class MigrateExecutable

class MigrateExecutable implements MigrateExecutableInterface {
    use StringTranslationTrait;
    
    /**
     * The configuration of the migration to do.
     *
     * @var \Drupal\migrate\Plugin\MigrationInterface
     */
    protected $migration;
    
    /**
     * Status of one row.
     *
     * The value is a MigrateIdMapInterface::STATUS_* constant, for example:
     * STATUS_IMPORTED.
     *
     * @var int
     */
    protected $sourceRowStatus;
    
    /**
     * The ratio of the memory limit at which an operation will be interrupted.
     *
     * @var float
     */
    protected $memoryThreshold = 0.85;
    
    /**
     * The PHP memory_limit expressed in bytes.
     *
     * @var int
     */
    protected $memoryLimit;
    
    /**
     * The configuration values of the source.
     *
     * @var array
     */
    protected $sourceIdValues;
    
    /**
     * An array of counts. Initially used for cache hit/miss tracking.
     *
     * @var array
     */
    protected $counts = [];
    
    /**
     * The source.
     *
     * @var \Drupal\migrate\Plugin\MigrateSourceInterface
     */
    protected $source;
    
    /**
     * The event dispatcher.
     *
     * @var \Symfony\Contracts\EventDispatcher\EventDispatcherInterface
     */
    protected $eventDispatcher;
    
    /**
     * Migration message service.
     *
     * @var \Drupal\migrate\MigrateMessageInterface
     *
     * @todo https://www.drupal.org/node/2822663 Make this protected.
     */
    public $message;
    
    /**
     * Constructs a MigrateExecutable and verifies and sets the memory limit.
     *
     * @param \Drupal\migrate\Plugin\MigrationInterface $migration
     *   The migration to run.
     * @param \Drupal\migrate\MigrateMessageInterface $message
     *   (optional) The migrate message service.
     * @param \Symfony\Contracts\EventDispatcher\EventDispatcherInterface $event_dispatcher
     *   (optional) The event dispatcher.
     */
    public function __construct(MigrationInterface $migration, ?MigrateMessageInterface $message = NULL, ?EventDispatcherInterface $event_dispatcher = NULL) {
        $this->migration = $migration;
        $this->message = $message ?: new MigrateMessage();
        $this->getIdMap()
            ->setMessage($this->message);
        $this->eventDispatcher = $event_dispatcher;
        // Record the memory limit in bytes
        $limit = trim(ini_get('memory_limit'));
        if ($limit == '-1') {
            $this->memoryLimit = PHP_INT_MAX;
        }
        else {
            $this->memoryLimit = Bytes::toNumber($limit);
        }
    }
    
    /**
     * Returns the source.
     *
     * Makes sure source is initialized based on migration settings.
     *
     * @return \Drupal\migrate\Plugin\MigrateSourceInterface
     *   The source.
     */
    protected function getSource() {
        if (!isset($this->source)) {
            $this->source = $this->migration
                ->getSourcePlugin();
        }
        return $this->source;
    }
    
    /**
     * Gets the event dispatcher.
     *
     * @return \Symfony\Contracts\EventDispatcher\EventDispatcherInterface
     */
    protected function getEventDispatcher() {
        if (!$this->eventDispatcher) {
            $this->eventDispatcher = \Drupal::service('event_dispatcher');
        }
        return $this->eventDispatcher;
    }
    
