feat: automatic db creation and migration

backend-php/k-api.php

@@ -1,4 +1,6 @@
 <?php
+const UPDATES_STATUS_FILE = "k-api.updates-status.php";
+const SQL_UPDATES_FOLDER = "./sql-updates";
 
 /** @param callable(_K_Api): void $apiFun */
 function CreateApi(callable $apiFun, bool $devmode = false)
@@ -66,13 +68,41 @@ class _K_Api
                     $_a = "unknown return type ($_type), (available bool, array, numeric, string)";
                 }
                 die("ERROR: " . $_a);
-                return;
             }
 
             return;
         }
     }
 
+    public function useUpdates(PDO $db)
+    {
+        $currentVersion = file_get_contents(UPDATES_STATUS_FILE);
+        if ($currentVersion === false) {
+            file_put_contents(UPDATES_STATUS_FILE, "<?php // -1");
+            $currentVersion = -1;
+        } else {
+            $currentVersion = intval(substr($currentVersion, 9));
+        }
+        $files = glob(SQL_UPDATES_FOLDER . '/*.sql');
+        $updateVersion = null;
+        foreach ($files as $file) {
+            if (!is_file($file)) {
+                continue;
+            }
+            $version = intval(basename($file, '.sql'));
+            if ($version > $currentVersion) {
+                $db->exec(file_get_contents($file));
+                $updateVersion = $version;
+            }
+        }
+        if ($updateVersion !== null) {
+            file_put_contents(
+                UPDATES_STATUS_FILE,
+                "<?php // " . $updateVersion
+            );
+        }
+    }
+
     public function end()
     {
         if (!$this->has_exec) {