<?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);

/**
 * Retrieve a list of all active migrations, ordered by dependencies. To be
 * recognized, a class must be non-abstract, and derived from MigrationBase.
 *
 * @return
 *  Array of migration objects, keyed by the machine name.
 */
function migrate_migrations() {
  static $migrations = array();
  if (!empty($migrations)) {
    return $migrations;
  }

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

  $result = db_select('migrate_status', 'ms')
            ->fields('ms', array('machine_name', 'class_name', 'arguments'))
            ->execute();
  foreach ($result as $row) {
    if (class_exists($row->class_name)) {
      $reflect = new ReflectionClass($row->class_name);
      if (!$reflect->isAbstract() && $reflect->isSubclassOf('MigrationBase')) {
        $arguments = unserialize($row->arguments);
        if (!$arguments || !is_array($arguments)) {
          $arguments = array();
        }
        $migration = MigrationBase::getInstance($row->machine_name,
          $row->class_name, $arguments);
        $dependencies = $migration->getDependencies();
        if (count($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)));
    }
  }

  // Scan modules with dependencies - we'll take 20 passes at it before
  // giving up
  // TODO: Can we share code with _migrate_class_list()?
  $iterations = 0;
  while (count($dependent_migrations) > 0) {
    if ($iterations++ > 20) {
      $migration_names = implode(',', array_keys($dependent_migrations));
      throw new MigrateException(t('Failure to sort migration list - most likely due ' .
            'to circular dependencies involving !migration_names',
      array('!migration_names' => $migration_names)));
    }
    foreach ($dependent_migrations as $name => $migration) {
      $ready = TRUE;
      // Scan all the dependencies for this class and make sure they're all
      // in the final list
      foreach ($migration->getDependencies() as $dependency) {
        if (!isset($migrations[$dependency])) {
          $ready = FALSE;
          break;
        }
      }
      if ($ready) {
        // Yes they are! Move this class to the final list
        $migrations[$name] = $migration;
        unset($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) {
    $final_migrations[$migration->getGroup()->getName()][$machine_name] = $migration;
  }
  // Then flatten the list
  $migrations = array();
  foreach ($final_migrations as $group_name => $group_migrations) {
    foreach ($group_migrations as $machine_name => $migration) {
      $migrations[$machine_name] = $migration;
    }
  }

  return $migrations;
}

/**
 * On cache clear, scan the Drupal code registry for any new migration classes
 * for us to register in migrate_status.
 */
function migrate_flush_caches() {
  // Get list of modules implementing Migrate API
  $modules = array_keys(migrate_get_module_apis(TRUE));

  // Get list of classes we already know about
  $existing_classes = db_select('migrate_status', 'ms')
                      ->fields('ms', array('class_name'))
                      ->execute()
                      ->fetchCol();

  // Discover class names registered with Drupal by modules implementing our API
  $result = db_select('registry', 'r')
            ->fields('r', array('name'))
            ->condition('type', 'class')
            ->condition('module', $modules, 'IN')
            ->condition('filename', '%.test', 'NOT LIKE')
            ->execute();

  foreach ($result as $record) {
    $class_name = $record->name;
    // If we already know about this class, skip it
    if (isset($existing_classes[$class_name])) {
      continue;
    }

    // Validate it's an implemented subclass of the parent class
    // Ignore errors
    try {
      $class = new ReflectionClass($class_name);
    }
    catch (Exception $e) {
      continue;
    }
    if (!$class->isAbstract() && $class->isSubclassOf('MigrationBase')) {
      // Verify that it's not a dynamic class (the implementor will be responsible
      // for registering those).
      $dynamic = call_user_func(array($class_name, 'isDynamic'));
      if (!$dynamic) {
        // OK, this is a new non-dynamic migration class, register it
        MigrationBase::registerMigration($class_name);
      }
    }
  }
}

