#[allow(unused_imports)]
use log::{debug, error, info, trace, warn};

use std::{
    sync::mpsc::{Sender, Receiver},
    thread::JoinHandle,
    mem::ManuallyDrop,
    ptr::read,
    time::Duration,
};

use crate::subengine::Subengine;

//--SubengineController Implementation--------------------------------------------------------------
/// Handle to manage an [`Subengine`]. 
///
/// The `SubengineController` runs the [`Engine`] in a separated thread with some control code to
/// allow control from the main thread. SubengineControllers are used by the [`Controller`] to
/// interact with Subengines.
#[derive(Debug)]
pub struct SubengineController {
    tx: Sender<SubengineCommand>,
    rx: Receiver<SubengineResponse>,
    handle: ManuallyDrop<JoinHandle<()>>,
}

impl Drop for SubengineController {
    fn drop(&mut self) {
        self.exec(SubengineCommand::Stop);
        unsafe { let _ = ManuallyDrop::into_inner(read(&mut self.handle)).join(); }
        debug!("SubengineController dropped !");
    }
}

impl SubengineController {
    /// Creates a new `SubengineController` from a given [`Engine`]. Since the latter will be moved
    /// to a separated thread, it must implement the [`Send`] trait.
    pub fn new<E: 'static>(engine: E) -> SubengineController
    where 
        E: Subengine + std::marker::Send,
    {
        use std::{
            thread,
            sync::mpsc::channel,
        };

        debug!("Creating SubengineController...");
        let (tx, e_rx) = channel();
        let (e_tx, rx) = channel();

        let handle = thread::spawn(move || {
            trace!("Subengine thread started !");
            loop {
                //TODO manage errors
                match e_rx.recv().unwrap() {
                    SubengineCommand::Run => engine.run(),
                    SubengineCommand::Stop => return,
                };
                e_tx.send(SubengineResponse::Done).unwrap();
            }
        });

        SubengineController {
            tx,
            rx,
            handle: ManuallyDrop::new(handle),
        }
    }

    /// Sends a command to the [`Subengine`]. This is function is not blocking and WILL NOT check if
    /// the command was received.
    pub fn exec(&self, cmd: SubengineCommand) {
        self.tx.send(cmd).unwrap();
    }

    /// Blocking function, waits for the [`Subengine`] to finish executing the last command given.
    pub fn wait_for_exec(&self, timeout: Duration) -> Result<(),SubengineWaitError> {
        match self.rx.recv_timeout(timeout) {
            Err(_) => Err(SubengineWaitError::NoResponse),
            Ok(val) => match val {
                SubengineResponse::Done => Ok(()),
                //_ => Err(SubengineWaitError::BadResponse),
        }}
    }
}

//--SubengineCommand enum---------------------------------------------------------------------------
/// Commands that can be sent to an [`Subengine`] via an `EngineController`.
#[derive(Debug)]
pub enum SubengineCommand {
    Run,
    Stop,
}

//--SubengineWaitError enum-------------------------------------------------------------------------
/// Errors that can be returned by the wait_for_exec function.
#[derive(Debug)]
pub enum SubengineWaitError {
    NoResponse,
    BadResponse,
}

//--SubengineResponse enum--------------------------------------------------------------------------
#[derive(Debug)]
enum SubengineResponse {
    Done,
}

//--Tests-------------------------------------------------------------------------------------------
#[cfg(test)]
mod tests {
    use super::*;
    use crate::subengine::TestSubengine;

    #[test]
    fn test_new_drop() {
        let (test_subengine, _test_rx)  = TestSubengine::new("run"); 
        let _subengine_controller = SubengineController::new(test_subengine);
    }

    #[test]
    fn test_exec() {
        let (test_subengine, test_rx)  = TestSubengine::new("run"); 
        let subengine_controller = SubengineController::new(test_subengine);

        subengine_controller.exec(SubengineCommand::Run);
        let response = test_rx.recv_timeout(Duration::from_millis(10)).unwrap();
        assert_eq!(response, "run");
    }

    #[test]
    fn test_wait_for_exec() {
        let (test_subengine, _test_rx)  = TestSubengine::new("run"); 
        let subengine_controller = SubengineController::new(test_subengine);

        subengine_controller.exec(SubengineCommand::Run);
        subengine_controller.wait_for_exec(Duration::from_millis(10)).unwrap();
    }

}