class ModuleHandler

class ModuleHandler implements ModuleHandlerInterface {
    
    /**
     * List of loaded files.
     *
     * @var array
     *   An associative array whose keys are file paths of loaded files, relative
     *   to the application's root directory.
     */
    protected $loadedFiles;
    
    /**
     * List of installed modules.
     *
     * @var \Drupal\Core\Extension\Extension[]
     */
    protected $moduleList;
    
    /**
     * Boolean indicating whether modules have been loaded.
     *
     * @var bool
     */
    protected $loaded = FALSE;
    
    /**
     * List of hook implementations keyed by hook name.
     *
     * @var array
     */
    protected $implementations;
    
    /**
     * List of hooks where the implementations have been "verified".
     *
     * @var true[]
     *   Associative array where keys are hook names.
     */
    protected $verified;
    
    /**
     * Information returned by hook_hook_info() implementations.
     *
     * @var array
     */
    protected $hookInfo;
    
    /**
     * Cache backend for storing module hook implementation information.
     *
     * @var \Drupal\Core\Cache\CacheBackendInterface
     */
    protected $cacheBackend;
    
    /**
     * Whether the cache needs to be written.
     *
     * @var bool
     */
    protected $cacheNeedsWriting = FALSE;
    
    /**
     * List of alter hook implementations keyed by hook name(s).
     *
     * @var array
     */
    protected $alterFunctions;
    
    /**
     * The app root.
     *
     * @var string
     */
    protected $root;
    
    /**
     * A list of module include file keys.
     *
     * @var array
     */
    protected $includeFileKeys = [];
    
    /**
     * Constructs a ModuleHandler object.
     *
     * @param string $root
     *   The app root.
     * @param array $module_list
     *   An associative array whose keys are the names of installed modules and
     *   whose values are Extension class parameters. This is normally the
     *   %container.modules% parameter being set up by DrupalKernel.
     * @param \Drupal\Core\Cache\CacheBackendInterface $cache_backend
     *   Cache backend for storing module hook implementation information.
     *
     * @see \Drupal\Core\DrupalKernel
     * @see \Drupal\Core\CoreServiceProvider
     */
    public function __construct($root, array $module_list, CacheBackendInterface $cache_backend) {
        $this->root = $root;
        $this->moduleList = [];
        foreach ($module_list as $name => $module) {
            $this->moduleList[$name] = new Extension($this->root, $module['type'], $module['pathname'], $module['filename']);
        }
        $this->cacheBackend = $cache_backend;
    }
    
    /**
     * {@inheritdoc}
     */
    public function load($name) {
        if (isset($this->loadedFiles[$name])) {
            return TRUE;
        }
        if (isset($this->moduleList[$name])) {
            $this->moduleList[$name]
                ->load();
            $this->loadedFiles[$name] = TRUE;
            return TRUE;
        }
        return FALSE;
    }
    
    /**
     * {@inheritdoc}
     */
    public function loadAll() {
        if (!$this->loaded) {
            foreach ($this->moduleList as $name => $module) {
                $this->load($name);
            }
            $this->loaded = TRUE;
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function reload() {
        $this->loaded = FALSE;
        $this->loadAll();
    }
    
    /**
     * {@inheritdoc}
     */
    public function isLoaded() {
        return $this->loaded;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getModuleList() {
        return $this->moduleList;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getModule($name) {
        if (isset($this->moduleList[$name])) {
            return $this->moduleList[$name];
        }
        throw new UnknownExtensionException(sprintf('The module %s does not exist.', $name));
    }
    
    /**
     * {@inheritdoc}
     */
    public function setModuleList(array $module_list = []) {
        $this->moduleList = $module_list;
        // Reset the implementations, so a new call triggers a reloading of the
        // available hooks.
        $this->resetImplementations();
    }
    
    /**
     * {@inheritdoc}
     */
    public function addModule($name, $path) {
        $this->add('module', $name, $path);
    }
    
    /**
     * {@inheritdoc}
     */
    public function addProfile($name, $path) {
        $this->add('profile', $name, $path);
    }
    
