<?php
// $Id: custom_pagers.module,v 1.6 2008-06-17 21:20:32 eaton Exp $

/**
 * Implementation of hook_menu().
 */
function custom_pagers_menu() {
  $items = array();

  $access = user_access('administer custom pagers');
  $items['admin/build/custom_pagers'] = array(
    'title' => 'Custom pagers',
    'description' => 'Add custom pagers for content types.',
    'page callback' => 'custom_pagers_page',
    'access arguments' => array('administer custom pagers'),
    'file' => 'custom_pagers.admin.inc',
  );

  $items['admin/build/custom_pagers/add'] = array(
    'path' => 'admin/build/custom_pagers/add',
    'title' => 'Add custom pager',
    'type' => MENU_CALLBACK,
    'page callback' => 'drupal_get_form',
    'page arguments' => array('custom_pagers_form'),
    'access arguments' => array('administer custom pagers'),
    'file' => 'custom_pagers.admin.inc',
  );

  $items['admin/build/custom_pagers/edit'] = array(
    'title' => 'Edit custom pager',
    'type' => MENU_CALLBACK,
    'page callback' => 'drupal_get_form',
    'page arguments' => array('custom_pagers_form', 4),
    'access arguments' => array('administer custom pagers'),
    'file' => 'custom_pagers.admin.inc',
  );

  return $items;
}

function custom_pagers_perm() {
  return array('administer custom pagers', 'use php in custom pagers');
}

function custom_pagers_theme() {
  return array(
    'custom_pager' => array(
      'arguments' => array(
        'nav_array' => NULL,
        'node' => NULL,
        'pager' => NULL,
        'position' => 'bottom',
      ),
      'template' => 'custom-pager',
    ),
  );
}

function custom_pagers_nodeapi(&$node, $op, $teaser, $page) {
  switch ($op) {
    case 'view':
      // We want to make sure we don't try to output when print.module is active.
      // It's a bit of special casing but it doesn't do much harm.
      if ($teaser == false && empty($node->printing)) {
        $pagers = _custom_pagers_load_all_pagers();
        foreach ($pagers as $pager) {
          if ($pager->position != 'block' && _custom_pagers_visibility($pager, $node)) {
            $nav_array = custom_pager_build_nav($pager, $node);
            if ($nav_array['current_index'] != -1) {
              switch ($pager->position) {
                case 'top':
                  $node->content['custom_pager_top'][$pager->pid] = array('#value' => theme('custom_pager', $nav_array, $node, $pager, 'top'));
                  break;
                case 'bottom':
                  $node->content['custom_pager_bottom'][$pager->pid] = array('#value' => theme('custom_pager', $nav_array, $node, $pager, 'bottom'));
                  break;
                case 'both':
                  $node->content['custom_pager_top'][$pager->pid] = array('#value' => theme('custom_pager', $nav_array, $node, $pager, 'top'));
                  $node->content['custom_pager_bottom'][$pager->pid] = array('#value' => theme('custom_pager', $nav_array, $node, $pager, 'bottom'));
                  break;
              }
            }
          }
        }
        if (isset($node->content['custom_pager_top'])) {
          $node->content['custom_pager_top']['#weight'] = -100;
        }
        if (isset($node->content['custom_pager_bottom'])) {
          $node->content['custom_pager_bottom']['#weight'] = 100;
        }
      }
      break;
    case 'update':
    case 'insert':
    case 'delete':
      // If a user makes any changes to a node, we want to make sure that
      // their pager cache is cleared. It's ugly, but it should prevent some
      // of the nastier cache-went-stale issues.
      unset($_SESSION['custom_pagers']);
      break;
  }
}

/**
 * Implementation of hook_block().
 *
 * Generates a block with a pager for the current node.
 */
function custom_pagers_block($op = 'list', $delta = 0) {
  if ($op == 'list') {
    $pagers = _custom_pagers_load_all_pagers();
    foreach ($pagers as $pager) {
      if ($pager->position == 'block') {
        $blocks[$pager->pid]['info'] = $pager->title;
      }
    }
    return $blocks;
  }
  else if ($op == 'view' && arg(0) == 'node' && $node = menu_get_object()) {
    $pagers = _custom_pagers_load_all_pagers();
    if ($pager = $pagers[$delta]) {
      if ($pager->position == 'block' && _custom_pagers_visibility($pager, $node)) {
        $nav_array = custom_pager_build_nav($pager, $node);
        if ($nav_array['current_index'] != -1) {
          if (module_exists('token')) {
            $block['subject'] = token_replace($pager->title, 'node', $node);
          }
          else {
            $block['subject'] = $pager->title;
          }
          $block['content'] = theme('custom_pager', $nav_array, $node, $pager, 'block');
          return $block;
        }
      }
    }
  }
}

function _custom_pagers_load_pager($pid) {
  $sql = 'SELECT * FROM {custom_pager} WHERE pid = %d';
  $result = db_query($sql, $pid);
  $pager = db_fetch_object($result);
  return $pager;
}

function _custom_pagers_load_all_pagers($refresh = FALSE) {
  static $pagers;
  if ($refresh || !isset($pagers)) {
    $sql = 'SELECT * FROM {custom_pager}';
    $result = db_query($sql);

