storage: add storage interface and registration

This also fixes bugs in the Hooks registration.

hooks.go

@@ -16,9 +16,6 @@ package trakr
 
 import "github.com/jzelinskie/trakr/bittorrent"
 
-// HookConstructor is a function used to create a new instance of a Hook.
-type HookConstructor func(interface{}) (Hook, error)
-
 // Hook abstracts the concept of anything that needs to interact with a
 // BitTorrent client's request and response to a BitTorrent tracker.
 type Hook interface {
@@ -26,6 +23,9 @@ type Hook interface {
 	HandleScrape(context.Context, bittorrent.ScrapeRequest, bittorrent.ScrapeResponse) error
 }
 
+// HookConstructor is a function used to create a new instance of a Hook.
+type HookConstructor func(interface{}) (Hook, error)
+
 var preHooks = make(map[string]HookConstructor)
 
 // RegisterPreHook makes a HookConstructor available by the provided name.
@@ -44,7 +44,7 @@ func RegisterPreHook(name string, con HookConstructor) {
 
 // NewPreHook creates an instance of the given PreHook by name.
 func NewPreHook(name string, config interface{}) (Hook, error) {
-	con := preHooks[name]
+	con, ok := preHooks[name]
 	if !ok {
 		return nil, fmt.Errorf("trakr: unknown PreHook %q (forgotten import?)", name)
 	}
@@ -69,7 +69,7 @@ func RegisterPostHook(name string, con HookConstructor) {
 
 // NewPostHook creates an instance of the given PostHook by name.
 func NewPostHook(name string, config interface{}) (Hook, error) {
-	con := preHooks[name]
+	con, ok := preHooks[name]
 	if !ok {
 		return nil, fmt.Errorf("trakr: unknown PostHook %q (forgotten import?)", name)
 	}

storage.go

@@ -0,0 +1,97 @@
+package trakr
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/jzelinskie/trakr/bittorrent"
+	"github.com/jzelinskie/trakr/stopper"
+)
+
+// ErrResourceDoesNotExist is the error returned by all delete methods in the
+// store if the requested resource does not exist.
+var ErrResourceDoesNotExist = bittorrent.ClientError(errors.New("resource does not exist"))
+
+// PeerStore is an interface that abstracts the interactions of storing and
+// manipulating Peers such that it can be implemented for various data stores.
+type PeerStore interface {
+	// PutSeeder adds a Seeder to the Swarm identified by the provided infoHash.
+	PutSeeder(infoHash bittorrent.InfoHash, p bittorrent.Peer) error
+
+	// DeleteSeeder removes a Seeder from the Swarm identified by the provided
+	// infoHash.
+	//
+	// If the Swarm or Peer does not exist, this function should return
+	// ErrResourceDoesNotExist.
+	DeleteSeeder(infoHash bittorrent.InfoHash, p bittorrent.Peer) error
+
+	// PutLeecher adds a Leecher to the Swarm identified by the provided
+	// infoHash.
+	PutLeecher(infoHash bittorrent.InfoHash, p bittorrent.Peer) error
+
+	// DeleteLeecher removes a Leecher from the Swarm identified by the provided
+	// infoHash.
+	//
+	// If the Swarm or Peer does not exist, this function should return
+	// ErrResourceDoesNotExist.
+	DeleteLeecher(infoHash bittorrent.InfoHash, p bittorrent.Peer) error
+
+	// GraduateLeecher promotes a Leecher to a Seeder in the Swarm identified by
+	// the provided infoHash.
+	//
+	// If the given Peer is not present as a Leecher, add the Peer as a Seeder
+	// and return no error.
+	GraduateLeecher(infoHash bittorrent.InfoHash, p bittorrent.Peer) error
+
+	// AnnouncePeers is a best effort attempt to return Peers from the Swarm
+	// identified by the provided infoHash. The returned Peers are required to be
+	// either all IPv4 or all IPv6.
+	//
+	// The returned Peers should strive be:
+	// - as close to length equal to numWant as possible without going over
+	// - all IPv4 or all IPv6 depending on the provided ipv6 boolean
+	// - if seeder is true, should ideally return more leechers than seeders
+	// - if seeder is false, should ideally return more seeders than leechers
+	AnnouncePeers(infoHash bittorrent.InfoHash, seeder bool, numWant int, ipv6 bool) (peers []bittorrent.Peer, err error)
+
+	// CollectGarbage deletes all Peers from the PeerStore which are older than
+	// the cutoff time. This function must be able to execute while other methods
+	// on this interface are being executed in parallel.
+	CollectGarbage(cutoff time.Time) error
+
+	// Stopper is an interface that expects a Stop method to stops the PeerStore.
+	// For more details see the documentation in the stopper package.
+	stopper.Stopper
+}
+
+// PeerStoreConstructor is a function used to create a new instance of a
+// PeerStore.
+type PeerStoreConstructor func(interface{}) (PeerStore, error)
+
+var peerStores = make(map[string]PeerStoreConstructors)
+
+// RegisterPeerStore makes a PeerStoreConstructor available by the provided
+// name.
+//
+// If this function is called twice with the same name or if the
+// PeerStoreConstructor is nil, it panics.
+func RegisterPeerStore(name string, con PeerStoreConstructor) {
+	if con == nil {
+		panic("trakr: could not register nil PeerStoreConstructor")
+	}
+
+	if _, dup := peerStore[name]; dup {
+		panic("trakr: could not register duplicate PeerStoreConstructor: " + name)
+	}
+
+	peerStores[name] = con
+}
+
+// NewPeerStore creates an instance of the given PeerStore by name.
+func NewPeerStore(name, config interface{}) (PeerStore, error) {
+	con, ok := peerStores[name]
+	if !ok {
+		return nil, fmt.Errorf("trakr: unknown PeerStore %q (forgotten import?)", name)
+	}
+	return con(config)
+}