Allow plugins depend on environment

Fixes #98

src/mibew/libs/classes/Mibew/Controller/PluginController.php

@@ -205,7 +205,7 @@ class PluginController extends AbstractController
             $plugins[] = array(
                 'name' => $plugin_name,
                 'version' => $plugin->isInstalled() ? $plugin->getInstalledVersion() : $plugin->getVersion(),
-                'dependencies' => $plugin->getDependencies(),
+                'dependencies' => array_merge($plugin->getSystemRequirements(), $plugin->getDependencies()),
                 'enabled' => $plugin->isEnabled(),
                 'installed' => $plugin->isInstalled(),
                 'needsUpdate' => $plugin->needsUpdate(),

src/mibew/libs/classes/Mibew/Plugin/AbstractPlugin.php

@@ -136,6 +136,20 @@ abstract class AbstractPlugin
         return array();
     }
 
+    /**
+     * Implementation of
+     * {@link \Mibew\Plugin\PluginInterface::getSystemRequirements()}.
+     *
+     * Returns an empty array to tell the Plugin Manager that the plugin has
+     * no system requirements.
+     *
+     * @return array
+     */
+    public static function getSystemRequirements()
+    {
+        return array();
+    }
+
     /**
      * Implementation of {@link \Mibew\Plugin\PluginInterface::getInfo()}.
      *

src/mibew/libs/classes/Mibew/Plugin/PluginInfo.php

@@ -165,6 +165,18 @@ class PluginInfo
         return call_user_func(array($this->getClass(), 'getDependencies'));
     }
 
+    /**
+     * Returns system requirements of the plugin.
+     *
+     * @return array Requirements list. See
+     *   {@link \Mibew\Plugin\PluginInterface::getSystemRequirements()} for
+     *   details of the array structure.
+     */
+    public function getSystemRequirements()
+    {
+        return call_user_func(array($this->getClass(), 'getSystemRequirements'));
+    }
+
     /**
      * Returns list of dependent plugins.
      *
@@ -228,6 +240,31 @@ class PluginInfo
             && (version_compare($this->getVersion(), $this->getInstalledVersion()) > 0);
     }
 
+    /**
+     * Checks if the plugin has unsatisfied system requirements.
+     *
+     * @return bool
+     */
+    public function hasUnsatisfiedSystemRequirements()
+    {
+        $system_info = Utils::getSystemInfo();
+
+        foreach ($this->getSystemRequirements() as $lib => $required_version) {
+            // Check if the library exists
+            if (!isset($system_info[$lib])) {
+                return true;
+            }
+
+            // Check exact version of the library
+            $version_constrain = new VersionExpression($required_version);
+            if (!$version_constrain->satisfiedBy(new Version($system_info[$lib]))) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
     /**
      * Checks if the plugin can be enabled.
      *
@@ -240,6 +277,10 @@ class PluginInfo
             return false;
         }
 
+        if ($this->hasUnsatisfiedSystemRequirements()) {
+            return false;
+        }
+
         // Make sure all plugin's dependencies exist, are enabled and have
         // appropriate versions
         foreach ($this->getDependencies() as $plugin_name => $required_version) {

src/mibew/libs/classes/Mibew/Plugin/PluginInterface.php

@@ -82,6 +82,39 @@ interface PluginInterface
      */
     public static function getDependencies();
 
+    /**
+     * Returns list of plugin's system requirements.
+     *
+     * Each key in the array is a string with a requirement name. Each value is
+     * plugin version constrain.
+     *
+     * A requirement name can be on of the following:
+     *  - "mibew": Mibew core;
+     *  - "php": PHP used in the system;
+     *  - "ext-*": name of a PHP extension.
+     *
+     * A constrain can be in one of the following
+     * formats:
+     *  - "1.2.3": exact version number;
+     *  - ">1.2.3": grater than a specific version;
+     *  - ">=1.2.3": greater than a specific version or equal to it;
+     *  - "<1.2.3": less than a specific version;
+     *  - "<=1.2.3": less than a specific version or equal to it;
+     *  - "1.2.3 - 2.3.4": equals to ">=1.2.3 <=2.3.4";
+     *  - "~1.2.3": equivalent for ">=1.2.3 <1.3.0";
+     *  - "~1.2": equivalent for ">=1.2.0 <2.0.0";
+     *  - "^1.2.3" equivalent for ">=1.2.3 <2.0.0";
+     *  - "^0.1.2" equivalent for ">=0.1.2 <0.2.0";
+     *  - "1.2.x": equivalent for ">=1.2.0 <2.0.0";
+     *  - "1.x": equivalent for ">=1.0.0 <2.0.0";
+     *
+     * If the plugin have no system requirements an empty array should be
+     * returned.
+     *
+     * @return array List of plugin's requirements.
+     */
+    public static function getSystemRequirements();
+
     /**
      * Returns some info about plugin such as human-readable name, description,
      * version, etc.

src/mibew/libs/classes/Mibew/Plugin/PluginManager.php

@@ -140,6 +140,17 @@ class PluginManager
                 continue;
             }
 
+            if ($plugin_info->hasUnsatisfiedSystemRequirements()) {
+                trigger_error(
+                    sprintf(
+                        'Plugin "%s" has unsatisfied system requirements!',
+                        $plugin_info->getName()
+                    ),
+                    E_USER_WARNING
+                );
+                continue;
+            }
+
             $graph->addPlugin($plugin_info);
         }
 

src/mibew/libs/classes/Mibew/Plugin/Utils.php

@@ -115,6 +115,34 @@ class Utils
         return true;
     }
 
+    /**
+     * Returns list of environment items.
+     *
+     * @return array List of environment items. Each key is a string with one of
+     * the following value:
+     *  - "mibew": represents Mibew core;
+     *  - "php": represents PHP installed in the system;
+     *  - "ext-*": represents one of PHP extensions.
+     * Each value of the array is version of the item.
+     */
+    public static function getSystemInfo()
+    {
+        static $system = null;
+
+        if (is_null($system)) {
+            $system = array(
+                'php' => phpversion(),
+                'mibew' => MIBEW_VERSION,
+            );
+
+            foreach (get_loaded_extensions() as $ext) {
+                $system['ext-' . str_replace(' ', '-', $ext)] = phpversion($ext) ?: '0.0.0';
+            }
+        }
+
+        return $system;
+    }
+
     /**
      * This class should not be instantiated
      */