[redgifs] fix extraction (#724)

… and prepare for more potential extractors

gallery_dl/extractor/redgifs.py

@@ -9,13 +9,50 @@
 """Extractors for https://redgifs.com/"""
 
 from .gfycat import GfycatImageExtractor
+from ..cache import cache
 
 
 class RedgifsImageExtractor(GfycatImageExtractor):
     """Extractor for individual images from redgifs.com"""
     category = "redgifs"
-    pattern = r"(?:https?://)?redgifs\.com/watch/([A-Za-z]+)"
+    pattern = r"(?:https?://)?(?:www\.)?redgifs\.com/watch/([A-Za-z]+)"
     test = ("https://redgifs.com/watch/foolishforkedabyssiniancat", {
         "pattern": "https://giant.gfycat.com/FoolishForkedAbyssiniancat.mp4",
         "content": "f6e03f1df9a2ff2a74092f53ee7580d2fb943533",
     })
+
+    def _get_info(self, gfycat_id):
+        api = RedgifsAPI(self)
+        return api.gfycat(gfycat_id)
+
+
+class RedgifsAPI():
+
+    def __init__(self, extractor):
+        self.extractor = extractor
+        self.headers = {}
+
+    def gfycat(self, gfycat_id):
+        endpoint = "v1/gfycats/" + gfycat_id
+        return self._call(endpoint)["gfyItem"]
+
+    @cache(maxage=3600)
+    def _authenticate_impl(self):
+        url = "https://weblogin.redgifs.com/oauth/webtoken"
+        headers = {
+            "Referer": "https://www.redgifs.com/",
+            "Origin" : "https://www.redgifs.com",
+        }
+        data = {
+            "access_key": "dBLwVuGn9eq4dtXLs8WSfpjcYFY7bPQe"
+                          "AqGPSFgqeW5B9uzj2cMVhF63pTFF4Rg9",
+        }
+
+        response = self.extractor.request(
+            url, method="POST", headers=headers, json=data)
+        return "Bearer " + response.json()["access_token"]
+
+    def _call(self, endpoint):
+        self.headers["Authorization"] = self._authenticate_impl()
+        url = "https://napi.redgifs.com/" + endpoint
+        return self.extractor.request(url, headers=self.headers).json()