    /**
     * {@inheritdoc}
     */
    public function import() {
        // Only begin the import operation if the migration is currently idle.
        if ($this->migration
            ->getStatus() !== MigrationInterface::STATUS_IDLE) {
            $this->message
                ->display($this->t('Migration @id is busy with another operation: @status', [
                '@id' => $this->migration
                    ->id(),
                '@status' => $this->t($this->migration
                    ->getStatusLabel()),
            ]), 'error');
            return MigrationInterface::RESULT_FAILED;
        }
        $this->getEventDispatcher()
            ->dispatch(new MigrateImportEvent($this->migration, $this->message), MigrateEvents::PRE_IMPORT);
        // Knock off migration if the requirements haven't been met.
        try {
            $this->migration
                ->checkRequirements();
        } catch (RequirementsException $e) {
            $this->message
                ->display($this->t('Migration @id did not meet the requirements. @message', [
                '@id' => $this->migration
                    ->id(),
                '@message' => $e->getMessage(),
            ]), 'error');
            return MigrationInterface::RESULT_FAILED;
        }
        $this->migration
            ->setStatus(MigrationInterface::STATUS_IMPORTING);
        $source = $this->getSource();
        try {
            $source->rewind();
        } catch (\Exception $e) {
            $this->message
                ->display($this->t('Migration failed with source plugin exception: @e in @file line @line', [
                '@e' => $e->getMessage(),
                '@file' => $e->getFile(),
                '@line' => $e->getLine(),
            ]), 'error');
            $this->migration
                ->setStatus(MigrationInterface::STATUS_IDLE);
            return MigrationInterface::RESULT_FAILED;
        }
        // Get the process pipeline.
        $pipeline = FALSE;
        if ($source->valid()) {
            try {
                $pipeline = $this->migration
                    ->getProcessPlugins();
            } catch (MigrateException $e) {
                $row = $source->current();
                $this->sourceIdValues = $row->getSourceIdValues();
                $this->getIdMap()
                    ->saveIdMapping($row, [], $e->getStatus());
                $this->saveMessage($e->getMessage(), $e->getLevel());
            }
        }
        $return = MigrationInterface::RESULT_COMPLETED;
        if ($pipeline) {
            $id_map = $this->getIdMap();
            $destination = $this->migration
                ->getDestinationPlugin();
            while ($source->valid()) {
                $row = $source->current();
                $this->sourceIdValues = $row->getSourceIdValues();
                try {
                    foreach ($pipeline as $destination_property_name => $plugins) {
                        $this->processPipeline($row, $destination_property_name, $plugins, NULL);
                    }
                    $save = TRUE;
                } catch (MigrateException $e) {
                    $this->getIdMap()
                        ->saveIdMapping($row, [], $e->getStatus());
                    $msg = sprintf("%s:%s:%s", $this->migration
                        ->getPluginId(), $destination_property_name, $e->getMessage());
                    $this->saveMessage($msg, $e->getLevel());
                    $save = FALSE;
                } catch (MigrateSkipRowException $e) {
                    if ($e->getSaveToMap()) {
                        $id_map->saveIdMapping($row, [], MigrateIdMapInterface::STATUS_IGNORED);
                    }
                    if ($message = trim($e->getMessage())) {
                        $msg = sprintf("%s:%s: %s", $this->migration
                            ->getPluginId(), $destination_property_name, $message);
                        $this->saveMessage($msg, MigrationInterface::MESSAGE_INFORMATIONAL);
                    }
                    $save = FALSE;
                }
                if ($save) {
                    try {
                        $this->getEventDispatcher()
                            ->dispatch(new MigratePreRowSaveEvent($this->migration, $this->message, $row), MigrateEvents::PRE_ROW_SAVE);
                        $destination_ids = $id_map->lookupDestinationIds($this->sourceIdValues);
                        $destination_id_values = $destination_ids ? reset($destination_ids) : [];
                        $destination_id_values = $destination->import($row, $destination_id_values);
                        $this->getEventDispatcher()
                            ->dispatch(new MigratePostRowSaveEvent($this->migration, $this->message, $row, $destination_id_values), MigrateEvents::POST_ROW_SAVE);
                        if ($destination_id_values) {
                            // We do not save an idMap entry for config.
                            if ($destination_id_values !== TRUE) {
                                $id_map->saveIdMapping($row, $destination_id_values, $this->sourceRowStatus, $destination->rollbackAction());
                            }
                        }
                        else {
                            $id_map->saveIdMapping($row, [], MigrateIdMapInterface::STATUS_FAILED);
                            if (!$id_map->messageCount()) {
                                $message = $this->t('New object was not saved, no error provided');
                                $this->saveMessage($message);
                                $this->message
                                    ->display($message);
                            }
                        }
                    } catch (MigrateException $e) {
                        $this->getIdMap()
                            ->saveIdMapping($row, [], $e->getStatus());
                        $this->saveMessage($e->getMessage(), $e->getLevel());
                    } catch (\Exception $e) {
                        $this->getIdMap()
                            ->saveIdMapping($row, [], MigrateIdMapInterface::STATUS_FAILED);
                        $this->handleException($e);
                    }
                }
                $this->sourceRowStatus = MigrateIdMapInterface::STATUS_IMPORTED;
                // Check for memory exhaustion.
                if (($return = $this->checkStatus()) != MigrationInterface::RESULT_COMPLETED) {
                    break;
                }
                // If anyone has requested we stop, return the requested result.
                if ($this->migration
                    ->getStatus() == MigrationInterface::STATUS_STOPPING) {
                    $return = $this->migration
                        ->getInterruptionResult();
                    $this->migration
                        ->clearInterruptionResult();
                    break;
                }
                try {
                    $source->next();
                } catch (\Exception $e) {
                    $this->message
                        ->display($this->t('Migration failed with source plugin exception: @e in @file line @line', [
                        '@e' => $e->getMessage(),
                        '@file' => $e->getFile(),
                        '@line' => $e->getLine(),
                    ]), 'error');
                    $this->migration
                        ->setStatus(MigrationInterface::STATUS_IDLE);
                    return MigrationInterface::RESULT_FAILED;
                }
            }
        }
        $this->getEventDispatcher()
            ->dispatch(new MigrateImportEvent($this->migration, $this->message), MigrateEvents::POST_IMPORT);
        $this->migration
            ->setStatus(MigrationInterface::STATUS_IDLE);
        return $return;
    }
    
