<?php

/**
 * @file
 * API and drush commands to support migration of data from external sources
 * into a Drupal installation.
 */

// TODO:
// Continue hook_schema_alter() for map & message tables?
// Views hooks for map/message tables
// xlat support?
// Documentation
// Tests

define('MIGRATE_API_VERSION', 2);

define('MIGRATE_ACCESS_BASIC', 'migration information');
define('MIGRATE_ACCESS_ADVANCED', 'advanced migration information');

/**
 * Retrieve a list of all active migrations, ordered by dependencies. To be
 * recognized, a class must be non-abstract, and derived from MigrationBase.
 *
 * @param $reset
 *  If TRUE, the static cache of migrations will be flushed before attempting to
 *  reinstantiate all active migrations. This can be important for script runs
 *  where migration classes may be dynamically registered.
 *
 * @return
 *  Array of migration objects, keyed by the machine name.
 */
function migrate_migrations($reset = NULL) {
  static $migrations = array();
  if (!empty($migrations) && empty($reset)) {
    return $migrations;
  }

  // Get list of modules implementing Migrate API - mainly, we're looking to
  // make sure any dynamic migrations defined in hook_migrate_api() get registered.
  migrate_get_module_apis(TRUE);

  $dependencies_list = array();
  $dependent_migrations = array();
  $required_migrations = array();

  $result = db_select('migrate_status', 'ms')
            ->fields('ms', array('machine_name', 'class_name'))
            ->execute();
  foreach ($result as $row) {
    if (class_exists($row->class_name)) {
      $reflect = new ReflectionClass($row->class_name);
      if (!$reflect->isAbstract() && $reflect->isSubclassOf('MigrationBase')) {
        $migration = MigrationBase::getInstance($row->machine_name);
        if ($migration) {
          $dependencies = $migration->getDependencies();
          $dependencies_list[$row->machine_name] = $dependencies;
          if (count($dependencies) > 0) {
            // Set classes with dependencies aside for reordering
            $dependent_migrations[$row->machine_name] = $migration;
            $required_migrations += $dependencies;
          }
          else {
            // No dependencies, just add
            $migrations[$row->machine_name] = $migration;
          }
        }
      }
      else {
        MigrationBase::displayMessage(t('Class !class is no longer a valid concrete migration class',
                                      array('!class' => $row->class_name)));
      }
    }
    else {
      MigrationBase::displayMessage(t('Class !class no longer exists',
                                    array('!class' => $row->class_name)));
    }
  }

  $ordered_migrations = migrate_order_dependencies($dependencies_list);
  foreach ($ordered_migrations as $name) {
    if (!isset($migrations[$name])) {
      $migrations[$name] = $dependent_migrations[$name];
    }
  }

  // The migrations are now ordered according to their own dependencies - now order
  // them by group
  $groups = MigrateGroup::groups();
  // Seed the final list by properly-ordered groups.
  $final_migrations = array();
  foreach ($groups as $name => $group) {
    $final_migrations[$name] = array();
  }

  // Fill in the grouped list.
  foreach ($migrations as $machine_name => $migration) {
    if (!method_exists($migration, 'getGroup')) {
      MigrationBase::displayMessage(t('Migration !machine_name is not a valid Migration dependency.', array(
        '!machine_name' => $machine_name,
      )));
    }
    else {
      $final_migrations[$migration->getGroup()->getName()][$machine_name] = $migration;
    }
  }
  // Flatten the grouped list.
  $migrations = array();
  foreach ($final_migrations as $group_name => $group_migrations) {
    foreach ($group_migrations as $machine_name => $migration) {
      $migrations[$machine_name] = $migration;
    }
  }

  return $migrations;
}

/**
 * Invoke any available handlers attached to a given destination type.
 * If any handlers have dependencies defined, they will be invoked after
 * the specified handlers.
 *
 * @param $destination
 *  Destination type ('Node', 'User', etc.) - generally the same string as
 *  the destination class name without the MigrateDestination prefix.
 * @param $method
 *  Method name such as 'prepare' (called at the beginning of an import operation)
 *  or 'complete' (called at the end of an import operation).
 * @param ...
 *  Parameters to be passed to the handler.
 */
function migrate_handler_invoke_all($destination, $method) {
  $args = func_get_args();
  array_shift($args);
  array_shift($args);
  $return = array();
  $class_list = _migrate_class_list('MigrateDestinationHandler');
  $disabled = unserialize(variable_get('migrate_disabled_handlers', serialize(array())));
  foreach ($class_list as $class_name => $handler) {
    if (!in_array($class_name, $disabled) && $handler->handlesType($destination)
        && method_exists($handler, $method)) {
      migrate_instrument_start($class_name . '->' . $method);
      $result = call_user_func_array(array($handler, $method), $args);
      migrate_instrument_stop($class_name . '->' . $method);
      if (isset($result) && is_array($result)) {
        $return = array_merge($return, $result);
      }
      elseif (isset($result)) {
        $return[] = $result;
      }
    }
  }
  return $return;
}

