<?php

/**
 * @file
 * Module to enable adding a block to menu item.
 *
 * This allows an admin to select a block for a menu item as well as, or
 * instead of, a title and link. When the link is rendered, the block is
 * inserted in the containing element after the <a> tag.
 *
 *  Based heavily on menu_views.module.
 *
 * @link http://drupal.org/project/menu_views @endlink
 */

/**
 * Implements hook_menu().
 */
function menu_attach_block_menu() {
  return array(
    '<block>' => array(
      'page callback' => 'drupal_not_found',
      'access callback' => TRUE,
      'type' => MENU_CALLBACK,
    ),
  );
}

/**
 * Implements hook_theme().
 */
function menu_attach_block_theme() {
  return array(
    'menu_attach_block_wrapper' => array(
      'template' => 'menu_attach_block_wrapper',
      'arguments' => array('content' => NULL, 'orientation' => NULL),
    ),
  );
}

/**
 * Override theme_link().
 *
 * Render a block inside a link.
 *
 * @todo Implement a theme function to do the render.
 *
 * @param array $variables
 *   Array of theme variables as would be passed to theme_link().
 *
 * @return string
 *   HTML for a link with an attached block.
 */
function menu_attach_block_link(&$variables) {
  $block = FALSE;
  $options = $variables['options'];

  if (isset($options['menu_attach_block']) && !empty($options['menu_attach_block']['name'])) {
    $block = menu_attach_block_load_from_key($options['menu_attach_block']['name']);
  }

  // Render a block if one is attached to this link.
  if ($block) {
    $link = '';
    // Render the link with the block content afterwards.
    if ($variables['path'] != '<block>') {
      // Build the link manually instead of using l() to avoid getting caught in
      // theme_link() again.
      $link = '<a href="' . check_plain(url($variables['path'], $variables['options'])) . '"' . drupal_attributes($variables['options']['attributes']) . '>' . ($variables['options']['html'] ? $variables['text'] : check_plain($variables['text'])) . '</a>';
      $attributes = array(
        'class' => 'menu-attach-block-drop-link',
        'id' => $variables['path'] . '-drop-link-' . $variables['options']['menu_attach_block']['mlid'],
      );
      // Pass a space as the fragment parameter to get a <a href='# '> link.
      // @link http://bit.ly/zZXArS @endlink
      $l_options = array(
        'fragment' => ' ',
        'external' => TRUE,
        'attributes' => $attributes,
      );
      $link .= PHP_EOL . l(t('More'), '', $l_options);
    }
    // Get the block html.
    $block_output = menu_attach_block_block_render($block['module'], $block['delta']);
    if (!empty($block_output)) {

      $variables = array(
        'orientation' => $options['menu_attach_block']['orientation'],
        'content' => $block_output,
      );
      $block_output = theme('menu_attach_block_wrapper', $variables);
      return $link . $block_output;
    }
  }

  // Otherwise, pass through to the original theme function.
  return theme('menu_attach_block_link_default', $variables);
}

/**
 * Processes variables for menu_attach_block.tpl.php.
 *
 * @param array $variables
 *   Array of theme variables, with members:
 *    - content: HTML of embedded block.
 *    - orientation: Menu orientation: either horizontal or vertical.
 */
function template_preprocess_menu_attach_block_wrapper(&$variables) {
  // Add new CSS classes to be processed by template_process. This allows for
  // other preprocess functions to easily alter the list of classes for the
  // wrapper before they are output.
  $variables['classes_array'][] = drupal_html_class('orientation-' . $variables['orientation']);
}

/**
 * Implements hook_preprocess_HOOK().
 */
function menu_attach_block_preprocess_links(&$variables) {
  $attached_block = FALSE;
  // Very quick hacky check to prevent notices on install.
  // @todo Investigate in more detail.
  if (array_key_exists('links', $variables) && is_array($variables['links']) && count($variables['links'])) {
    foreach ($variables['links'] as $key => &$link) {
      if (
        is_array($link) &&
        array_key_exists('menu_attach_block', $link) &&
        empty($link['menu_attach_block']['name']) == FALSE
      ) {
        $attached_block = TRUE;

        $link['attributes']['class'][] = 'attached-block';
        // Rebuild the keys of the array, preserving the order. Array keys are
        // used for keys in the li element of link lists - @see theme_links.
        $new_links[$key . ' attached-block'] = $link;
      }
      else {
        $new_links[$key] = $link;
      }
    }
    if ($attached_block) {
      $variables['links'] = $new_links;
    }
  }
}

/**
 * Implements hook_theme_registry_alter().
 *
 * Intercepts hook_link().
 */
function menu_attach_block_theme_registry_alter(&$registry) {
  // Save previous value from registry in case another module/theme
  // overwrites link.
  $registry['menu_attach_block_link_default'] = $registry['link'];
  $registry['link']['function'] = 'menu_attach_block_link';
}

/**
 * Implements hook_form_FORM_ID_alter().
 *
 * Appends the attached view to the title of the menu item.
 */
function menu_attach_block_form_menu_overview_form_alter(&$form, &$form_state) {
  $elements = element_children($form);

  foreach ($elements as $mlid) {
    $element = &$form[$mlid];
    $block = array();
    // Only process menu items.
    if (isset($element['#item'])) {
      $item = &$element['#item'];
      $options = $item['options'];
      if (isset($options['menu_attach_block']) && !empty($options['menu_attach_block']['name'])) {
        $block = menu_attach_block_load_from_key($options['menu_attach_block']['name'], 'info');
        if ($block !== FALSE) {
          $info = $block[$block['delta']]['info'];
          $title = '';
          if ($item['link_path'] != '<block>') {
            // Manually create the link, otherwise it will be caught by
            // menu_attach_block_link().
            $title = '<a href="' . check_url(url($item['href'], $item['localized_options'])) . '"' . drupal_attributes($item['localized_options']['attributes']) . '>' . check_plain($item['title']) . '</a> ';
          }
          $link = l($info, 'admin/structure/block/manage/' . $block['module'] . '/' . $block['delta'] . '/configure');
          $element['title']['#markup'] = $title . '<div class="messages status block">Attached block:  ' . $link . ' </div>';
        }
      }
    }
  }
}