    /**
     * {@inheritdoc}
     */
    public function rollback() {
        // Only begin the rollback operation if the migration is currently idle.
        if ($this->migration
            ->getStatus() !== MigrationInterface::STATUS_IDLE) {
            $this->message
                ->display($this->t('Migration @id is busy with another operation: @status', [
                '@id' => $this->migration
                    ->id(),
                '@status' => $this->t($this->migration
                    ->getStatusLabel()),
            ]), 'error');
            return MigrationInterface::RESULT_FAILED;
        }
        // Announce that rollback is about to happen.
        $this->getEventDispatcher()
            ->dispatch(new MigrateRollbackEvent($this->migration), MigrateEvents::PRE_ROLLBACK);
        // Optimistically assume things are going to work out; if not, $return will be
        // updated to some other status.
        $return = MigrationInterface::RESULT_COMPLETED;
        $this->migration
            ->setStatus(MigrationInterface::STATUS_ROLLING_BACK);
        $id_map = $this->getIdMap();
        $destination = $this->migration
            ->getDestinationPlugin();
        // Loop through each row in the map, and try to roll it back.
        $id_map->rewind();
        while ($id_map->valid()) {
            $destination_key = $id_map->currentDestination();
            if ($destination_key) {
                $map_row = $id_map->getRowByDestination($destination_key);
                if (!isset($map_row['rollback_action']) || $map_row['rollback_action'] == MigrateIdMapInterface::ROLLBACK_DELETE) {
                    $this->getEventDispatcher()
                        ->dispatch(new MigrateRowDeleteEvent($this->migration, $destination_key), MigrateEvents::PRE_ROW_DELETE);
                    $destination->rollback($destination_key);
                    $this->getEventDispatcher()
                        ->dispatch(new MigrateRowDeleteEvent($this->migration, $destination_key), MigrateEvents::POST_ROW_DELETE);
                }
                // We're now done with this row, so remove it from the map.
                $id_map->deleteDestination($destination_key);
            }
            else {
                // If there is no destination key the import probably failed and we can
                // remove the row without further action.
                $source_key = $id_map->currentSource();
                $id_map->delete($source_key);
            }
            $id_map->next();
            // Check for memory exhaustion.
            if (($return = $this->checkStatus()) != MigrationInterface::RESULT_COMPLETED) {
                break;
            }
            // If anyone has requested we stop, return the requested result.
            if ($this->migration
                ->getStatus() == MigrationInterface::STATUS_STOPPING) {
                $return = $this->migration
                    ->getInterruptionResult();
                $this->migration
                    ->clearInterruptionResult();
                break;
            }
        }
        // Notify modules that rollback attempt was complete.
        $this->getEventDispatcher()
            ->dispatch(new MigrateRollbackEvent($this->migration), MigrateEvents::POST_ROLLBACK);
        $this->migration
            ->setStatus(MigrationInterface::STATUS_IDLE);
        return $return;
    }
    
