[downloader] Lay groundwork for external downloaders.

This comes with a very simply implementation for wget; the real work is in setting up the infrastructure.

7 files changed, 169 insertions, 14 deletions

diff --git a/youtube_dl/YoutubeDL.py b/youtube_dl/YoutubeDL.py
index e61e6c2a7..54e732943 100755
--- a/youtube_dl/YoutubeDL.py
+++ b/youtube_dl/YoutubeDL.py
@@ -219,6 +219,7 @@ class YoutubeDL(object):
     call_home:         Boolean, true iff we are allowed to contact the
                        youtube-dl servers for debugging.
     sleep_interval:    Number of seconds to sleep before each download.
+    external_downloader:  Executable of the external downloader to call.
 
 
     The following parameters are not used by YoutubeDL itself, they are used by
diff --git a/youtube_dl/__init__.py b/youtube_dl/__init__.py
index 7bd7295e2..3fc7dc5c2 100644
--- a/youtube_dl/__init__.py
+++ b/youtube_dl/__init__.py
@@ -330,6 +330,7 @@ def _real_main(argv=None):
         'source_address': opts.source_address,
         'call_home': opts.call_home,
         'sleep_interval': opts.sleep_interval,
+        'external_downloader': opts.external_downloader,
     }
 
     with YoutubeDL(ydl_opts) as ydl:
diff --git a/youtube_dl/downloader/__init__.py b/youtube_dl/downloader/__init__.py
index 2aca3cab5..eff1122c5 100644
--- a/youtube_dl/downloader/__init__.py
+++ b/youtube_dl/downloader/__init__.py
@@ -1,12 +1,13 @@
 from __future__ import unicode_literals
 
 from .common import FileDownloader
+from .external import get_external_downloader
+from .f4m import F4mFD
 from .hls import HlsFD
 from .hls import NativeHlsFD
 from .http import HttpFD
 from .mplayer import MplayerFD
 from .rtmp import RtmpFD
-from .f4m import F4mFD
 
 from ..utils import (
     determine_protocol,
@@ -27,6 +28,12 @@ def get_suitable_downloader(info_dict, params={}):
     protocol = determine_protocol(info_dict)
     info_dict['protocol'] = protocol
 
+    external_downloader = params.get('external_downloader')
+    if external_downloader is not None:
+        ed = get_external_downloader(external_downloader)
+        if ed.supports(info_dict):
+            return ed
+
     return PROTOCOL_MAP.get(protocol, HttpFD)
 
