// handleConn handles an individual client connection.
//
// It manages the connection, but passes channels on to `answer()`.
func (s *server) handleConn(conn net.Conn, conf *ssh.ServerConfig) {
	defer conn.Close()
	log.Info(s.c, "Accepted connection.")
	_, chans, reqs, err := ssh.NewServerConn(conn, conf)
	if err != nil {
		// Handshake failure.
		log.Errf(s.c, "Failed handshake: %s (%v)", err, conn)
		return
	}

	// Discard global requests. We're only concerned with channels.
	safely.GoDo(s.c, func() { ssh.DiscardRequests(reqs) })

	condata := sshConnection(conn)

	// Now we handle the channels.
	for incoming := range chans {
		log.Infof(s.c, "Channel type: %s\n", incoming.ChannelType())
		if incoming.ChannelType() != "session" {
			incoming.Reject(ssh.UnknownChannelType, "Unknown channel type")
		}

		channel, req, err := incoming.Accept()
		if err != nil {
			// Should close request and move on.
			panic(err)
		}
		safely.GoDo(s.c, func() { s.answer(channel, req, condata) })
	}
	conn.Close()
}

// Watch watches a given path, and executes a git check-repos for each event.
//
// It starts the watcher and then returns. The watcher runs on its own
// goroutine. To stop the watching, send the returned channel a bool.
//
// Params:
// - client (Watcher): An Etcd client.
// - path (string): The path to watch
func Watch(c cookoo.Context, p *cookoo.Params) (interface{}, cookoo.Interrupt) {

	// etcdctl -C $ETCD watch --recursive /deis/services
	path := p.Get("path", "/deis/services").(string)
	cli := p.Get("client", nil).(client.Client)
	k := client.NewKeysAPI(cli)

	watcher := k.Watcher(path, &client.WatcherOptions{Recursive: true})

	safely.GoDo(c, func() {
		for {
			// TODO: We should probably add cancellation support.
			response, err := watcher.Next(dctx())
			if err != nil {
				log.Errf(c, "Etcd Watch failed: %s", err)
			}
			if response.Node == nil {
				log.Infof(c, "Unexpected Etcd message: %v", response)
			}
			git := exec.Command("/home/git/check-repos")
			if out, err := git.CombinedOutput(); err != nil {
				log.Errf(c, "Failed git check-repos: %s", err)
				log.Infof(c, "Output: %s", out)
			}
		}
	})
	return nil, nil
}

// ParallelBuild runs multiple docker builds at the same time.
//
// Params:
//	-images ([]BuildImg): Images to build
// 	-alwaysFetch (bool): Default false. If set to true, this will always fetch
// 		the Docker image even if it already exists in the registry.
//
// Returns:
//
// 	- Waiter: A *sync.WaitGroup that is waiting for the docker downloads to finish.
//
// Context:
//
// This puts 'ParallelBuild.failN" (int) into the context to indicate how many failures
// occurred during fetches.
func ParallelBuild(c cookoo.Context, p *cookoo.Params) (interface{}, cookoo.Interrupt) {
	images := p.Get("images", []BuildImg{}).([]BuildImg)

	var wg sync.WaitGroup
	var m sync.Mutex
	var fails int

	for _, img := range images {
		img := img
		wg.Add(1)
		safely.GoDo(c, func() {
			log.Infof(c, "Starting build for %s (tag: %s)", img.Path, img.Tag)
			if _, err := buildImg(c, img.Path, img.Tag); err != nil {
				log.Errf(c, "Failed to build docker image: %s", err)
				m.Lock()
				fails++
				m.Unlock()
			}
			wg.Done()
		})

	}

	// Number of failures.
	c.Put("ParallelBuild.failN", fails)

	return &wg, nil
}

// ParallelBuild runs multiple docker builds at the same time.
//
// Params:
//	-images ([]BuildImg): Images to build
// 	-alwaysFetch (bool): Default false. If set to true, this will always fetch
// 		the Docker image even if it already exists in the registry.
//
// Returns:
//
// 	- Waiter: A *sync.WaitGroup that is waiting for the docker downloads to finish.
//
// Context:
//
// This puts 'ParallelBuild.failN" (int) into the context to indicate how many failures
// occurred during fetches.
func ParallelBuild(c cookoo.Context, p *cookoo.Params) (interface{}, cookoo.Interrupt) {
	images := p.Get("images", []BuildImg{}).([]BuildImg)

	var wg sync.WaitGroup
	var m sync.Mutex
	var fails int

	for _, img := range images {
		img := img

		// HACK: ensure "docker build" is serialized by allowing only one entry in
		// the WaitGroup. This works around the "simultaneous docker pull" bug.
		wg.Wait()
		wg.Add(1)
		safely.GoDo(c, func() {
			log.Infof(c, "Starting build for %s (tag: %s)", img.Path, img.Tag)
			if _, err := buildImg(c, img.Path, img.Tag); err != nil {
				log.Errf(c, "Failed to build docker image: %s", err)
				m.Lock()
				fails++
				m.Unlock()
			}
			wg.Done()
		})