    $pagers = array();
    while($pager = db_fetch_object($result)) {
      $pagers[$pager->pid] = $pager;
    }
  }
  return $pagers;
}

function _custom_pagers_save_pager($pager = NULL) {
  if (isset($pager->pid)) {
    drupal_write_record('custom_pager', $pager, array('pid'));
  }
  else {
    drupal_write_record('custom_pager', $pager);
  }
  cache_clear_all('custom_pagers_', 'cache', TRUE);
}

function _custom_pagers_delete_pager($pid) {
  $sql = 'DELETE FROM {custom_pager} WHERE pid = %d';
  db_query($sql, $pid);
}

function _custom_pagers_visibility($pager, $node) {
  $visible = FALSE;
  if (!empty($pager->visibility_php)) {
    // Use PHP code to generate the list.
    ob_start();
    $result = eval(trim($pager->visibility_php));
    $visible = ($result == TRUE);
    ob_end_clean();
  } elseif (!empty($pager->node_type)) {
    $visible = (strpos($pager->node_type, $node->type) !== FALSE);
  }
  return $visible;
}

function custom_pager_build_nav($pager, $node) {
  static $pager_cache;
  $list = array();

  // First we check the static function cache for this pager.
  // If it's already been built for this page-load, we'll use it.
  if (isset($pager_cache[$pager->pid])) {
    $list = explode(',', $pager_cache[$pager->pid]);
  }

  // If it doesn't give us a list, and the pager is set to cache its
  // data, we'll try to load from the current user's session. We do it
  // that way rather than via cache_set() because of the potential for
  // node_access violations. Each user's node list *could* be different.
  if (empty($list) && $pager->cache_list) {
    if ($cache = $_SESSION['custom_pagers'][$pager->pid]) {
      // We should probably set the pager cache lifetime to a configurable
      // value. If any nodes drop through the cracks, users won't see the
      // pager when they visit them. Five minutes should keep the pager from
      // thrashing. In the future, we'll want to develop a better strategy
      // for this.
      if ($cache['timestamp'] < (time() - 300)) {
        unset($_SESSION['custom_pagers'][$pager->pid]);
      }
      else {
        $list = explode(',', $_SESSION['custom_pagers'][$pager->pid]['data']);
      }
    }
  }

  // If $list is still empty, neither caching strategy produced a list.
  // Let's build it from scratch!
  if (empty($list)) {
    // If the pager uses PHP, execute the PHP and run with the list.
    // Otherwise, use a view to get a list of node ids.
    if (!empty($pager->list_php)) {
      // Use PHP code to generate the list.
      ob_start();
      $result = eval(trim($pager->list_php));
      if (is_array($result)) {
        $list = $result;
      }
      ob_end_clean();
    }
    elseif (module_exists('views') && $view = views_get_view($pager->view)) {
      // Get arguments for the view.
      if (isset($pager->args)) {
        $args = explode("\n", $pager->args);
        if (module_exists('token')) {
          $args = token_replace($args, 'node', $node);
        }
        $view->set_arguments($args);
      }

      // Make sure the query is not cached
      $view->is_cacheable = FALSE;
      $view->execute();

      if (isset($view->result)) {
        foreach($view->result as $result) {
          $list[] = $result->nid;
        }
      }
    }

    if ($pager->reverse_list) {
      $list = array_reverse($list);
    }
  }

  // If we get to this point, we want to cache what we've made.
  if ($pager->cache_list) {
    $_SESSION['custom_pagers'][$pager->pid]['data'] = implode(',', $list);
    $_SESSION['custom_pagers'][$pager->pid]['timestamp'] = time();
  }
  $pager_cache[$pager->pid] = $list;

  return pager_entries_by_val($node->nid, $list);
}

// Helper functions to pull proper entries from a list of nids.

function pager_entries_by_val($value, $list) {
  $list = array_values($list);
  foreach ($list as $k => $v) {
    if ($v == $value) {
      $key = $k;
    }
  }
  if (!isset($key)) {
    $key = -1;
  }
  return pager_entries_by_key($key, $list);
}

function pager_entries_by_key($key, $list, $increment = 1) {
  $list = array_values($list);
  $nav = array(
    'first' => $list[0],
    'prev' => $list[max($key - $increment, 0)],
    'next' => $list[min($key + $increment, (count($list) - 1))],
    'last' => $list[count($list) - 1],
    'full_list' => $list
  );

  foreach($nav as $k => $v) {
    if ($nav[$k] == $list[$key]) {
      $nav[$k] = NULL;
    }
  }

  $nav['current_index'] = $key;
  return $nav;
}

function custom_pagers_preprocess_custom_pager(&$vars) {
  drupal_add_css(drupal_get_path('module', 'custom_pagers') .'/custom_pagers.css');
  $node = $vars['node'];
  $pager = $vars['pager'];
  $nav = $vars['nav_array'];

  $vars['previous'] = !empty($nav['prev']) ? l(t('‹ previous'), 'node/'. $nav['prev']) : '';
  $vars['key'] = t('@count of @count_total', array('@count' => ($nav['current_index'] + 1), '@count_total' => count($nav['full_list'])));
  $vars['next'] =  !empty($nav['next']) ? l(t('next ›'), 'node/'. $nav['next']) : '';

  $vars['suggestions'][] = "custom-pager-{$vars['position']}";
  $vars['suggestions'][] = "custom-pager-$node->type";
  $vars['suggestions'][] = "custom-pager-$node->type-{$vars['position']}";
  $vars['suggestions'][] = "custom-pager-$pager->pid";
  $vars['suggestions'][] = "custom-pager-$pager->pid-{$vars['position']}";
}