plugins.twitch: Support VOD URLs with a time parameter.

This adds support for the ?t=00m0s URLs described here:
http://twitchtv.wordpress.com/2011/10/24/new-functionality-link-to-a-specific-time-in-a-vod/

src/livestreamer/plugins/justintv_common.py

@@ -9,14 +9,14 @@
 except ImportError:
     izip = zip
 
-from livestreamer.compat import urljoin
+from livestreamer.compat import urlparse, urljoin
 from livestreamer.exceptions import NoStreamsError, PluginError, StreamError
 from livestreamer.options import Options
 from livestreamer.plugin import Plugin
 from livestreamer.stream import (HTTPStream, HLSStream, FLVPlaylist,
                                  extract_flv_header_tags)
-from livestreamer.utils import (parse_json, res_json, res_xml, verifyjson,
-                                urlget)
+from livestreamer.utils import (parse_json, parse_qsd, res_json, res_xml,
+                                verifyjson, urlget)
 
 __all__ = ["PluginBase", "APIBase"]
 
@@ -118,8 +118,12 @@ def __init__(self, url):
             self.video_type = match.get("video_type")
             self.video_id = match.get("video_id")
             self.usher = UsherService(match.get("domain"))
+
+            parsed = urlparse(url)
+            self.params = parse_qsd(parsed.query)
         except AttributeError:
             self.channel = None
+            self.params = None
             self.video_id = None
             self.video_type = None
             self.usher = None

src/livestreamer/plugins/twitch.py

@@ -1,3 +1,5 @@
+import re
+
 from livestreamer.exceptions import PluginError, NoStreamsError
 from livestreamer.options import Options
 
@@ -9,6 +11,17 @@
 JustinTVAPIBase = justintv_common.APIBase
 
 
+def time_to_offset(t):
+    match = re.match(r"((?P<minutes>\d+)m)?((?P<seconds>\d+)s)?", t)
+    if match:
+        offset = int(match.group("minutes") or "0") * 60
+        offset += int(match.group("seconds") or "0")
+    else:
+        offset = 0
+
+    return offset
+
+
 class TwitchAPI(JustinTVAPIBase):
     def __init__(self):
         JustinTVAPIBase.__init__(self, host="twitch.tv")
@@ -75,6 +88,12 @@ def _get_video_streams(self):
             else:
                 raise
 
+        # Parse the "t" query parameter on broadcasts and adjust
+        # start offset if needed.
+        time_offset = self.params.get("t")
+        if time_offset and self.video_type == "a":
+            videos["start_offset"] = time_to_offset(self.params.get("t"))
+
         return self._create_playlist_streams(videos)