[mangadex] implement login with client credentials

unless the legacy method still works for your account,
login now requires 4 values:

- client-id
- client-secret
- username
- password

where 'client-id' and 'client-secret' are the credentials
of a personal API client.

> Public clients are not yet available.

docs/configuration.rst

@@ -7566,6 +7566,23 @@ How To
       as ``"api-key"`` and ``"api-secret"``
 
 
+extractor.mangadex.client-id & .client-secret
+---------------------------------------------
+Type
+    ``string``
+How To
+    * login and go to your `User Settings <https://mangadex.org/settings>`__
+    * open the "API Clients" section
+    * click "``+ Create``"
+    * choose a name
+    * click "``✔️ Create``"
+    * wait for approval / reload the page
+    * copy the value after "AUTOAPPROVED ACTIVE" in the form "personal-client-..."
+      and put it in your configuration file as ``"client-id"``
+    * click "``Get Secret``", then "``Copy Secret``",
+      and paste it into your configuration file as ``"client-secret"``
+
+
 extractor.reddit.client-id & .user-agent
 ----------------------------------------
 Type

docs/gallery-dl.conf

@@ -409,6 +409,8 @@
         },
         "mangadex":
         {
+            "client-id"    : "",
+            "client-secret": "",
             "username": "",
             "password": "",
 

gallery_dl/extractor/mangadex.py

@@ -29,11 +29,8 @@ class MangadexExtractor(Extractor):
     useragent = util.USERAGENT
     _cache = {}
 
-    def __init__(self, match):
-        Extractor.__init__(self, match)
-        self.uuid = match.group(1)
-
     def _init(self):
+        self.uuid = self.groups[0]
         self.api = MangadexAPI(self)
 
     def items(self):
@@ -199,7 +196,14 @@ class MangadexAPI():
         self.headers = {}
 
         self.username, self.password = extr._get_auth_info()
-        if not self.username:
+        if self.username:
+            self.client_id = cid = extr.config("client-id")
+            self.client_secret = extr.config("client-secret")
+            if cid:
+                self._authenticate_impl = self._authenticate_impl_client
+            else:
+                self._authenticate_impl = self._authenticate_impl_legacy
+        else:
             self.authenticate = util.noop
 
         server = extr.config("api-server")
@@ -249,19 +253,58 @@ class MangadexAPI():
             self._authenticate_impl(self.username, self.password)
 
     @cache(maxage=900, keyarg=1)
-    def _authenticate_impl(self, username, password):
+    def _authenticate_impl_client(self, username, password):
+        refresh_token = _refresh_token_cache((username, "personal"))
+        if refresh_token:
+            self.extractor.log.info("Refreshing access token")
+            data = {
+                "grant_type"   : "refresh_token",
+                "refresh_token": refresh_token,
+                "client_id"    : self.client_id,
+                "client_secret": self.client_secret,
+            }
+        else:
+            self.extractor.log.info("Logging in as %s", username)
+            data = {
+                "grant_type"   : "password",
+                "username"     : self.username,
+                "password"     : self.password,
+                "client_id"    : self.client_id,
+                "client_secret": self.client_secret,
+            }
+
+        self.extractor.log.debug("Using client-id '%s…'", self.client_id[:24])
+        url = ("https://auth.mangadex.org/realms/mangadex"
+               "/protocol/openid-connect/token")
+        data = self.extractor.request(
+            url, method="POST", data=data, fatal=None).json()
+
+        try:
+            access_token = data["access_token"]
+        except Exception:
+            raise exception.AuthenticationError(data.get("error_description"))
+
+        if refresh_token != data.get("refresh_token"):
+            _refresh_token_cache.update(
+                (username, "personal"), data["refresh_token"])
+
+        return "Bearer " + access_token
+
+    @cache(maxage=900, keyarg=1)
+    def _authenticate_impl_legacy(self, username, password):
         refresh_token = _refresh_token_cache(username)
         if refresh_token:
             self.extractor.log.info("Refreshing access token")
             url = self.root + "/auth/refresh"
-            data = {"token": refresh_token}
+            json = {"token": refresh_token}
         else:
             self.extractor.log.info("Logging in as %s", username)
             url = self.root + "/auth/login"
-            data = {"username": username, "password": password}
+            json = {"username": username, "password": password}
 
+        self.extractor.log.debug("Using legacy login method")
         data = self.extractor.request(
-            url, method="POST", json=data, fatal=None).json()
+            url, method="POST", json=json, fatal=None).json()
         if data.get("result") != "ok":
             raise exception.AuthenticationError()
 
@@ -329,6 +372,6 @@ class MangadexAPI():
                 return
 
 
-@cache(maxage=28*86400, keyarg=0)
+@cache(maxage=90*86400, keyarg=0)
 def _refresh_token_cache(username):
     return None