/**
 * Invoke any available handlers attached to a given field type.
 *
 * @param $entity
 *  The object we are building up before calling example_save().
 * @param $field_info
 *  Array of info on the field, from field_info_field().
 * @param $instance
 *  Array of info in the field instance, from field_info_instances().
 * @param $values
 *  Array of incoming values, to be transformed into the appropriate structure
 *  for the field type.
 * @param $method
 *  Handler method to call (defaults to prepare()).
 */
function migrate_field_handler_invoke_all($entity, array $field_info,
    array $instance, array $values, $method = 'prepare') {
  $return = array();
  $type = $field_info['type'];
  $class_list = _migrate_class_list('MigrateFieldHandler');
  $disabled = unserialize(variable_get('migrate_disabled_handlers',
                                       serialize(array())));
  $handler_called = FALSE;
  foreach ($class_list as $class_name => $handler) {
    if (!in_array($class_name, $disabled) && $handler->handlesType($type)
        && method_exists($handler, $method)) {
      migrate_instrument_start($class_name . '->' . $method);
      $result = call_user_func_array(array($handler, $method),
        array($entity, $field_info, $instance, $values));
      $handler_called = TRUE;
      migrate_instrument_stop($class_name . '->' . $method);
      if (isset($result) && is_array($result)) {
        $return = array_merge_recursive($return, $result);
      }
      elseif (isset($result)) {
        $return[] = $result;
      }
    }
  }

  if (!$handler_called && $method == 'prepare') {
    $handler = new MigrateDefaultFieldHandler();
    migrate_instrument_start('MigrateDefaultFieldHandler->prepare');
    $result = call_user_func_array(array($handler, 'prepare'),
      array($entity, $field_info, $instance, $values));
    migrate_instrument_stop('MigrateDefaultFieldHandler->prepare');
    if (isset($result) && is_array($result)) {
      $return = array_merge_recursive($return, $result);
    }
    elseif (isset($result)) {
      $return[] = $result;
    }
  }
  return $return;
}

/**
 * For a given parent class, identify and instantiate objects for any non-abstract
 * classes derived from the parent, returning an array of the objects indexed by
 * class name. The array will be ordered such that any classes with dependencies
 * are listed after the classes they are dependent on.
 *
 * @param $parent_class
 *  Name of a class from which results will be derived.
 * @return
 *  Array of objects, keyed by the class name.
 */
function _migrate_class_list($parent_class) {
  // Get info on modules implementing Migrate API
  static $module_info;
  if (!isset($module_info)) {
    $module_info = migrate_get_module_apis();
  }

  static $class_lists = array();
  if (!isset($class_lists[$parent_class])) {
    $class_lists[$parent_class] = array();
    if ($parent_class == 'MigrateDestinationHandler') {
      $handler_key = 'destination handlers';
    }
    else {
      $handler_key = 'field handlers';
    }
    // Add explicitly-registered handler classes
    foreach ($module_info as $info) {
      if (isset($info[$handler_key]) && is_array($info[$handler_key])) {
        foreach ($info[$handler_key] as $handler_class) {
          $class_lists[$parent_class][$handler_class] = new $handler_class();
        }
      }
    }
  }
  return $class_lists[$parent_class];
}

/**
 * Implements hook_hook_info().
 */
function migrate_hook_info() {
  // Look for hook_migrate_api() in example.migrate.inc.
  $hooks['migrate_api'] = array(
    'group' => 'migrate',
  );
  $hooks['migrate_api_alter'] = array(
    'group' => 'migrate',
  );
  return $hooks;
}

/**
 * Implementation of hook_permission().
 */
function migrate_permission() {
  return array(
    MIGRATE_ACCESS_BASIC => array(
      'title' => t('Access to basic migration information'),
    ),
    MIGRATE_ACCESS_ADVANCED => array(
      'title' => t('Access to advanced migration information'),
    ),
  );
}

