<?php

/**
 * This class provides several approaches for querying data from the database:
 *
 *   # Async queries: Used under MySQLi with MySQLnd.
 *   # Parallel queries: Used under HPHP.
 *   # Multi queries: Used under MySQLi or HPHP.
 *   # Single queries: Used under MySQL.
 *
 * The class automatically decides which approach to use. Usage is like with
 * other futures:
 *
 *   $futures = array();
 *   $futures[] = new QueryFuture($conn1, 'SELECT 1');
 *   $futures[] = new QueryFuture($conn1, 'DELETE FROM table');
 *   $futures[] = new QueryFuture($conn2, 'SELECT 2');
 *
 *   foreach (new FutureIterator($futures) as $future) {
 *     try {
 *       $result = $future->resolve();
 *     } catch (AphrontQueryException $ex) {
 *     }
 *   }
 *
 * `$result` contains a list of dicts for select queries or number of modified
 * rows for modification queries.
 */
final class QueryFuture extends Future {

  private static $futures = array();

  private $conn;
  private $query;
  private $id;
  private $async;
  private $profilerCallID;

  public function __construct(
    AphrontDatabaseConnection $conn,
    $pattern/* , ... */) {

    $this->conn = $conn;

    $args = func_get_args();
    $args = array_slice($args, 2);
    $this->query = vqsprintf($conn, $pattern, $args);

    self::$futures[] = $this;
    $this->id = last_key(self::$futures);
  }

  public function isReady() {
    if ($this->canResolve()) {
      return true;
    }

    if (!$this->async) {
      $profiler = PhutilServiceProfiler::getInstance();
      $this->profilerCallID = $profiler->beginServiceCall(
        array(
          'type'    => 'query',
          'query'   => $this->query,
          'async'   => true,
        ));

      $this->async = $this->conn->asyncQuery($this->query);
      return false;
    }

    $conns = array();
    $asyncs = array();
    foreach (self::$futures as $id => $future) {
      if ($future->async) {
        $conns[$id] = $future->conn;
        $asyncs[$id] = $future->async;
      }
    }

    $this->processResults($this->conn->resolveAsyncQueries($conns, $asyncs));

    if ($this->canResolve()) {
      return true;
    }
    return false;
  }

  private function processResults(array $results) {
    foreach ($results as $id => $result) {
      $future = self::$futures[$id];
      if ($result instanceof Exception) {
        $future->exception = $result;
      } else {
        $future->result = $result;
      }
      unset(self::$futures[$id]);
      if ($future->profilerCallID) {
        $profiler = PhutilServiceProfiler::getInstance();
        $profiler->endServiceCall($future->profilerCallID, array());
      }
    }
  }
}