<?php
// Hoplite
// Copyright (c) 2013 Blue Static
//
// This program is free software: you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by the Free
// Software Foundation, either version 3 of the License, or any later version.
//
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
// more details.
//
// You should have received a copy of the GNU General Public License along with
// this program.  If not, see <http://www.gnu.org/licenses/>.

namespace hoplite\views;

require_once HOPLITE_ROOT . '/views/cache_backend.php';

/*!
  An instance of CacheBackend that stores compiled templates in a database
  table accessed through a PDO object.
*/
class PDOCacheBackend implements CacheBackend
{
  /*! @var \PDO The dat abase to use. */
  protected $db = NULL;

  /*! @var \PDOStatement Used to query for cached templates. */
  protected $fetch_statement = NULL;

  /*! @var \PDOStatement Used to insert new templates. */
  protected $insert_statement = NULL;

  /*! @var \PDOStatement Used to expire out-of-date templates. */
  protected $delete_statement = NULL;

  /*! @var string Base query for a multi-fetch operation. */
  protected $fetch_multi_query = "";

  /*!
    Constructor that prepares the database statements.

    @param \PDO The connected database object.
    @param string Name of the database table to store templates in.
    @param string Column in which the template name is stored.
    @param string Column in which the template data is stored.
    @param string Column in which the template last modified time is stored.
  */
  public function __construct(\PDO $db,
                              $table_name,
                              $name_column_name = 'name',
                              $data_column_name = 'template',
                              $timestamp_column_name = 'timestamp')
  {
    $this->db = $db;

    $this->fetch_statement = $db->Prepare("
        SELECT `$data_column_name` AS template,
            `$timestamp_column_name` AS timestamp
        FROM $table_name
        WHERE `$name_column_name` IN (:name)
    ");

    $this->insert_statement = $db->Prepare("
        INSERT INTO `$table_name`
            (`$name_column_name`, `$data_column_name`, `$timestamp_column_name`)
        VALUES
            (:name, :template, :timestamp)
    ");

    $this->delete_statement = $db->Prepare("
        DELETE FROM `$table_name`
        WHERE `$name_column_name` = :name
    ");

    $this->fetch_multi_query = "
        SELECT `$name_column_name` AS name,
            `$data_column_name` AS template,
            `$timestamp_column_name` AS timestamp
        FROM $table_name
        WHERE `$name_column_name` IN ";
  }

  public function GetTemplateDataForName($name, $modification_time)
  {
    $this->fetch_statement->Execute(array('name' => $name));
    $tpl = $this->fetch_statement->FetchObject();
    if (!$tpl)
      return NULL;

    if ($tpl->timestamp < $modification_time) {
      $this->delete_statement->Execute(array('name' => $name));
      return NULL;
    }

    return $tpl->template;
  }

  public function StoreCompiledTemplate($name, $modification_time, $data)
  {
    $this->insert_statement->Execute(array(
        'name'      => $name,
        'timestamp' => $modification_time,
        'template'  => $data,
    ));
  }

  public function GetMultipleTemplates(Array $fetch_templates)
  {
    $placeholders = array_fill(0, count($fetch_templates), '?');
    $stmt = $this->db->Prepare($this->fetch_multi_query . '(' . implode(',', $placeholders) . ')');
    $stmt->Execute(array_keys($fetch_templates));

    $templates = array();
    while (($template = $stmt->FetchObject())) {
      if ($template->timestamp >= $fetch_templates[$template->name])
        $templates[$template->name] = $template->template;
    }
    return $templates;
  }
}