<?php

namespace Drupal\Core\Entity\Sql;

use Drupal\Core\Entity\ContentEntityTypeInterface;
use Drupal\Core\Field\FieldStorageDefinitionInterface;

/**
 * Defines a default table mapping class.
 */
class DefaultTableMapping implements TableMappingInterface {

  /**
   * The entity type definition.
   *
   * @var \Drupal\Core\Entity\ContentEntityTypeInterface
   */
  protected $entityType;

  /**
   * The field storage definitions of this mapping.
   *
   * @var \Drupal\Core\Field\FieldStorageDefinitionInterface[]
   */
  protected $fieldStorageDefinitions = [];

  /**
   * A list of field names per table.
   *
   * This corresponds to the return value of
   * TableMappingInterface::getFieldNames() except that this variable is
   * additionally keyed by table name.
   *
   * @var array[]
   */
  protected $fieldNames = [];

  /**
   * A list of database columns which store denormalized data per table.
   *
   * This corresponds to the return value of
   * TableMappingInterface::getExtraColumns() except that this variable is
   * additionally keyed by table name.
   *
   * @var array[]
   */
  protected $extraColumns = [];

  /**
   * A mapping of column names per field name.
   *
   * This corresponds to the return value of
   * TableMappingInterface::getColumnNames() except that this variable is
   * additionally keyed by field name.
   *
   * This data is derived from static::$storageDefinitions, but is stored
   * separately to avoid repeated processing.
   *
   * @var array[]
   */
  protected $columnMapping = [];

  /**
   * A list of all database columns per table.
   *
   * This corresponds to the return value of
   * TableMappingInterface::getAllColumns() except that this variable is
   * additionally keyed by table name.
   *
   * This data is derived from static::$storageDefinitions, static::$fieldNames,
   * and static::$extraColumns, but is stored separately to avoid repeated
   * processing.
   *
   * @var array[]
   */
  protected $allColumns = [];

  /**
   * Constructs a DefaultTableMapping.
   *
   * @param \Drupal\Core\Entity\ContentEntityTypeInterface $entity_type
   *   The entity type definition.
   * @param \Drupal\Core\Field\FieldStorageDefinitionInterface[] $storage_definitions
   *   A list of field storage definitions that should be available for the
   *   field columns of this table mapping.
   */
  public function __construct(ContentEntityTypeInterface $entity_type, array $storage_definitions) {
    $this->entityType = $entity_type;
    $this->fieldStorageDefinitions = $storage_definitions;
  }

  /**
   * {@inheritdoc}
   */
  public function getTableNames() {
    return array_unique(array_merge(array_keys($this->fieldNames), array_keys($this->extraColumns)));
  }

  /**
   * {@inheritdoc}
   */
  public function getAllColumns($table_name) {
    if (!isset($this->allColumns[$table_name])) {
      $this->allColumns[$table_name] = [];

      foreach ($this->getFieldNames($table_name) as $field_name) {
        $this->allColumns[$table_name] = array_merge($this->allColumns[$table_name], array_values($this->getColumnNames($field_name)));
      }

      // There is just one field for each dedicated storage table, thus
      // $field_name can only refer to it.
      if (isset($field_name) && $this->requiresDedicatedTableStorage($this->fieldStorageDefinitions[$field_name])) {
        // Unlike in shared storage tables, in dedicated ones field columns are
        // positioned last.
        $this->allColumns[$table_name] = array_merge($this->getExtraColumns($table_name), $this->allColumns[$table_name]);
      }
      else {
        $this->allColumns[$table_name] = array_merge($this->allColumns[$table_name], $this->getExtraColumns($table_name));
      }
    }
    return $this->allColumns[$table_name];
  }

  /**
   * {@inheritdoc}
   */
  public function getFieldNames($table_name) {
    if (isset($this->fieldNames[$table_name])) {
      return $this->fieldNames[$table_name];
    }
    return [];
  }

  /**
   * {@inheritdoc}
   */
  public function getFieldTableName($field_name) {
    $result = NULL;

    if (isset($this->fieldStorageDefinitions[$field_name])) {
      // Since a field may be stored in more than one table, we inspect tables
      // in order of relevance: the data table if present is the main place
      // where field data is stored, otherwise the base table is responsible for
      // storing field data. Revision metadata is an exception as it's stored
      // only in the revision table.
      // @todo The table mapping itself should know about entity tables. See
      //   https://www.drupal.org/node/2274017.
      /** @var \Drupal\Core\Entity\Sql\SqlContentEntityStorage $storage */
      $storage = \Drupal::entityManager()->getStorage($this->entityType->id());
      $storage_definition = $this->fieldStorageDefinitions[$field_name];
      $table_names = [
        $storage->getDataTable(),
        $storage->getBaseTable(),
        $storage->getRevisionTable(),
        $this->getDedicatedDataTableName($storage_definition),
      ];

