From 0b85ba9f329a061418c1761c050ef3197074a51d Mon Sep 17 00:00:00 2001
From: DC <dcposch@dcpos.ch>
Date: Tue, 19 Apr 2016 20:28:13 -0700
Subject: [PATCH] Show an error when adding a dupe torrent

This works around a WebTorrent bug where calling client.add(torrentFilePath) to add a duplicate torrent -- in other words, one whose infoHash we're already torrenting -- creates a new torrent object and later throws an error. Inconsistently, calling client.add(magnetURI) or client.add(infoHash) to add a duplicate torrent returns the existing torrent object that we're already torrenting and doesn't throw an error.

This also fixes a prety nasty bug where pasting a dupe magnet link changed the torrentKey of an existing torrent, breaking the communication between the main and WebTorrent windows

Fixes #364
---
 renderer/index.js      | 2 +-
 renderer/webtorrent.js | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/renderer/index.js b/renderer/index.js
index 24b9145d..bd127e7d 100644
--- a/renderer/index.js
+++ b/renderer/index.js
@@ -717,7 +717,7 @@ function torrentError (torrentKey, message) {
 
   // TODO: WebTorrent should have semantic errors
   if (message.startsWith('There is already a swarm')) {
-    onError(new Error('Couldn\'t add duplicate torrent'))
+    onError(new Error('Can\'t add duplicate torrent'))
   } else if (!torrentSummary) {
     onError(message)
   } else {
diff --git a/renderer/webtorrent.js b/renderer/webtorrent.js
index e5a9cf4a..48a769bb 100644
--- a/renderer/webtorrent.js
+++ b/renderer/webtorrent.js
@@ -77,6 +77,12 @@ function startTorrenting (torrentKey, torrentID, path, fileModtimes) {
   } catch (err) {
     return ipc.send('wt-error', torrentKey, err.message)
   }
+  // If we add a duplicate magnet URI or infohash, WebTorrent returns the
+  // existing torrent object! (If we add a duplicate torrent file, it creates a
+  // new torrent object and raises an error later.) Workaround:
+  if (torrent.key) {
+    return ipc.send('wt-error', torrentKey, 'Can\'t add duplicate torrent')
+  }
   torrent.key = torrentKey
   addTorrentEvents(torrent)
   return torrent