<?php

/**
 * ChadoPrefixExtender
 *
 * A query extender that for select queries. By extending the
 * SelectQueryExtender class, we can make sure that chado tables
 *
 * @see https://www.drupal.org/docs/7/api/database-api/dynamic-queries/extenders
 */
class ChadoPrefixExtender extends SelectQueryExtender {

  /**
   * A static cache for Chado tables.
   *
   * @var array
   */
  protected static $chado_tables = [];

  /**
   * A replacement for db_select when querying Chado.
   *
   * Use this function instead of db_select when querying Chado tables.
   *
   * @param string|\SelectQuery $table
   *   The base table for this query. May be a
   *   string or another SelectQuery object. If a query object is passed, it
   *   will be used as a subselect.
   * @param string $alias
   *   The alias for the base table of this query.
   * @param array $options
   *   An array of options to control how the query
   *   operates.
   *
   * @return \SelectQuery
   *   A new SelectQuery object for this connection.
   *
   * @ingroup tripal_chado_query_api
   */
  public static function select($table, $alias = NULL, array $options = []) {
    // Since the table could also be a SelectQuery object, we should verify that
    // it is a string first.
    if (is_string($table)) {
      $table = static::getTable($table);
    }

    // If the alias is null, determine a safe alias. db_select fails to generate
    // a safe alias when the table name is prefixed with "public.".
    if (is_null($alias)) {
      $alias = static::makeAlias($table);
    }

    // Create a select query
    $query = db_select($table, $alias, $options);
    return $query->extend('ChadoPrefixExtender');
  }

  /**
   * Overwrites the join to prefix table names.
   *
   * @param string $table
   *   Table to join.
   * @param string $alias
   *   Alias for joined table.
   * @param string $condition
   *   Operation for joining.
   * @param array $arguments
   *   Additional arguments.
   *
   * @return $this
   *   The current object.
   *
   * @ingroup tripal_chado_query_api
   */
  public function join($table, $alias = NULL, $condition = NULL, $arguments = []) {
    $table = static::getTable($table);

    if (is_null($alias)) {
      $alias = static::makeAlias($table);
    }

    $this->query->join($table, $alias, $condition, $arguments);

    return $this;
  }


  /**
   * Checks if a table is a chado table.
   *
   * @param string $table
   *
   * @return bool
   */
  public static function isChadoTable($table) {
    if (empty(static::$chado_tables)) {
      static::$chado_tables = chado_get_table_names(TRUE);
    }

    return in_array($table, static::$chado_tables);
  }

  /**
   * If the table name has a schema name as a prefix, replace it with the
   * correct schema name.
   *
   * @param string $table
   *   The table name.
   *
   * @return string
   *   The table with the correct prefix.
   *
   * @see chado_replace_schema_prefix()
   */
  public static function getTable($table) {
    // No schema was provided.
    if (strpos($table, '.') === FALSE) {
      // If this is a chado table, add the chado prefix. Otherwise, add the
      // public prefix.
      if (static::isChadoTable($table)) {
        $table = "chado.{$table}";
      }
      else {
        $table = "public.{$table}";
      }
    }

    // Now that the schema has been set, we can replace it with the correct
    // name. Note that schema names can be altered by developers so we need to
    // to run the following function to obtain the final name.
    $table = chado_replace_schema_prefix($table);

    return $table;
  }

  /**
   * Create a safe alias.
   *
   * @param string $table Table name.
   *
   * @return string
   *    The safe alias.
   */
  public static function makeAlias($table) {
    return str_replace('.', '_', $table);
  }
}