    /**
     * Get the ID map from the current migration.
     *
     * @return \Drupal\migrate\Plugin\MigrateIdMapInterface
     *   The ID map.
     */
    protected function getIdMap() {
        return $this->migration
            ->getIdMap();
    }
    
    /**
     * {@inheritdoc}
     */
    public function processRow(Row $row, ?array $process = NULL, $value = NULL) {
        foreach ($this->migration
            ->getProcessPlugins($process) as $destination => $plugins) {
            $this->processPipeline($row, $destination, $plugins, $value);
        }
    }
    
    /**
     * Runs a process pipeline.
     *
     * @param \Drupal\migrate\Row $row
     *   The $row to be processed.
     * @param string $destination
     *   The destination property name.
     * @param array $plugins
     *   The process pipeline plugins.
     * @param mixed $value
     *   (optional) Initial value of the pipeline for the destination.
     *
     * @see \Drupal\migrate\MigrateExecutableInterface::processRow
     *
     * @throws \Drupal\migrate\MigrateException
     */
    protected function processPipeline(Row $row, string $destination, array $plugins, $value) {
        $multiple = FALSE;
        
        /** @var \Drupal\migrate\Plugin\MigrateProcessInterface $plugin */
        foreach ($plugins as $plugin) {
            $definition = $plugin->getPluginDefinition();
            // Many plugins expect a scalar value but the current value of the
            // pipeline might be multiple scalars (this is set by the previous plugin)
            // and in this case the current value needs to be iterated and each scalar
            // separately transformed.
            if ($multiple && !$definition['handle_multiples']) {
                $new_value = [];
                if (!is_array($value)) {
                    throw new MigrateException(sprintf('Pipeline failed at %s plugin for destination %s: %s received instead of an array,', $plugin->getPluginId(), $destination, $value));
                }
                $break = FALSE;
                foreach ($value as $scalar_value) {
                    $plugin->reset();
                    try {
                        $new_value[] = $plugin->transform($scalar_value, $this, $row, $destination);
                    } catch (MigrateSkipProcessException $e) {
                        $new_value[] = NULL;
                        $break = TRUE;
                    } catch (MigrateException $e) {
                        // Prepend the process plugin id to the message.
                        $message = sprintf("%s: %s", $plugin->getPluginId(), $e->getMessage());
                        throw new MigrateException($message);
                    }
                    if ($plugin->isPipelineStopped()) {
                        $break = TRUE;
                    }
                }
                $value = $new_value;
                if ($break) {
                    break;
                }
            }
            else {
                $plugin->reset();
                try {
                    $value = $plugin->transform($value, $this, $row, $destination);
                } catch (MigrateSkipProcessException) {
                    $value = NULL;
                    break;
                } catch (MigrateException $e) {
                    // Prepend the process plugin id to the message.
                    $message = sprintf("%s: %s", $plugin->getPluginId(), $e->getMessage());
                    throw new MigrateException($message);
                }
                if ($plugin->isPipelineStopped()) {
                    break;
                }
                $multiple = $plugin->multiple();
            }
        }
        // Ensure all values, including nulls, are migrated.
        if ($plugins) {
            if (isset($value)) {
                $row->setDestinationProperty($destination, $value);
            }
            else {
                $row->setEmptyDestinationProperty($destination);
            }
        }
    }
    
    /**
     * Fetches the key array for the current source record.
     *
     * @return array
     *   The current source IDs.
     */
    protected function currentSourceIds() {
        return $this->getSource()
            ->getCurrentIds();
    }
    