    /**
     * Adds a module or profile to the list of currently active modules.
     *
     * @param string $type
     *   The extension type; either 'module' or 'profile'.
     * @param string $name
     *   The module name; e.g., 'node'.
     * @param string $path
     *   The module path; e.g., 'core/modules/node'.
     */
    protected function add($type, $name, $path) {
        $pathname = "{$path}/{$name}.info.yml";
        $filename = file_exists($this->root . "/{$path}/{$name}.{$type}") ? "{$name}.{$type}" : NULL;
        $this->moduleList[$name] = new Extension($this->root, $type, $pathname, $filename);
        $this->resetImplementations();
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildModuleDependencies(array $modules) {
        foreach ($modules as $module) {
            $graph[$module->getName()]['edges'] = [];
            if (isset($module->info['dependencies']) && is_array($module->info['dependencies'])) {
                foreach ($module->info['dependencies'] as $dependency) {
                    $dependency_data = Dependency::createFromString($dependency);
                    $graph[$module->getName()]['edges'][$dependency_data->getName()] = $dependency_data;
                }
            }
        }
        $graph_object = new Graph($graph);
        $graph = $graph_object->searchAndSort();
        foreach ($graph as $module_name => $data) {
            $modules[$module_name]->required_by = isset($data['reverse_paths']) ? $data['reverse_paths'] : [];
            $modules[$module_name]->requires = isset($data['paths']) ? $data['paths'] : [];
            $modules[$module_name]->sort = $data['weight'];
        }
        return $modules;
    }
    
    /**
     * {@inheritdoc}
     */
    public function moduleExists($module) {
        return isset($this->moduleList[$module]);
    }
    
    /**
     * {@inheritdoc}
     */
    public function loadAllIncludes($type, $name = NULL) {
        foreach ($this->moduleList as $module => $filename) {
            $this->loadInclude($module, $type, $name);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function loadInclude($module, $type, $name = NULL) {
        if ($type == 'install') {
            // Make sure the installation API is available
            include_once $this->root . '/core/includes/install.inc';
        }
        $name = $name ?: $module;
        $key = $type . ':' . $module . ':' . $name;
        if (isset($this->includeFileKeys[$key])) {
            return $this->includeFileKeys[$key];
        }
        if (isset($this->moduleList[$module])) {
            $file = $this->root . '/' . $this->moduleList[$module]
                ->getPath() . "/{$name}.{$type}";
            if (is_file($file)) {
                require_once $file;
                $this->includeFileKeys[$key] = $file;
                return $file;
            }
            else {
                $this->includeFileKeys[$key] = FALSE;
            }
        }
        return FALSE;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getHookInfo() {
        if (!isset($this->hookInfo)) {
            if ($cache = $this->cacheBackend
                ->get('hook_info')) {
                $this->hookInfo = $cache->data;
            }
            else {
                $this->buildHookInfo();
                $this->cacheBackend
                    ->set('hook_info', $this->hookInfo);
            }
        }
        return $this->hookInfo;
    }
    
    /**
     * Builds hook_hook_info() information.
     *
     * @see \Drupal\Core\Extension\ModuleHandler::getHookInfo()
     */
    protected function buildHookInfo() {
        $this->hookInfo = [];
        // Make sure that the modules are loaded before checking.
        $this->reload();
        // $this->invokeAll() would cause an infinite recursion.
        foreach ($this->moduleList as $module => $filename) {
            $function = $module . '_hook_info';
            if (function_exists($function)) {
                $result = $function();
                if (isset($result) && is_array($result)) {
                    $this->hookInfo = NestedArray::mergeDeep($this->hookInfo, $result);
                }
            }
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function getImplementations($hook) {
        $implementations = $this->getImplementationInfo($hook);
        return array_keys($implementations);
    }
    
    /**
     * {@inheritdoc}
     */
    public function writeCache() {
        if ($this->cacheNeedsWriting) {
            $this->cacheBackend
                ->set('module_implements', $this->implementations);
            $this->cacheNeedsWriting = FALSE;
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function resetImplementations() {
        $this->implementations = NULL;
        $this->hookInfo = NULL;
        $this->alterFunctions = NULL;
        // We maintain a persistent cache of hook implementations in addition to the
        // static cache to avoid looping through every module and every hook on each
        // request. Benchmarks show that the benefit of this caching outweighs the
        // additional database hit even when using the default database caching
        // backend and only a small number of modules are enabled. The cost of the
        // $this->cacheBackend->get() is more or less constant and reduced further
        // when non-database caching backends are used, so there will be more
        // significant gains when a large number of modules are installed or hooks
        // invoked, since this can quickly lead to
        // \Drupal::moduleHandler()->implementsHook() being called several thousand
        // times per request.
        $this->cacheBackend
            ->set('module_implements', []);
        $this->cacheBackend
            ->delete('hook_info');
    }
    
    /**
     * {@inheritdoc}
     */
    public function implementsHook($module, $hook) {
        $function = $module . '_' . $hook;
        if (function_exists($function)) {
            return TRUE;
        }
        // If the hook implementation does not exist, check whether it lives in an
        // optional include file registered via hook_hook_info().
        $hook_info = $this->getHookInfo();
        if (isset($hook_info[$hook]['group'])) {
            $this->loadInclude($module, 'inc', $module . '.' . $hook_info[$hook]['group']);
            if (function_exists($function)) {
                return TRUE;
            }
        }
        return FALSE;
    }
    
