//
// Eventum
//   Copyright (C) 2020 Toshiaki Takada
//
// Unix Domain Socket Client.
//

use std::cell::RefCell;
use std::io::Read;
use std::io::Write;
use std::path::PathBuf;
use std::sync::Arc;
use std::sync::Weak;
use std::sync::Mutex;
use std::time::Duration;

//use log::debug;
use mio::net::UnixStream;

use super::core::*;

/// Trait UdsClient handler.
pub trait UdsClientHandler {
    /// callback when client connects to server.
    fn handle_connect(&self, entry: &UdsClient) -> Result<(), EventError>;

    /// callback when client detects server disconnected.
    fn handle_disconnect(&self, entry: &UdsClient) -> Result<(), EventError>;

    /// callback when client received message.
    fn handle_message(&self, entry: &UdsClient) -> Result<(), EventError>;
}

//unsafe impl Send for UdsClient {}
//unsafe impl Sync for UdsClient {}

/// Unix Domain Socket client entry, created per connect.
pub struct UdsClient {
    /// UdsClient Inner.
    inner: RefCell<Option<Arc<UdsClientInner>>>,
}

/// UdsClient implementation.
impl UdsClient {
    /// Constructor.
    pub fn new() -> UdsClient {
        UdsClient {
            inner: RefCell::new(None),
        }
    }

    /// Release inner.
    pub fn release(&self) {
        self.inner.replace(None);
    }

    /// Return UdsClientInner.
    pub fn get_inner(&self) -> Arc<UdsClientInner> {
        if let Some(ref mut inner) = *self.inner.borrow_mut() {
            return inner.clone();
        }

        // should not happen.
        panic!("No inner exists");
    }

    /// Start UdsClient.
    pub fn start(
        event_manager: Arc<Mutex<EventManager>>,
        handler: Arc<dyn UdsClientHandler>,
        path: &PathBuf,
    ) -> Arc<Mutex<UdsClient>> {
        let client = Arc::new(Mutex::new(UdsClient::new()));
        let inner = Arc::new(UdsClientInner::new(
            client.clone(),
            event_manager.clone(),
            handler.clone(),
            path,
        ));

        client.lock().unwrap().inner.borrow_mut().replace(inner);
        client
    }

    /// Connect to server.
    pub fn connect(&self) {
        let inner = self.get_inner();
        let event_manager = inner.get_event_manager();

        match inner.connect(self) {
            Ok(_) => {
                if let Some(ref mut stream) = *inner.stream.borrow_mut() {
                    if let Err(_) = event_manager
                        .lock()
                        .unwrap()
                        .register_read_write(stream, inner.clone())
                    {
                        self.connect_timer();
                    }
                }
            }
            Err(_) => self.connect_timer(),
        }
    }

    /// Start connect timer.
    pub fn connect_timer(&self) {
        let inner = self.get_inner();
        let event_manager = inner.get_event_manager();

        event_manager
            .lock()
            .unwrap()
            .register_timer(Duration::from_secs(5), inner.clone());
    }

    /// Send message.
    pub fn stream_send(&self, message: &str) -> Result<(), EventError> {
        self.get_inner().stream_send(message)
    }

    /// Receive message.
    pub fn stream_read(&self) -> Result<String, EventError> {
        self.get_inner().stream_read()
    }
}

impl Drop for UdsClient {
    fn drop(&mut self) {
        println!("Drop UdsClient");

        let inner = self.inner.replace(None);
        drop(inner);
    }
}

unsafe impl Send for UdsClientInner {}
unsafe impl Sync for UdsClientInner {}

/// UdsClient Inner.
pub struct UdsClientInner {
    /// Server path.
    path: PathBuf,

    /// UdsClient.
    client: Weak<Mutex<UdsClient>>,

    /// Event manager.
    event_manager: Arc<Mutex<EventManager>>,

    /// Message Client handler.
    handler: RefCell<Arc<dyn UdsClientHandler>>,

    /// Client stream.
    stream: RefCell<Option<UnixStream>>,
}

/// UdsClientInner implementation.
impl UdsClientInner {
    /// Constructdor.
    pub fn new(
        client: Arc<Mutex<UdsClient>>,
        event_manager: Arc<Mutex<EventManager>>,
        handler: Arc<dyn UdsClientHandler>,
        path: &PathBuf,
    ) -> UdsClientInner {
        UdsClientInner {
            path: path.clone(),
            client: Arc::downgrade(&client),
            event_manager: event_manager,
            handler: RefCell::new(handler),
            stream: RefCell::new(None),
        }
    }

