create cache functions (#37)

composer.json

@@ -11,7 +11,8 @@
     "require": {
         "php": ">=7.4",
         "ext-ldap": ">=7.4",
-        "phpmailer/phpmailer": "^6.5.0"
+        "phpmailer/phpmailer": "^6.5.0",
+        "symfony/cache": ">=v5.4"
     },
     "require-dev": {
         "phpunit/phpunit": ">=8",

src/Ltb/Cache.php

@@ -0,0 +1,112 @@
+<?php namespace Ltb;
+
+use Symfony\Component\Cache\Adapter\FilesystemAdapter;
+
+class Cache {
+
+    // symfony cache instance
+    public $cache = null;
+
+    public function __construct(
+                          $namespace = 'ltbCache',
+                          $defaultLifetime = 0,
+                          $directory = null
+                      )
+    {
+
+        $this->cache = new FilesystemAdapter(
+            $namespace,
+            $defaultLifetime,
+            $directory
+        );
+
+        // Clean cache from expired entries
+        $this->cache->prune();
+
+    }
+
+    # Generate a cache entry containing a token,
+    # expiring after $cache_form_expiration seconds
+    function generate_form_token($cache_form_expiration)
+    {
+        $formtoken = hash('sha256', bin2hex(random_bytes(16)));
+        $cachedToken = $this->cache->getItem($formtoken);
+        $cachedToken->set($formtoken);
+        $cachedToken->expiresAfter($cache_form_expiration);
+        $this->cache->save($cachedToken);
+        error_log("generated form token: " .
+                  $formtoken .
+                  " valid for $cache_form_expiration s");
+        return $formtoken;
+    }
+
+    # Verify that give token exist in cache
+    # and if it exists, remove it from cache
+    function verify_form_token($formtoken)
+    {
+        $result = "";
+        $cachedToken = $this->cache->getItem($formtoken);
+        if( $cachedToken->isHit() && $cachedToken->get() == $formtoken )
+        {
+            # Remove token from cache entry
+            $this->cache->deleteItem($formtoken);
+        }
+        else
+        {
+            error_log("Invalid form token: sent: $formtoken, stored: " .
+                      $cachedToken->get());
+            $result = "invalidformtoken";
+        }
+        return $result;
+    }
+
+
+    # Get a token from the cache
+    # return the content of the content (can be an array, a string)
+    function get_token($tokenid)
+    {
+        $cached_token = $this->cache->getItem($tokenid);
+        $cached_token_content = $cached_token->get();
+
+        if($cached_token->isHit())
+        {
+            return $cached_token_content;
+        }
+        else
+        {
+            return null;
+        }
+    }
+
+    # Save a token to the cache
+    function save_token($content, $tokenid = null, $cache_token_expiration = null)
+    {
+        $msg = "";
+        if(is_null($tokenid))
+        {
+            $tokenid = hash('sha256', bin2hex(random_bytes(16)));
+            $msg .= "Generated cache entry with id: $tokenid";
+        }
+        else
+        {
+            $msg .= "Saving existing cache entry with id: $tokenid";
+        }
+
+        $cached_token = $this->cache->getItem($tokenid);
+        $cached_token->set( $content );
+
+        if(!is_null($cache_token_expiration))
+        {
+            $cached_token->expiresAfter($cache_token_expiration);
+            $msg .= ", valid for $cache_token_expiration s";
+        }
+
+        $this->cache->save($cached_token);
+        error_log($msg);
+
+        return $tokenid;
+    }
+
+}
+
+?>