Merge pull request #792 from fp7/master
[youtube-dl] / youtube_dl / FileDownloader.py
index be9e4918ec0983eaf8e188a46acf090ff8deb4de..7139adf6bb6490b31dc3661b0fc220df30b0dad2 100644 (file)
@@ -17,6 +17,7 @@ if os.name == 'nt':
     import ctypes
 
 from .utils import *
+from .InfoExtractors import get_info_extractor
 
 
 class FileDownloader(object):
@@ -78,9 +79,16 @@ class FileDownloader(object):
     updatetime:        Use the Last-modified header to set output file timestamps.
     writedescription:  Write the video description to a .description file
     writeinfojson:     Write the video description to a .info.json file
-    writesubtitles:    Write the video subtitles to a .srt file
+    writesubtitles:    Write the video subtitles to a file
+    onlysubtitles:     Downloads only the subtitles of the video
+    allsubtitles:      Downloads all the subtitles of the video
+    listsubtitles:     Lists all available subtitles for the video
+    subtitlesformat:   Subtitle format [sbv/srt] (default=srt)
     subtitleslang:     Language of the subtitles to download
     test:              Download only first bytes to test the downloader.
+    keepvideo:         Keep the video file after post-processing
+    min_filesize:      Skip files smaller than this size
+    max_filesize:      Skip files larger than this size
     """
 
     params = None
@@ -94,13 +102,14 @@ class FileDownloader(object):
         """Create a FileDownloader object with the given options."""
         self._ies = []
         self._pps = []
+        self._progress_hooks = []
         self._download_retcode = 0
         self._num_downloads = 0
         self._screen_file = [sys.stdout, sys.stderr][params.get('logtostderr', False)]
         self.params = params
 
         if '%(stitle)s' in self.params['outtmpl']:
-            self.to_stderr(u'WARNING: %(stitle)s is deprecated. Use the %(title)s and the --restrict-filenames flag(which also secures %(uploader)s et al) instead.')
+            self.report_warning(u'%(stitle)s is deprecated. Use the %(title)s and the --restrict-filenames flag(which also secures %(uploader)s et al) instead.')
 
     @staticmethod
     def format_bytes(bytes):
@@ -204,7 +213,7 @@ class FileDownloader(object):
             # already of type unicode()
             ctypes.windll.kernel32.SetConsoleTitleW(ctypes.c_wchar_p(message))
         elif 'TERM' in os.environ:
-            sys.stderr.write('\033]0;%s\007' % message.encode(preferredencoding()))
+            self.to_screen('\033]0;%s\007' % message, skip_eol=True)
 
     def fixed_template(self):
         """Checks if the output template is fixed."""
@@ -223,13 +232,47 @@ class FileDownloader(object):
             self.to_stderr(message)
         if self.params.get('verbose'):
             if tb is None:
-                tb_data = traceback.format_list(traceback.extract_stack())
-                tb = u''.join(tb_data)
+                if sys.exc_info()[0]:  # if .trouble has been called from an except block
+                    tb = u''
+                    if hasattr(sys.exc_info()[1], 'exc_info') and sys.exc_info()[1].exc_info[0]:
+                        tb += u''.join(traceback.format_exception(*sys.exc_info()[1].exc_info))
+                    tb += compat_str(traceback.format_exc())
+                else:
+                    tb_data = traceback.format_list(traceback.extract_stack())
+                    tb = u''.join(tb_data)
             self.to_stderr(tb)
         if not self.params.get('ignoreerrors', False):
-            raise DownloadError(message)
+            if sys.exc_info()[0] and hasattr(sys.exc_info()[1], 'exc_info') and sys.exc_info()[1].exc_info[0]:
+                exc_info = sys.exc_info()[1].exc_info
+            else:
+                exc_info = sys.exc_info()
+            raise DownloadError(message, exc_info)
         self._download_retcode = 1
 
