[instagram] Add support for GraphSidecar media types (#201)

* [instagram] Add support for GraphSidecar media types

Refactor _extract_postpage() to always return a list of medias.

Fetch common keywords and gracefully handle GraphSidecar media type
by extracting each single media and adding `sidecar_media_id' and
`sidecar_shortcode' keywords to indicate the parent of sidecar
childrens.

While here join the copyright comment lines in a single one.

Closes #178.

* [instagram] Use `yield from' instead of `for ... yield' (thanks @mikf)!

* [instagram] Adjust filename for GraphSidecar medias

Add a possible leading `media_id' of the sidecar for GraphSidecar
media.

Thanks to @mikf for the suggestion!

* [instagram] Add extra metadata for youtube-dl in GraphSidecar childrens

GraphSidecar children ytdl: URLs when consumed by youtube-dl
redirects to the URL of their parent.  In GraphSidecar-s with
multiple GraphVideo-s this leads to downloading the same video
multiple times.

Add a `_ytdl_index' field to indicate the index of the youtube-dl
playlist corresponding the children of the sidecar.

This will be used by the `ytdl' downloader.

gallery_dl/extractor/instagram.py

@@ -1,7 +1,6 @@
 # -*- coding: utf-8 -*-
 
-# Copyright 2018 Leonardo Taccari
-# Copyright 2019 Mike Fährmann
+# Copyright 2018-2019 Leonardo Taccari, Mike Fährmann
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License version 2 as
@@ -19,7 +18,7 @@ class InstagramExtractor(Extractor):
     """Base class for instagram extractors"""
     category = "instagram"
     directory_fmt = ("{category}", "{username}")
-    filename_fmt = "{media_id}.{extension}"
+    filename_fmt = "{sidecar_media_id:?/_/}{media_id}.{extension}"
     archive_fmt = "{media_id}"
     root = "https://www.instagram.com"
 
@@ -32,11 +31,6 @@ def items(self):
             if data['typename'] == 'GraphImage':
                 yield Message.Url, data['display_url'], \
                     text.nameext_from_url(data['display_url'], data)
-            elif data['typename'] == 'GraphSidecar':
-                # TODO: Extract all images in edge_sidecar_to_children
-                # TODO: instead of just extracting the main one!
-                yield Message.Url, data['display_url'], \
-                    text.nameext_from_url(data['display_url'], data)
             elif data['typename'] == 'GraphVideo':
                 yield Message.Url, \
                     'ytdl:{}/p/{}/'.format(self.root, data['shortcode']), data
@@ -50,20 +44,48 @@ def _extract_postpage(self, url):
         shared_data = self._extract_shared_data(page)
         media = shared_data['entry_data']['PostPage'][0]['graphql']['shortcode_media']
 
-        return {
-            'media_id': media['id'],
-            'shortcode': media['shortcode'],
-            'typename': media['__typename'],
-            'display_url': media['display_url'],
-            'height': text.parse_int(media['dimensions']['height']),
-            'width': text.parse_int(media['dimensions']['width']),
+        common = {
             'comments': text.parse_int(media['edge_media_to_comment']['count']),
             'likes': text.parse_int(media['edge_media_preview_like']['count']),
             'owner_id': media['owner']['id'],
             'username': media['owner']['username'],
             'fullname': media['owner']['full_name'],
         }
 
+        medias = []
+        if media['__typename'] == 'GraphSidecar':
+            yi = 0
+            for n in media['edge_sidecar_to_children']['edges']:
+                children = n['node']
+                ytdl_metadata = {}
+                if children['__typename'] == 'GraphVideo':
+                    yi += 1
+                    ytdl_metadata['_ytdl_index'] = yi
+                medias.append({
+                    'media_id': children['id'],
+                    'shortcode': children['shortcode'],
+                    'typename': children['__typename'],
+                    'display_url': children['display_url'],
+                    'height': text.parse_int(children['dimensions']['height']),
+                    'width': text.parse_int(children['dimensions']['width']),
+                    'sidecar_media_id': media['id'],
+                    'sidecar_shortcode': media['shortcode'],
+                    **common,
+                    **ytdl_metadata,
+                })
+        else:
+            medias.append({
+                'media_id': media['id'],
+                'shortcode': media['shortcode'],
+                'typename': media['__typename'],
+                'display_url': media['display_url'],
+                'height': text.parse_int(media['dimensions']['height']),
+                'width': text.parse_int(media['dimensions']['width']),
+                **common,
+            })
+
+        return medias
+
     def _extract_profilepage(self, url):
         page = self.request(url).text
         shared_data = self._extract_shared_data(page)
@@ -86,7 +108,7 @@ def _extract_profilepage(self, url):
 
             for s in shortcodes:
                 url = '{}/p/{}/'.format(self.root, s)
-                yield self._extract_postpage(url)
+                yield from self._extract_postpage(url)
 
             if not has_next_page:
                 break
@@ -133,18 +155,13 @@ class InstagramImageExtractor(InstagramExtractor):
 
         # GraphSidecar
         ("https://www.instagram.com/p/BoHk1haB5tM/", {
-            "pattern": r"https://[^/]+\.(cdninstagram\.com|fbcdn\.net)"
-                       r"/vp/[0-9a-f]+/[0-9A-F]+/t51.2885-15/e35"
-                       r"/40758827_2138611023072230_4073975203662780931_n.jpg",
+            "count": 5,
             "keyword": {
+                "sidecar_media_id": "1875629777499953996",
+                "sidecar_shortcode": "BoHk1haB5tM",
                 "comments": int,
-                "height": int,
                 "likes": int,
-                "media_id": "1875629777499953996",
-                "shortcode": "BoHk1haB5tM",
-                "typename": "GraphSidecar",
                 "username": "instagram",
-                "width": int,
             }
         }),
 
@@ -170,7 +187,7 @@ def __init__(self, match):
 
     def instagrams(self):
         url = '{}/p/{}/'.format(self.root, self.shortcode)
-        return (self._extract_postpage(url),)
+        return self._extract_postpage(url)
 
 
 class InstagramUserExtractor(InstagramExtractor):