/**
 * Get a list of modules that support the current migrate API.
 */
function migrate_get_module_apis($reset = FALSE) {
  static $cache = NULL;
  if ($reset) {
    $cache = NULL;
  }
  if (!isset($cache)) {
    $cache = array();
    foreach (module_implements('migrate_api') as $module) {
      $function = $module . '_migrate_api';
      $info = $function();
      if (isset($info['api']) && $info['api'] == MIGRATE_API_VERSION) {
        $cache[$module] = $info;
      }
      else {
        drupal_set_message(t('%function supports Migrate API version %modversion,
          Migrate module API version is %version - migration support not loaded.',
          array('%function' => $function, '%modversion' => $info['api'],
                '%version' => MIGRATE_API_VERSION)));
      }
    }

    // Allow modules to alter the migration information.
    drupal_alter('migrate_api', $cache);
  }

  return $cache;
}

/**
 * Register any migrations defined in hook_migrate_api().
 *
 * @param array $machine_names
 *  If populated, only (re)register the specified migrations.
 */
function migrate_static_registration($machine_names = array()) {
  $module_info = migrate_get_module_apis(TRUE);
  foreach ($module_info as $module => $info) {
    // Register any groups defined via the hook.
    if (isset($info['groups']) && is_array($info['groups'])) {
      foreach ($info['groups'] as $name => $arguments) {
        $title = $arguments['title'];
        unset($arguments['title']);
        MigrateGroup::register($name, $title, $arguments);
      }
    }
    // Register any migrations defined via the hook.
    if (isset($info['migrations']) && is_array($info['migrations'])) {
      foreach ($info['migrations'] as $machine_name => $arguments) {
        // If we have an explicit list to register, skip any not in the list.
        if (!empty($machine_names) && !in_array($machine_name, $machine_names)) {
          continue;
        }
        $class_name = $arguments['class_name'];
        unset($arguments['class_name']);
        // Call the right registerMigration implementation. Note that this means
        // that classes that override registerMigration() must always call it
        // directly, they cannot register those classes by defining them in
        // hook_migrate_api() and expect their extension to be called.
        if (is_subclass_of($class_name, 'Migration')) {
          Migration::registerMigration($class_name, $machine_name, $arguments);
        }
        else {
          MigrationBase::registerMigration($class_name, $machine_name, $arguments);
        }
      }
    }

  }
}

/**
 * Do a topological sort on our dependencies graph.
 */
function migrate_order_dependencies($dependencies) {
  $visited = array();
  $list = array();

  foreach (array_keys($dependencies) as $name) {
    $visited[$name] = FALSE;
  }

  foreach (array_keys($dependencies) as $name) {
    migrate_visit_dependent($dependencies, $name, $list, $visited);
  }

  return $list;
}

/**
 * Depth-first search for independent migrations.
 */
function migrate_visit_dependent($dependencies, $name, &$list, &$visited) {
  if ($visited[$name]) {
    if ($list[$name]) {
      return;
    }
    else {
      throw new MigrateException(t('Failure to sort migration list due to circular dependencies involving %name.', array('%name' => $name)));
    }
  }

  $visited[$name] = TRUE;
  if (isset($dependencies[$name])) {
    foreach ($dependencies[$name] as $dependent) {
      migrate_visit_dependent($dependencies, $dependent, $list, $visited);
    }
  }

  $list[$name] = $name;
}

/**
 * Implements hook_watchdog().
 * Find the migration that is currently running and notify it.
 *
 * @param array $log_entry
 */
function migrate_watchdog($log_entry) {
  // Ensure that the Migration class exists, as different bootstrap phases may
  // not have included migration.inc yet.
  if (class_exists('Migration') && $migration = Migration::currentMigration()) {
    switch ($log_entry['severity']) {
      case WATCHDOG_EMERGENCY:
      case WATCHDOG_ALERT:
      case WATCHDOG_CRITICAL:
      case WATCHDOG_ERROR:
        $severity = MigrationBase::MESSAGE_ERROR;
        break;
      case WATCHDOG_WARNING:
        $severity = MigrationBase::MESSAGE_WARNING;
        break;
      case WATCHDOG_NOTICE:
        $severity = MigrationBase::MESSAGE_NOTICE;
        break;
      case WATCHDOG_DEBUG:
      case WATCHDOG_INFO:
      default:
        $severity = MigrationBase::MESSAGE_INFORMATIONAL;
        break;
    }
    $variables = is_array($log_entry['variables']) ? $log_entry['variables'] : array();
    $migration->saveMessage(t($log_entry['message'], $variables), $severity);
  }
}