	}

	// Number of failures.
	c.Put("ParallelBuild.failN", fails)

	return &wg, nil
}

// Watch watches a given path, and executes a git check-repos for each event.
//
// It starts the watcher and then returns. The watcher runs on its own
// goroutine. To stop the watching, send the returned channel a bool.
//
// Params:
// - client (Watcher): An Etcd client.
// - path (string): The path to watch
//
// Returns:
// 	- chan bool: Send this a message to stop the watcher.
func Watch(c cookoo.Context, p *cookoo.Params) (interface{}, cookoo.Interrupt) {
	// etcdctl -C $ETCD watch --recursive /deis/services
	path := p.Get("path", "/deis/services").(string)
	cli, ok := p.Has("client")
	if !ok {
		return nil, errors.New("No etcd client found.")
	}
	client := cli.(Watcher)

	// Stupid hack because etcd watch seems to be broken, constantly complaining
	// that the JSON it received is malformed.
	safely.GoDo(c, func() {
		for {
			response, err := client.Watch(path, 0, true, nil, nil)
			if err != nil {
				log.Errf(c, "Etcd Watch failed: %s", err)
				time.Sleep(50 * time.Millisecond)
				continue
			}

			if response.Node == nil {
				log.Infof(c, "Unexpected Etcd message: %v", response)
			}
			git := exec.Command("/home/git/check-repos")
			if out, err := git.CombinedOutput(); err != nil {
				log.Errf(c, "Failed git check-repos: %s", err)
				log.Infof(c, "Output: %s", out)
			}
		}

	})

	return nil, nil

}

// UpdateHostPort intermittently notifies etcd of the builder's address.
//
// If `port` is specified, this will notify etcd at 10 second intervals that
// the builder is listening at $HOST:$PORT, setting the TTL to 20 seconds.
//
// This will notify etcd as long as the local sshd is running.
//
// Params:
// 	- base (string): The base path to write the data: $base/host and $base/port.
// 	- host (string): The hostname
// 	- port (string): The port
// 	- client (Setter): The client to use to write the data to etcd.
// 	- sshPid (int): The PID for SSHD. If SSHD dies, this stops notifying.
func UpdateHostPort(c cookoo.Context, p *cookoo.Params) (interface{}, cookoo.Interrupt) {

	base := p.Get("base", "").(string)
	host := p.Get("host", "").(string)
	port := p.Get("port", "").(string)
	client := p.Get("client", nil).(Setter)
	sshd := p.Get("sshdPid", 0).(int)

	// If no port is specified, we don't do anything.
	if len(port) == 0 {
		log.Infof(c, "No external port provided. Not publishing details.")
		return false, nil
	}

	var ttl uint64 = 20

	if err := setHostPort(client, base, host, port, ttl); err != nil {
		log.Errf(c, "Etcd error setting host/port: %s", err)
		return false, err
	}

	// Update etcd every ten seconds with this builder's host/port.
	safely.GoDo(c, func() {
		ticker := time.NewTicker(10 * time.Second)
		for range ticker.C {
			//log.Infof(c, "Setting SSHD host/port")
			if _, err := os.FindProcess(sshd); err != nil {
				log.Errf(c, "Lost SSHd process: %s", err)
				break
			} else {
				if err := setHostPort(client, base, host, port, ttl); err != nil {
					log.Errf(c, "Etcd error setting host/port: %s", err)
					break
				}
			}
		}
		ticker.Stop()
	})

	return true, nil
}

// listen handles accepting and managing connections. However, since closer
// is len(1), it will not block the sender.
func (s *server) listen(l net.Listener, conf *ssh.ServerConfig, closer chan interface{}) error {
	cxt := s.c
	log.Info(cxt, "Accepting new connections.")
	defer l.Close()

