use log::info;
use std::sync::{Arc, Mutex};

use dbus_crossroads::Crossroads;
use dbus_tokio::connection;
use dbus::{
    message::MatchRule,
    nonblock::SyncConnection,
    channel::{Sender, MatchingReceiver},
    Path,
};

pub struct Endpoint<T: Send + Clone + 'static> {
    connection: Arc<SyncConnection>,
    implementation: T,
}

impl<T: Send + Clone + 'static> Endpoint<T> {
    pub fn new(implementation: T) -> Self {
        let (resource, connection) = connection::new_session_sync().unwrap();
        
        // The resource is a task that should be spawned onto a tokio compatible
        // reactor ASAP. If the resource ever finishes, you lost connection to D-Bus.
        //
        // To shut down the connection, both call _handle.abort() and drop the connection.
        let _handle = tokio::spawn(async {
            let err = resource.await;
            panic!("Lost connection to D-Bus: {}", err);
        });

        Self { 
            connection, 
            implementation
        }
    }

    pub async fn register<F, R>(
        &self, 
        name: &str,
        path: &str,
        register_fn: F
    )
    where
        F: Fn(&mut Crossroads) -> R,
        R: IntoIterator<Item = dbus_crossroads::IfaceToken<T>>,
    {
        let dbus_path = String::from(path);

        self.connection
            .request_name(name, false, true, false)
            .await
            .expect("Unable to acquire dbus name");

        let mut cr = Crossroads::new();

        // Enable async support for the crossroads instance. 
        // (Currently irrelevant since dbus generates sync code)
        cr.set_async_support(Some((
            self.connection.clone(),
            Box::new(|x| {
                tokio::spawn(x);
            }),
        )));

        // Register the daemon as a D-Bus object with multiple interfaces
        let tokens: Vec<_> = register_fn(&mut cr).into_iter().collect();
        cr.insert(dbus_path, &tokens, self.implementation.clone());

        // Start receiving messages.
        self.connection.start_receive(
            MatchRule::new_method_call(),
            Box::new(move |msg, conn| 
                cr.handle_message(msg, conn).is_ok()
            ),
        );

        info!(target: "dbus", "Registered endpoint at {} with {} interfaces", path, tokens.len());
    }

    pub fn send_signal<S>(&self, path: &str, signal: S) -> Result<u32, ()>
    where
        S: dbus::message::SignalArgs + dbus::arg::AppendAll,
    {
        let message = signal.to_emit_message(&Path::new(path).unwrap());
        self.connection.send(message)
    }
}