/**
 * Implements hook_form_FORM_ID_alter().
 *
 * Inserts a block selector.
 */
function menu_attach_block_form_menu_edit_item_alter(&$form, &$form_state) {
  if (isset($form['link_path']['#description'])) {
    $form['link_path']['#description'] .= ' ' . t('Enter %block to disable the link and display only the attached block.', array('%block' => '<block>'));
  }
  $form['menu_attach_block'] = array(
    '#type' => 'fieldset',
    '#title' => t('Attach block'),
    '#description' => t('Choose a block to be rendered as part of this menu item.'),
    '#collapsible' => FALSE,
    '#collapsed' => FALSE,
    '#prefix' => '<div id="menu-block">',
    '#suffix' => '</div>',
    '#tree' => TRUE,
  );
  $options = array();
  // @todo Change to use code similar to that in block_admin_display().
  $blocks = _block_rehash();

  foreach ($blocks as $block) {
    $options[$block['module'] . '|' . $block['delta']] = $block['info'];
  }
  asort($options);
  $form['menu_attach_block']['name'] = array(
    '#type' => 'select',
    '#title' => t('Block'),
    '#empty_option' => t('- None -'),
    '#description' => t('Select a block to attach.'),
    '#default_value' => isset($form['options']['#value']['menu_attach_block']['name']) ? $form['options']['#value']['menu_attach_block']['name'] : '',
    '#options' => $options,
  );

  $form['menu_attach_block']['orientation'] = array(
    '#type' => 'select',
    '#title' => t('Menu orientation'),
    '#default_value' => isset($form['options']['#value']['menu_attach_block']['name']) ? $form['options']['#value']['menu_attach_block']['name'] : 'horizontal',
    '#options' => array('horizontal' => t('Horizontal'), 'vertical' => t('Vertical')),
  );
  // Inject handlers.
  $form['#validate'] = array_merge(array('menu_attach_block_menu_edit_item_validate'), $form['#validate']);
  $form['#submit'] = array_merge(array('menu_attach_block_menu_edit_item_submit'), $form['#submit']);
}

/**
 * Validate handler for menu_edit_item form.
 */
function menu_attach_block_menu_edit_item_validate($form, &$form_state) {
  // Only run this validation when the form is fully submitted.
  if ($form_state['submitted']) {
    if ($form_state['values']['link_path'] == '<block>' && $form_state['values']['menu_attach_block']['name'] == '') {
      form_set_error('menu_attach_block][name', t('The link path has been set to %block. You must select a block to attach to this menu item.', array('%block' => '<block>')));
    }
  }
}

/**
 * Submit handler for menu_edit_item form.
 *
 * @todo Handle removal of block attachments from menu items.
 */
function menu_attach_block_menu_edit_item_submit($form, &$form_state) {
  // Save menu_attach_blocks values in the links options.
  $values = &$form_state['values'];
  if (isset($values['menu_attach_block'])) {
    $values['menu_attach_block']['mlid'] = $values['original_item']['mlid'];
    $values['menu_attach_block']['plid'] = $values['original_item']['plid'];
    $values['options']['menu_attach_block'] = $values['menu_attach_block'];
  }


  unset($values['menu_attach_block']);
}

/**
 * Loads a block object using a menu_attach_block key.
 *
 * Block references are saved in the menu object in the format module|delta.
 *
 * @param string $key
 *   Key as saved by the menu admin form, in the format module|delta.
 * @param string $hook
 *   name of hook_block implementation to call to get extra data about a block.
 *   Do not include the 'block_' prefix.
 *
 * @return array
 *   Fully loaded block array.
 *
 * @see http://api.drupal.org/api/search/7/hook_block
 */
function menu_attach_block_load_from_key($key, $hook = FALSE) {
  $block = (array) call_user_func_array('block_load', explode('|', $key));
  // If no 'theme' key is set, then there is no such block.
  if (!array_key_exists('theme', $block)) {
    return FALSE;
  }
  if ($hook) {
    // Hack for hook_block_info for blocks with numeric keys.
    if ($hook === 'info' && is_numeric($block['delta'])) {
      $info = module_invoke($block['module'], 'block_info', $block['delta']);
      $info = $info[$block['delta']];
      $block[$block['delta']] = $info;
    }
    else {
      $block = array_merge($block, (array) module_invoke($block['module'], 'block_' . $hook, $block['delta']));
    }
  }
  return $block;
}

/**
 * Helper function to render a block's HTML.
 *
 * @param string $module
 *   Name of module that implements the block.
 * @param string $delta
 *   Unique ID of the block.
 *
 * @return string
 *   HTML of rendered block.
 *
 * @see http://drupal.org/node/26502#comment-4705330
 */
function menu_attach_block_block_render($module, $delta) {
  $block = block_load($module, $delta);
  $block_content = _block_render_blocks(array($block));
  $build = _block_get_renderable_array($block_content);
  $block_rendered = drupal_render($build);
  return $block_rendered;
}