class MigrationState

class MigrationState {
    use MessengerTrait;
    use StringTranslationTrait;
    
    /**
     * Source module upgrade state when all its migrations are complete.
     *
     * @var string
     */
    const FINISHED = 'finished';
    
    /**
     * Source module upgrade state when all its migrations are not complete.
     *
     * @var string
     */
    const NOT_FINISHED = 'not_finished';
    
    /**
     * The field plugin manager service.
     *
     * @var \Drupal\Core\Extension\ModuleHandler
     */
    protected $moduleHandler;
    
    /**
     * The field plugin manager service.
     *
     * @var \Drupal\migrate_drupal\Plugin\MigrateFieldPluginManagerInterface
     */
    protected $fieldPluginManager;
    
    /**
     * An array of migration states declared for each source migration.
     *
     * States are keyed by version. Each value is an array keyed by name of the
     * source module and the value is an array of all the states declared for this
     * source module.
     *
     * @var array
     */
    protected $stateBySource;
    
    /**
     * An array of destinations declared for each source migration.
     *
     * Destinations are keyed by version. Each value is an array keyed by the name
     * of the source module and the value is an array of the destination modules.
     *
     * @var array
     */
    protected $declaredBySource;
    
    /**
     * An array of migration source and destinations derived from migrations.
     *
     * The key is the source version and the value is an array where the key is
     * the source module and the value is an array of destinations derived from
     * migration plugins.
     *
     * @var array
     */
    protected $discoveredBySource;
    
    /**
     * An array of migration source and destinations.
     *
     * Values are derived from migration plugins and declared states. The key is
     * the source version and the value is an array where the key is the source
     * module and the value is an array of declared or derived destinations.
     *
     * @var array
     */
    protected $destinations = [];
    
    /**
     * Array of enabled modules.
     *
     * @var array
     */
    protected $enabledModules = [];
    
    /**
     * Construct a new MigrationState object.
     *
     * @param \Drupal\migrate_drupal\Plugin\MigrateFieldPluginManagerInterface $fieldPluginManager
     *   Field plugin manager.
     * @param \Drupal\Core\Extension\ModuleHandlerInterface $moduleHandler
     *   Module handler.
     * @param \Drupal\Core\Messenger\MessengerInterface $messenger
     *   Messenger service.
     * @param \Drupal\Core\StringTranslation\TranslationInterface $stringTranslation
     *   String translation service.
     */
    public function __construct(MigrateFieldPluginManagerInterface $fieldPluginManager, ModuleHandlerInterface $moduleHandler, MessengerInterface $messenger, TranslationInterface $stringTranslation) {
        $this->fieldPluginManager = $fieldPluginManager;
        $this->moduleHandler = $moduleHandler;
        $this->enabledModules = array_keys($this->moduleHandler
            ->getModuleList());
        $this->enabledModules[] = 'core';
        $this->messenger = $messenger;
        $this->stringTranslation = $stringTranslation;
    }
    
    /**
     * Gets the upgrade states for all enabled source modules.
     *
     * @param string $version
     *   The legacy drupal version.
     * @param array $source_system_data
     *   The data from the source site system table.
     * @param array $migrations
     *   An array of migrations.
     *
     * @return array
     *   An associative array of data with keys of state, source modules and a
     *   value which is a comma separated list of destination modules.
     */
    public function getUpgradeStates($version, array $source_system_data, array $migrations) {
        return $this->buildUpgradeState($version, $source_system_data, $migrations);
    }
    
    /**
     * Gets migration state information from *.migrate_drupal.yml.
     *
     * @return array
     *   An association array keyed by module of the finished and not_finished
     *   migrations for each module.
     * */
    protected function getMigrationStates() {
        // Always instantiate a new YamlDiscovery object so that we always search on
        // the up-to-date list of modules.
        $discovery = new YamlDiscovery('migrate_drupal', array_map(function ($value) {
            return $value . '/migrations/state';
        }, $this->moduleHandler
            ->getModuleDirectories()));
        return $discovery->findAll();
    }
    
    /**
     * Determines migration state for each source module enabled on the source.
     *
     * If there are no migrations for a module and no declared state the state is
     * set to NOT_FINISHED. When a module does not need any migrations, such as
     * Overlay, a state of finished is declared in system.migrate_drupal.yml.
     *
     * If there are migrations for a module the following happens. If the
     * destination module is 'core' the state is set to FINISHED. If there are
     * any occurrences of 'not_finished' in the *.migrate_drupal.yml information
     * for this source module then the state is set to NOT_FINISHED. And finally,
     * if there is an occurrence of 'finished' the state is set to FINISHED.
     *
     * @param string $version
     *   The legacy drupal version.
     * @param array $source_system_data
     *   The data from the source site system table.
     * @param array $migrations
     *   An array of migrations.
     *
     * @return array
     *   An associative array of data with keys of state, source modules and a
     *   value which is a comma separated list of destination modules.
     *   Example.
     *
     * @code
     * [
     *   'finished' => [
     *     'menu' => [
     *       'menu_link_content','menu_ui','system'
     *     ]
     *   ],
     * ]
     * @endcode
     */
    protected function buildUpgradeState($version, array $source_system_data, array $migrations) {
        // Remove core profiles from the system data.
        unset($source_system_data['module']['standard'], $source_system_data['module']['minimal']);
        $this->buildDiscoveredDestinationsBySource($version, $migrations, $source_system_data);
        $this->buildDeclaredStateBySource($version);
        $upgrade_state = [];
        // Loop through every source module that is enabled on the source site.
        foreach ($source_system_data['module'] as $module) {
            // The source plugins check requirements requires that all
            // source_modules are enabled so do the same here.
            if ($module['status']) {
                $source_module = $module['name'];
                $upgrade_state[$this->getSourceState($version, $source_module)][$source_module] = implode(', ', $this->getDestinationsForSource($version, $source_module));
            }
        }
        foreach ($upgrade_state as $key => $value) {
            ksort($upgrade_state[$key]);
        }
        return $upgrade_state;
    }
    
