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    // Copyright 2015-2017 Parity Technologies (UK) Ltd.
    // This file is part of Parity.

    // Parity 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.

    // Parity 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 Parity.  If not, see <http://www.gnu.org/licenses/>.

    use std::sync::Arc;
    use std::thread::{JoinHandle, self};
    use std::sync::atomic::{AtomicBool, Ordering as AtomicOrdering};
    use crossbeam::sync::chase_lev;
    use service::{HandlerId, IoChannel, IoContext};
    use IoHandler;
    use panics::*;
    use std::cell::Cell;

    use std::sync::{Condvar as SCondvar, Mutex as SMutex};

    const STACK_SIZE: usize = 16*1024*1024;

    thread_local! {
    	/// Stack size
    	/// Should be modified if it is changed in Rust since it is no way
    	/// to know or get it
    	pub static LOCAL_STACK_SIZE: Cell<usize> = Cell::new(::std::env::var("RUST_MIN_STACK").ok().and_then(|s| s.parse().ok()).unwrap_or(2 * 1024 * 1024));
    }

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

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

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

    impl Worker {
    	/// Creates a new worker instance.
    	pub fn new<Message>(index: usize,
    						stealer: chase_lev::Stealer<Work<Message>>,
    						channel: IoChannel<Message>,
    						wait: Arc<SCondvar>,
    						wait_mutex: Arc<SMutex<()>>,
    						panic_handler: Arc<PanicHandler>
    					   ) -> Worker
    					where Message: Send + Sync + Clone + '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!("IO Worker #{}", index)).spawn(
    			move || {
    				LOCAL_STACK_SIZE.with(|val| val.set(STACK_SIZE));
    				panic_handler.catch_panic(move || {
    					Worker::work_loop(stealer, channel.clone(), wait, wait_mutex.clone(), deleting)
    				}).expect("Error starting panic handler")
    			})
    			.expect("Error creating worker thread"));
    		worker
    	}

    	fn work_loop<Message>(stealer: chase_lev::Stealer<Work<Message>>,
    						channel: IoChannel<Message>, wait: Arc<SCondvar>,
    						wait_mutex: Arc<SMutex<()>>,
    						deleting: Arc<AtomicBool>)
    						where Message: Send + Sync + Clone + 'static {
    		loop {
    			{
    				let lock = wait_mutex.lock().expect("Poisoned work_loop mutex");
    				if deleting.load(AtomicOrdering::Acquire) {
    					return;
    				}
    				let _ = wait.wait(lock);
    			}

    			while !deleting.load(AtomicOrdering::Acquire) {
    				match stealer.steal() {
    					chase_lev::Steal::Data(work) => Worker::do_work(work, channel.clone()),
    					_ => break,
    				}
    			}
    		}
    	}

    	fn do_work<Message>(work: Work<Message>, channel: IoChannel<Message>) where Message: Send + Sync + Clone + '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().expect("Poisoned work_loop mutex");
    		self.deleting.store(true, AtomicOrdering::Release);
    		self.wait.notify_all();
    		if let Some(thread) = self.thread.take() {
    			thread.join().ok();
    		}
    		trace!(target: "shutdown", "[IoWorker] Closed");
    	}
    }

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