+    def report_warning(self, message):
+        '''
+        Print the message to stderr, it will be prefixed with 'WARNING:'
+        If stderr is a tty file the 'WARNING:' will be colored
+        '''
+        if sys.stderr.isatty():
+            _msg_header=u'\033[0;33mWARNING:\033[0m'
+        else:
+            _msg_header=u'WARNING:'
+        warning_message=u'%s %s' % (_msg_header,message)
+        self.to_stderr(warning_message)
+
+    def report_error(self, message, tb=None):
+        '''
+        Do the same as trouble, but prefixes the message with 'ERROR:', colored
+        in red if stderr is a tty file.
+        '''
+        if sys.stderr.isatty():
+            _msg_header = u'\033[0;31mERROR:\033[0m'
+        else:
+            _msg_header = u'ERROR:'
+        error_message = u'%s %s' % (_msg_header, message)
+        self.trouble(error_message, tb)
+
     def slow_down(self, start_time, byte_counter):
         """Sleep if the download speed is over the rate limit."""
         rate_limit = self.params.get('ratelimit', None)
@@ -261,7 +304,7 @@ class FileDownloader(object):
                 return
             os.rename(encodeFilename(old_filename), encodeFilename(new_filename))
         except (IOError, OSError) as err:
-            self.trouble(u'ERROR: unable to rename file')
+            self.report_error(u'unable to rename file')
 
     def try_utime(self, filename, last_modified_hdr):
         """Try to set the last-modified time of the given file."""
@@ -285,9 +328,9 @@ class FileDownloader(object):
         """ Report that the description file is being written """
         self.to_screen(u'[info] Writing video description to: ' + descfn)
 
-    def report_writesubtitles(self, srtfn):
+    def report_writesubtitles(self, sub_filename):
         """ Report that the subtitles file is being written """
-        self.to_screen(u'[info] Writing video subtitles to: ' + srtfn)
+        self.to_screen(u'[info] Writing video subtitles to: ' + sub_filename)
 
     def report_writeinfojson(self, infofn):
         """ Report that the metadata file has been written """
@@ -301,7 +344,11 @@ class FileDownloader(object):
         """Report download progress."""
         if self.params.get('noprogress', False):
             return
-        self.to_screen(u'\r[download] %s of %s at %s ETA %s' %
+        if self.params.get('progress_with_newline', False):
+            self.to_screen(u'[download] %s of %s at %s ETA %s' %
+                (percent_str, data_len_str, speed_str, eta_str))
+        else:
+            self.to_screen(u'\r[download] %s of %s at %s ETA %s' %
                 (percent_str, data_len_str, speed_str, eta_str), skip_eol=True)
         self.to_cons_title(u'youtube-dl - %s of %s at %s ETA %s' %
                 (percent_str.strip(), data_len_str.strip(), speed_str.strip(), eta_str.strip()))
@@ -342,7 +389,13 @@ class FileDownloader(object):
             template_dict = dict(info_dict)
 
             template_dict['epoch'] = int(time.time())
-            template_dict['autonumber'] = u'%05d' % self._num_downloads
+            autonumber_size = self.params.get('autonumber_size')
+            if autonumber_size is None:
+                autonumber_size = 5
+            autonumber_templ = u'%0' + str(autonumber_size) + u'd'
+            template_dict['autonumber'] = autonumber_templ % self._num_downloads
+            if template_dict['playlist_index'] is not None:
+                template_dict['playlist_index'] = u'%05d' % template_dict['playlist_index']
 
             sanitize = lambda k,v: sanitize_filename(
                 u'NA' if v is None else compat_str(v),
@@ -352,8 +405,11 @@ class FileDownloader(object):
 
             filename = self.params['outtmpl'] % template_dict
             return filename
-        except (ValueError, KeyError) as err:
-            self.trouble(u'ERROR: invalid system charset or erroneous output template')
+        except KeyError as err:
+            self.trouble(u'ERROR: Erroneous output template')
+            return None
+        except ValueError as err:
+            self.trouble(u'ERROR: Insufficient system charset ' + repr(preferredencoding()))
             return None
 
