added login

app/scripts/functions.php

@@ -0,0 +1,34 @@
+<?php
+
+include("database_queries.php");
+
+function check_login($con) {
+    
+    if(isset($_SESSION['user_id'])) {
+        
+        $id = $_SESSION['user_id'];
+        if(check_user_id($con, $id)) {
+            return get_user_data_id($con, $id);
+        } else {
+            header("Location: login.php");
+            die;
+        }
+    } else {
+        header("Location: login.php");
+        die;
+    }
+}
+
+function generate_salt() {
+    return substr(bin2hex(random_bytes(128)), 0, 128);
+}
+
+function generate_user_id($username, $salt) {
+    $uname = $username . $salt;
+    return hash('sha3-512', $uname);
+}
+
+function generate_password_hash($password, $salt) {
+    $pword = $password . $salt;
+    return hash('sha3-512', $pword);
+}