    /**
     * Builds migration source and destination module information.
     *
     * @param string $version
     *   The legacy Drupal version.
     * @param array $migrations
     *   The discovered migrations.
     * @param array $source_system_data
     *   The data from the source site system table.
     */
    protected function buildDiscoveredDestinationsBySource($version, array $migrations, array $source_system_data) {
        $discovered_upgrade_paths = [];
        $table_data = [];
        foreach ($migrations as $migration) {
            $migration_id = $migration->getPluginId();
            $source_module = $migration->getSourcePlugin()
                ->getSourceModule();
            if (!$source_module) {
                $this->messenger()
                    ->addError($this->t('Source module not found for @migration_id.', [
                    '@migration_id' => $migration_id,
                ]));
            }
            $destination_module = $migration->getDestinationPlugin()
                ->getDestinationModule();
            if (!$destination_module) {
                $this->messenger()
                    ->addError($this->t('Destination module not found for @migration_id.', [
                    '@migration_id' => $migration_id,
                ]));
            }
            if ($source_module && $destination_module) {
                $discovered_upgrade_paths[$source_module][] = $destination_module;
                $table_data[$source_module][$destination_module][$migration_id] = $migration->label();
            }
        }
        // Add entries for the field plugins to discovered_upgrade_paths.
        $definitions = $this->fieldPluginManager
            ->getDefinitions();
        foreach ($definitions as $definition) {
            // This is not strict so that we find field plugins with an annotation
            // where the Drupal core version is an integer and when it is a string.
            if (in_array($version, $definition['core'])) {
                $source_module = $definition['source_module'];
                $destination_module = $definition['destination_module'];
                $discovered_upgrade_paths[$source_module][] = $destination_module;
                $table_data[$source_module][$destination_module][$definition['id']] = $definition['id'];
            }
        }
        ksort($table_data);
        foreach ($table_data as $source_module => $destination_module_info) {
            ksort($table_data[$source_module]);
        }
        $this->discoveredBySource[$version] = array_map('array_unique', $discovered_upgrade_paths);
    }
    
    /**
     * Gets migration data from *.migrate_drupal.yml sorted by source module.
     *
     * @param string $version
     *   The legacy Drupal version.
     */
    protected function buildDeclaredStateBySource($version) {
        $migration_states = $this->getMigrationStates();
        $state_by_source = [];
        $dest_by_source = [];
        $states = [
            static::FINISHED,
            static::NOT_FINISHED,
        ];
        foreach ($migration_states as $info) {
            foreach ($states as $state) {
                if (isset($info[$state][$version])) {
                    foreach ($info[$state][$version] as $source => $destination) {
                        // Add the state.
                        $state_by_source[$source][] = $state;
                        // Add the destination modules.
                        $dest_by_source += [
                            $source => [],
                        ];
                        $dest_by_source[$source] = array_merge($dest_by_source[$source], (array) $destination);
                    }
                }
            }
        }
        $this->stateBySource[$version] = array_map('array_unique', $state_by_source);
        $this->declaredBySource[$version] = array_map('array_unique', $dest_by_source);
    }
    
    /**
     * Tests if a destination exists for the given source module.
     *
     * @param string $version
     *   Source version of Drupal.
     * @param string $source_module
     *   Source module.
     *
     * @return string
     *   Migration state, either 'finished' or 'not_finished'.
     */
    protected function getSourceState($version, $source_module) {
        // The state is finished only when no declarations of 'not_finished'
        // were found and each destination module is enabled.
        if (!($destinations = $this->getDestinationsForSource($version, $source_module))) {
            // No discovered or declared state.
            return MigrationState::NOT_FINISHED;
        }
        if (!isset($this->stateBySource[$version][$source_module])) {
            // No declared state.
            return MigrationState::NOT_FINISHED;
        }
        if (in_array(MigrationState::NOT_FINISHED, $this->stateBySource[$version][$source_module], TRUE) || !in_array(MigrationState::FINISHED, $this->stateBySource[$version][$source_module], TRUE)) {
            return MigrationState::NOT_FINISHED;
        }
        if (array_diff($destinations, $this->enabledModules)) {
            return MigrationState::NOT_FINISHED;
        }
        return MigrationState::FINISHED;
    }
    
    /**
     * Get net destinations for source module.
     *
     * @param string $version
     *   Source version.
     * @param string $source_module
     *   Source module.
     *
     * @return array
     *   Destination modules either declared by {modulename}.migrate_drupal.yml
     *   files or discovered from migration plugins.
     */
    protected function getDestinationsForSource($version, $source_module) {
        if (!isset($this->destinations[$version][$source_module])) {
            $this->discoveredBySource[$version] += [
                $source_module => [],
            ];
            $this->declaredBySource[$version] += [
                $source_module => [],
            ];
            $destination = array_unique(array_merge($this->discoveredBySource[$version][$source_module], $this->declaredBySource[$version][$source_module]));
            sort($destination);
            $this->destinations[$version][$source_module] = $destination;
        }
        return $this->destinations[$version][$source_module];
    }

}