     def _match_entry(self, info_dict):
@@ -362,19 +418,133 @@ class FileDownloader(object):
         title = info_dict['title']
         matchtitle = self.params.get('matchtitle', False)
         if matchtitle:
-            matchtitle = matchtitle.decode('utf8')
             if not re.search(matchtitle, title, re.IGNORECASE):
                 return u'[download] "' + title + '" title did not match pattern "' + matchtitle + '"'
         rejecttitle = self.params.get('rejecttitle', False)
         if rejecttitle:
-            rejecttitle = rejecttitle.decode('utf8')
             if re.search(rejecttitle, title, re.IGNORECASE):
                 return u'"' + title + '" title matched reject pattern "' + rejecttitle + '"'
         return None
+        
+    def extract_info(self, url, download = True, ie_name = None):
+        '''
+        Returns a list with a dictionary for each video we find.
+        If 'download', also downloads the videos.
+         '''
+        suitable_found = False
+        
+        #We copy the original list
+        ies = list(self._ies)
+
+        if ie_name is not None:
+            #We put in the first place the given info extractor
+            first_ie = get_info_extractor(ie_name)()
+            first_ie.set_downloader(self)
+            ies.insert(0, first_ie)
+
+        for ie in ies:
+            # Go to next InfoExtractor if not suitable
+            if not ie.suitable(url):
+                continue
+
+            # Warn if the _WORKING attribute is False
+            if not ie.working():
+                self.to_stderr(u'WARNING: the program functionality for this site has been marked as broken, '
+                               u'and will probably not work. If you want to go on, use the -i option.')
+
+            # Suitable InfoExtractor found
+            suitable_found = True
+
+            # Extract information from URL and process it
+            try:
+                ie_results = ie.extract(url)
+                if ie_results is None: # Finished already (backwards compatibility; listformats and friends should be moved here)
+                    break
+                results = []
+                for ie_result in ie_results:
+                    if not 'extractor' in ie_result:
+                        #The extractor has already been set somewhere else
+                        ie_result['extractor'] = ie.IE_NAME
+                    results.append(self.process_ie_result(ie_result, download))
+                return results
+            except ExtractorError as de: # An error we somewhat expected
+                self.trouble(u'ERROR: ' + compat_str(de), de.format_traceback())
+                break
+            except Exception as e:
+                if self.params.get('ignoreerrors', False):
+                    self.trouble(u'ERROR: ' + compat_str(e), tb=compat_str(traceback.format_exc()))
+                    break
+                else:
+                    raise
+        if not suitable_found:
+                self.trouble(u'ERROR: no suitable InfoExtractor: %s' % url)
+        
+    def process_ie_result(self, ie_result, download = True):
+        """
+        Take the result of the ie and return a list of videos.
+        For url elements it will search the suitable ie and get the videos
+        For playlist elements it will process each of the elements of the 'entries' key
+        
+        It will also download the videos if 'download'.
+        """
+        result_type = ie_result.get('_type', 'video') #If not given we suppose it's a video, support the dafault old system
+        if result_type == 'video':
+            if 'playlist' not in ie_result:
+                #It isn't part of a playlist
+                ie_result['playlist'] = None
+                ie_result['playlist_index'] = None
+            if download:
+                #Do the download:
+                self.process_info(ie_result)
+            return ie_result
+        elif result_type == 'url':
+            #We get the video pointed by the url
+            result = self.extract_info(ie_result['url'], download, ie_name = ie_result['ie_key'])[0]
+            return result
+        elif result_type == 'playlist':
+            #We process each entry in the playlist
+            playlist = ie_result.get('title', None) or ie_result.get('id', None)
+            self.to_screen(u'[download] Downloading playlist: %s'  % playlist)
+
+            playlist_results = []
+
+            n_all_entries = len(ie_result['entries'])
+            playliststart = self.params.get('playliststart', 1) - 1
+            playlistend = self.params.get('playlistend', -1)
+
+            if playlistend == -1:
+                entries = ie_result['entries'][playliststart:]
+            else:
+                entries = ie_result['entries'][playliststart:playlistend]
+
+            n_entries = len(entries)
+
+            self.to_screen(u"[%s] playlist '%s': Collected %d video ids (downloading %d of them)" %
+                (ie_result['extractor'], playlist, n_all_entries, n_entries))
+
+            for i,entry in enumerate(entries,1):
+                self.to_screen(u'[download] Downloading video #%s of %s' %(i, n_entries))
+                entry_result = self.process_ie_result(entry, False)
+                entry_result['playlist'] = playlist
+                entry_result['playlist_index'] = i + playliststart
+                #We must do the download here to correctly set the 'playlist' key
+                if download:
+                    self.process_info(entry_result)
+                playlist_results.append(entry_result)
+            result = ie_result.copy()
+            result['entries'] = playlist_results
+            return result
 
