<?php

/**
 * Implementation of hook_menu().
 * 
 * A single menu item, used by the AHAH/AJAX callback when clicking on the plus
 * icon on a page.
 */
function tree_widget_menu(){
  return array(
    'term-reference-tree/%/%/%/%taxonomy_term/%' => array(
      'title' => 'tree_widget callback',
      'title callback' => FALSE,
      'page callback' => 'tree_widget_page_callback',
      'page arguments' => array(
        1,
        2,
        3,
        4,
        5
      ),
      'delivery callback' => 'ajax_deliver',
      'access callback' => 'tree_widget_access_callback',
      'access arguments' => array(
        1,
        2,
        3,
        4
      )
    )
  );
}

/**
 * Implements hook_field_widget_settings_form().
 */
function tree_widget_field_widget_settings_form($field, $instance){
  $form = array();
  if($instance['widget']['type'] == 'tree_widget'){
    $form['leaves_only'] = array(
      '#type' => 'checkbox',
      '#title' => t('Leaves only'),
      '#description' => t("Don't allow the user to select items that have children"),
      '#default_value' => isset($instance['widget']['settings']['leaves_only']) ? $instance['widget']['settings']['leaves_only'] : 0,
      '#return_value' => 1
    );
  }
  return $form;
}

/**
 * Callback used to return the additional HTML for a branch in a tree
 */
function tree_widget_page_callback($entity, $field_name, $bundle, $term, $element_id){
  // Note, we do not need to worry about default values here, as all boxes that
  // were default checked will already be on the web page, therefore all 
  // checkboxes being asked for will not be checked.
  // Load the field instance first, so that we can check settings.
  $field_instance = field_info_instance($entity, $field_name, $bundle);
  $field = field_info_field($field_name);
  $variables = array(
    'vid' => $term->vid,
    'tid' => $term->tid,
    'element' => array(
      '#name' => $element_id,
      '#multiple' => $field['cardinality'],
      '#leaves_only' => $field_instance['widget']['settings']['leaves_only']
    )
  );
  return theme('options_tree', $variables);
}

/**
 * Access callback.  Checks that the user has editing privileges for this form.
 */
function tree_widget_access_callback($field_name, $term){
  // For now, we simply return TRUE.
  return TRUE;
}

/**
 * Implements hook_field_widget_info().
 */
function tree_widget_field_widget_info(){
  return array(
    'tree_widget' => array(
      'label' => 'Tree widget',
      'field types' => array(
        'taxonomy_term_reference'
      ),
      'behaviors' => array(
        'multiple values' => FIELD_BEHAVIOR_CUSTOM,
        'default value' => FIELD_BEHAVIOR_DEFAULT
      )
    )
  );
}

/**
 * Implements hook_element_info().
 */
function tree_widget_element_info(){
  $types = array(
    'options_tree' => array(
      '#input' => true,
      '#theme' => array(
        'options_tree'
      ),
      '#pre_render' => array(
        'form_pre_render_conditional_form_element'
      )
    )
  );
  return $types;
}

/**
 * Implements hook_theme().
 */
function tree_widget_theme(){
  return array(
    'options_tree' => array(
      'render element' => 'element'
    ),
    'options_tree_term' => array(
      'term' => 'term',
      'tid' => 'tid',
      'vid' => 'vid',
      'ancestors' => 'ancestors'
    ),
    'options_tree_expand_button' => array(
      'field_id' => 'field_id',
      'term' => 'term',
      'open' => FALSE,
      'children' => TRUE
    )
  );
}

/**
 * 
 */
function theme_options_tree_expand_button($variables){
  // Check if the term has any children, if so, we need to return a plus, else
  // we return a blank.
  $output = "<span id=\"{$variables['field_id']}__{$variables['term']->tid}\" class=\"options_tree_plus ";
  if($variables['children']){
    if($variables['open']){
      $output .= 'minus';
    }else{
      $output .= 'plus';
    }
  }else{
    $output .= 'leaf';
  }
  return $output . '"><img src="' . base_path() . drupal_get_path('module', 'tree_widget') . '/images/blank.gif" width="16px" height="16px" /></span>';
}

/**
 * Returns HTML for an options_tree form element.
 *
 * @param $variables
 * An associative array containing:
 * - element: An associative array containing the properties of the element.
 */
function theme_options_tree($variables){
  $root_terms = array();
  // Get the terms that need to be displayed
  if(isset($variables['tid'])){
    $term = taxonomy_term_load($variables['tid']);
    $root_terms = taxonomy_get_tree($term->vid, $variables['tid'], 1);
    $num_vocabularies = 1;
  }elseif(!isset($variables['vid'])){
    $vocabularies = array();
    $num_vocabularies = 0;
    foreach($variables['element']['#vocabularies'] as $voc_name){
      $num_vocabularies++;
      $vocabulary = taxonomy_vocabulary_machine_name_load($voc_name);
      if($vocabulary){
        $root_terms = array_merge($root_terms, taxonomy_get_tree($vocabulary->vid, 0, 1));
      }
    }
  }
  // Get the root terms.  
  $output = '<ul class="tree_widget">';
  // Get the terms that need to be displayed
  $variables['ancestors'] = _tree_widget_get_ancestors_and_siblings($variables['element']['#default_value']);
  $titles_set = array();
  foreach($root_terms as $term){
    if($num_vocabularies > 1 && !$term->parents[0] && !isset($titles_set[$term->vid])){
      $titles_set[$term->vid] = TRUE;
      $vocabulary = taxonomy_vocabulary_load($term->vid);
      $output .= "<label>" . check_plain($vocabulary->name) . "</label>";
    }
    // Missing variables for:
    // vid, tid
    $variables['term'] = $term;
    $output .= theme('options_tree_term', $variables);
  }
  return $output . '</ul>';
}

