verify playlist entries

As it turned out not all playlist entries contain valid URLs. In
order to find a valid URL we iterate over the playlist and check
if the server of the current item is available.

The first valid server found will be used for the channel URL.

resources/lib/audioaddict/play.py

@@ -3,6 +3,8 @@
     Functionality triggered if the user starts/plays a channel.
 """
 
+import urlparse
+import requests
 import xbmcplugin
 
 from audioaddict.api import AudioAddictApi
@@ -20,7 +22,8 @@ def play_stream(addon, settings):
     stream_key = get_stream_key(addon, network)
     playlist = get_playlist(addon, network_key, stream_key, channel_key)
 
-    stream_url = "%s|User-Agent=%s&Referer=%s" % (playlist[0],
+    channel_url = get_valid_channel_url(playlist)
+    stream_url = "%s|User-Agent=%s&Referer=%s" % (channel_url,
                                                   settings.user_agent,
                                                   network.referer)
 
@@ -59,3 +62,19 @@ def get_playlist(addon, network_key, stream_key, channel_key):
             raise e
 
     return playlist
+
+
+def get_valid_channel_url(playlist):
+    for channel_url in playlist:
+        parsed_url = urlparse.urlparse(channel_url)
+        if server_available(parsed_url.netloc):
+            return channel_url
+
+
+def server_available(domain):
+    try:
+        response = requests.head("http://%s" % domain)
+    except requests.exceptions.ConnectionError as e:
+        return False
+
+    return True