     def process_info(self, info_dict):
         """Process a single dictionary returned by an InfoExtractor."""
 
+        #We increment the download the download count here to match the previous behaviour.
+        self.increment_downloads()
+        
+        info_dict['fulltitle'] = info_dict['title']
+        if len(info_dict['title']) > 200:
+            info_dict['title'] = info_dict['title'][:197] + u'...'
+
         # Keep for backwards compatibility
         info_dict['stitle'] = info_dict['title']
 
@@ -419,7 +589,7 @@ class FileDownloader(object):
             if dn != '' and not os.path.exists(dn): # dn is already encoded
                 os.makedirs(dn)
         except (OSError, IOError) as err:
-            self.trouble(u'ERROR: unable to create directory ' + compat_str(err))
+            self.report_error(u'unable to create directory ' + compat_str(err))
             return
 
         if self.params.get('writedescription', False):
@@ -429,20 +599,47 @@ class FileDownloader(object):
                 with io.open(encodeFilename(descfn), 'w', encoding='utf-8') as descfile:
                     descfile.write(info_dict['description'])
             except (OSError, IOError):
-                self.trouble(u'ERROR: Cannot write description file ' + descfn)
+                self.report_error(u'Cannot write description file ' + descfn)
                 return
 
         if self.params.get('writesubtitles', False) and 'subtitles' in info_dict and info_dict['subtitles']:
             # subtitles download errors are already managed as troubles in relevant IE
             # that way it will silently go on when used with unsupporting IE
-            try:
-                srtfn = filename.rsplit('.', 1)[0] + u'.srt'
-                self.report_writesubtitles(srtfn)
-                with io.open(encodeFilename(srtfn), 'w', encoding='utf-8') as srtfile:
-                    srtfile.write(info_dict['subtitles'])
-            except (OSError, IOError):
-                self.trouble(u'ERROR: Cannot write subtitles file ' + descfn)
-                return
+            subtitle = info_dict['subtitles'][0]
+            (sub_error, sub_lang, sub) = subtitle
+            sub_format = self.params.get('subtitlesformat')
+            if sub_error:
+                self.report_warning("Some error while getting the subtitles")
+            else:
+                try:
+                    sub_filename = filename.rsplit('.', 1)[0] + u'.' + sub_lang + u'.' + sub_format
+                    self.report_writesubtitles(sub_filename)
+                    with io.open(encodeFilename(sub_filename), 'w', encoding='utf-8') as subfile:
+                        subfile.write(sub)
+                except (OSError, IOError):
+                    self.report_error(u'Cannot write subtitles file ' + descfn)
+                    return
+            if self.params.get('onlysubtitles', False):
+                return 
+
+        if self.params.get('allsubtitles', False) and 'subtitles' in info_dict and info_dict['subtitles']:
+            subtitles = info_dict['subtitles']
+            sub_format = self.params.get('subtitlesformat')
+            for subtitle in subtitles:
+                (sub_error, sub_lang, sub) = subtitle
+                if sub_error:
+                    self.report_warning("Some error while getting the subtitles")
+                else:
+                    try:
+                        sub_filename = filename.rsplit('.', 1)[0] + u'.' + sub_lang + u'.' + sub_format
+                        self.report_writesubtitles(sub_filename)
+                        with io.open(encodeFilename(sub_filename), 'w', encoding='utf-8') as subfile:
+                                subfile.write(sub)
+                    except (OSError, IOError):
+                        self.trouble(u'ERROR: Cannot write subtitles file ' + descfn)
+                        return
+            if self.params.get('onlysubtitles', False):
+                return 
 