    /**
     * {@inheritdoc}
     */
    public function invoke($module, $hook, array $args = []) {
        if (!$this->implementsHook($module, $hook)) {
            return;
        }
        $function = $module . '_' . $hook;
        return call_user_func_array($function, $args);
    }
    
    /**
     * {@inheritdoc}
     */
    public function invokeAll($hook, array $args = []) {
        $return = [];
        $implementations = $this->getImplementations($hook);
        foreach ($implementations as $module) {
            $function = $module . '_' . $hook;
            $result = call_user_func_array($function, $args);
            if (isset($result) && is_array($result)) {
                $return = NestedArray::mergeDeep($return, $result);
            }
            elseif (isset($result)) {
                $return[] = $result;
            }
        }
        return $return;
    }
    
    /**
     * {@inheritdoc}
     */
    public function invokeDeprecated($description, $module, $hook, array $args = []) {
        $result = $this->invoke($module, $hook, $args);
        $this->triggerDeprecationError($description, $hook);
        return $result;
    }
    
    /**
     * {@inheritdoc}
     */
    public function invokeAllDeprecated($description, $hook, array $args = []) {
        $result = $this->invokeAll($hook, $args);
        $this->triggerDeprecationError($description, $hook);
        return $result;
    }
    
    /**
     * Triggers an E_USER_DEPRECATED error if any module implements the hook.
     *
     * @param string $description
     *   Helpful text describing what to do instead of implementing this hook.
     * @param string $hook
     *   The name of the hook.
     */
    private function triggerDeprecationError($description, $hook) {
        $modules = array_keys($this->getImplementationInfo($hook));
        if (!empty($modules)) {
            $message = 'The deprecated hook hook_' . $hook . '() is implemented in these functions: ';
            $implementations = array_map(function ($module) use ($hook) {
                return $module . '_' . $hook . '()';
            }, $modules);
            @trigger_error($message . implode(', ', $implementations) . '. ' . $description, E_USER_DEPRECATED);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function alter($type, &$data, &$context1 = NULL, &$context2 = NULL) {
        // Most of the time, $type is passed as a string, so for performance,
        // normalize it to that. When passed as an array, usually the first item in
        // the array is a generic type, and additional items in the array are more
        // specific variants of it, as in the case of array('form', 'form_FORM_ID').
        if (is_array($type)) {
            $cid = implode(',', $type);
            $extra_types = $type;
            $type = array_shift($extra_types);
            // Allow if statements in this function to use the faster isset() rather
            // than !empty() both when $type is passed as a string, or as an array
            // with one item.
            if (empty($extra_types)) {
                unset($extra_types);
            }
        }
        else {
            $cid = $type;
        }
        // Some alter hooks are invoked many times per page request, so store the
        // list of functions to call, and on subsequent calls, iterate through them
        // quickly.
        if (!isset($this->alterFunctions[$cid])) {
            $this->alterFunctions[$cid] = [];
            $hook = $type . '_alter';
            $modules = $this->getImplementations($hook);
            if (!isset($extra_types)) {
                // For the more common case of a single hook, we do not need to call
                // function_exists(), since $this->getImplementations() returns only
                // modules with implementations.
                foreach ($modules as $module) {
                    $this->alterFunctions[$cid][] = $module . '_' . $hook;
                }
            }
            else {
                // For multiple hooks, we need $modules to contain every module that
                // implements at least one of them.
                $extra_modules = [];
                foreach ($extra_types as $extra_type) {
                    $extra_modules = array_merge($extra_modules, $this->getImplementations($extra_type . '_alter'));
                }
                // If any modules implement one of the extra hooks that do not implement
                // the primary hook, we need to add them to the $modules array in their
                // appropriate order. $this->getImplementations() can only return
                // ordered implementations of a single hook. To get the ordered
                // implementations of multiple hooks, we mimic the
                // $this->getImplementations() logic of first ordering by
                // $this->getModuleList(), and then calling
                // $this->alter('module_implements').
                if (array_diff($extra_modules, $modules)) {
                    // Merge the arrays and order by getModuleList().
                    $modules = array_intersect(array_keys($this->moduleList), array_merge($modules, $extra_modules));
                    // Since $this->getImplementations() already took care of loading the
                    // necessary include files, we can safely pass FALSE for the array
                    // values.
                    $implementations = array_fill_keys($modules, FALSE);
                    // Let modules adjust the order solely based on the primary hook. This
                    // ensures the same module order regardless of whether this if block
                    // runs. Calling $this->alter() recursively in this way does not
                    // result in an infinite loop, because this call is for a single
                    // $type, so we won't end up in this code block again.
                    $this->alter('module_implements', $implementations, $hook);
                    $modules = array_keys($implementations);
                }
                foreach ($modules as $module) {
                    // Since $modules is a merged array, for any given module, we do not
                    // know whether it has any particular implementation, so we need a
                    // function_exists().
                    $function = $module . '_' . $hook;
                    if (function_exists($function)) {
                        $this->alterFunctions[$cid][] = $function;
                    }
                    foreach ($extra_types as $extra_type) {
                        $function = $module . '_' . $extra_type . '_alter';
                        if (function_exists($function)) {
                            $this->alterFunctions[$cid][] = $function;
                        }
                    }
                }
            }
        }
        foreach ($this->alterFunctions[$cid] as $function) {
            $function($data, $context1, $context2);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function alterDeprecated($description, $type, &$data, &$context1 = NULL, &$context2 = NULL) {
        // Invoke the alter hook. This has the side effect of populating
        // $this->alterFunctions.
        $this->alter($type, $data, $context1, $context2);
        // The $type parameter can be an array. alter() will deal with this
        // internally, but we have to extract the proper $cid in order to discover
        // implementations.
        $cid = $type;
        if (is_array($type)) {
            $cid = implode(',', $type);
            $extra_types = $type;
            $type = array_shift($extra_types);
        }
        if (!empty($this->alterFunctions[$cid])) {
            $message = 'The deprecated alter hook hook_' . $type . '_alter() is implemented in these functions: ' . implode(', ', $this->alterFunctions[$cid]) . '.';
            @trigger_error($message . ' ' . $description, E_USER_DEPRECATED);
        }
    }
    
