From fb2b62617563f5c314f318abe378334375eec320 Mon Sep 17 00:00:00 2001
From: Matt Joiner <anacrolix@gmail.com>
Date: Mon, 1 Dec 2014 16:37:40 -0600
Subject: [PATCH] Don't send constructed MetaInfo down a channel when it's
 available, build it on demand

---
 client.go                   | 31 +++++++++++++++++--------------
 cmd/magnet-metainfo/main.go |  7 ++-----
 torrent.go                  | 28 ++++++++++++++++++++++++++--
 3 files changed, 45 insertions(+), 21 deletions(-)

diff --git a/client.go b/client.go
index 1e45d7dc..d16257fe 100644
--- a/client.go
+++ b/client.go
@@ -1339,21 +1339,24 @@ func (cl *Client) setMetaData(t *torrent, md metainfo.Info, bytes []byte) (err e
 	cl.downloadStrategy.TorrentStarted(t)
 	// TODO(anacrolix): I think this should be made available as a method, the
 	// channel only acts as a signal that the metadata has become available.
-	select {
-	case t.gotMetainfo <- &metainfo.MetaInfo{
-		Info: metainfo.InfoEx{
-			Info: md,
-		},
-		CreationDate: time.Now().Unix(),
-		Comment:      "metadata set in client",
-		CreatedBy:    "go.torrent",
-		// TODO(anacrolix): Expose trackers given when torrent added.
-	}:
-	default:
-		panic("shouldn't block")
+	// select {
+	// case t.gotMetainfo <- &metainfo.MetaInfo{
+	// 	Info: metainfo.InfoEx{
+	// 		Info: md,
+	// 	},
+	// 	CreationDate: time.Now().Unix(),
+	// 	Comment:      "metadata set in client",
+	// 	CreatedBy:    "go.torrent",
+	// 	// TODO(anacrolix): Expose trackers given when torrent added.
+	// }:
+	// default:
+	// 	panic("shouldn't block")
+	// }
+	if err := cl.saveTorrentFile(t); err != nil {
+		log.Printf("error saving torrent file for %s: %s", t, err)
 	}
 	close(t.gotMetainfo)
-	t.gotMetainfo = nil
+	// t.gotMetainfo = nil
 	return
 }
 
@@ -1368,7 +1371,7 @@ func newTorrent(ih InfoHash, announceList [][]string, halfOpenLimit int) (t *tor
 		closing:           make(chan struct{}),
 		ceasingNetworking: make(chan struct{}),
 
-		gotMetainfo: make(chan *metainfo.MetaInfo, 1),
+		gotMetainfo: make(chan struct{}),
 
 		HalfOpen: make(map[string]struct{}, halfOpenLimit),
 	}
diff --git a/cmd/magnet-metainfo/main.go b/cmd/magnet-metainfo/main.go
index 9e73c919..a356e802 100644
--- a/cmd/magnet-metainfo/main.go
+++ b/cmd/magnet-metainfo/main.go
@@ -27,12 +27,9 @@ func main() {
 		wg.Add(1)
 		go func() {
 			defer wg.Done()
-			mi, ok := <-t.GotMetainfo
+			<-t.GotMetainfo
+			mi := t.MetaInfo()
 			t.Close()
-			if !ok {
-				log.Printf("no metainfo for %q", t.Name())
-				return
-			}
 			f, err := os.Create(mi.Info.Name + ".torrent")
 			if err != nil {
 				log.Fatalf("error creating torrent metainfo file: %s", err)
diff --git a/torrent.go b/torrent.go
index 1e4302b7..40fb3d58 100644
--- a/torrent.go
+++ b/torrent.go
@@ -80,8 +80,8 @@ type torrent struct {
 	MetaData     []byte
 	metadataHave []bool
 
-	gotMetainfo chan *metainfo.MetaInfo
-	GotMetainfo <-chan *metainfo.MetaInfo
+	gotMetainfo chan struct{}
+	GotMetainfo <-chan struct{}
 }
 
 func (t *torrent) addrActive(addr string) bool {
@@ -355,6 +355,30 @@ func (t *torrent) haveInfo() bool {
 	return t.Info != nil
 }
 
+// TODO: Include URIs that weren't converted to tracker clients.
+func (t *torrent) AnnounceList() (al [][]string) {
+	for _, tier := range t.Trackers {
+		var l []string
+		for _, tr := range tier {
+			l = append(l, tr.URL())
+		}
+		al = append(al, l)
+	}
+	return
+}
+
+func (t *torrent) MetaInfo() *metainfo.MetaInfo {
+	return &metainfo.MetaInfo{
+		Info: metainfo.InfoEx{
+			Info: *t.Info.Info,
+		},
+		CreationDate: time.Now().Unix(),
+		Comment:      "dynamic metainfo from client",
+		CreatedBy:    "go.torrent",
+		AnnounceList: t.AnnounceList(),
+	}
+}
+
 func (t *torrent) BytesLeft() (left int64) {
 	if !t.haveInfo() {
 		return -1
-- 
2.48.1