         if self.params.get('writeinfojson', False):
             infofn = filename + u'.info.json'
@@ -451,7 +648,7 @@ class FileDownloader(object):
                 json_info_dict = dict((k, v) for k,v in info_dict.items() if not k in ['urlhandle'])
                 write_json_file(json_info_dict, encodeFilename(infofn))
             except (OSError, IOError):
-                self.trouble(u'ERROR: Cannot write metadata to JSON file ' + infofn)
+                self.report_error(u'Cannot write metadata to JSON file ' + infofn)
                 return
 
         if not self.params.get('skip_download', False):
@@ -463,17 +660,17 @@ class FileDownloader(object):
                 except (OSError, IOError) as err:
                     raise UnavailableVideoError()
                 except (compat_urllib_error.URLError, compat_http_client.HTTPException, socket.error) as err:
-                    self.trouble(u'ERROR: unable to download video data: %s' % str(err))
+                    self.report_error(u'unable to download video data: %s' % str(err))
                     return
                 except (ContentTooShortError, ) as err:
-                    self.trouble(u'ERROR: content too short (expected %s bytes and served %s)' % (err.expected, err.downloaded))
+                    self.report_error(u'content too short (expected %s bytes and served %s)' % (err.expected, err.downloaded))
                     return
 
             if success:
                 try:
                     self.post_process(filename, info_dict)
                 except (PostProcessingError) as err:
-                    self.trouble(u'ERROR: postprocessing: %s' % str(err))
+                    self.report_error(u'postprocessing: %s' % str(err))
                     return
 
     def download(self, url_list):
@@ -482,70 +679,49 @@ class FileDownloader(object):
             raise SameFileError(self.params['outtmpl'])
 
         for url in url_list:
-            suitable_found = False
-            for ie in self._ies:
-                # Go to next InfoExtractor if not suitable
-                if not ie.suitable(url):
-                    continue
-
-                # Warn if the _WORKING attribute is False
-                if not ie.working():
-                    self.to_stderr(u'WARNING: the program functionality for this site has been marked as broken, '
-                                   u'and will probably not work. If you want to go on, use the -i option.')
-
-                # Suitable InfoExtractor found
-                suitable_found = True
-
-                # Extract information from URL and process it
-                try:
-                    videos = ie.extract(url)
-                except ExtractorError as de: # An error we somewhat expected
-                    self.trouble(u'ERROR: ' + compat_str(de), de.format_traceback())
-                    break
-                except Exception as e:
-                    if self.params.get('ignoreerrors', False):
-                        self.trouble(u'ERROR: ' + compat_str(e), tb=compat_str(traceback.format_exc()))
-                        break
-                    else:
-                        raise
-
-                if len(videos or []) > 1 and self.fixed_template():
-                    raise SameFileError(self.params['outtmpl'])
-
-                for video in videos or []:
-                    video['extractor'] = ie.IE_NAME
-                    try:
-                        self.increment_downloads()
-                        self.process_info(video)
-                    except UnavailableVideoError:
-                        self.trouble(u'\nERROR: unable to download video')
-
-                # Suitable InfoExtractor had been found; go to next URL
-                break
-
-            if not suitable_found:
-                self.trouble(u'ERROR: no suitable InfoExtractor: %s' % url)
+            try:
+                #It also downloads the videos
+                videos = self.extract_info(url)
+            except UnavailableVideoError:
+                self.trouble(u'\nERROR: unable to download video')
+            except MaxDownloadsReached:
+                self.to_screen(u'[info] Maximum number of downloaded files reached.')
+                raise
 