    /**
     * Provides information about modules' implementations of a hook.
     *
     * @param string $hook
     *   The name of the hook (e.g. "help" or "menu").
     *
     * @return mixed[]
     *   An array whose keys are the names of the modules which are implementing
     *   this hook and whose values are either a string identifying a file in
     *   which the implementation is to be found, or FALSE, if the implementation
     *   is in the module file.
     */
    protected function getImplementationInfo($hook) {
        if (!isset($this->implementations)) {
            $this->implementations = [];
            $this->verified = [];
            if ($cache = $this->cacheBackend
                ->get('module_implements')) {
                $this->implementations = $cache->data;
            }
        }
        if (!isset($this->implementations[$hook])) {
            // The hook is not cached, so ensure that whether or not it has
            // implementations, the cache is updated at the end of the request.
            $this->cacheNeedsWriting = TRUE;
            // Discover implementations.
            $this->implementations[$hook] = $this->buildImplementationInfo($hook);
            // Implementations are always "verified" as part of the discovery.
            $this->verified[$hook] = TRUE;
        }
        elseif (!isset($this->verified[$hook])) {
            if (!$this->verifyImplementations($this->implementations[$hook], $hook)) {
                // One or more of the implementations did not exist and need to be
                // removed in the cache.
                $this->cacheNeedsWriting = TRUE;
            }
            $this->verified[$hook] = TRUE;
        }
        return $this->implementations[$hook];
    }
    
    /**
     * Builds hook implementation information for a given hook name.
     *
     * @param string $hook
     *   The name of the hook (e.g. "help" or "menu").
     *
     * @return mixed[]
     *   An array whose keys are the names of the modules which are implementing
     *   this hook and whose values are either a string identifying a file in
     *   which the implementation is to be found, or FALSE, if the implementation
     *   is in the module file.
     *
     * @throws \RuntimeException
     *   Exception thrown when an invalid implementation is added by
     *   hook_module_implements_alter().
     *
     * @see \Drupal\Core\Extension\ModuleHandler::getImplementationInfo()
     */
    protected function buildImplementationInfo($hook) {
        $implementations = [];
        $hook_info = $this->getHookInfo();
        foreach ($this->moduleList as $module => $extension) {
            $include_file = isset($hook_info[$hook]['group']) && $this->loadInclude($module, 'inc', $module . '.' . $hook_info[$hook]['group']);
            // Since $this->implementsHook() may needlessly try to load the include
            // file again, function_exists() is used directly here.
            if (function_exists($module . '_' . $hook)) {
                $implementations[$module] = $include_file ? $hook_info[$hook]['group'] : FALSE;
            }
        }
        // Allow modules to change the weight of specific implementations, but avoid
        // an infinite loop.
        if ($hook != 'module_implements_alter') {
            // Remember the original implementations, before they are modified with
            // hook_module_implements_alter().
            $implementations_before = $implementations;
            // Verify implementations that were added or modified.
            $this->alter('module_implements', $implementations, $hook);
            // Verify new or modified implementations.
            foreach (array_diff_assoc($implementations, $implementations_before) as $module => $group) {
                // If an implementation of hook_module_implements_alter() changed or
                // added a group, the respective file needs to be included.
                if ($group) {
                    $this->loadInclude($module, 'inc', "{$module}.{$group}");
                }
                // If a new implementation was added, verify that the function exists.
                if (!function_exists($module . '_' . $hook)) {
                    throw new \RuntimeException("An invalid implementation {$module}_{$hook} was added by hook_module_implements_alter()");
                }
            }
        }
        return $implementations;
    }
    
