// Package stream defines a structure to communication between inputs and outputs
package stream

import (
	"sync"
)

// Stream makes packages able to subscribe to an incoming stream
type Stream struct {
	// Incoming data come from this channel
	Broadcast chan<- []byte

	// Use a map to be able to delete an item
	outputs map[chan []byte]struct{}

	// Count clients for statistics
	nbClients int

	// Mutex to lock outputs map
	lock sync.Mutex
}

// New creates a new stream.
func New() *Stream {
	s := &Stream{}
	broadcast := make(chan []byte, 1024)
	s.Broadcast = broadcast
	s.outputs = make(map[chan []byte]struct{})
	s.nbClients = 0
	go s.run(broadcast)
	return s
}

func (s *Stream) run(broadcast <-chan []byte) {
	for msg := range broadcast {
		s.lock.Lock()
		for output := range s.outputs {
			select {
			case output <- msg:
			default:
				// If full, do a ring buffer
				// Check that output is not of size zero
				if len(output) > 1 {
					<-output
				}
			}
		}
		s.lock.Unlock()
	}

	// Incoming chan has been closed, close all outputs
	s.lock.Lock()
	for ch := range s.outputs {
		delete(s.outputs, ch)
		close(ch)
	}
	s.lock.Unlock()
}

// Close the incoming chan, this will also delete all outputs
func (s *Stream) Close() {
	close(s.Broadcast)
}

// Register a new output on a stream.
func (s *Stream) Register(output chan []byte) {
	s.lock.Lock()
	defer s.lock.Unlock()
	s.outputs[output] = struct{}{}
}

// Unregister removes an output.
// If hidden in true, then do not count this client.
func (s *Stream) Unregister(output chan []byte) {
	s.lock.Lock()
	defer s.lock.Unlock()

	// Make sure we did not already close this output
	_, ok := s.outputs[output]
	if ok {
		delete(s.outputs, output)
		close(output)
	}
}

// ClientCount returns the number of clients
func (s *Stream) ClientCount() int {
	return s.nbClients
}

// IncrementClientCount increments the number of clients
func (s *Stream) IncrementClientCount() {
	s.nbClients++
}

// DecrementClientCount decrements the number of clients
func (s *Stream) DecrementClientCount() {
	s.nbClients--
}