/**
 * Resource functions modeled on Drupal's timer functions
 */

/**
 * Save memory usage with the specified name. If you start and stop the same
 * memory name multiple times, the measured differences will be accumulated.
 *
 * @param name
 *   The name of the memory measurement.
 */
function migrate_memory_start($name) {
  global $_migrate_memory;

  $_migrate_memory[$name]['start'] = memory_get_usage();
  $_migrate_memory[$name]['count'] =
    isset($_migrate_memory[$name]['count']) ? ++$_migrate_memory[$name]['count'] : 1;
}

/**
 * Read the current memory value without recording the change.
 *
 * @param name
 *   The name of the memory measurement.
 * @return
 *   The change in bytes since the last start.
 */
function migrate_memory_read($name) {
  global $_migrate_memory;

  if (isset($_migrate_memory[$name]['start'])) {
    $stop = memory_get_usage();
    $diff = $stop - $_migrate_memory[$name]['start'];

    if (isset($_migrate_memory[$name]['bytes'])) {
      $diff += $_migrate_memory[$name]['bytes'];
    }
    return $diff;
  }
  return $_migrate_memory[$name]['bytes'];
}

/**
 * Stop the memory counter with the specified name.
 *
 * @param name
 *   The name of the memory measurement.
 * @return
 *   A memory array. The array contains the number of times the memory has been
 *   started and stopped (count) and the accumulated memory difference value in bytes.
 */
function migrate_memory_stop($name) {
  global $_migrate_memory;

  if (isset($_migrate_memory[$name])) {
    if (isset($_migrate_memory[$name]['start'])) {
      $stop = memory_get_usage();
      $diff = $stop - $_migrate_memory[$name]['start'];
      if (isset($_migrate_memory[$name]['bytes'])) {
        $_migrate_memory[$name]['bytes'] += $diff;
      }
      else {
        $_migrate_memory[$name]['bytes'] = $diff;
      }
      unset($_migrate_memory[$name]['start']);
    }

    return $_migrate_memory[$name];
  }
}

/**
 * Start measuring time and (optionally) memory consumption over a section of code.
 * Note that the memory consumption measurement is generally not useful in
 * lower areas of the code, where data is being generated that will be freed
 * by the next call to the same area. For example, measuring the memory
 * consumption of db_query is not going to be helpful.
 *
 * @param $name
 *  The name of the measurement.
 * @param $include_memory
 *  Measure both memory and timers. Defaults to FALSE (timers only).
 */
function migrate_instrument_start($name, $include_memory = FALSE) {
  global $_migrate_track_memory, $_migrate_track_timer;
  if ($_migrate_track_memory && $include_memory) {
    migrate_memory_start($name);
  }
  if ($_migrate_track_timer) {
    timer_start($name);
  }
}

/**
 * Stop measuring both memory and time consumption over a section of code.
 *
 * @param $name
 *  The name of the measurement.
 */
function migrate_instrument_stop($name) {
  global $_migrate_track_memory, $_migrate_track_timer;
  if ($_migrate_track_timer) {
    timer_stop($name);
  }
  if ($_migrate_track_memory) {
    migrate_memory_stop($name);
  }
}

/**
 * Call hook_migrate_overview for overall documentation on implemented migrations.
 */
function migrate_overview() {
  $overview = '';
  $results = module_invoke_all('migrate_overview');
  foreach ($results as $result) {
    $overview .= $result . ' ';
  }
  return $overview;
}

/**
 * Implements hook_modules_enabled.
 */
function migrate_modules_enabled($modules) {
  if (array_intersect($modules, module_implements('migrate_api'))) {
    migrate_static_registration();
  }
}

/**
 * Implements hook_module_implements_alter().
 */
function migrate_module_implements_alter(&$implementation, $hook) {
  // Ensure that the Migration class exists, as different bootstrap phases may
  // not have included migration.inc yet.
  if (class_exists('Migration') && $migration = Migration::currentMigration()) {
    $disable_hooks = $migration->getDisableHooks();
    if (isset($disable_hooks[$hook])) {
      foreach ($disable_hooks[$hook] as $module) {
        unset($implementation[$module]);
      }
    }
  }
}