Add announce --event flag

cmd/torrent/announce.go

@@ -7,9 +7,11 @@ import (
 
 	"github.com/anacrolix/torrent"
 	"github.com/anacrolix/torrent/tracker"
+	"github.com/anacrolix/torrent/tracker/udp"
 )
 
 type AnnounceCmd struct {
+	Event    udp.AnnounceEvent
 	Tracker  string           `arg:"positional"`
 	InfoHash torrent.InfoHash `arg:"positional"`
 }
@@ -21,6 +23,7 @@ func announceErr(flags AnnounceCmd) error {
 			InfoHash: flags.InfoHash,
 			Port:     uint16(torrent.NewDefaultClientConfig().ListenPort),
 			NumWant:  -1,
+			Event:    flags.Event,
 		},
 	}.Do()
 	if err != nil {

tracker/udp/addr-family.go

@@ -0,0 +1 @@
+package udp

tracker/udp/announce.go

@@ -2,6 +2,7 @@ package udp
 
 import (
 	"encoding"
+	"fmt"
 
 	"github.com/anacrolix/dht/v2/krpc"
 )
@@ -24,9 +25,21 @@ type AnnounceRequest struct {
 
 type AnnounceEvent int32
 
+func (me *AnnounceEvent) UnmarshalText(text []byte) error {
+	for key, str := range announceEventStrings {
+		if string(text) == str {
+			*me = AnnounceEvent(key)
+			return nil
+		}
+	}
+	return fmt.Errorf("unknown event")
+}
+
+var announceEventStrings = []string{"", "completed", "started", "stopped"}
+
 func (e AnnounceEvent) String() string {
 	// See BEP 3, "event", and https://github.com/anacrolix/torrent/issues/416#issuecomment-751427001.
-	return []string{"", "completed", "started", "stopped"}[e]
+	return announceEventStrings[e]
 }
 
 type AnnounceResponsePeers interface {

tracker/udp/server/server.go

@@ -0,0 +1 @@
+package server