Add session to_file and from_file

Signed-off-by: Nikolaos Karaolidis <nick@karaolidis.com>

fbchat/_session.py

@@ -19,7 +19,8 @@ SERVER_JS_DEFINE_REGEX = re.compile(
     r'(?:"ServerJS".{,100}\.handle\({.*"define":)'
     r'|(?:ServerJS.{,100}\.handleWithCustomApplyEach\(ScheduledApplyEach,{.*"define":)'
     r'|(?:require\("ServerJSDefine"\)\)?\.handleDefines\()'
-    r'|(?:"require":\[\["ScheduledServerJS".{,100}"define":)')
+    r'|(?:"require":\[\["ScheduledServerJS".{,100}"define":)'
+)
 SERVER_JS_DEFINE_JSON_DECODER = json.JSONDecoder()
 
 
@@ -112,7 +113,7 @@ def login_cookies(at: datetime.datetime):
 
 
 def client_id_factory() -> str:
-    return hex(int(random.random() * 2 ** 31))[2:]
+    return hex(int(random.random() * 2**31))[2:]
 
 
 def find_form_request(html: str):
@@ -324,8 +325,8 @@ class Session:
                     "sec-fetch-mode": "navigate",
                     "sec-fetch-site": "same-origin",
                     "sec-fetch-user": "?1",
-                    "upgrade-insecure-requests": "1"
-                }
+                    "upgrade-insecure-requests": "1",
+                },
             )
         except requests.RequestException as e:
             _exception.handle_requests_error(e)
@@ -554,3 +555,30 @@ class Session:
         data["__user"] = self.user.id
         j = self._post("/message_share_attachment/fromURI/", data)
         return j["payload"]["share_data"]
+
+    def to_file(self, filename):
+        """Save the session to a file.
+
+        Args:
+            filename: The file to save the session to
+
+        Example:
+            >>> session = fbchat.Session.from_cookies(cookies)
+            >>> session.to_file("session.json")
+        """
+        with open(filename, "w") as f:
+            json.dump(self.get_cookies(), f)
+
+    @classmethod
+    def from_file(cls, filename):
+        """Load a session from a file.
+
+        Args:
+            filename: The file to load the session from
+
+        Example:
+            >>> session = fbchat.Session.from_file("session.json")
+        """
+        with open(filename, "r") as f:
+            cookies = json.load(f)
+        return cls.from_cookies(cookies)