      // Collect field columns.
      $field_columns = [];
      foreach (array_keys($storage_definition->getColumns()) as $property_name) {
        $field_columns[] = $this->getFieldColumnName($storage_definition, $property_name);
      }

      foreach (array_filter($table_names) as $table_name) {
        $columns = $this->getAllColumns($table_name);
        // We assume finding one field column belonging to the mapping is enough
        // to identify the field table.
        if (array_intersect($columns, $field_columns)) {
          $result = $table_name;
          break;
        }
      }
    }

    if (!isset($result)) {
      throw new SqlContentEntityStorageException("Table information not available for the '$field_name' field.");
    }

    return $result;
  }

  /**
   * {@inheritdoc}
   */
  public function getColumnNames($field_name) {
    if (!isset($this->columnMapping[$field_name])) {
      $this->columnMapping[$field_name] = [];
      if (isset($this->fieldStorageDefinitions[$field_name]) && !$this->fieldStorageDefinitions[$field_name]->hasCustomStorage()) {
        foreach (array_keys($this->fieldStorageDefinitions[$field_name]->getColumns()) as $property_name) {
          $this->columnMapping[$field_name][$property_name] = $this->getFieldColumnName($this->fieldStorageDefinitions[$field_name], $property_name);
        }
      }
    }
    return $this->columnMapping[$field_name];
  }

  /**
   * {@inheritdoc}
   */
  public function getFieldColumnName(FieldStorageDefinitionInterface $storage_definition, $property_name) {
    $field_name = $storage_definition->getName();

    if ($this->allowsSharedTableStorage($storage_definition)) {
      $column_name = count($storage_definition->getColumns()) == 1 ? $field_name : $field_name . '__' . $property_name;
    }
    elseif ($this->requiresDedicatedTableStorage($storage_definition)) {
      if ($property_name == TableMappingInterface::DELTA) {
        $column_name = 'delta';
      }
      else {
        $column_name = !in_array($property_name, $this->getReservedColumns()) ? $field_name . '_' . $property_name : $property_name;
      }
    }
    else {
      throw new SqlContentEntityStorageException("Column information not available for the '$field_name' field.");
    }

    return $column_name;
  }

  /**
   * Adds field columns for a table to the table mapping.
   *
   * @param string $table_name
   *   The name of the table to add the field column for.
   * @param string[] $field_names
   *   A list of field names to add the columns for.
   *
   * @return $this
   */
  public function setFieldNames($table_name, array $field_names) {
    $this->fieldNames[$table_name] = $field_names;
    // Force the re-computation of the column list.
    unset($this->allColumns[$table_name]);
    return $this;
  }

  /**
   * {@inheritdoc}
   */
  public function getExtraColumns($table_name) {
    if (isset($this->extraColumns[$table_name])) {
      return $this->extraColumns[$table_name];
    }
    return [];
  }

  /**
   * Adds a extra columns for a table to the table mapping.
   *
   * @param string $table_name
   *   The name of table to add the extra columns for.
   * @param string[] $column_names
   *   The list of column names.
   *
   * @return $this
   */
  public function setExtraColumns($table_name, array $column_names) {
    $this->extraColumns[$table_name] = $column_names;
    // Force the re-computation of the column list.
    unset($this->allColumns[$table_name]);
    return $this;
  }

  /**
   * Checks whether the given field can be stored in a shared table.
   *
   * @param \Drupal\Core\Field\FieldStorageDefinitionInterface $storage_definition
   *   The field storage definition.
   *
   * @return bool
   *   TRUE if the field can be stored in a dedicated table, FALSE otherwise.
   */
  public function allowsSharedTableStorage(FieldStorageDefinitionInterface $storage_definition) {
    return !$storage_definition->hasCustomStorage() && $storage_definition->isBaseField() && !$storage_definition->isMultiple();
  }

  /**
   * Checks whether the given field has to be stored in a dedicated table.
   *
   * @param \Drupal\Core\Field\FieldStorageDefinitionInterface $storage_definition
   *   The field storage definition.
   *
   * @return bool
   *   TRUE if the field can be stored in a dedicated table, FALSE otherwise.
   */
  public function requiresDedicatedTableStorage(FieldStorageDefinitionInterface $storage_definition) {
    return !$storage_definition->hasCustomStorage() && !$this->allowsSharedTableStorage($storage_definition);
  }

