added login functionality *hard coded* user

app.py

@@ -5,19 +5,68 @@ from resume_screener import ResumeScreener
 from user_documentation import UserDocumentation
 from home import Home
 
-UserDocPage = st.Page(UserDocumentation, title="User Documentation")
-ResumeScreenerPage = st.Page(ResumeScreener, title="Resume Screener")
-HomePage = st.Page(Home, title="Home")
-
-pages = {
-    "Dashboard": [
-        HomePage,
-        ResumeScreenerPage,
-    ],
-    "Resources": [
-        UserDocPage,
-    ],
-}
-
-pg = st.navigation(pages)
-pg.run()
+UserDocPage = st.Page(UserDocumentation, title="User Documentation", icon=":material/help:")
+ResumeScreenerPage = st.Page(ResumeScreener, title="Resume Screener", icon=":material/recent_actors:")
+HomePage = st.Page(Home, title="Home", icon=":material/home:")
+
+
+if "LOGGED_IN" not in st.session_state:
+    st.session_state.LOGGED_IN = False
+
+if st.session_state.LOGGED_IN:
+    pages = {
+        "Dashboard": [
+            HomePage,
+            ResumeScreenerPage,
+        ],
+        "Resources": [
+            UserDocPage,
+        ]
+    }
+
+    pg = st.navigation(pages)
+    pg.run()
+
+else:
+    col1, col2, col3 = st.columns(spec=[1, 3, 1])
+
+    with col2:
+        st.title("Login")
+        username = st.text_input("Email Address", value="johndoe@hr.company.com")
+        password = st.text_input("Password", type="password")
+
+        if st.button("Login"):
+
+            class UnregisteredUser(Exception):
+                """
+                Represents an exception when the user is not registered.
+                """
+
+                def __init__(self, message="User not registered"):
+                    self.message = message
+                    super().__init__(self.message)
+
+            class IncompleteDetails(Exception):
+                """
+                Represents an exception when the user's details are incomplete.
+                """
+
+                def __init__(self, message="Incomplete details"):
+                    self.message = message
+                    super().__init__(self.message)
+
+            #imaginary db calls for existing user, if user is in imaginary db, user is logged in
+            try:
+                if username == "johndoe@hr.company.com" and password == "password":
+                    st.session_state.LOGGED_IN = True
+                    st.rerun()
+
+                if username == "" or password == "":
+                    raise IncompleteDetails
+
+                raise UnregisteredUser
+
+            except UnregisteredUser as e:
+                st.error(e)
+            except IncompleteDetails as e:
+                st.error(e)