Implement user authentication and registration; enhance error handling and database interaction in API

api/auth/login.php

@@ -0,0 +1,50 @@
+<?php
+// Load API Library
+require "../api.php";
+
+$api = new gbAPI(false);
+
+// Check Request Body
+if ($_SERVER["REQUEST_METHOD"] !== "POST") {
+    $api->answer(400, [
+        "error" => "false_request_method",
+        "error_text" => "Only POST allowed"
+    ]);
+}
+
+if (!isset($_POST["username"]) || !isset($_POST["password"])) {
+    $api->answer(400, [
+        "error" => "missing_fields",
+        "error_text" => "Some fields are missing"
+    ]);
+}
+
+$username = $_POST["username"];
+$password = $_POST["password"];
+
+// Prepare SQL Command
+$hash = hash("sha256", $password);
+
+$command = "SELECT username, password FROM users WHERE username = :username AND password = :password";
+$args = [
+    ":username" => $username,
+    ":password" => $password
+];
+
+// Execute SQL Command
+$result = $api->dbCommand($command, true, true, $args);
+
+// Check Result
+if ($result) {
+    // Login successful. Generate Auth Token
+    $token = $api->generateToken($username);
+
+    // Set cookies
+    setcookie("auth_token", $token, time() + 86400, "/");
+    setcookie("username", $username, time() + 86400, "/");
+}else{
+    $api->answer(401, [
+        "error" => "unauthorized",
+        "error_text" => "A user with this password does not exists."
+    ]);
+}