  /**
   * Gets a list of dedicated table names for this mapping.
   *
   * @return string[]
   *   An array of table names.
   */
  public function getDedicatedTableNames() {
    $table_mapping = $this;
    $definitions = array_filter($this->fieldStorageDefinitions, function($definition) use ($table_mapping) { return $table_mapping->requiresDedicatedTableStorage($definition); });
    $data_tables = array_map(function($definition) use ($table_mapping) { return $table_mapping->getDedicatedDataTableName($definition); }, $definitions);
    $revision_tables = array_map(function($definition) use ($table_mapping) { return $table_mapping->getDedicatedRevisionTableName($definition); }, $definitions);
    $dedicated_tables = array_merge(array_values($data_tables), array_values($revision_tables));
    return $dedicated_tables;
  }

  /**
   * {@inheritdoc}
   */
  public function getReservedColumns() {
    return ['deleted'];
  }

  /**
   * Generates a table name for a field data table.
   *
   * @param \Drupal\Core\Field\FieldStorageDefinitionInterface $storage_definition
   *   The field storage definition.
   * @param bool $is_deleted
   *   (optional) Whether the table name holding the values of a deleted field
   *   should be returned.
   *
   * @return string
   *   A string containing the generated name for the database table.
   */
  public function getDedicatedDataTableName(FieldStorageDefinitionInterface $storage_definition, $is_deleted = FALSE) {
    if ($is_deleted) {
      // When a field is a deleted, the table is renamed to
      // {field_deleted_data_FIELD_UUID}. To make sure we don't end up with
      // table names longer than 64 characters, we hash the unique storage
      // identifier and return the first 10 characters so we end up with a short
      // unique ID.
      return "field_deleted_data_" . substr(hash('sha256', $storage_definition->getUniqueStorageIdentifier()), 0, 10);
    }
    else {
      return $this->generateFieldTableName($storage_definition, FALSE);
    }
  }

  /**
   * Generates a table name for a field revision archive table.
   *
   * @param \Drupal\Core\Field\FieldStorageDefinitionInterface $storage_definition
   *   The field storage definition.
   * @param bool $is_deleted
   *   (optional) Whether the table name holding the values of a deleted field
   *   should be returned.
   *
   * @return string
   *   A string containing the generated name for the database table.
   */
  public function getDedicatedRevisionTableName(FieldStorageDefinitionInterface $storage_definition, $is_deleted = FALSE) {
    if ($is_deleted) {
      // When a field is a deleted, the table is renamed to
      // {field_deleted_revision_FIELD_UUID}. To make sure we don't end up with
      // table names longer than 64 characters, we hash the unique storage
      // identifier and return the first 10 characters so we end up with a short
      // unique ID.
      return "field_deleted_revision_" . substr(hash('sha256', $storage_definition->getUniqueStorageIdentifier()), 0, 10);
    }
    else {
      return $this->generateFieldTableName($storage_definition, TRUE);
    }
  }

  /**
   * Generates a safe and unambiguous field table name.
   *
   * The method accounts for a maximum table name length of 64 characters, and
   * takes care of disambiguation.
   *
   * @param \Drupal\Core\Field\FieldStorageDefinitionInterface $storage_definition
   *   The field storage definition.
   * @param bool $revision
   *   TRUE for revision table, FALSE otherwise.
   *
   * @return string
   *   The final table name.
   */
  protected function generateFieldTableName(FieldStorageDefinitionInterface $storage_definition, $revision) {
    $separator = $revision ? '_revision__' : '__';
    $table_name = $storage_definition->getTargetEntityTypeId() . $separator . $storage_definition->getName();
    // Limit the string to 48 characters, keeping a 16 characters margin for db
    // prefixes.
    if (strlen($table_name) > 48) {
      // Use a shorter separator, a truncated entity_type, and a hash of the
      // field UUID.
      $separator = $revision ? '_r__' : '__';
      // Truncate to the same length for the current and revision tables.
      $entity_type = substr($storage_definition->getTargetEntityTypeId(), 0, 34);
      $field_hash = substr(hash('sha256', $storage_definition->getUniqueStorageIdentifier()), 0, 10);
      $table_name = $entity_type . $separator . $field_hash;
    }
    return $table_name;
  }

}