    /**
     * Verifies an array of implementations loaded from the cache, by including
     * the lazy-loaded $module.$group.inc, and checking function_exists().
     *
     * @param string[] $implementations
     *   Implementation "group" by module name.
     * @param string $hook
     *   The hook name.
     *
     * @return bool
     *   TRUE, if all implementations exist.
     *   FALSE, if one or more implementations don't exist and need to be removed
     *     from the cache.
     */
    protected function verifyImplementations(&$implementations, $hook) {
        $all_valid = TRUE;
        foreach ($implementations as $module => $group) {
            // If this hook implementation is stored in a lazy-loaded file, include
            // that file first.
            if ($group) {
                $this->loadInclude($module, 'inc', "{$module}.{$group}");
            }
            // It is possible that a module removed a hook implementation without
            // the implementations cache being rebuilt yet, so we check whether the
            // function exists on each request to avoid undefined function errors.
            // Since ModuleHandler::implementsHook() may needlessly try to
            // load the include file again, function_exists() is used directly here.
            if (!function_exists($module . '_' . $hook)) {
                // Clear out the stale implementation from the cache and force a cache
                // refresh to forget about no longer existing hook implementations.
                unset($implementations[$module]);
                // One of the implementations did not exist and needs to be removed in
                // the cache.
                $all_valid = FALSE;
            }
        }
        return $all_valid;
    }
    
    /**
     * Parses a dependency for comparison by drupal_check_incompatibility().
     *
     * @param string $dependency
     *   A dependency string, which specifies a module dependency, and optionally
     *   the project it comes from and versions that are supported. Supported
     *   formats include:
     *   - 'module'
     *   - 'project:module'
     *   - 'project:module (>=version, version)'.
     *
     * @return array
     *   An associative array with three keys:
     *   - 'name' includes the name of the thing to depend on (e.g. 'foo').
     *   - 'original_version' contains the original version string (which can be
     *     used in the UI for reporting incompatibilities).
     *   - 'versions' is a list of associative arrays, each containing the keys
     *     'op' and 'version'. 'op' can be one of: '=', '==', '!=', '<>', '<',
     *     '<=', '>', or '>='. 'version' is one piece like '4.5-beta3'.
     *   Callers should pass this structure to drupal_check_incompatibility().
     *
     * @deprecated in drupal:8.7.0 and is removed from drupal:9.0.0.
     *   Use \Drupal\Core\Extension\Dependency::createFromString() instead.
     *
     * @see https://www.drupal.org/node/2756875
     */
    public static function parseDependency($dependency) {
        @trigger_error(__METHOD__ . ' is deprecated. Use \\Drupal\\Core\\Extension\\Dependency::createFromString() instead. See https://www.drupal.org/node/2756875', E_USER_DEPRECATED);
        $dependency = Dependency::createFromString($dependency);
        $result = [
            'name' => $dependency->getName(),
            'project' => $dependency->getProject(),
            'original_version' => $dependency['original_version'],
            'versions' => $dependency['versions'],
        ];
        return array_filter($result);
    }
    
    /**
     * {@inheritdoc}
     */
    public function getModuleDirectories() {
        $dirs = [];
        foreach ($this->getModuleList() as $name => $module) {
            $dirs[$name] = $this->root . '/' . $module->getPath();
        }
        return $dirs;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getName($module) {
        try {
            return \Drupal::service('extension.list.module')->getName($module);
        } catch (UnknownExtensionException $e) {
            @trigger_error('Calling ModuleHandler::getName() with an unknown module is deprecated in Drupal 8.7.0 and support for this will be removed in Drupal 9.0.0, check that the module exists before calling this method. See https://www.drupal.org/node/3024541.', E_USER_DEPRECATED);
            return $module;
        }
    }

}