 
diff --git a/youtube_dl/downloader/common.py b/youtube_dl/downloader/common.py
index 82c917d92..c35c42c1d 100644
--- a/youtube_dl/downloader/common.py
+++ b/youtube_dl/downloader/common.py
@@ -325,3 +325,24 @@ class FileDownloader(object):
         # See YoutubeDl.py (search for progress_hooks) for a description of
         # this interface
         self._progress_hooks.append(ph)
+
+    def _debug_cmd(self, args, subprocess_encoding, exe=None):
+        if not self.params.get('verbose', False):
+            return
+
+        if exe is None:
+            exe = os.path.basename(args[0])
+
+        if subprocess_encoding:
+            str_args = [
+                a.decode(subprocess_encoding) if isinstance(a, bytes) else a
+                for a in args]
+        else:
+            str_args = args
+        try:
+            import pipes
+            shell_quote = lambda args: ' '.join(map(pipes.quote, str_args))
+        except ImportError:
+            shell_quote = repr
+        self.to_screen('[debug] %s command line: %s' % (
+            exe, shell_quote(str_args)))
diff --git a/youtube_dl/downloader/external.py b/youtube_dl/downloader/external.py
new file mode 100644
index 000000000..c05596255
--- /dev/null
+++ b/youtube_dl/downloader/external.py
@@ -0,0 +1,131 @@
+from __future__ import unicode_literals
+
+import os.path
+import subprocess
+import sys
+
+from .common import FileDownloader
+from ..utils import (
+    encodeFilename,
+    std_headers,
+)
+
+
+class ExternalFD(FileDownloader):
+    def real_download(self, filename, info_dict):
+        self.report_destination(filename)
+        tmpfilename = self.temp_name(filename)
+
+        retval = self._call_downloader(tmpfilename, info_dict)
+        if retval == 0:
+            fsize = os.path.getsize(encodeFilename(tmpfilename))
+            self.to_screen('\r[%s] Downloaded %s bytes' % (self.get_basename(), fsize))
+            self.try_rename(tmpfilename, filename)
+            self._hook_progress({
+                'downloaded_bytes': fsize,
+                'total_bytes': fsize,
+                'filename': filename,
+                'status': 'finished',
+            })
+            return True
+        else:
+            self.to_stderr('\n')
+            self.report_error('%s exited with code %d' % (
+                self.get_basename(), retval))
+            return False
+
+    @classmethod
+    def get_basename(cls):
+        return cls.__name__[:-2].lower()
+
+    @property
+    def exe(self):
+        return self.params.get('external_downloader')
+
+    @classmethod
+    def supports(cls, info_dict):
+        return info_dict['protocol'] in ('http', 'https', 'ftp', 'ftps')
+
+    def _calc_headers(self, info_dict):
+        res = std_headers.copy()
+
+        ua = info_dict.get('user_agent')
+        if ua is not None:
+            res['User-Agent'] = ua
+
+        cookies = self._calc_cookies(info_dict)
+        if cookies:
+            res['Cookie'] = cookies
+
+        return res
+
+    def _calc_cookies(self, info_dict):
+        class _PseudoRequest(object):
+            def __init__(self, url):
+                self.url = url
+                self.headers = {}
+                self.unverifiable = False
+
+            def add_unredirected_header(self, k, v):
+                self.headers[k] = v
+
+            def get_full_url(self):
+                return self.url
+
+            def is_unverifiable(self):
+                return self.unverifiable
+
+            def has_header(self, h):
+                return h in self.headers
+
+        pr = _PseudoRequest(info_dict['url'])
+        self.ydl.cookiejar.add_cookie_header(pr)
+        return pr.headers.get('Cookie')
+
+    def _call_downloader(self, tmpfilename, info_dict):
+        """ Either overwrite this or implement _make_cmd """
+        cmd = self._make_cmd(tmpfilename, info_dict)
+
+        if sys.platform == 'win32' and sys.version_info < (3, 0):
+            # Windows subprocess module does not actually support Unicode
+            # on Python 2.x
+            # See http://stackoverflow.com/a/9951851/35070
+            subprocess_encoding = sys.getfilesystemencoding()
+            cmd = [a.encode(subprocess_encoding, 'ignore') for a in cmd]
+        else:
+            subprocess_encoding = None
+        self._debug_cmd(cmd, subprocess_encoding)
+
+        p = subprocess.Popen(
+            cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+        stdout, stderr = p.communicate()
+        if p.returncode != 0:
+            self.to_stderr(stderr)
+        return p.returncode
+
+
+class WgetFD(ExternalFD):
+    def _make_cmd(self, tmpfilename, info_dict):
+        cmd = [self.exe, '-O', tmpfilename, '-nv', '--no-cookies']
+        for key, val in self._calc_headers(info_dict).items():
+            cmd += ['--header', '%s: %s' % (key, val)]
+        cmd += ['--', info_dict['url']]
+        return cmd
+
+
+_BY_NAME = dict(
+    (klass.get_basename(), klass)
+    for name, klass in globals().items()
+    if name.endswith('FD') and name != 'ExternalFD'
+)
+
+
+def list_external_downloaders():
+    return sorted(_BY_NAME.keys())
+
+
+def get_external_downloader(external_downloader):
+    """ Given the name of the executable, see whether we support the given
+        downloader . """
+    bn = os.path.basename(external_downloader)
+    return _BY_NAME[bn]
diff --git a/youtube_dl/downloader/rtmp.py b/youtube_dl/downloader/rtmp.py
index 5346cb9a0..6dbbc053c 100644
--- a/youtube_dl/downloader/rtmp.py
+++ b/youtube_dl/downloader/rtmp.py
@@ -152,19 +152,7 @@ class RtmpFD(FileDownloader):
         else:
             subprocess_encoding = None
 
-        if self.params.get('verbose', False):
-            if subprocess_encoding:
-                str_args = [
-                    a.decode(subprocess_encoding) if isinstance(a, bytes) else a
-                    for a in args]
-            else:
-                str_args = args
-            try:
-                import pipes
-                shell_quote = lambda args: ' '.join(map(pipes.quote, str_args))
-            except ImportError:
-                shell_quote = repr
-            self.to_screen('[debug] rtmpdump command line: ' + shell_quote(str_args))
+        self._debug_cmd(args, subprocess_encoding, exe='rtmpdump')
 
         RD_SUCCESS = 0
         RD_FAILED = 1
diff --git a/youtube_dl/options.py b/youtube_dl/options.py
index 262c60013..b38b8349f 100644
--- a/youtube_dl/options.py
+++ b/youtube_dl/options.py
@@ -5,6 +5,7 @@ import optparse
 import shlex
 import sys
 
+from .downloader.external import list_external_downloaders
 from .compat import (
     compat_expanduser,
     compat_getenv,
@@ -389,6 +390,11 @@ def parseOpts(overrideArguments=None):
         '--playlist-reverse',
         action='store_true',
         help='Download playlist videos in reverse order')
+    downloader.add_option(
+        '--external-downloader',
+        dest='external_downloader', metavar='COMMAND',
+        help='(experimental) Use the specified external downloader. '
+             'Currently supports %s' % ','.join(list_external_downloaders()))
 
     workarounds = optparse.OptionGroup(parser, 'Workarounds')
     workarounds.add_option(