    /**
     * {@inheritdoc}
     */
    public function saveMessage($message, $level = MigrationInterface::MESSAGE_ERROR) {
        $this->getIdMap()
            ->saveMessage($this->sourceIdValues, $message, $level);
    }
    
    /**
     * Takes an Exception object and both saves and displays it.
     *
     * Pulls in additional information on the location triggering the exception.
     *
     * @param \Exception $exception
     *   Object representing the exception.
     * @param bool $save
     *   (optional) Whether to save the message in the migration's mapping table.
     *   Set to FALSE in contexts where this doesn't make sense.
     */
    protected function handleException(\Exception $exception, $save = TRUE) {
        $result = Error::decodeException($exception);
        $message = $result['@message'] . ' (' . $result['%file'] . ':' . $result['%line'] . ')';
        if ($save) {
            $this->saveMessage($message);
        }
        $this->message
            ->display($message, 'error');
    }
    
    /**
     * Checks for exceptional conditions, and display feedback.
     */
    protected function checkStatus() {
        if ($this->memoryExceeded()) {
            return MigrationInterface::RESULT_INCOMPLETE;
        }
        return MigrationInterface::RESULT_COMPLETED;
    }
    
    /**
     * Tests whether we've exceeded the desired memory threshold.
     *
     * If so, output a message.
     *
     * @return bool
     *   TRUE if the threshold is exceeded, otherwise FALSE.
     */
    protected function memoryExceeded() {
        $usage = $this->getMemoryUsage();
        $pct_memory = $usage / $this->memoryLimit;
        if (!($threshold = $this->memoryThreshold)) {
            return FALSE;
        }
        if ($pct_memory > $threshold) {
            $this->message
                ->display($this->t('Memory usage is @usage (@pct% of limit @limit), reclaiming memory.', [
                '@pct' => round($pct_memory * 100),
                '@usage' => ByteSizeMarkup::create($usage, NULL, $this->stringTranslation),
                '@limit' => ByteSizeMarkup::create($this->memoryLimit, NULL, $this->stringTranslation),
            ]), 'warning');
            $usage = $this->attemptMemoryReclaim();
            $pct_memory = $usage / $this->memoryLimit;
            // Use a lower threshold - we don't want to be in a situation where we keep
            // coming back here and trimming a tiny amount
            if ($pct_memory > 0.9 * $threshold) {
                $this->message
                    ->display($this->t('Memory usage is now @usage (@pct% of limit @limit), not enough reclaimed, starting new batch', [
                    '@pct' => round($pct_memory * 100),
                    '@usage' => ByteSizeMarkup::create($usage, NULL, $this->stringTranslation),
                    '@limit' => ByteSizeMarkup::create($this->memoryLimit, NULL, $this->stringTranslation),
                ]), 'warning');
                return TRUE;
            }
            else {
                $this->message
                    ->display($this->t('Memory usage is now @usage (@pct% of limit @limit), reclaimed enough, continuing', [
                    '@pct' => round($pct_memory * 100),
                    '@usage' => ByteSizeMarkup::create($usage, NULL, $this->stringTranslation),
                    '@limit' => ByteSizeMarkup::create($this->memoryLimit, NULL, $this->stringTranslation),
                ]), 'warning');
                return FALSE;
            }
        }
        else {
            return FALSE;
        }
    }
    
    /**
     * Returns the memory usage so far.
     *
     * @return int
     *   The memory usage.
     */
    protected function getMemoryUsage() {
        return memory_get_usage();
    }
    
    /**
     * Tries to reclaim memory.
     *
     * @return int
     *   The memory usage after reclaim.
     */
    protected function attemptMemoryReclaim() {
        // First, try resetting Drupal's static storage - this frequently releases
        // plenty of memory to continue.
        drupal_static_reset();
        // Entity storage can blow up with caches, so clear it out.
        \Drupal::service('entity.memory_cache')->deleteAll();
        // @todo Explore resetting the container.
        // Run garbage collector to further reduce memory.
        gc_collect_cycles();
        return memory_get_usage();
    }

}