    /// Connect to server.
    pub fn connect(&self, client: &UdsClient) -> Result<(), EventError> {
        match UnixStream::connect(&self.path) {
            Ok(stream) => {
                self.stream.borrow_mut().replace(stream);
                let _ = self.handler.borrow_mut().handle_connect(client);
                Ok(())
            }
            Err(_) => Err(EventError::ConnectError("UDS".to_string())),
        }
    }

    /// Return event manager.
    pub fn get_event_manager(&self) -> Arc<Mutex<EventManager>> {
        self.event_manager.clone()
    }

    /// Send a message through UnixStream.
    pub fn stream_send(&self, message: &str) -> Result<(), EventError> {
        match *self.stream.borrow_mut() {
            Some(ref mut stream) => {
                if let Err(_err) = stream.write_all(message.as_bytes()) {
                    return Err(EventError::WriteError("UDS".to_string()));
                }
            }
            None => return Err(EventError::WriteError("UDS".to_string())),
        }

        Ok(())
    }

    /// Receive a message through UnixStream.
    /// Return UTF8 string. If it is empty, consider an error.
    pub fn stream_read(&self) -> Result<String, EventError> {
        match *self.stream.borrow_mut() {
            Some(ref mut stream) => {
                let mut buffer = Vec::new();

                if let Err(err) = stream.read_to_end(&mut buffer) {
                    if err.kind() != std::io::ErrorKind::WouldBlock {
                        return Err(EventError::ReadError(err.to_string()));
                    }
                }

                let str = std::str::from_utf8(&buffer).unwrap();
                if str.len() > 0 {
                    let message = String::from(str);
                    Ok(message)
                } else {
                    Err(EventError::ReadError(
                        "Empty string from stream".to_string(),
                    ))
                }
            }
            None => Err(EventError::NoStream),
        }
    }
}

impl Drop for UdsClientInner {
    fn drop(&mut self) {
        println!("Drop UdsClientInner");
    }
}

/// EventHandler implementation for UdsClient.
impl EventHandler for UdsClientInner {
    /// Handle event.
    fn handle(&self, e: EventType) -> Result<(), EventError> {
        match e {
            EventType::TimerEvent => {
                // Reconnect timer expired.
                let client = self.client.upgrade().unwrap();
                let client = client.lock().unwrap();
                client.connect();

                Ok(())
            }
            EventType::ReadEvent => {
                let handler = self.handler.borrow_mut();
                let client = self.client.upgrade().unwrap();
                let client = client.lock().unwrap();

                // Dispatch message to message handler.
                if let Err(_) = handler.handle_message(&*client) {
                    // If read causes an error, most likely server disconnected,
                    // so schedule reconnect.
                    client.connect_timer();
                }

                Ok(())
            }
            EventType::ErrorEvent => {
                self.stream.borrow_mut().take();

                // TODO: Schedule reconnect timer.
                let client = self.client.upgrade().unwrap();
                let client = client.lock().unwrap();
                client.connect_timer();

                let handler = self.handler.borrow_mut();

                // Dispatch message to Client message handler.
                handler.handle_disconnect(&*client)
            }
            _ => Err(EventError::InvalidEvent),
        }
    }
}


#[cfg(test)]
mod tests {
    use super::*;
    use std::path::Path;

    struct TestClientHandler {
    }

    impl UdsClientHandler for TestClientHandler {
        /// callback when client connects to server.
        fn handle_connect(&self, _entry: &UdsClient) -> Result<(), EventError> {
            Ok(())
        }

        /// callback when client detects server disconnected.
        fn handle_disconnect(&self, _entry: &UdsClient) -> Result<(), EventError> {
            Ok(())
        }

        /// callback when client received message.
        fn handle_message(&self, _entry: &UdsClient) -> Result<(), EventError> {
            Ok(())
        }
    }

    #[test]
    pub fn test_uds_client() {
        let mut path = PathBuf::new();
        path.push("/tmp/test_uds.sock");
        let em = EventManager::new();
        let handler = TestClientHandler { };
        {
            let uds_client = UdsClient::start(Arc::new(Mutex::new(em)),
                                              Arc::new(handler), &path);
            drop(uds_client);
        }
    }
}