         return self._download_retcode
 
     def post_process(self, filename, ie_info):
-        """Run the postprocessing chain on the given file."""
+        """Run all the postprocessors on the given file."""
         info = dict(ie_info)
         info['filepath'] = filename
+        keep_video = None
         for pp in self._pps:
-            info = pp.run(info)
-            if info is None:
-                break
+            try:
+                keep_video_wish,new_info = pp.run(info)
+                if keep_video_wish is not None:
+                    if keep_video_wish:
+                        keep_video = keep_video_wish
+                    elif keep_video is None:
+                        # No clear decision yet, let IE decide
+                        keep_video = keep_video_wish
+            except PostProcessingError as e:
+                self.to_stderr(u'ERROR: ' + e.msg)
+        if keep_video is False and not self.params.get('keepvideo', False):
+            try:
+                self.to_screen(u'Deleting original file %s (pass -k to keep)' % filename)
+                os.remove(encodeFilename(filename))
+            except (IOError, OSError):
+                self.report_warning(u'Unable to remove downloaded video file')
 
-    def _download_with_rtmpdump(self, filename, url, player_url, page_url):
+    def _download_with_rtmpdump(self, filename, url, player_url, page_url, play_path):
         self.report_destination(filename)
         tmpfilename = self.temp_name(filename)
 
         # Check for rtmpdump first
         try:
-            subprocess.call(['rtmpdump', '-h'], stdout=(file(os.path.devnull, 'w')), stderr=subprocess.STDOUT)
+            subprocess.call(['rtmpdump', '-h'], stdout=(open(os.path.devnull, 'w')), stderr=subprocess.STDOUT)
         except (OSError, IOError):
-            self.trouble(u'ERROR: RTMP download detected but "rtmpdump" could not be run')
+            self.report_error(u'RTMP download detected but "rtmpdump" could not be run')
             return False
 
         # Download using rtmpdump. rtmpdump returns exit code 2 when
@@ -556,6 +732,8 @@ class FileDownloader(object):
             basic_args += ['-W', player_url]
         if page_url is not None:
             basic_args += ['--pageUrl', page_url]
+        if play_path is not None:
+            basic_args += ['-y', play_path]
         args = basic_args + [[], ['-e', '-k', '1']][self.params.get('continuedl', False)]
         if self.params.get('verbose', False):
             try:
@@ -579,11 +757,19 @@ class FileDownloader(object):
                 retval = 0
                 break
         if retval == 0:
-            self.to_screen(u'\r[rtmpdump] %s bytes' % os.path.getsize(encodeFilename(tmpfilename)))
+            fsize = os.path.getsize(encodeFilename(tmpfilename))
+            self.to_screen(u'\r[rtmpdump] %s bytes' % fsize)
             self.try_rename(tmpfilename, filename)
+            self._hook_progress({
+                'downloaded_bytes': fsize,
+                'total_bytes': fsize,
+                'filename': filename,
+                'status': 'finished',
+            })
             return True
         else:
-            self.trouble(u'\nERROR: rtmpdump exited with code %d' % retval)
+            self.to_stderr(u"\n")
+            self.report_error(u'rtmpdump exited with code %d' % retval)
             return False
 
     def _do_download(self, filename, info_dict):
@@ -592,19 +778,26 @@ class FileDownloader(object):
         # Check file already present
         if self.params.get('continuedl', False) and os.path.isfile(encodeFilename(filename)) and not self.params.get('nopart', False):
             self.report_file_already_downloaded(filename)
+            self._hook_progress({
+                'filename': filename,
+                'status': 'finished',
+            })
             return True
 
         # Attempt to download using rtmpdump
         if url.startswith('rtmp'):
             return self._download_with_rtmpdump(filename, url,
                                                 info_dict.get('player_url', None),
-                                                info_dict.get('page_url', None))
+                                                info_dict.get('page_url', None),
+                                                info_dict.get('play_path', None))
 
         tmpfilename = self.temp_name(filename)
         stream = None
 
         # Do not include the Accept-Encoding header
         headers = {'Youtubedl-no-compression': 'True'}
+        if 'user_agent' in info_dict:
+            headers['Youtubedl-user-agent'] = info_dict['user_agent']
         basic_request = compat_urllib_request.Request(url, None, headers)
         request = compat_urllib_request.Request(url, None, headers)
 
