Implement login via rest_api

backend/api-docs.txt

@@ -0,0 +1,47 @@
+WARNING:-
+    This api is not yet capable of handling any exceptions that may arise when opened for the first time
+
+
+_____________________
+Login:-
+    URL:- /login
+
+    Method:- POST
+
+    Data Type:- Form Data
+
+    Data content:- {
+            user_name: "<user name>",
+            password: "<password>"
+        }
+
+    Response:-
+        200 OK:-
+            Data:- No
+            Note:- Assume login completed.
+
+        400 Bad Request:-
+            Content Type:- text/plain
+            Note:- user_name or password not given a Form Data.
+            Data:- What is missing will be mentioned.
+
+        403 Forbidden:-
+            Content Type:- text/plain
+            Note:- user_name or password is wrong, can display the response data to user.
+            Data:- What is wrong will be mentioned
+
+    Example:-
+        formData = new FormData();
+        formData.append('name', 'John');
+        formData.append('password', 'John123');
+        fetch(
+            "/login",
+            {
+                body: formData,
+                method: "post"
+            }
+        );
+
+        This will give a response status 200 with no data if login is done.
+        This will return a 403 if the user gave wrong name or password.
+_____________________

backend/rest_api.py

@@ -1,5 +1,8 @@
-from flask import Flask, send_file, abort, Response
 from os import path
+from flask import Flask, request, send_file, abort, Response
+from werkzeug.datastructures import ImmutableMultiDict
+
+from data_handler import DataHandler
 
 
 app: Flask = Flask(__name__)
@@ -15,6 +18,44 @@ def handle_get(url_path: str = "index.html") -> Response:
     response: Response = send_file(requested_file_path)
     response.status = 200
     if path.isfile(requested_file_path):
-        print('a')
         return send_file(requested_file_path)
     abort(404)
+
+
+class QueryHandler:
+    """
+    This is the bridge between the frontend and DataHandler class
+    """
+    __data_handler: DataHandler
+
+    @staticmethod
+    @app.post("/login")
+    def login() -> Response:
+        """
+        Logs the user in
+        """
+        data: ImmutableMultiDict[str, str] = request.form
+        if "user_name" not in data:
+            return Response(
+                    "user_name not given",
+                    400,
+                    content_type="text/plain"
+            )
+        if "password" not in data:
+            return Response(
+                    "password is not given",
+                    400,
+                    content_type="text/plain"
+            )
+
+        try:
+            QueryHandler.__data_handler = \
+                    DataHandler(data["user_name"], data["password"])
+        except ValueError as value_error:
+            return Response(
+                    str(value_error),
+                    403,
+                    content_type="text/plain"
+            )
+
+        return Response(status=200)