// package swarm implements a connection muxer with a pair of channels
// to synchronize all network communication.
package swarm

import (
	"fmt"
	"sync"

	inet "github.com/jbenet/go-ipfs/p2p/net"
	addrutil "github.com/jbenet/go-ipfs/p2p/net/swarm/addr"
	peer "github.com/jbenet/go-ipfs/p2p/peer"
	eventlog "github.com/jbenet/go-ipfs/util/eventlog"

	context "github.com/jbenet/go-ipfs/Godeps/_workspace/src/code.google.com/p/go.net/context"
	ctxgroup "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-ctxgroup"
	ma "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr"
	ps "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-peerstream"
	psy "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-peerstream/transport/yamux"
)

var log = eventlog.Logger("swarm2")

var PSTransport = psy.DefaultTransport

// Swarm is a connection muxer, allowing connections to other peers to
// be opened and closed, while still using the same Chan for all
// communication. The Chan sends/receives Messages, which note the
// destination or source Peer.
//
// Uses peerstream.Swarm
type Swarm struct {
	swarm *ps.Swarm
	local peer.ID
	peers peer.Peerstore
	connh ConnHandler

	// dialing is a channel for the current peers being dialed.
	// this way, we dont kick off N dials simultaneously.
	dialing   map[peer.ID]chan struct{}
	dialingmu sync.Mutex

	cg ctxgroup.ContextGroup
}

// NewSwarm constructs a Swarm, with a Chan.
func NewSwarm(ctx context.Context, listenAddrs []ma.Multiaddr,
	local peer.ID, peers peer.Peerstore) (*Swarm, error) {

	if len(listenAddrs) > 0 {
		filtered := addrutil.FilterUsableAddrs(listenAddrs)
		if len(filtered) < 1 {
			return nil, fmt.Errorf("swarm cannot use any addr in: %s", listenAddrs)
		}
		listenAddrs = filtered
	}

	s := &Swarm{
		swarm:   ps.NewSwarm(PSTransport),
		local:   local,
		peers:   peers,
		cg:      ctxgroup.WithContext(ctx),
		dialing: map[peer.ID]chan struct{}{},
	}

	// configure Swarm
	s.cg.SetTeardown(s.teardown)
	s.SetConnHandler(nil) // make sure to setup our own conn handler.

	return s, s.listen(listenAddrs)
}

func (s *Swarm) teardown() error {
	return s.swarm.Close()
}

// CtxGroup returns the Context Group of the swarm
func (s *Swarm) CtxGroup() ctxgroup.ContextGroup {
	return s.cg
}

// Close stops the Swarm.
func (s *Swarm) Close() error {
	return s.cg.Close()
}

// StreamSwarm returns the underlying peerstream.Swarm
func (s *Swarm) StreamSwarm() *ps.Swarm {
	return s.swarm
}

// SetConnHandler assigns the handler for new connections.
// See peerstream. You will rarely use this. See SetStreamHandler
func (s *Swarm) SetConnHandler(handler ConnHandler) {

	// handler is nil if user wants to clear the old handler.
	if handler == nil {
		s.swarm.SetConnHandler(func(psconn *ps.Conn) {
			s.connHandler(psconn)
		})
		return
	}

	s.swarm.SetConnHandler(func(psconn *ps.Conn) {
		// sc is nil if closed in our handler.
		if sc := s.connHandler(psconn); sc != nil {
			// call the user's handler. in a goroutine for sync safety.
			go handler(sc)
		}
	})
}

// SetStreamHandler assigns the handler for new streams.
// See peerstream.
func (s *Swarm) SetStreamHandler(handler inet.StreamHandler) {
	s.swarm.SetStreamHandler(func(s *ps.Stream) {
		handler(wrapStream(s))
	})
}

// NewStreamWithPeer creates a new stream on any available connection to p
func (s *Swarm) NewStreamWithPeer(p peer.ID) (*Stream, error) {
	// if we have no connections, try connecting.
	if len(s.ConnectionsToPeer(p)) == 0 {
		log.Debug("Swarm: NewStreamWithPeer no connections. Attempting to connect...")
		if _, err := s.Dial(context.Background(), p); err != nil {
			return nil, err
		}
	}
	log.Debug("Swarm: NewStreamWithPeer...")

	st, err := s.swarm.NewStreamWithGroup(p)
	return wrapStream(st), err
}

// StreamsWithPeer returns all the live Streams to p
func (s *Swarm) StreamsWithPeer(p peer.ID) []*Stream {
	return wrapStreams(ps.StreamsWithGroup(p, s.swarm.Streams()))
}

// ConnectionsToPeer returns all the live connections to p
func (s *Swarm) ConnectionsToPeer(p peer.ID) []*Conn {
	return wrapConns(ps.ConnsWithGroup(p, s.swarm.Conns()))
}

// Connections returns a slice of all connections.
func (s *Swarm) Connections() []*Conn {
	return wrapConns(s.swarm.Conns())
}

// CloseConnection removes a given peer from swarm + closes the connection
func (s *Swarm) CloseConnection(p peer.ID) error {
	conns := s.swarm.ConnsWithGroup(p) // boom.
	for _, c := range conns {
		c.Close()
	}
	return nil
}

// Peers returns a copy of the set of peers swarm is connected to.
func (s *Swarm) Peers() []peer.ID {
	conns := s.Connections()

	seen := make(map[peer.ID]struct{})
	peers := make([]peer.ID, 0, len(conns))
	for _, c := range conns {
		p := c.RemotePeer()
		if _, found := seen[p]; found {
			continue
		}

		seen[p] = struct{}{}
		peers = append(peers, p)
	}
	return peers
}

// LocalPeer returns the local peer swarm is associated to.
func (s *Swarm) LocalPeer() peer.ID {
	return s.local
}