IoContext::new(channel, work.handler_id), work.token);
            }
            WorkType::Timeout => {
                work.handler
                    .timeout(&IoContext::new(channel, work.handler_id), work.token);
            }
            WorkType::Message(message) => {
                work.handler
                    .message(&IoContext::new(channel, work.handler_id), &*message);
            }
        }
    }
}

impl Drop for Worker {
    fn drop(&mut self) {
        trace!(target: "shutdown", "[IoWorker] Closing...");
        let _ = self.wait_mutex.lock();
        self.deleting.store(true, AtomicOrdering::SeqCst);
        self.wait.notify_all();
        if let Some(thread) = self.thread.take() {
            thread.join().ok();
        }
        trace!(target: "shutdown", "[IoWorker] Closed");
    }
}