From f4fd09ffd5d1e9f218267b2206a90aa998cbcd9d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Roman=20Le=20N=C3=A9grate?= <roman.lenegrate@gmail.com>
Date: Mon, 16 Mar 2015 00:20:06 +0100
Subject: [PATCH] [mixcloud] Try preview server first, then further numbers

---
 test/test_mixcloud.py            | 16 ++++++++++
 youtube_dl/extractor/mixcloud.py | 53 +++++++++++++++++++++++++-------
 2 files changed, 58 insertions(+), 11 deletions(-)
 create mode 100644 test/test_mixcloud.py

diff --git a/test/test_mixcloud.py b/test/test_mixcloud.py
new file mode 100644
index 000000000..56fbe4c87
--- /dev/null
+++ b/test/test_mixcloud.py
@@ -0,0 +1,16 @@
+import unittest
+from youtube_dl.extractor.mixcloud import server_numbers
+
+class TestMixcloud(unittest.TestCase):
+    def test_server_numbers(self):
+        self.assertEqual([n for n in server_numbers(2, (1, 5))],
+            [2, 3, 1, 4, 5])
+        self.assertEqual([n for n in server_numbers(1, (1, 5))],
+            [1, 2, 3, 4, 5])
+        self.assertEqual([n for n in server_numbers(5, (1, 5))],
+            [5, 4, 3, 2, 1])
+        self.assertEqual([n for n in server_numbers(-1, (1, 5))],
+            [-1, 1, 2, 3, 4, 5])
+
+if __name__ == '__main__':
+    unittest.main()
diff --git a/youtube_dl/extractor/mixcloud.py b/youtube_dl/extractor/mixcloud.py
index 63510ce89..254a71940 100644
--- a/youtube_dl/extractor/mixcloud.py
+++ b/youtube_dl/extractor/mixcloud.py
@@ -1,6 +1,7 @@
 from __future__ import unicode_literals
 
 import re
+import itertools
 
 from .common import InfoExtractor
 from ..compat import (
@@ -13,10 +14,11 @@ from ..utils import (
     parse_iso8601,
 )
 
-
 class MixcloudIE(InfoExtractor):
     _VALID_URL = r'^(?:https?://)?(?:www\.)?mixcloud\.com/([^/]+)/([^/]+)'
     IE_NAME = 'mixcloud'
+    STREAM_PART_RE = r'\bstream(\d+)\b'
+    SERVER_NUMBERS_BOUNDARIES = (1, 30)
 
     _TESTS = [{
         'url': 'http://www.mixcloud.com/dholbach/cryptkeeper/',
@@ -48,20 +50,22 @@ class MixcloudIE(InfoExtractor):
         },
     }]
 
-    def _get_url(self, track_id, template_url):
-        server_count = 30
-        for i in range(server_count):
-            url = template_url % i
+    def _get_url(self, track_id, song_url):
+        mobj = re.search(self.STREAM_PART_RE, song_url)
+        if mobj is None:
+          raise ExtractorError('Unexpected preview URL format: no stream%d')
+        server_nr = int(mobj.group(1))
+        for nr in server_numbers(server_nr, self.SERVER_NUMBERS_BOUNDARIES):
+            url = re.sub(self.STREAM_PART_RE, 'stream%d' % nr, song_url)
             try:
                 # We only want to know if the request succeed
                 # don't download the whole file
                 self._request_webpage(
                     HEADRequest(url), track_id,
-                    'Checking URL %d/%d ...' % (i + 1, server_count + 1))
+                    'Checking URL %d/%d ...' % (nr, self.SERVER_NUMBERS_BOUNDARIES[-1]))
                 return url
             except ExtractorError:
                 pass
-
         return None
 
     def _real_extract(self, url):
@@ -73,10 +77,10 @@ class MixcloudIE(InfoExtractor):
         webpage = self._download_webpage(url, track_id)
 
         preview_url = self._search_regex(
-            r'\bm-play-on-spacebar\b.*\n?.*\bm-preview="([^"]+)"', webpage, 'preview url')
-        song_url = re.sub(r'\.mp3$', '.m4a', preview_url.replace('/previews/', '/c/m4a/64/'))
-        template_url = re.sub(r'(stream\d+)', 'stream%d', song_url)
-        final_song_url = self._get_url(track_id, template_url)
+            r'\bm-play-on-spacebar\b.*\n?.*\bm-preview="([^"]+).mp3"',
+            webpage, 'preview url')
+        song_url = preview_url.replace('/previews/', '/c/m4a/64/') + '.m4a'
+        final_song_url = self._get_url(track_id, song_url)
         if final_song_url is None:
             raise ExtractorError('Unable to extract track url')
 
@@ -117,3 +121,30 @@ class MixcloudIE(InfoExtractor):
             'view_count': view_count,
             'like_count': like_count,
         }
+
+def server_numbers(first, boundaries):
+    """ Server numbers to try in descending order of probable availability.
+    Starting from first (i.e. the number of the server hosting the preview file)
+    and going further and further up to the higher boundary and down to the
+    lower one in an alternating fashion. Namely:
+
+        server_numbers(2, (1, 5))
+
+        # Where the preview server is 2, min number is 1 and max is 5.
+        # Yields: 2, 3, 1, 4, 5
+
+    Why not random numbers or increasing sequences? Since from what I've seen,
+    full length files seem to be hosted on servers whose number is closer to
+    that of the preview; to be confirmed.
+    """
+
+    if len(boundaries) != 2:
+        raise ValueError("boundaries should be a two-element tuple")
+    min, max = boundaries
+    highs = range(first + 1, max + 1)
+    lows = range(first - 1, min - 1, -1)
+    rest = filter(None,
+        itertools.chain.from_iterable(itertools.izip_longest(highs, lows)))
+    yield first
+    for n in rest:
+        yield n