/**
 * 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.
 * If any handlers have dependencies defined, they will be invoked after
 * the specified handlers.
 *
 * @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');
  $disabled = unserialize(variable_get('migrate_disabled_handlers', serialize(array())));
  foreach ($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, $values));
      migrate_instrument_stop($class_name . '->' . $method);
      if (isset($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.
 * @param $existing
 *  Instances already known, which don't need to be instantiated.
 * @return
 *  Array of objects, keyed by the class name.
 */
function _migrate_class_list($parent_class, array $existing = array()) {
  // Get list of modules implementing Migrate API
  static $modules;
  if (!isset($modules)) {
    $modules = array_keys(migrate_get_module_apis());
  }

  static $class_lists = array();
  if (!isset($class_lists[$parent_class])) {
    $class_lists[$parent_class] = array();
    $dependent_classes = array();
    $required_classes = array();
    // Discover class names registered with Drupal by modules implementing our API
    $result = db_select('registry', 'r')
              ->fields('r', array('name'))
              ->condition('type', 'class')
              ->condition('module', $modules, 'IN')
              ->condition('filename', '%.test', 'NOT LIKE')
              ->execute();

    foreach ($result as $record) {
      // Validate it's an implemented subclass of the parent class
      // We can get funky errors here, ignore them (and the class that caused them)
      try {
        $class = new ReflectionClass($record->name);
      }
      catch (Exception $e) {
        continue;
      }
      if (!$class->isAbstract() && $class->isSubclassOf($parent_class)) {
        // If the constructor has required parameters, this may fail. We will
        // silently ignore - it is up to the implementor of such a class to
        // instantiate it in hook_migrations_alter().
        try {
          $object = new $record->name;
        }
        catch (Exception $e) {
          unset($object);
        }
        if (isset($object)) {
          $dependencies = $object->getDependencies();
          if (count($dependencies) > 0) {
            // Set classes with dependencies aside for reordering
            $dependent_classes[$record->name] = $object;
            $required_classes += $dependencies;
          }
          else {
            // No dependencies, just add
            $class_lists[$parent_class][$record->name] = $object;
          }
        }
      }
    }

    // Validate that each depended-on class at least exists
    foreach ($required_classes as $class_name) {
      if ((!isset($dependent_classes[$class_name])) && !isset($class_lists[$parent_class][$class_name])) {
        throw new MigrateException(t('Dependency on non-existent class !class - make sure ' .
            'you have added the file defining !class to the .info file.',
          array('!class' => $class_name)));
      }
    }

    // Scan modules with dependencies - we'll take 20 passes at it before
    // giving up
    $iterations = 0;
    while (count($dependent_classes) > 0) {
      if ($iterations++ > 20) {
        $class_names = implode(',', array_keys($dependent_classes));
        throw new MigrateException(t('Failure to sort class list - most likely due ' .
            'to circular dependencies involving !class_names.',
          array('!class_names' => $class_names)));
      }
      foreach ($dependent_classes as $name => $object) {
        $ready = TRUE;
        // Scan all the dependencies for this class and make sure they're all
        // in the final list
        foreach ($object->getDependencies() as $dependency) {
          if (!isset($class_lists[$parent_class][$dependency])) {
            $ready = FALSE;
            break;
          }
        }
        if ($ready) {
          // Yes they are! Move this class to the final list
          $class_lists[$parent_class][$name] = $object;
          unset($dependent_classes[$name]);
        }
      }
    }
  }
  return $class_lists[$parent_class];
}

/**
 * Implements hook_hook_info().
 */
function migrate_hook_info() {
  $hooks['migrate_api'] = array(
    'group' => 'migrate',
  );
  return $hooks;
}

/*
 * Implements hook_migrate_api().
 */
function migrate_migrate_api() {
  $api = array(
    'api' => MIGRATE_API_VERSION,
  );
  return $api;
}

/**
 * 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)));
      }
    }
  }

  return $cache;
}

/**
 * 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;
}