function theme_options_tree_term($variables){
  $checkbox_variables = array(
    'element' => array(
      '#id' => $variables['element']['#id'] . '-' . $variables['term']->tid,
      '#name' => $variables['element']['#name'] . '[]',
      '#return_value' => $variables['term']->tid
    )
  );
  $variables['tid'] = $variables['term']->tid;
  $display_text = check_plain($variables['term']->name);
  // If we're only showing leaves, then we need only return a basic <li> element  
  // Does this term have children, if so, return the basic element
  $children = taxonomy_get_children($variables['term']->tid, $variables['term']->vid);
  if($variables['element']['#leaves_only'] && count($children)){
    $input_type = 'hidden';
    unset($checkbox_variables['element']['#name']);
    unset($checkbox_variables['element']['#id']);
    $checkbox_variables['element']['#value'] = $variables['term']->tid;
  }else{
    if($variables['element']['#multiple'] == 1){
      $input_type = 'radio';
      if(isset($variables['element']['#default_value'][0])){
        $checkbox_variables['element']['#value'] = $variables['element']['#default_value'][0];
      }else{
        $checkbox_variables['element']['#value'] = '';
      }
    }else{
      $input_type = 'checkbox';
      if(isset($variables['element']['#default_value']) && array_search($variables['term']->tid, $variables['element']['#default_value']) !== FALSE){
        $checkbox_variables['element']['#checked'] = TRUE;
      }else{
        $checkbox_variables['element']['#checked'] = FALSE;
      }
    }
  }
  return '<li>' . theme('options_tree_expand_button', array(
    'field_id' => $variables['element']['#name'],
    'term' => $variables['term'],
    'children' => count(taxonomy_get_children($variables['term']->tid, $variables['term']->vid)),
    'open' => isset($variables['ancestors'][$variables['term']->tid])
  )) . '<label>' . theme($input_type, $checkbox_variables) . $display_text . '</label>' . (isset($variables['ancestors'][$variables['term']->tid]) ? theme('options_tree', $variables) : '') . '</li>';
}

/**
 * Returns all the ancestors of the default terms
 */
function _tree_widget_get_ancestors_and_siblings($tids){
  $ancestors = array();
  foreach($tids as $tid){
    $parents = taxonomy_get_parents_all($tid);
    // Note, we remove the final term from the list, we don't need that.
    array_shift($parents);
    foreach($parents as $parent){
      $ancestors[$parent->tid] = $parent;
    }
  }
  return $ancestors;
}

/**
 * Implements hook_widget_field_form().
 */
function tree_widget_field_widget_form(&$form, &$form_state, $field, $instance, $langcode, $items, $delta, $element){
  // TODO - Add default values ? Is this still a TODO?
  $default_value = array();
  foreach($items as $item){
    $default_value[] = $item['tid'];
  }
  $vocabularies = array();
  foreach($field['settings']['allowed_values'] as $voc){
    if($voc['vocabulary']){
      $vocabularies[] = $voc['vocabulary'];
    }
  }
  $element += array(
    '#type' => 'options_tree',
    '#attached' => array(
      'css' => array(
        drupal_get_path('module', 'tree_widget') . '/css/tree_widget.css'
      ),
      'js' => array(
        drupal_get_path('module', 'tree_widget') . '/js/tree_widget.js' => array(
          'type' => 'file'
        ),
        array(
          'data' => array(
            'tree_widget' => array(
              $instance['field_name'] => array(
                'callback' => url("term-reference-tree/{$instance['entity_type']}/{$instance['field_name']}/{$instance['bundle']}"),
                'max' => $field['cardinality']
              )
            )
          ),
          'type' => 'setting'
        )
      )
    ),
    '#multiple' => $field['cardinality'],
    '#vocabularies' => $vocabularies,
    '#tid' => 0,
    '#value_callback' => '_tree_widget_widget_set_values',
    '#default_value' => $default_value,
    '#leaves_only' => isset($instance['widget']['settings']['leaves_only']) ? $instance['widget']['settings']['leaves_only'] : 0,
    '#element_validate' => array(
      '_tree_widget_widget_validate'
    )
  );
  if($field['cardinality'] > 1){
    $element['#description'] .= '<div class="description">' . t('Select up to !number options.', array(
      '!number' => $field['cardinality']
    )) . '</div>';
  }
  return $element;
}

/**
 * Set the values based on the user input
 */
function _tree_widget_widget_set_values($element, $input = FALSE, $form_state = array()){
  // First, we need to flatten stuff, due to the silly "[und]".
  $parts = preg_split('/[\[\]]/', $element['#name'], -1, PREG_SPLIT_NO_EMPTY);
  if(isset($form_state['input'][$parts[0]])){
    $values = array();
    $input = $form_state['input'];
    foreach($parts as $part){
      $input = $input[$part];
    }
    if(is_array($input)){
      foreach($input as $tid){
        $values[] = array(
          'tid' => $tid
        );
      }
    }
    return $values;
  }else{
    return array();
  }
}

/**
 * Validates the terms selected are all leaves.
 */
function _tree_widget_widget_validate(&$element, &$form_state){
  // Check we've set only leaves (if required).
  if($element['#leaves_only']){
    foreach($element['#value'] as $tid){
      if(count(taxonomy_get_children($tid['tid']))){
        form_set_error($element['#field_name'], t('You must only select leaf terms.'));
      }
    }
  }
  // Check the count is allowed
  if($element['#multiple'] > 0 && count($element['#value']) > $element['#multiple']){
    form_set_error($element['#field_name'], t('You have selected too many terms, only !number allowed', array(
      '!number' => format_plural($element['#multiple'], 'one is', '!number are', array(
        '!number' => $element['#multiple']
      ))
    )));
  }
  return $element;
}