eventbus abstraction + initial events (#17)

event/bus.go

+package event
+
+import "io"
+
+// SubscriptionOpt represents a subscriber option. Use the options exposed by the implementation of choice.
+type SubscriptionOpt = func(interface{}) error
+
+// EmitterOpt represents an emitter option. Use the options exposed by the implementation of choice.
+type EmitterOpt = func(interface{}) error
+
+// CancelFunc closes a subscriber.
+type CancelFunc = func()
+
+// Emitter represents an actor that emits events onto the eventbus.
+type Emitter interface {
+	io.Closer
+
+	// Emit emits an event onto the eventbus. If any channel subscribed to the topic is blocked,
+	// calls to Emit will block.
+	//
+	// Calling this function with wrong event type will cause a panic.
+	Emit(evt interface{})
+}
+
+// Bus is an interface for a type-based event delivery system.
+type Bus interface {
+	// Subscribe creates a new subscription.
+	//
+	// Failing to drain the channel may cause publishers to block. CancelFunc must return after
+	// last send to the channel.
+	//
+	// Example:
+	// ch := make(chan EventT, 10)
+	// defer close(ch)
+	// cancel, err := eventbus.Subscribe(ch)
+	// defer cancel()
+	Subscribe(typedChan interface{}, opts ...SubscriptionOpt) (CancelFunc, error)
+
+	// Emitter creates a new event emitter.
+	//
+	// eventType accepts typed nil pointers, and uses the type information for wiring purposes.
+	//
+	// Example:
+	// em, err := eventbus.Emitter(new(EventT))
+	// defer em.Close() // MUST call this after being done with the emitter
+	// em.Emit(EventT{})
+	Emitter(eventType interface{}, opts ...EmitterOpt) (Emitter, error)
+}

event/doc.go

+// Package event contains the abstractions for a local event bus, along with the standard events
+// that libp2p subsystems may emit.
+//
+// Source code is arranged as follows:
+// 	* doc.go: this file.
+//	* bus.go: abstractions for the event bus.
+//	* rest: event structs, sensibly categorised in files by entity, and following this naming convention:
+//          Evt[Entity (noun)][Event (verb past tense / gerund)]
+//    The past tense is used to convey that something happened, whereas the gerund form of the verb (-ing)
+//    expresses that a process is in progress. Examples: EvtConnEstablishing, EvtConnEstablished.
+package event

event/protocol.go

+package event
+
+import (
+	peer "github.com/libp2p/go-libp2p-core/peer"
+	protocol "github.com/libp2p/go-libp2p-core/protocol"
+)
+
+// EvtPeerProtocolsUpdated should be emitted when a peer we're connected to adds or removes protocols from their stack.
+type EvtPeerProtocolsUpdated struct {
+	// Peer is the peer whose protocols were updated.
+	Peer peer.ID
+	// Added enumerates the protocols that were added by this peer.
+	Added []protocol.ID
+	// Removed enumerates the protocols that were removed by this peer.
+	Removed []protocol.ID
+}
+
+// EvtLocalProtocolsUpdated should be emitted when stream handlers are attached or detached from the local host.
+// For handlers attached with a matcher predicate (host.SetStreamHandlerMatch()), only the protocol ID will be
+// included in this event.
+type EvtLocalProtocolsUpdated struct {
+	// Added enumerates the protocols that were added locally.
+	Added []protocol.ID
+	// Removed enumerates the protocols that were removed locally.
+	Removed []protocol.ID
+}

host/host.go

@@ -7,6 +7,7 @@ import (
 	"context"
 
 	"github.com/libp2p/go-libp2p-core/connmgr"
+	"github.com/libp2p/go-libp2p-core/event"
 	"github.com/libp2p/go-libp2p-core/network"
 	"github.com/libp2p/go-libp2p-core/peer"
 	"github.com/libp2p/go-libp2p-core/peerstore"
@@ -68,4 +69,7 @@ type Host interface {
 
 	// ConnManager returns this hosts connection manager
 	ConnManager() connmgr.ConnManager
+
+	// EventBus returns the hosts eventbus
+	EventBus() event.Bus
 }

protocol/id.go

@@ -7,3 +7,23 @@ type ID string
 const (
 	TestingID ID = "/p2p/_testing"
 )
+
+// ConvertFromStrings is a convenience function that takes a slice of strings and
+// converts it to a slice of protocol.ID.
+func ConvertFromStrings(ids []string) (res []ID) {
+	res = make([]ID, 0, len(ids))
+	for _, id := range ids {
+		res = append(res, ID(id))
+	}
+	return res
+}
+
+// ConvertToStrings is a convenience function that takes a slice of protocol.ID and
+// converts it to a slice of strings.
+func ConvertToStrings(ids []ID) (res []string) {
+	res = make([]string, 0, len(ids))
+	for _, id := range ids {
+		res = append(res, string(id))
+	}
+	return res
+}