@@ -661,6 +854,10 @@ class FileDownloader(object):
                             # the one in the hard drive.
                             self.report_file_already_downloaded(filename)
                             self.try_rename(tmpfilename, filename)
+                            self._hook_progress({
+                                'filename': filename,
+                                'status': 'finished',
+                            })
                             return True
                         else:
                             # The length does not match, we start the download over
@@ -673,12 +870,21 @@ class FileDownloader(object):
                 self.report_retry(count, retries)
 
         if count > retries:
-            self.trouble(u'ERROR: giving up after %s retries' % retries)
+            self.report_error(u'giving up after %s retries' % retries)
             return False
 
         data_len = data.info().get('Content-length', None)
         if data_len is not None:
             data_len = int(data_len) + resume_len
+            min_data_len = self.params.get("min_filesize", None)
+            max_data_len =  self.params.get("max_filesize", None)
+            if min_data_len is not None and data_len < min_data_len:
+                self.to_screen(u'\r[download] File is smaller than min-filesize (%s bytes < %s bytes). Aborting.' % (data_len, min_data_len))
+                return False
+            if max_data_len is not None and data_len > max_data_len:
+                self.to_screen(u'\r[download] File is larger than max-filesize (%s bytes > %s bytes). Aborting.' % (data_len, max_data_len))
+                return False
+
         data_len_str = self.format_bytes(data_len)
         byte_counter = 0 + resume_len
         block_size = self.params.get('buffersize', 1024)
@@ -700,12 +906,13 @@ class FileDownloader(object):
                     filename = self.undo_temp_name(tmpfilename)
                     self.report_destination(filename)
                 except (OSError, IOError) as err:
-                    self.trouble(u'ERROR: unable to open for writing: %s' % str(err))
+                    self.report_error(u'unable to open for writing: %s' % str(err))
                     return False
             try:
                 stream.write(data_block)
             except (IOError, OSError) as err:
-                self.trouble(u'\nERROR: unable to write data: %s' % str(err))
+                self.to_stderr(u"\n")
+                self.report_error(u'unable to write data: %s' % str(err))
                 return False
             if not self.params.get('noresizebuffer', False):
                 block_size = self.best_block_size(after - before, len(data_block))
@@ -719,11 +926,20 @@ class FileDownloader(object):
                 eta_str = self.calc_eta(start, time.time(), data_len - resume_len, byte_counter - resume_len)
                 self.report_progress(percent_str, data_len_str, speed_str, eta_str)
 
+            self._hook_progress({
+                'downloaded_bytes': byte_counter,
+                'total_bytes': data_len,
+                'tmpfilename': tmpfilename,
+                'filename': filename,
+                'status': 'downloading',
+            })
+
             # Apply rate limit
             self.slow_down(start, byte_counter - resume_len)
 
         if stream is None:
-            self.trouble(u'\nERROR: Did not get any data blocks')
+            self.to_stderr(u"\n")
+            self.report_error(u'Did not get any data blocks')
             return False
         stream.close()
         self.report_finish()
@@ -735,4 +951,31 @@ class FileDownloader(object):
         if self.params.get('updatetime', True):
             info_dict['filetime'] = self.try_utime(filename, data.info().get('last-modified', None))
 
+        self._hook_progress({
+            'downloaded_bytes': byte_counter,
+            'total_bytes': byte_counter,
+            'filename': filename,
+            'status': 'finished',
+        })
+
         return True
+
+    def _hook_progress(self, status):
+        for ph in self._progress_hooks:
+            ph(status)
+
+    def add_progress_hook(self, ph):
+        """ ph gets called on download progress, with a dictionary with the entries
+        * filename: The final filename
+        * status: One of "downloading" and "finished"
+
+        It can also have some of the following entries:
+
+        * downloaded_bytes: Bytes on disks
+        * total_bytes: Total bytes, None if unknown
+        * tmpfilename: The filename we're currently writing to
+
+        Hooks are guaranteed to be called at least once (with status "finished")
+        if the download is successful.
+        """
+        self._progress_hooks.append(ph)