	// FIXME: Since Accept blocks, closer may not be checked often enough.
	for {
		log.Info(cxt, "Checking closer.")
		if len(closer) > 0 {
			<-closer
			log.Info(cxt, "Shutting down SSHD listener.")
			return nil
		}
		conn, err := l.Accept()
		if err != nil {
			log.Warnf(cxt, "Error during Accept: %s", err)
			// We shouldn't kill the listener because of an error.
			return err
		}
		safely.GoDo(cxt, func() {
			s.handleConn(conn, conf)
		})
	}
}

// KillOnExit kills PIDs when the program exits.
//
// Otherwise, this blocks until an os.Interrupt or os.Kill is received.
//
// Params:
//  This treats Params as a map of process names (unimportant) to PIDs. It then
// attempts to kill all of the pids that it receives.
func KillOnExit(c cookoo.Context, p *cookoo.Params) (interface{}, cookoo.Interrupt) {
	sigs := make(chan os.Signal, 1)
	signal.Notify(sigs, os.Interrupt, os.Kill)

	safely.GoDo(c, func() {
		log.Info(c, "Builder is running.")

		<-sigs

		c.Log("info", "Builder received signal to stop.")
		pids := p.AsMap()
		killed := 0
		for name, pid := range pids {
			if pid, ok := pid.(int); ok {
				if proc, err := os.FindProcess(pid); err == nil {
					log.Infof(c, "Killing %s (pid=%d)", name, pid)
					proc.Kill()
					killed++
				}
			}
		}
	})
	return nil, nil
}

// Watch watches a given path, and executes a git check-repos for each event.
//
// It starts the watcher and then returns. The watcher runs on its own
// goroutine. To stop the watching, send the returned channel a bool.
//
// Params:
// - client (Watcher): An Etcd client.
// - path (string): The path to watch
//
// Returns:
// 	- chan bool: Send this a message to stop the watcher.
func Watch(c cookoo.Context, p *cookoo.Params) (interface{}, cookoo.Interrupt) {
	// etcdctl -C $ETCD watch --recursive /deis/services
	path := p.Get("path", "/deis/services").(string)
	cli, ok := p.Has("client")
	if !ok {
		return nil, errors.New("No etcd client found.")
	}
	client := cli.(Watcher)

	// Stupid hack because etcd watch seems to be broken, constantly complaining
	// that the JSON it received is malformed.
	safely.GoDo(c, func() {
		for {
			response, err := client.Watch(path, 0, true, nil, nil)
			if err != nil {
				log.Errf(c, "Etcd Watch failed: %s", err)
				time.Sleep(50 * time.Millisecond)
				continue
			}

			if response.Node == nil {
				log.Infof(c, "Unexpected Etcd message: %v", response)
			}
			git := exec.Command("/home/git/check-repos")
			if out, err := git.CombinedOutput(); err != nil {
				log.Errf(c, "Failed git check-repos: %s", err)
				log.Infof(c, "Output: %s", out)
			}
		}

	})

	return nil, nil

	/* Watch seems to be broken. So we do this stupid watch loop instead.
	receiver := make(chan *etcd.Response)
	stop := make(chan bool)
	// Buffer the channels so that we don't hang waiting for go-etcd to
	// read off the channel.
	stopetcd := make(chan bool, 1)
	stopwatch := make(chan bool, 1)


	// Watch for errors.
	safely.GoDo(c, func() {
		// When a receiver is passed in, no *Response is ever returned. Instead,
		// Watch acts like an error channel, and receiver gets all of the messages.
		_, err := client.Watch(path, 0, true, receiver, stopetcd)
		if err != nil {
			log.Infof(c, "Watcher stopped with error '%s'", err)
			stopwatch <- true
			//close(stopwatch)
		}
	})
	// Watch for events
	safely.GoDo(c, func() {
		for {
			select {
			case msg := <-receiver:
				if msg.Node != nil {
					log.Infof(c, "Received notification %s for %s", msg.Action, msg.Node.Key)
				} else {
					log.Infof(c, "Received unexpected etcd message: %v", msg)
				}
				git := exec.Command("/home/git/check-repos")
				if out, err := git.CombinedOutput(); err != nil {
					log.Errf(c, "Failed git check-repos: %s", err)
					log.Infof(c, "Output: %s", out)
				}
			case <-stopwatch:
				c.Logf("debug", "Received signal to stop watching events.")
				return
			}
		}
	})
	// Fan out stop requests.
	safely.GoDo(c, func() {
		<-stop
		stopwatch <- true
		stopetcd <- true
		close(stopwatch)
		close(stopetcd)
	})

	return stop, nil
	*/
}